Staff Profiles

I am an active member of the Curriculum Development Group in ECM, and working on the development Electro-Mechanical and Robotic degrees in Engineering.

Modules taught

Also I teach the following modules:

• U04596 Advanced Analog Electronics
• U04685 Group Design Applications
• U04595 Advanced Digital Electronics
• U04681 Advanced Automotive Electronics
• U04504 Design and practice I- Electronics part
• UG project supervision
• MSc project supervision

Supervision

  I am a Director of studies for the following PhD students:

•  David Carugo, “High resolution spherical acoustic radiation measurement system for musical instruments”.
• Sam Kamperis "Optimisations of computationally complex algorithms for polyhedra, 3D Polyhedral Mappings.
• Saddam S M Zourob “Increasing signal to noise ratio, and minimising artefacts in biomedical (ECG) instrumentation systems”.
• Nabil Yassine "Driver awareness sensing", in conjunction with Professor Bhaskar Choubry of the University of Oxford.

             Second supervisor:

• Gokhan Budan "Road side unit system design with V21 communications"

Research interests include: biomedical electronics, RF circuits, automotive electronics, robotics.

Research group membership

Electronics and Communications

Research grants and awards

• £42,750 HEIF 5 Business Enterprise Fund. Proof of Concept. Electrical Impedance Mammography (co-investigator), 2016-2017.
• £10,000, Research Excellence Award, September 2017 to July 2018, K Hayatleh & S Barker, to work on “Superior Instrumentation Amplifier and Active Electrodes for eliminating artefacts in biomedical equipment.
• £4,000, International Collaborative Research and Travel Awards,September 2017 to July 2018, K Hayatleh & S Barker. This is to work with Prof Laura M. Schreiber, Scientific Director and Chair of Cellular and Molecular Imaging, Würzburg University Hospital, Comprehensive Heart Failure Center (CHFC) Würzburg, Germany; Prof. Hubert Spiesberger, University of Mainz, Germany; and Prof. Cristiana Sebu University of Malta,  Funds have also been provided to Steve Barker and myself by Prof Laura M. Schreiber for our initial visit 2 day to Würzburg University Hospital in December 2017.

Research projects

Driver Awareness Monitoring by Analysing Blink rate and Head Tilt.

Increasing Signal to Noise Ratio, and Minimising Artefacts in Biomedical Systems.

Design and development of Current Driver systems for enhancement of MRI systems resoultion.

Research impact

Electrical Impedance Tomography (EIT)

Oxford Brookes has a long involvement with the development of biomedical instrumentation and imaging techniques. The group at Oxford Brookes is one of the most productive and long standing groups working on Electrical Impedance Tomography (EIT) worldwide and has made a number of important contributions to the theoretical and practical aspects of this problem. EIT is a non-invasive, portable and low-cost imaging tool with important applications in medicine. The reconstruction techniques and the Electrical Impedance Tomographs developed were tested in clinical trials in the Churchill and John Radcliffe Hospitals in Oxford. Novel current-mode design techniques are applied not only to EIT, but also to other areas of medical instrumentation such as a new design for Electrical Impedance Cardiography (EIG) and integrated circuit pH sensors based on Ion Sensitive Field Effect Transistors (ISFET) technology.

The research on the theoretical work on EIT and the practical development of imaging devices at Oxford Brookes led to three European patent applications [I10-I12] and also contributed towards three US patents [I5-I7], the development of EIDORS [I3] which provides free software algorithms for forward and inverse modelling for Electrical Impedance Tomography (EIT) and Diffusion based Optical Tomography, in medical and industrial settings, and to share data and promote collaboration between groups working these fields.

 Artefact Reduction in Biomedical Electronic Systems 

Nearly all medical equipment which is based on passive electrodes being attached to patients suffers from artefacts (unwanted noise). Artefacts can cause a wide range of distortion effects, which impacts on the performance of the initial stages of the system – which is normally an instrumentation amplifier (IA).  These effects can range from minor blurring to significant distortion being added to the desired signals from the body, which consequently can affect the interpretation of medical results.  There have been numerous research projects offering various solutions to eliminate or reduce artefacts from in electronic biomedical systems, and the vast majority of these are based on the assumption that artefacts are due to noise generated by the movement of electrodes whilst attached to patients.  As a result, nearly all existing methods for the removal of artefacts in medical equipment are based upon filtering, smoothing and averaging – with both analog and digital electronics approaches being used.  Such approaches may be suitable if the cause of the artefacts is purely random. However, these approaches are not always effective with artefacts generated by the movement of electrodes. In this research, we will apply new real-time signal processing techniques to design and develop circuitry that significantly reduces these unwanted signals, by specifically focusing on the various causes of artefacts due to the movement of electrodes.  Additionally, we will be applying new design techniques to the design of the IA.

Further information

/ecm/research/engineering/simulation-modelling-and-systems-integration/

/ecm/research/computing/communications--media-and-electronic-technologies/

Journal articles

• Borislav Dimitrov *, Khaled Hayatleh, Steve Barker, Gordana Collier, Suleiman Sharkh, Andrew Cruden, 'A Buck-Boost Transformerless DC-DC Converter Based on IGBT Modules for Fast Charge of Electric Vehicles'
  Journal of Low Power Electronics and Applications 9 (3) (2020)
  ISSN: 2079-9292
  Abstract

  A transformer-less Buck-Boost DC-DC converter in usage for the fast-charge of electric vehicles, based on powerful high-voltage IGBT (Isolated Gate Bipolar Transistor) modules is analyzed, designed and experimentally verified. The main advantages of this topology are: simple structure on the converter’s power stage; a wide range of the output voltage, capable to support nowadays vehicles on-board battery packs; efficiency and power density accepted to be high enough for such class of hard-switched converters. A precise estimation of the loss, dissipated in the converter’s basic modes of operation – Buck, Boost, and Buck-Boost is presented. The analysis shows an approach of loss minimization, based on switching frequency reduction during the Buck-Boost operation mode. Such a technique guarantees stable thermal characteristics during the entire operation, i.e. battery charge cycle. As the Buck-Boost mode takes place when Buck and Boost modes cannot support the output voltage, operating as a combination of them, it can be considered as critically dependent on the characteristics of the semiconductors. With this, the necessary duty cycle and voltage range, determined with respect to the input-output voltages and power losses, require additional study to be conducted. Additionally, the tolerance of the applied switching frequencies for the most versatile silicon-based powerful IGBT modules is analyzed and experimentally verified. Finally, several important characteristics, such as transients during switch-on and switch-off, IGBTs voltage tails, critical duty cycles, etc., are depicted experimentally with oscillograms, obtained by an experimental model. 
  

  Website 
• Rajasekhar Nagulapalli, Khaled Hayatleh, Steve Barker, 'A positive feedback-based op-amp gain enhancement technique for high precision applications'
  Journal of Circuits, Systems, and Computers (2020)
  ISSN: 0218-1266 eISSN: 1793-6454
  Abstract

  A power-efficient, voltage gain enhancement technique for op-amps has been described. The proposed technique is robust against Process, Voltage, and Temperature (PVT) variations. It exploits a positive feedback-based gain enhancement technique without any latch-up issue, as opposed to previously proposed conductance cancellation techniques. In the proposed technique, four additional transconductance-stages (gm stages) are used to boost the gain of the main gm stage. The additional gm stages do not significantly increase the power dissipation. A prototype was designed in 65nm CMOS technology. It results in 81dB voltage gain, which is 21dB higher than the existing gainboosting technique. The proposed opamp works with as low a power supply as 0.8V, without compromising the performance, whereas the traditional gain-enhancement techniques start losing
  gain below a 1.1V supply. The circuit draws a total static current of 295μA and occupies 5000μm2 of silicon area.
  

