Low-power bulk-driven feed-forward reverse nested miller compensated OTA with high drive capability

This paper presents a two-stage sub-threshold current mirror, bulk-driven OTA, which utilizes reverse nested Miller and feed-forward frequency compensation techniques to ensure stable operation, while driving widespread capacitive loads from 1 pF up to 1 nF. This two-stage OTA provides a 60 dB open loop gain, 25 kHz gain bandwidth, 82° phase margin and 91 dB common mode rejection ratio driving 15 pF capacitive load. It is biased using a single 0.5 V supply and has provided an average slew rate of 15 V/ms, reduced total harmonic distortion of - 40 dB for 0.5 Vpp signal swing, consuming 120 nW power and 240 nA total bias current in its unity gain configuration. The total harmonic distortion get reduced to -76 dB for small signal swing of 10 mVpp. The performance results of proposed OTA have been obtained using EDA Tanner 13.0 simulator tool in 0.18 μm standard n-tub CMOS technology.