Bulk-driven feed-forward compensated sub-threshold low-voltage OTA to drive high capacitive load

Abstract

This paper presents a three-stage low-voltage bulk-driven sub-threshold class AB current mirror load operational transconductance amplifier (OTA) which utilizes FVF based input core and feed-forward compensation techniques for its low-voltage operation to drive high capacitive load. This three-stage OTA provides a gain of 94.4 dB, gain bandwidth (GBW) of 14.2 kHz and phase margin (PM) of 64 degree with load capacitor (Cl) and two small compensation capacitors (Cc1 and Cc2) of 100 pF, 2 pF and 0.02 pF, respectively. This OTA has ensured the total harmonic distortion (THD) of −49 dB for 0.5 Vpp input signal of 200 Hz frequency, while driving 100 pF load in its unity gain configuration. Biased with a single supply of 0.5 V it has consumed quiescent power of 104 nW. It offered high common mode rejection ratio (cMRR) and power supply rejection ratio (PSRR) of 138 dB and 81 dB, respectively at 1 Hz. Simulations results are performed using standard n-tub 180 nm CMOS process with UMc technology file in cadence spectre environment.