  Website 
• R. Nagulapalli, K. Hayatleh, S Barker, 'A VGA Linearity improvement technique for ECG analog front-end in 65nm CMOS'
  Journal of Circuits, Systems, and Computers (2019)
  ISSN: 0218-1266 eISSN: 1793-6454
  Abstract

  This paper presents a 65nm CMOS low-power, highly linear variable gain amplifier (VGA) suitable for biomedical applications. Typical biological signal amplitudes are in the 0.5-100mV range, and therefore require circuits with a wide dynamic range. Existing VGA architectures mostly exhibit a poor linearity, due to very low local feedback loopgain. A technique to increase the loop-gain has been explored by adding additional feedback to the tail current source of the input differential pair. Stability analysis of the proposed technique was undertaken with pole-zero analysis. A prototype of Analog Front End (AFE) has been designed to provide 25-50dB gain, and post-layout simulations showed a 15dB reduction in the harmonic distortion for 20mV pk-pk input signal compared to the conventional architecture. The circuit occupies 3,108μm2 silicon area and consumes 0.43μA from a 1.2V power supply.
  

  Website 
• Mathew M, Hart BL, Hayatleh K, 'Design of a low-current shunt-feedback transimpedance amplifier with inherent loop-stability'
  Analog Integrated Circuits and Signal Processing 99 (2019) pp.539-545
  ISSN: 0925-1030 eISSN: 1573-1979
  Abstract

  In this paper we propose a new architecture for enhancing the performance of a transimpedance amplifier (TIA) used for low-currents, and in particular, that used in biosensing. It is usually the first block in biomedical acquisition systems for converting a current in the nanoampere and picoampere range into a proportional voltage, with an amplitude suitable for further processing. There exist two main amplifier topologies for achieving this, current-mode and shunt-feedback mode. This paper introduces a shunt-feedback amplifier that embodies current-mode operation and thereby offers the advantages of both existing schemes. A conventional shunt-feedback amplifier has a number of stages and requires compensation components to achieve stability of the feedback loop. The exemplary circuit described is inherently stable because a high gain is effectively achieved in one stage that has a dominant pole controlling the frequency response. Exhibiting complementary symmetry, the configuration has an input port that is very close to earth potential. This enables the configuration to handle bidirectional input signals such are as met with in electrochemical ampero-metric biosensors. For the 0.35µm process adopted and ±3.3V rail supplies, the power dissipation is 330µW. With a transimpedance gain of 120dBohm the incremental input and output resistances are less than 2ohm and the -3dB bandwidth for non-optical input currents is 8.2MHz. The input referred noise current is 3.5pA/√Hz.
  

  Website 
• Cecotti M, Larmine J, Fellows N, Hayatleh K, 'Development of an Autonomous Battery Electric Vehicle'
  SAE Technical Papers (2019)
  ISSN: 0148-7191
  Abstract

  Autonomous vehicles have been shown to increase safety for drivers, passengers and pedestrians and can also be used to maximize traffic flow, thereby reducing emissions and congestion. At the same time, governments around the world are promoting the usage of Battery Electric Vehicles (BEVs) to reduce and control the emissions of CO2. This has made the development of autonomous vehicles and electric vehicles a very active research area and has prompted a significant amount of government funding. This paper presents the detailed design of a low-cost platform for the development of an autonomous electric vehicle. In particular, it focuses on the design of the electrical architecture and the control strategy, tailored around the usage of affordable sensors and actuators. The specifications of the components are extensively discussed in relation to the performance target. The aim is to provide a comprehensive guide for the development of the remotely controlled platform, in order to lower the entry barrier for the development of autonomous electric vehicles.

  Website 
• R. Nagulapalli, K. Hayatleh, S. Barker, B. Yassine, S. Zourob, S. Raparthy, N. Yassine, 'A Start-up Assisted Fully Differential Folded Cascode Opamp'
  Journal of Circuits, Systems, and Computers 28 (10) (2018)
  ISSN: 0218-1266 eISSN: 1793-6454
  Abstract

  This paper explains the hidden positive feedback in the two-stage fully differential amplifier through external feedback resistors, and possible DC latch-up during the amplifier start-up. The biasing current selection among the cascode branches have been explained intuitively, With reference to previous literature. To avoid the latch-up problem irrespective of the transistor bias currents a novel, hysteresis based start-up circuit is proposed. An 87dB, 250MHz unity gain bandwidth amplifier has been developed in 65nm CMOS Technology and post-layout simulations demonstrate no start-up failures out of 1000 Monte-Carlo (6-Sigma) simulations. The circuit draws 126uA from a 1.2V supply and occupies the 2184um2 area.
  

