This paper presents a power efficient, bulk driven, source degenerated fully differential operational transconductance amplifier (OTA), operating in the subthreshold region. The input part of the OTA consists of a bulk driven source degenerated differential pair and cross coupled transistors to improve the linearity of OTA. It consists of a bulk driven pair to reduce the supply voltage and to improve the linearity. The proposed fully differential OTA has utilized self-cascode current mirror loads which increases the output impedance and hence the overall intrinsic gain. A subthreshold region is adopted to reduce the power consumption of the circuit. For a 200 mVpp sinusoidal input at 100 Hz, a total harmonic distortion (THD) of −58.56 dB is achieved. The gain, gain bandwidth (GBW), phase margin (PM) and gain margin (GM) values obtained were 48.4 dB, 3.1 KHz, 80 • and 19.01 dB, respectively. The common mode rejection ratio (CMRR), power supply rejection ratio (PSRR) and slew rate +/− values were 146.3 dB, 83 dB and 99.56/100 V/ms, respectively. The circuit is capable of operating under a supply voltage of 0.8 V with a power consumption of 59.04 nW, which proves that the circuit is suitable for portable biomedical devices. The proposed circuit is simulated in CADENCE environment virtuoso using LFoundry 150 nm Complementary metal oxide semiconductor (CMOS) process technology.
In this paper, a bilinear (first order) current mode universal filter is presented using a single current differencing buffered amplifier (CDBA). The main feature of this proposed circuit configuration is that it can provide all the filter responses i.e. low-pass, high-pass and all-pass responses. Noting the fact that first order filter realizes low-pass, high-pass and all-pass responses only. It uses single CDBA and minimum passive components that is one resistor and one grounded capacitor only to realize all the filter responses. The active and passive sensitivities of the cut-off frequency (ω0) are very low. The proposed circuit topology is verified by simulating the circuit on PSPICE using TSMC 0.35um CMOS process parameters with supply voltages of +/-2.5V and biasing currents of 30uA. The simulated and theoretical results were found to be in good agreement with each other. (Abstract)
A boxcar signal averager using Intel 8085AH, an 8-bit microprocessor developed for processing free-induction decay (FID) signals from a pulsed nuclear-magnetic-resonance (NMR) spectrometer, is described. The boxcar signal averager works either in single-point mode or in scan mode. In addition to the software developed, the constructional features, circuit details, and the operation of the boxcar are discussed in detail.
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