A 90nm low power OTA using adaptive bias

Low power class AB operational transconductance amplifier (OTA)which is fully differential operating at low voltage 0.4 V supply designed in low cost 90nm technology is proposed in this paper. Differential pairs such as P channel and N channel with complementary input configuration are used in input stage to achieve input common mode range (ICMR) which is full rail to rail. For increasing slew rate without sacrificing power consumption adaptive bias circuits are used hence amplifier works in class AB. The common mode feed forward circuit (CMFF) is employed for maximizing common mode rejection ratio (CMRR). To make system power efficient whole amplifier operates in weak inversion region. After designing layout of an op amp, Simulation with parasitic is carried out and shows that DC gain of 51.15 dB, 876.5 kHz unity gain bandwidth (UGB)with 77.7° phase margin for 10 pF capacitive load and slew rate of 0.1 V/μs; CMRR and PSRR are 116.9 and 97.30 dB respectively. The proposed OTA dissipates very less power of 4.78 μW and shows ability to use in applications where less energy is mandatory.