  Website 
• R. Nagulapalli, K. Hayatleh, S. Barker, A.A. Tammam, N. Yassine, B. Yassine, M. Ben-Esmael., 'A Low Noise Amplifier Suitable for Biomedical Recording Analog Front-End in 65nm CMOS Technology'
  Journal of Circuits, Systems, and Computers 28 (8) (2018)
  ISSN: 0218-1266 eISSN: 1793-6454
  Abstract This paper presents a fully integrated Front-end, low noise amplifier, dedicated to the processing of various types of bio-medical signals, such as Electrocardiogram (ECG), Electroencephalography (EEG), Axon Action Potential (AAP). A novel noise reduction technique, for an operational transconductance amplifier (OTA), has been proposed. This adds a current steering branch parallel to the differential pair, with a view to reducing the noise contribution by the cascode current sources. Hence, this reduces the overall input referred noise of the Low Noise Amplifier (LNA), without adding any additional power. The proposed technique implemented in 65nm CMOS technology achieves 30dB closed loop voltage gain, 0.05Hz lower cut-off frequency and 100MHz 3-dB bandwidth. It operates at 1.2V power supply and draws 1µA static current. The prototype described in this paper occupies 3300µm2silicon area.Website 
• R. Nagulapalli, K. Hayatleh, S. Barker, A.A. Tammam, P. Georgiou* & F. J. Lidgey, 'A 0.55V Bandgap reference with a 59ppm/0c Temperature coefficient'
  Journal of Circuits, Systems, and Computers 28 (7) (2018)
  ISSN: 0218-1266 eISSN: 1793-6454
  Abstract This paper presents a novel low power, low voltage CMOS bandgap reference (BGR) that overcomes the problems with existing BJT-based reference circuits, by using a MOS transistor operating in subthreshold region. A proportional to absolute temperature (PTAT) voltage is generated by exploiting the self-bias cascode branch, while a Complementary to Absolute Temperature (CTAT) voltage is generated by using the threshold voltage of the transistor. The proposed circuit is implemented in 65nm CMOS technology. Post-layout simulation results show that the proposed circuit works with a supply voltage of 0.55V, and generates a 286mV reference voltage with a temperature coefficient of 59ppm/°C. The circuit takes 413nA current from 0.55V supply and occupies 0.00986mm2 of active area .Website 
• K Hayatleh, S Zourob, R Nagulapalli,S Barker, N Yassine, P Georgiou*, F J Lidgey, 'A High Performance Skin Impedance Measurement Circuit for Biomedical Applications'
  Journal of Circuits, Systems, and Computers 28 (7) (2018)
  ISSN: 0218-1266 eISSN: 1793-6454
  Abstract This paper describes a high-performance impedance measurement circuit for the application of skin impedance measurement in the early detection of skin cancer. A CMRR improvement technique has been adopted for OTAs to reduce the impact of high frequency common mode interference. A modified 3-OTA IA has been proposed to help with the impedance measurement. Such systems offer a quick, non-invasive and painless procedure, thus having considerable advantages over the currently used approach, which is based upon the testing of a biopsy sample. The sensor has been implemented in 65nm CMOS technology and post layout simulations confirms the theoretical claims we made and sensor exhibits sensitivity. Circuit consumes 45uW from 1.5V power supply. The circuit occupies 0.01954mm2 silicon area. Website 
• R. Nagulapalli, K. Hayatleh, S. Barker, P. Georgiou & F. J. Lidgey, 'A High Value, Linear and Tunable CMOS Pseudo Resistor for Bio-medical Applications'
  Journal of Circuits, Systems, and Computers 28 (6) (2018)
  ISSN: 0218-1266 eISSN: 1793-6454
  Abstract A sub-threshold MOS based pseudo resistor featuring a very high value and ultra-low distortion is proposed. A band-pass neural amplifier with a very low high-pass cutoff frequency is designed, to demonstrate the linearity of the proposed resistor. A BJT less CTAT current generator has been introduced to minimize the temperature drift of the resistor and make tuning easier. The stand-alone resistor has achieved 0.5% better linearity and a 12% improved temperature coefficient over the existing architectures. A neural amplifier has been designed with the proposed resistor as a feedback element. It demonstrated 31dB mid-band gain and a lowpass cutoff frequency of 0.85Hz. The circuit operates from a 1V supply and draws 950nA current at room temperature. Website 
• R. Nagulapalli, K. Hayatleh, S. Barker, S. Zourob, N. Yassine, S. Raparthy and A. A. Tammam, 'A novel high CMRR Trans-Impedance Instrumentation Amplifier for biomedical applications'
  Analog Integrated Circuits and Signal Processing (2018)
  ISSN: 0925-1030 eISSN: 1573-1979
  Abstract A compact high gain current mode instrumentation amplifier (IA) has been proposed for biomedical imaging applications. Conventional IAs rely on several matching resistors which occupies a lot of silicon area, the input and output common mode voltages are exactly same and the maximum applied signal amplitude is limited by internal node voltage swings. The present proposal eliminates the need for matching resistors by processing signals in the current mode. Hence input amplitudes are no longer limited by the voltage headroom and input and output common-mode voltages can be independent. An amplifier with a differential gain greater than 52dB and a common mode rejection ratio (CMRR) greater than 120dB has been implemented in 65nm CMOS Technology and Post layout simulations were presented. The total circuit occupies 4500um2 silicon area and circuit consumes ~260μA from 1.8V power supply.Website 
• R Nagulapalli, K Hayatleh, S Barker, S Zourob, N Yassine, 'An OTA Gain Enhancement Technique for low power biomedical applications'
  Analog Integrated Circuits and Signal Processing 95 (3) (2018) pp.387-394
  ISSN: 0925-1030 eISSN: 1573-1979
  Abstract The performance requirement of an operational trans-conductance amplifier (OTA) for the high gain and low power neural recording frontend has been addressed in this paper. A novel split differential pair technique is proposed to improve the gain of the OTA without any additional bias current requirements. The design demonstrates a significant performance enhancement when compared to existing techniques, such as gain-boosting and recycling. A qualitative and quantitative treatment is presented to explore the impact of the split ratio on the performance parameters of gain, bandwidth, and linearity. A prototype implemented in TSMC 65 nm CMOS technology achieved 68 dB open loop-gain (13 dB higher than the conventional circuit) and a 17 kHz 3-dB bandwidth. A linearity of − 62 dB has been achieved with 7 mV pk–pk signal at the input. The circuit operates from a 1 V supply and draws 0.6 uA static current. The prototype occupies 3300 um2 silicon area.Website 
• S Zourob, K Hayatleh, S Barker, R Nagulapalli, N Yassine, R Ramsbottom and F J Lidgey, 'Increasing Signal to Noise Ratio and Minimizing Artefacts in Biomedical Instrumentation Systems'
  Analog Integrated Circuits and Signal Processing 95 (3) (2018) pp.403-408
  ISSN: 0925-1030 eISSN: 1573-1979
  Abstract Capturing a near-perfect, artefact free signal is an ideal of biomedicine. However, this depends on the removal of different types of artefact, all of which can be considered unwanted noise on the desired signal. Failure to remove artefacts could lead to a clinical misinterpretation of the results. All medical equipment such as electrocardiogram systems which use electrodes attached to patients suffer from artefacts, with effects ranging from minor blurring to significant distortion of the output signal(s). For this reason, it is important to identify how artefacts can influence the output signal. In this paper, we propose a new technique to detect and minimise movement artefacts using strain gauges embedded into the electrodes.Website 
• N. Yassine, S. Barker, K. Hayatleh, B. Choubey, R. Nagulapalli, 'Simulation of Driver Fatigue Monitoring via Blink Rate Detection, using 65nm CMOS Technology'
  Analog Integrated Circuits and Signal Processing 95 (3) (2018) pp.409-414
  ISSN: 0925-1030 eISSN: 1573-1979
  Abstract This paper proposes a system to detect and measure blink rate to determine fatigue levels. The method involved analysing specific frames to determine that a blink occurred, and then monitoring the time between successive blinks. The program was simulated in python using a Raspberry Pi Zero and a standard USB camera. For the blink rate detection block, a gate level schematic was implemented in Cadence software using 65nm CMOS technology. The design was based around an asynchronous 6-bit based edge counter which was designed using D-flip-flops. The simulation calculated the average blink rate and compared this to the most recent blink rate. The outcome would determine if an alarm signal should be sent to the alarm. The system consumed 130uA from a 1.2V power supply. Website 
• G. Budan, K. Hayatleh, D. Morrey, P. Ball, P. Shadbolt, 'An Analysis of Vehicle-to-Infrastructure Communications for Non-Signalised Intersection Control under Mixed Driving Behaviour'
  Analog Integrated Circuits and Signal Processing 95 (3) (2018) pp.415-422
  ISSN: 0925-1030 eISSN: 1573-1979
  Abstract Intersection control has an important role in the management of urban traffic to ensure safety, high traffic flow and to prevent congestion. Recently, a growing body of literature has been reported on the theme of non-signalised intersection control in which traffic lights are replaced with intelligent road side units. Data from several studies suggest that non-signalised control could reduce vehicle delays and fuel consumption significantly whilst ensuring safety. However, there is little published data on the impact of the mixed driving behaviour with human-driven vehicles and autonomous vehicles. This paper investigates the emerging role of connectivity and vehicle autonomy in the context of traffic control under the mixed driving behaviour scenario. The concepts of vehicle-to-infrastructure (V2I) communications and multi-agent systems are central to achieving a robust and reliable traffic-light-free intersection control. Comprehensive computer simulation results on a four-way intersection indicate over 96% reduced average vehicle delay and 37% less fuel consumption with the non-signalised control solution compared to the traffic light control. The outcome of this study offers some important insights into enabling cooperation between vehicles and traffic infrastructure via V2I communications, in order to make more efficient real-time decisions about traffic conditions, whilst ensuring a higher degree of safety.Website 
• Nagulapalli R, Hayatleh K, Barker S, Raparthy S, Yassine N, Lidgey FJ, 'A 0.6V MOS-only voltage reference for bio-medical applications with 40ppm/0c temperature drift'
  Journal of Circuits, Systems, and Computers 27 (8) (2018)
  ISSN: 0218-1266 eISSN: 1793-6454
  Abstract This paper exploits the CMOS beta multiplier circuit to synthesize a temperature independent
  voltage reference suitable for low voltage and ultra-low power bio-medical applications. The
  technique presented here uses only MOS transistors to generate PTAT and CTAT currents. A selfbiasing technique has been used to minimize the temperature and power supply dependency. A prototype in 65nm CMOS has been developed and occupies 0.0039mm, and at room temperature it generates a 204mV reference voltage with 1.3mV drift over a wide temperature range (from -40 to 1250C). This has been designed to operate with a power supply voltage down to 0.6V and consumes 1.8uA current from the supply. The simulated temperature coefficient is 40ppm/0C.Website 
• Nagulapalli R, Hayatleh K, Barker S, Raparthy S, Lidgey FJ, 'A CMOS blood cancer detection sensor based on frequency deviation detection.'
  Analog Integrated Circuits and Signal Processing 92 (3) (2017) pp.437-442
  ISSN: 0925-1030 eISSN: 1573-1979
  Abstract This paper proposes a technique to detect Leukaemia (blood cancer) based on the frequency modulation of a relaxation oscillator by changes in the dielectric constant of blood cells. A novel 16-bit frequency detector with a digital output has been proposed to detect the frequency difference between two oscillators based on healthy blood and Leukaemic blood. A circuit has been designed, to operate on a 1.2V supply, post layout simulations shows 0.35mA current consumption. The chip Area including pads~0.6mm∗0.45mmWebsite 
• Ben-Esmael M, Mathew M, Hart BL, Hayatleh K, 'Technique for increasing the output impedance of CMOS regulated cascode circuits.'
  Journal of Circuits, Systems, and Computers 25 (10) (2016)
  ISSN: 0218-1266 eISSN: 1793-6454
  Abstract A technique is proposed for the design of a modified CMOS regulated cascode having an output impedance significantly greater than that of a conventional regulated cascode. Simulation results for an illustrative design, operating at 10µA from a 1V supply, show an increase in output resistance from 636MΩ and output bandwidth of 55kHz for a conventional circuit to 6.68GΩ and 389kHz, respectively, for the proposed design.
  Website 
• Tammam AA, Hayatleh K, Barker S, Terzopoulos N, 'Theoretical Study of the Circuit Architecture of the Basic CFOA and Testing Techniques'
  International Journal of Electronics 103 (9) (2016) pp.1475-1497
  ISSN: 0020-7217
  Abstract
  This paper examines the closed-loop characteristics of the basic CFOA, and in particular, the dynamic response.  Additionally, it also examines the design and advantages of the CFOA regarding its ability to provide a significantly constant closed-loop bandwidth for closed-loop voltage gain. Secondly, the almost limitless slew–rate provided by the class AB input stage that makes it superior to the VOA counterpart. Additionally; this paper also concerns the definitions and measurements of the terminal parameters of the CFOA, regarded as a ‘black box’. It does not deal with the way that these parameters are related to the properties of the active passive and active components of a particular circuit configuration. Simulation is used in terminal parameter determination: this brings with it the facility of using test conditions that would not normally prevail in a laboratory test on silicon implementations of the CFOAs. Thus, we can apply 1mA and 1mV test signals from, respectively, infinite and zero source impedances that range in frequency from d.c to some tens of GHz. Also, we assume the existence of resistors with identical Ohmic value and very high value ideal capacitors. Where appropriate, practical test methods are referred to physical laboratory prototypes.
   
