Two-stage large capacitive load amplifier with embedded capacitor-multiplier compensation

摘要

This paper proposes a low-voltage, low-power, two-stage operational transconductance amplifier (OTA) for driving large capacitive loads. The embedded capacitor-multiplier compensation mechanism facilitates using a very small Miller capacitor which generates widely separated left-half-plane (LHP) poles without introducing a right-half-plane (RHP) zero. Besides, it provides a feedforward signal path to create a LHP zero and therefore significantly improves the stability of the OTA. Furthermore, a simple but efficient Class AB output stage is used to achieve fast setting response and avoid extra static power dissipation. The proposed OTA was designed in a standard 0.35-mum CMOS technology. Detailed simulation results demonstrate that when driving 1000 pF capacitive load, the OTA has 77-dB gain, 1.41-MHz unit-gain frequency (UGF) and 0.6-V/mus average slew rate while dissipating only 45 muW under 1.5-V supply.