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School of Engineering, Computing and Mathematics
Faculty of Technology, Design and Environment
In this paper, a low voltage bandgap reference circuit has been proposed. The introduction of a modified beta multiplier bias circuit decreased the mismatch caused by the PMOS transistors opamp contribution. By shifting the fixed resistors to the NMOSs drain side, the beta multiplier bias was able to minimise threshold mismatch between the two NMOS transistors. A 200-point MC simulation showed 0.9mV standard deviation, with a 0.34% accuracy. The simulated temperature coefficient was 64ppm/0C. The proposed circuit consumed 5.04µW of power from a 0.45V power supply voltage. A prototype was implemented in 65nm CMOS technology occupying a 2888µm2 silicon area, with the nominal value of the reference at 261mV.
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.
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.
Traditional BGR circuits require a 1.05V supply due to the VBE of the BJT. Deep submicron CMOS technologies are limiting the supply voltage to less than 940mV. Hence there is a strong motivation to design them at lower supply voltages. The supply voltage limitation in conventional BGR is described qualitatively in this paper. Further, a current mirror-assisted technique has been proposed to enable BGR operational at0.82V supply. A prototype was developed in 65nm TSMC CMOS technology and post-layout simulation results were performed. A self-bias opamp has been exploited to minimize the systematic offset. Proposed BGR targeted at 450mV works from 0.82-1.05V supply without having any degradation in the performance while keeping the integrated noise of 15.2μV and accuracy of 23.4ppm/0C. Further, the circuit consumes 21μWof power and occupies 73*32μm2 silicon area.
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.
Integrated low noise neural amplifiers become recently practical in CMOS technologies. In this paper, a lownoise 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.