  Website 
• Tammam AA, Hayatleh K, Barker S, Ben-Esmael M, Terzopoulos N, 'Improved designs for current feedback op-amps'
  International Journal of Electronics Letters 4 (2) (2015) pp.215-227
  ISSN: 2168-1724
  Abstract The performance of the current feedback op-amps (CFOAs) is very much determined by the input stage of CFOAs, including common-mode rejection ratio (CMRR). Two new CFOAs topologies are presented in this article: one topology uses a cascoding technique, and the second one uses a bootstrapping technique, both of which provide a much better CMRR and lower DC offset voltage than the conventional CFOAs. Moreover, the new CFOAs design exhibits an extended high frequency bandwidth, with a gain accuracy improvement. Applications requiring constant bandwidth with variable (closed loop) gain will benefit from the proposed topologies.Website 
• Fonseca H, Hayatleh K, Terzopoulos N, Lidgey FJ, Sebu C, 'An investigation on the discrete-time nature of excess phase and jitter'
  International Journal of Electronics 101 (6) (2014) pp.856-864
  ISSN: 0020-7217
  Abstract

  Excess phase in oscillators or phase locked loops is a very important design specification typically modelled as a continuous time signal. In this paper we explain why, when the quantity of interest is jitter, excess phase should be treated as a discrete quantity.  This treatment helps explaining noise folding in frequency dividers and analyse its consequences in Phase Locked Loops. 

  Website 
• Terzopoulos N, Hayatleh K, Sebu C, Lidgey FJ, Ben-Esmael M, Tammam AA, Barker S, 'Analysis and design of a high precision- high output impedance tissue current driver for medical applications'
  Journal of Circuits, Systems, and Computers 23 (8) (2014)
  ISSN: 0218-1266 eISSN: 1793-6454
  Abstract

  This paper describes the design and operation of a high output impedance tissue current driver circuit, for use in medical electronics, such as Electrical Impedance Tomography (EIT).  This novel architecture was designed for implementation in bipolar technology, to meet the specifications for EIT, namely operating frequency range 10 kHz–1 MHz with a target output resistance of 16 MW.  Simulation results are presented, showing that the current source more than met the minimum specification for EIT.

  
  Website 
• Regan AJ, Lidgey FJ, Betteridge M, Georgiou P, Toumazou C, Hayatleh K, Dibble JR, 'Novel GPU Approach In Predicting The Directional Trend Of The S&P 500'
  Proceedings of the World Academy of Science, Engineering and Technology 8 (8) (2014) pp.2745-2748
  ISSN: 2010-376X eISSN: 2010-3778
  Abstract

  Our goal is development of an algorithm capable of predicting the directional trend of the Standard and Poor’s 500 index (S&P 500).  Extensive research has been published attempting to predict different financial markets using historical data testing on an in-sample and trend basis, with many authors employing excessively complex mathematical techniques.  In reviewing and evaluating these in-sample methodologies, it became evident that this approach was unable to achieve sufficiently reliable prediction performance for commercial exploitation. For these reasons, we moved to an out-of-sample strategy based on linear regression analysis of an extensive set of financial data correlated with historical closing prices of the S&P 500. We are pleased to report a directional trend accuracy of greater than 55% for tomorrow (t+1) in predicting the S&P 500.

  Website 
• Ben-Esmael M, Hart BL, Hayatleh K, Lidgey FJ, 'CMRR-Bandwidth Extension Technique for CMOS Differential Amplifiers'
  International Journal of Electronics and Communications. AEU 68 (10) (2014) pp.990-993
  ISSN: 1434-8411
  Abstract

  An exemplary design demonstrates how to extend the common-mode rejection ratio (CMRR) bandwidth of a CMOS differential amplifier. The design presented uses MOSFETs with a channel length of 180nm. A novel circuit technique is employed that partially compensates for the output capacitance of the tail current sink, thereby more than quadrupling the CMRR bandwidth in the example considered.

  
  Website 
• Mathew M, Hart BL, Hayatleh K, 'Minimal Power Start-Up Circuit Design for Self-Biased CMOS Current Generators'
  International Journal of Electronics Letters 2 (2) (2014) pp.65-71
  ISSN: 2168-1724
  Abstract

  A new start-up circuit configuration, with minimal standby power dissipation, is proposed for CMOS self-biased current generators. Using standard 0.13µm CMOS technology, simulation results show that for a supply voltage range 1.8V to 2.5V, and a temperature range −40ºC to +85ºC, the circuit standby power dissipation is less than 20nW.

  Website 
• Tammam AA, Hayatleh K, Sebu C, Lidgey FJ, Terzopoulos N, Ben-Esmael M, 'Wide-Bandwidth CFOA with High CMRR Performance'
  International Journal of Electronics and Communications. AEU 68 (4) (2013) pp.329-335
  ISSN: 1434-8411
  Abstract In this paper the authors analyze the conventional current-feedback operational amplifier (CFOA) in terms of common-mode-rejection ratio (CMRR) performance, and having identified the mechanism primarily responsible for the CMRR, they propose two new architecture CFOAs. These new CFOAs are further developed, and modified to provide improved bandwidth, AC gain accuracy and high CMRR performance. The key features of the two proposed new CFOAs are the designs of the internal voltage followers which have two separate biasing currents with a similar dynamic architecture to that of the conventional CFOA. The magnitude of one bias current determines the value of the maximum CMRR, and the second can be used to maximize bandwidth.Website 
• Hayatleh K, Terzopoulos N, Hart BL, 'Designing a Very High Output Resistance Current Source for Medical Applications'
  International Journal of Electronics 99 (2012) pp.1739-1752
  ISSN: 0020-7217
  Abstract A new technique is proposed for the design of a current source, in bipolar technology, with a very high output resistance and low output capacitance. Such a technique is useful in electrical impedance tomography applications. The DC relationships of the basic topology are established. Then, based on the analysis of a simplified equivalent circuit, an expression is formulated for the output resistance and tested against simulation results for both ideal and practical biasing circuits. The effect of circuit capacitances, and in particular, the role of the collector-base capacitance of the output transistor, in determining the output impedance as a function of frequency is considered. Finally, a new circuit is shown to have an incremental output resistance exceeding 200 GΩ.Website 
• Barry T, Fuller G, Hayatleh K, 'Infrared temperature measurement for remote monitoring in cold climates'
  Measurement Science and Technology 23 (2012)
  ISSN: 0957-0233 eISSN: 1361-6501
  Abstract

  This paper presents a novel method of non-contact infrared thermometry optimized for remote monitoring in cold climates. The method consists of selectively heating the optics of the instrument in order to prevent ice forming on the lens and blocking infrared energy. A self-calibration method is used to remove the errors caused by thermal shock when the heaters are cycled. Applications for this instrument include the monitoring of roads and railways to detect ice as well as long-term environmental studies. The self-calibration technique is shown to maintain an accuracy of ±1 °C in ambient temperatures as low as −20 °C. This compares with errors of over 20 °C in a conventional infrared thermometer.

  Website 
• Mathew M, Hart B, Hayatleh K, 'Rail-supply insensitive cmos current generator'
  International Journal of Electronics 99 (11) (2012) pp.1569-1574
  ISSN: 0020-7217
  Abstract

  The theoretical background and a selection of simulated results are presented for a 10-‰µA PTAT current generator that is a modified CMOS version of an existing bipolar configuration. Using standard 0.35-‰µm CMOS technology, the circuit exhibits a current variation of less than 0.01% when the supply rail voltage is changed from 0.5 to 10-‰V.

  Website 
• Rogers M, Hayatleh K, Lidgey F, Joy A, 'High-speed low-voltage cmos line driver for serdes applications'
  International Journal of Electronics 100 (4) (2012) pp.575-581
  ISSN: 0020-7217
  Abstract

  The challenge facing SerDes (Serialiser De-Serialiser) designers is common with all current communications technologies. Industry advances show a trend to increase speed, reduce power and improve efficiency. In this article a novel line driver that can operate at speeds of up to 40 Gbps with a power supply of 1-‰V and a power consumption of 4.54-‰mW/Gb/s is presented. Pre-distortion on the front-end is used to maintain signal integrity.

  Website 
• Pookaiyaudom P, Worapishet A, Lidgey F, Hayatleh K, Toumazou C, 'Measurement of cell and bacterial activity using array-based isfet chemical current-conveyor in weak-inversion'
  IEEE International Symposium on Circuits and Systems (2012) pp.2059-2062
  ISSN: 0271-4302
  Abstract

  The ISFET chemical current conveyor (CCCII+) was first reported by the authors at ISCAS 2008. In this paper a new application of the CCCII+ is presented, namely to provide a direct means of measuring cell and bacterial activity. The measurement system is based on an array of unmodified ISFET CCCII+ sensors each of which when operated in weak inversion gives an output corresponding to the time derivative of hydrogen ions. Combining each of the CCCII+ time derivative outputs in the array using the analog computational versatility of the CCCII+ current output stage provides a signal corresponding to cell and bacterial activity. The design has been fully simulated using Triple-well 0.18-μm CMOS technology and the results presented in this paper show that a viable system for direct measurement of cell and bacterial activity can be obtain, further confirming the utility of the CCCII+ for another biochemical sensing application.

  Website 
• Mathew M, Hart BL, Hayatleh K, Lidgey FJ, 'Low-voltage, wide-range, current-controlled DC current generator'
  International Journal of Electronics 98 (11) (2011) pp.1123-1127
  ISSN: 0020-7217
  Abstract

  Operating from a 1 V rail supply, a proposed CMOS current-controlled DC current generator can function as a repeater, attenuator or amplifier over the input current range, 1 µA to 1 mA, with a current-transfer ratio accuracy better than 1% using IBM technology, characterised by a process with a 0.13 µm minimum feature size. In repeater mode, the incremental output resistance exceeds 30 MΩ for an output current of 500 µA at an output voltage of 0.20 V, and exceeds 1 MΩ for an output current of 1 mA at an output voltage of 0.22 V. For zero input current, the circuit dissipation is 117 µW

  Website 
• Pookaiyaudom P, Seelanan P, Lidgey F, Hayatleh K, Toumazou C, 'Measurement of urea, creatinine and urea to creatinine ratio using enzyme based chemical current conveyor (CCCII+)'
  Sensors and Actuators B: Chemical 153 (2) (2011) pp.453-459
  ISSN: 0925-4005
  Abstract

  A system potentially capable of providing continuous analogue computation of (i) urea concentration, (ii) creatinine concentration and (iii) urea-to-creatinine ratio, important markers for the prediction of renal failure is described. The system utilises two enzyme modified chemical current-conveyors, CCCII+, to obtain the outputs directly related to the urea and creatinine concentrations. The devices have been separately prepared by immobilising urease and creatinine deiminase (CD) enzymes onto the input ISFET surfaces. The primary experimental results of the system demonstrate a linear response covering a normal physiological range of urea between 2.5 and 8.3 mM and creatinine between 44 and 106 μM. We propose that this system has the potential for real-time monitoring and suitable for medical determination for renal dysfunctionality.

  Website 
• Barry T, Fuller G, Hayatleh K, Lidgey J, 'Self-calibrating infrared thermometer for low-temperature measurement'
  IEEE Transactions on Instrumentation and Measurement 60 (6) (2011) pp.2047-2052
  ISSN: 0018-9456
  Abstract

  This paper presents a self-calibration technique for the removal of measurement errors caused by thermal gradients in thermopile-based infrared thermometry, particularly when measuring low temperatures. Applications for this self-calibration method include low-temperature measurement in the food industry and infrared thermometers for remote temperature monitoring in cold climates. The self-calibration technique reported in this paper is shown to reduce the measurement error to within $pm 1 ^{circ}hbox{C}$ within 5 s of an extreme thermal shock, compared with an uncompensated thermometer that does not recover until the thermal gradient is removed. The root-mean-square temperature noise for the duration of the thermal shock test is less than 0.2 $^{circ}hbox{C}$. This technique is the subject of a patent application and can be applied to any infrared thermometer utilizing a thermopile, regardless of the thermopile size and geometry.

  Website 
• Thanapitak S, Pookaiyaudom P, Seelanan P, Lidgey F, Hayatleh K, Toumazou C, 'Verification of ISFET response time for millisecond range ion stimulus using electronic technique'
  Electronics Letters 47 (10) (2011) pp.586-588
  ISSN: 0013-5194 eISSN: 1350-911X
  Abstract

  The ion sensitive field effect transistor (ISFET) is a popular sensor in biomedical electronics and has been used to date mainly for relatively low speed applications, such as measurement of pH of common biomedical fluids. However, there is a growing interest in sensing rapidly changing ion activity for applications including chemical synapse and rapid DNA sequencing. In this reported work, it is demonstrated that the response time of the ISFET is sufficient for these applications. The results obtained are used to determine the factors that affect high speed chemical sensing with the ISFET.

  Website 
• Tammam A, Hart B , Hayatleh K, 'Open loop output characteristics of a current feedback operational amplifier'
  64 (12) (2010) pp.1196-1202
  Abstract The output characteristics of the basic current feedback operational amplifier (CFOA) in the linear region, on open-loop, would not appear to have been treated in the literature. This is possibly because it is not straightforward to determine, the problem being that the output saturates without the closed-loop connection. This paper considers a theoretical discussion that explains the results of simulation. Website 
• Wu R, Lidgey F, Hayatleh K, Hart B, 'Differential amplifier with improved gain-accuracy and linearity'
  International Journal of Circuit Theory and Applications 38 (8) (2010) pp.829-844
  ISSN: 0098-9886
  Abstract

  A novel circuit design technique is presented which improves gain-accuracy and linearity in differential amplifiers. The technique employs negative impedance compensation and results demonstrate a significant performance improvement in precision, lowering sensitivity, and wide dynamic range. A theoretical underpinning is given together with the results of a demonstrator differential input/output amplifier with gain of 12 dB. The simulation results show that, with the novel method, both the gain-accuracy and linearity can be improved greatly. Especially, the linearity improvement in IMD can get to more than 23 dB with a required gain.

  Website 
• Hayatleh K, Tammam A, Hart B, 'Analysis of the input stage of the CFOA'
  AEÜ - International Journal of Electronics and Communications / Archiv für Elektronik und Übertragungstechnik 64 (4) (2010) pp.344-350
  ISSN: 1434-8411
  Abstract

  The input stage design in current-feedback operational amplifiers (CFOAs) is primarily responsible for determining the performance of the amplifier, including input voltage range, input referred offset voltage and DC input current. This paper focuses on analysis of the input stage of the conventional CFOA. The outcome of the work gives clear insight into the operation of the CFOA and establishes the mechanisms responsible for determining these parameters.

  Website 
• Chen C, Hayatleh K, Hart B, Lidgey F, 'Flipped Voltage Follower Ddesign Technique for Maximised Linear Operation '
  2 (8) (2010) pp.665-667
  Abstract The results of comparative DC simulation tests confirm that a proposed modification to the feedback circuit of a Flipped Voltage Follower (FVF), to produce a type of"Folded" Flipped Voltage Follower (FFVF), is capable of maximising the linear DC operating range for given values of supply rail voltage and operating current. Website 
• Chen C, Hayatleh K, Hart B, Lidgey F, 'Wideband MOSFET differential V/I converter'
  97 (4) (2010) pp.389-395
  Abstract This article presents a proposed modified flipped voltage follower for applications in a wideband MOSFET differential V/I converter using IBM 0.13 μm technology. Operating with ±2.5 V supply rails, the transconductance is nominally 3.3 mS for an input differential signal voltage range of 0.5 V, and the -3 dB bandwidth exceeds 4 GHz. The THD measured at 1 MHz for a differential input signal of 500 mVp-p is less than -82 dB, and is still below -50 dB at 1 GHz. Website 
• Pookaiyaudom P, Lidgey F, Hayatleh K, Seelanan P, Toumazou C, 'Chemical current conveyor (CCCII+): System design and verification for buffer index/capacity measurement'
  Sensors and Actuators B: Chemical 147 (1) (2010) pp.228-233
  ISSN: 0925-4005
  Abstract

  The pH and buffer index/capacity of a biomedical fluid, such as blood, provide useful clinical data for decisions on diagnosis and appropriate treatment. In this paper a novel system that has the capability of producing a useful miniaturised biosensor based, clinical instrument system providing simultaneous outputs of both pH and buffer index/capacity (β) is described. The system uses an ISFET as the primary sensing element and is based on the author's chemical current conveyor (CCCII+). A prototype has been constructed, and the results verify both the concept and viability of practical measuring system for pH and β.

  Website 
• Mathew M, Hayatleh K, Hart B, 'A high-transconductance voltage-to-current converter design'
  29 (6) (2009) pp.1123-1140
  Abstract This paper describes the design of a high-transconductance, wide-band, temperature-insensitive bipolar differential voltage-to-current converter, the transconductance of which is determined by a chosen degeneration resistor. Detailed illustrations of current and voltage traces are included to clarify circuit operation. Comparison with previously published designs shows that this converter provides better linearity, with very low temperature sensitivity and excellent transconductance predictability. Simulation results show that the proposed circuit, with a nominal transconductance of 5 mS, has a Total Harmonic Distortion (THD) better than 70 dB at 10 MHz, with a degeneration resistor of 400 Ω over an input voltage range of 350 mV for supply voltages of ±2.5 V. The analysis and simulation comparisons are in good agreement. Website 
• Charalampidis N, Spasos M , Mallios N, Hayatleh K, Lidgey F, 'A High-Frequency Voltage-Follower with Global Feedback'
  5 (8) (2008) pp.335-344
  Abstract A popular form for a voltage-follower (VF) with global feedback is a voltage operational amplifier (Op-Amp) with 100% negative feedback. Nevertheless, with currently available Op-Amps it is unable to meet high frequency specifications. This paper presents a high frequency voltage-follower based on an overall feedback technique. Despite the global feedback loop, the design presented small-signal bandwidth higher than 3GHz and gain flatness to within 0.1dB up to 170MHz. Due to this feedback loop, the circuits exhibits very high input and very low output impedance. In addition, the output voltage swing achieved is some ±3V, with an input offset current of around 130nA and an offset voltage in the range of 200uV. The proposed circuit is very stable, due to the stability technique used, maintaining low distortion. The total harmonic distortion (THD) of the circuit is better than -65dB and the intermodulation distortion (IMD) is some -70dB, for capacitive loads up to 10pF. The analysis of the novel circuit has been carried out for operating temperatures from -20oC to +100oC, using Analog Devices" extra fast complementary transistors. The power dissipation is some 52mW on a ±5V power supply, although it can be reduced to ±3.3V, without affecting significantly the performance, depending on the application.
• Hayatleh K, Green M, Lidgey F, 'A low-distortion folded-cascode voltage current converter'
  Analog Integrated Circuits and Signal Processing 3 (2) (2007) pp.66-72
  ISSN: 1744-2400
  Abstract This paper presents a differential voltage-current converter, based on two compound emitter-followers with emitter-degeneration implemented in a folded-cascode topology. Significant improvement in linear operating range is obtained with this design compared with the classical voltage-current (V-I) converter, which is based on an emitter-degenerated emitter coupled pair (ECP), due to the feedback technique employed with complementary compound emitter-followers in addition to emitter-degeneration. The proposed design also provides less total harmonic distortion (THD) compared with that obtained from a conventional emitter-degenerated ECP design, operating under the same bias conditions. Simulations carried out using PSpice give a 14dB improvement achieved in THD for a transconductance value of 1mS, for differential input signals up to 500mVp-p at a test frequency of 1MHz and supply voltages of ±2.5V. This design can be used as a subsystem for radio frequency mixer and analogue filter circuits. The predicted improvements in performance of this new design have been confirmed by comparative simulation tests.Website 
• Hayatleh K, Terzopoulos N, Hart BL, 'A Very High Output Resistance Current Source'
  Measurement Science and Technology 18 (2007) pp.N9-N11
  Website 
• Hayatleh K, Tammam A A, Hart B L, 'Novel input stages for current feedback operational amplifiers'
  50 (3) (2007) pp.163-183
  Abstract This paper considers the trade-offs involved in the design of six new input stages intended to improve the performance of a current feedback operational amplifier (CFOA), over that possible using an established input circuit configuration, with respect to three major characteristics, viz, common mode rejection ratio (CMRR), offset voltage and slew-rate.Website 
• Hayatleh K, Hart B L, Lidgey F J, Tammam A A, 'A novel current-feedback op-amp exploiting bootstrapping techniques'
  94 (12) (2007) pp.1157 - 1170
  Abstract The operation of the conventional current feedback operational amplifier (CFOA) is reviewed and its performance parameters used as benchmarks in the development of a new input stage architecture that provides a common-mode rejection ratio (CMRR) improvement of some 45 dB and offset voltage less than 10 mV.Website 
• Green M, Hayatleh K, Lidgey F, 'PTAT Direct Current Converter for Bias Circuit Applications'
  Electronics Letters 42 (2006) pp.530-531
  ISSN: 0013-5194 eISSN: 1350-911X
  Abstract A novel proportional to absolute temperature (PTAT) current converter is presented. Output current gain ratios in excess of 50 are possible without the use of an operational amplifier. Simulation measurements show an output temperature coefficient within 15 ppm/°C of the reference current over the temperature range of -40 to +85°C.Website 
• Green M, Hayatleh K, Lidgey F, 'Temperature-independent Direct Current Converter Technique'
  Electronics Letters 41 (23) (2005) pp.1258-1259
  ISSN: 0013-5194 eISSN: 1350-911X
  Abstract A novel temperature-independent direct current converter, the subject of a patent application number GB051623.8, is presented. Conversion ratios from less than unity to in excess of 50 are possible. Simulation measurements show an output temperature coefficient as low as 16 ppm/°C over the temperature range -40 to +85°C.Website 
• Terzopoulos N, Hayatleh K, Hart B, Lidgey FJ, McLeod C, 'A Novel Bipolar-drive Circuit for Medical Applications'
  Physiological Measurement 26 (2005) pp.N21-N27
  ISSN: 0967-3334 eISSN: 1361-6579
  Website 
• Wu R, Lidgey FJ, Hayatleh K, 'Using the T Feedback Network With the Current Feedback Operational Amplifier'
  International Journal of Electronics 91 (2005) pp.685-695
  ISSN: 0020-7217
  Website 
• Wu R, Lidgey FJ, Hayatleh K, 'Frequency Performance Compensation of Operational Amplifiers With the T Feedback Network'
  Analog Integrated Circuits and Signal Processing 41 (2004) pp.79-83
  ISSN: 0925-1030
  
• Tammam AA, Hayatleh K, Lidgey FJ, 'High Cmrr Current-feedback Operational Ampli'
  International Journal of Electronics 90 (2003) pp.87-97
  ISSN: 0020-7217
  Website 
• Lee J, Hayatleh K, Lidgey FJ, Drew J, 'Linear Bi-cmos Transconductance for Gm-c Filter Applications'
  Journal of Circuits Systems and Computers 11 (2002) pp.219-230
  ISSN: 0218-1266 eISSN: 1793-6454
  
• Lidgey J, Hayatleh K, 'Are Current Conveyors Finally Coming of Age?'
  Electronics World 106 (2000) pp.322-324
  ISSN: 1365-4675
  
• Hayatleh K, Lidgey FJ, Porta S, 'Comparing Dual Current-conveyor Configurations'
  Journal of Circuits Systems and Computers 6 (1997) pp.475-484
  ISSN: 0218-1266 eISSN: 1793-6454
  
• Lidgey FJ, Hayatleh K, 'Current-feedback Operational Amplifiers and Applications'
  Electronics and Communication Engineering Journal 9 (1997) pp.176-182
  
• HAYATLEH K, PORTA S, LIDGEY FJ, 'Temperature Independent Current Conveyor Precision Rectifier'
  Electronics Letters 30 (1995) pp.2091-2093
  ISSN: 0013-5194 eISSN: 1350-911X
  

Conference papers

• D Carugo, K Hayatleh, FJ Lidgey,D Sharp, 'Sensor grid design for high resolution 3D acoustic measurements of musical instruments'
  (2019) pp.388-395
  ISBN: 9781510889309
  
• R. Nagulapalli, K. Hayatleh, S. Barker, S Zourob, N.Yassine & B Naresh Kumar Reddy, 'A Technique to Reduce the Capacitor size in Two Stage Miller compensated opamp'
  (2018)
  ISBN: 9781538644300
  Abstract

  In this paper two stage Miller compensated opamp has been discussed qualitatively and quantitatively. A modification to the conventional compensation network has been proposed, which will reduce the capacitor size hence circuit area. Transfer function for the newly proposed solution has been derived and explained the results. A prototype was developed in 65nm TSMC CMOS technology and simulation results have been presented. Amplifier achieved 60dB low frequency gain, 12MHz bandwidth and 55° phase margin while consuming 650uW power from 1.2V power supply. Circuit occupies 5348um 2 silicon area.
  

  Website 
• R. Nagulapalli, K. Hayatleh, S. Barker, S Zourob, N.Yassine & B N Kumar, 'High Performance Circuit Techniques for Neural Front-End design in 65nm CMOS'
  (2018)
  ISBN: 9781538644300
  Abstract

  Integrated low noise neural amplifiers become recently practical in CMOS technologies. In this paper, a low
  noise OTA technique has been proposed while keeping the power consumption constant. A capacitive feedback, ac coupled 46dB amplifier with high pass cutoff frequency close to the 90Hz has been achieved. The proposed amplifier has been implemented in 65nm CMOS technology; at room temperature circuit consumes 323uA current from 1.2V power supply. The circuit occupies 2627um2 silicon area.
  

  Website 
• Nagulapalli R, Hayatleh K, Barker S, Zourob S, Yassine N, Venkatareddy A, 'A compact high gain opamp for Bio-medical applications in 45nm CMOS technology'
  (2018) pp.231-235
  ISBN: 9781509037749
  Abstract In this paper a low opamp compensation technique suitable for the bio-medical application has been proposed and intuitive explained the existing compensation techniques. The Present technique relies on the passive damping factor control rather power hungry damping. Implemented in 45nm CMOS technology and simulated with Spectre. Simulation results shows that 100dB dc gain, well compensated 25MHz bandwidth opamp while driving a 1pF capacitive load. Draws with 12uW power consumption from 1V supply and occupying 0.004875mm² silicon area.Website 
• Nagulapalli R, Hayatleh K, Barker S, Zourob S, Yassine N, Sridevi S, 'A bio-medical compatible Self-bias opamp in 45nm CMOS technology'
  (2017)
  ISBN: 9781538617168
  Abstract In this paper a low power, high gain self bias opamp suitable for biomedical applications has been described. A novel trans conductance boosting technique is introduced without having any additional power consumption. A simple technique of biasing the opamp has been introduced for very low offset and without having any requirement for external reference circuit. A prototype of two stage amplifier design presented to verify the proposed technique and described its robustness across PVT variations by showing simulation results. The design is implemented in 45nm CMOS technology and simulated with Spectre. Simulation results show that the proposed opamp exhibits FOM of 625 and 2 times better than state of art. The circuit consumes 26uW from 1.5V supply and occupying 0.00282mm2 silicon area.Website 
• Barker S, Izadi H, Crook NT, Hayatleh K, Rolf M, Hughes P, Fellows N, 'Natural head movement for HRI with a muscular-skeletal head and neck robot'
  (2017) pp.587-592
  eISSN: 1944-9437 ISBN: 9781538635186
  Abstract This paper presents a study of the movements of a humanoid head-and-neck robot called Eddie. Eddie has a musculo-skeletal structure similar to that found in human necks enabling it to perform head movements that are comparable with human head movements. This study compares the movements of Eddie with those of a more conventional robotic neck structure and with those of a human head. Results show that Eddie’s movements are perceived as significantly more natural and by trend more lifelike than the conventional head’s. No differences were found with respect to the impression of humanlikeness, consciousness, and elegance.
   
  Website 
• Nagulapalli R, Hayatleh K, Barker S, Zourob S, Venkatreddy S, 'A novel current reference in 45nm cmos technology'
  (2017)
  ISBN: 9781509032396
  Abstract In this paper a novel CMOS temperature and supply voltage independent current reference has been proposed. This design is based on the subtraction of two scaled version PTAT (proportional to absolute temperature) currents to provide a temperature independent current reference. The design was simulated with Spectre, and implemented in 45nm CMOS technology. Simulation results shows that the proposed current reference achieves temperature coefficient of 22ppm/⁰C against temperature variation of -400C –1200C and line sensitivity of 337ppm/V against supply variation of 0.6–1.8V, while consuming 135uW from 1.8V supply and occupying 5184um²Website 
• Nagulapalli R, Hayatleh K, Barker S, Zourob D, Venkatreddy S, 'A CMOS technology friendly Wider bandwidth Opamp Frequency Compensation'
  (2017)
  ISBN: 9781509032396
  Abstract In this a paper a novel CMOS technology friendly opamp compensation has been presented and explained intuitively miller compensation pole splitting. Present technique utilizes grounded capacitor and having better PSRR. Open loop transfer functions have been derived to show the proposed technique is low power for the same bandwidth. Implemented in 65nm CMOS technology and simulated with Spectre. Simulation results shows that the proposed opamp achieves FOM ~83333.Opamp consumes 25uA from 1V supply and occupying 5184um² silicon area.Website 
• Nagulapalli R, Hayatleh K, Barker S, Zourob S, Yassine N, Sridevi S, 'A microwatt low voltage bandgap reference for bio-medical applications'
  (2017) pp.61-65
  ISBN: 9781509067015
  Abstract In this paper a microwatt low voltage bandgap reference suitable for the bio-medical application. The Present technique relies on the principle of generating CTAT and PTAT without using any (Bipolar Junction Transistor) BJT and adding them with a proper scaling factor for minimal temperature sensitive reference voltage. Beta multiplier reference circuit has been explored to generate CTAT and PTAT. Implemented in 45nm CMOS technology and simulated with Spectre. Simulation results shows that the proposed reference circuit exhibits 1.2% variation at nominal 745mV output voltage. The circuit consumes 16uW from 0.8V supply and occupying 0.004875mm² silicon area.
   
  Website 
• Barker S, Fuente L, Hayatleh K, Fellows N, Steil JJ, Crook N, 'Design of a Biologically Inspired Humanoid Neck'
  (15820238) (2015) pp.25-30
  ISBN: 978-1-4673-9674-5 eISBN: 978-1-4673-9675-2
  Abstract This paper presents the design of a novel anthropomorphic robotic neck. It mimics the range of movements found in the human neck, actuated by pneumatic artificial muscles. The proposed humanoid neck simulates the anatomical functionality and structure of a human neck. Specifications are made according to biological, anatomical and behavioural data. The preliminary results show that the proposed humanoid neck is able to deliver the range of movements and head velocities comparable to those observed in human necks. These results also demonstrate that biologically inspired musculoskeletal robotic systems represent a reliable and robust platform to investigate motion development.Website 
• Hayatleh K, Terzopoulos N, Hart B, 'Designing a Very High Output Resistance Current Source'
  Proceedings of the 13th Wseas International Conference on Recent Advances in Circuits (2009) pp.182-190
  
• Charalampidis N, Hayatleh K, Hart BL, Lidgey FJ, 'A Wide Bandwidth Voltage-follower With Low Distortion and High Slew Rate'
  2006 13th Ieee International Conference on Electronics, Circuits and Systems, Vols 1-3 (2008) pp.256-259
  
• Mathew M, Hayatleh K, Hart BL, Lidgey FJ, 'Linear Differential Voltage-current Converter'
  2007 Ph.d Research in Microelectronics and Electronics (2008) pp.217-220
  
• Mathew M, Hayatleh K, Hart BL, Lidgey FJ, 'Low-distortion, Emitter-coupled, Differential Voltage-to-current Converters'
  2007 50th Midwest Symposium on Circuits and Systems, Vols 1-3 (2008) pp.29-32
  
• Mathew M, Hayatleh K, Hart BL, Lidgey FJ, 'A Low-distortion Transconductance Amplifier'
  2008 International Conference on Design and Technology of Integrated Systems in Nanoscale (2008) pp.145-149
  Website 
• Hart BL, Hayatleh K, Lidgey FJ, 'A Single Rail Dc Voltage-to-current-converter'
  2008 International Conference on Design and Technology of Integrated Systems in Nanoscale (2008) pp.7-10
  Website 
• Charalampidis N, Hayatleh K, Hart BL, Lidgey FJ, 'A High-speed Low-distortion Voltage-follower'
  2006 3rd International Conference on Electrical and Electronics Engineering (2007) pp.120-123
  
• Terzopoulos N, Hayatleh K, Hart B, Lidgey FJ, 'The Collector-base Resistance of a Bjt'
  Proceedings of the 2005 European Conference on Circuit Theory and Design, Vol 3 (2006) pp.209-212
  
• Charalampidis N, Hayatleh K, Hart BL, Lidgey FJ, 'A High Frequency Low Distortion Voltage-follower'
  2006 International Conference on Communications, Circuits and Systems Proceedings, Vols 1-4 (2006) pp.2291-2294
  
• Tammam AA, Hayatleh K, Hart B, Lidgey FJ, 'A Hierarchy of Input Stages for Current Feedback Operational Amplifiers'
  2004 Ieee International Symposium on Circuits and Systems, Vol 1, Proceedings (2004) pp.821-824
  
• Tammam AA, Hayatleh K, Hart B, Lidgey FJ, 'High Performance Current-feedback Op-amps'
  2004 Ieee International Symposium on Circuits and Systems, Vol 1, Proceedings (2004) pp.825-828
  
• Tammam AA, Hayatleh K, Lidgey FJ, 'Novel High Performance Current-feedback Op-amp'
  2002 Ieee International Symposium on Circuits and Systems, Vol I, Proceedings (2003) pp.705-708
  
• Lee J, Hayatleh K, Lidgey FJ, 'Modified Gilbert Transconductance Multipler'
  2002 Ieee International Symposium on Circuits and Systems, Vol I, Proceedings (2003) pp.733-736
  
• Lee J, Hayatleh K, Lidgey F, Drew J, 'Tuneable Linear Transconductance Cell for Gm-c Filter Applications'
  2002 Ieee International Symposium on Circuits and Systems, Vol Iv, Proceedings (2003) pp.253-256
  
• Hayatleh K, Su WJ, Lidgey FJ, 'Improved Current-feedback Op-amp With Good Dc and Cmrr Performance'
  Iscas 99: Proceedings of the 1999 Ieee International Symposium on Circuits and Systems, Vol 2 (1999) pp.263-266
  
• Hayatleh K, Lidgey FJ, Porta S, 'Wideband Current-mode Absolute Value Circuits'
  Iscas 98 - Proceedings of the 1998 International Symposium on Circuits and Systems, Vols 1-6 (1998) pp.539-542
  
• HAYATLEH K, PORTA S, LIDGEY FJ, 'High Frequency Performance of Current-mode Precision Full Wave Rectifiers'
  1994 Ieee International Symposium on Circuits and Systems, Vol 5 (1995) pp.E401-E404
  

Other publications

• R. Nagulapalli, K. Hayatleh, S. Barker, A. A. Tammam, F. J. Lidgey and N. Yassine, 'A High Sensitivity and Low Power Circuit for the Measurement of Abnormal Blood Cell Levels'
  Journal of Circuits, Systems, and Computers (2019) ISSN: 0218-1266 eISSN: 1793-6454
  Abstract

  This paper describes a technique to detect blood cell levels based on the time-period modulation of a relaxation oscillator loaded with an Inter Digitated Capacitor (IDC). A digital readout circuit has been proposed to measure the time-period difference between the two oscillators loaded with samples of healthy and (potentially) unhealthy blood. A prototype circuit was designed in 65nm CMOS technology and post-layout simulations shows 15.25aF sensitivity. The total circuit occupies 2184µm2 silicon area and consumes 216µA from a 1V power supply. 

  
  
  Website 
• HAYATLEH K, LIDGEY FJ, PORTA S, 'Degradation Mechanisms in Operational-amplifier Precision Rectifiers'
  Ieee Transactions on Circuits and Systems I-fundamental Theory and Applications 42 (1995) pp.479-485

Areas of expertise

Working on RF circuit designs

Working on biomedical circuits and systems for non-invasive and non-radiating methods for continuously monitoring things such as breast cancer tumours and blood glucose levels, with the data being transferred wirelessly to physicians for diagnosis.

 Developing techniques to detect/monitor skin cancer and leukaemia.

Working on improving the resolution of MRI scanners and methods to reduce the electrical noise picked up by biomedical electrodes.  

Developing automotive electronics systems.  These include driver fatigue monitoring to reduce accidents, head-up displays, and enhanced sensor and control systems for autonomous vehicles.

Membership of professional bodies

Senior member of the IEEE (SMIEEE) 

Editorial Member:

• Regional Editors for the International Journal of Electronics and Communications:

http://www.sciencedirect.com/science/journal/14348411

• Associate Editor to the Journal of Circuits, Systems, and Computer: http://www.worldscinet.com/jcsc/mkt/editorial.shtml
• Guest editor of the Journal of Analog Integrated Circuits and Signal Processing, June 2018, Volume 95, issue 3, B Choubey, K Hayatleh & A P James.

Conferences

Conferences /Workshop/ Research visits

• Technical Chair of the Oxford Circuits and Systems Conference (OXCAS 2017) at Somerville College, University of Oxford on Tuesday 19th September 2017.  I worked with Dr Steve Barker and Prof Bhaskar Choubey at the University of Oxford to organise and run this conference.  Other academic institutions, including Imperial College and UCL were also involved as partners in the enterprise.  The event was very well attended, and ran extremely successfully.  This was very much due to the full sponsorship and prizes for the event from the IET and Fujitsu.  Oxford Brookes and Oxford University plan to make this a bi-annual event. 

Other experience

Further information

External examiner :  Univeristy of Brighton,  Birmingham City University,  University of west England.

PhD examinations: Imperial college, UCL, Birmingham university, Greenwich  university.

I received my BEng in June 1992 from Oxford Brookes University and subsequent PhD in March 1996 from Oxford Brookes University in collaboration with Imperial College, London. His research interests are in the area of electronic circuits and systems for RF and biomedical applications. Current projects are in transconductance amplifier design for high frequency RF applications, amplifier linearisation, current feedback op-amp development, automotive electronics, high accuracy voltage buffer and high output impedance current source design and a low-voltage high-speed CMOS line driver for SerDes applications. I have over 100 publications in the above areas of research. I have been a keynote speaker at conferences in this area. I am currently the lead for electronics in the Biomedical Imaging and Instrumentation Research Team at Oxford Brookes University, UK.

Press, publicity and reviews

2 projects (EIT and Robotics) have been shown on BBC TV, and discussed on local radio.