A 175.2-mW 4-Stage OTA With Wide Load Range (400 pF–12 nF) Using Active Parallel Compensation

Multistage amplifiers are a reliable method of achieving high gain in systems where the voltage supply is low. The common practice is to prefer 3-stage amplifiers over 4-stage ones when a gain of <;120 dB is required, since the former are easier to compensate. In this article, we employ four stages to relax the constraints on each stage. An extension of the single Miller-capacitor compensation and active-parallel compensation to a 4-stage operational transconductance amplifier (OTA) design in this work is capable of driving a capacitor range of 400 pF to 12 nF(30×) by consuming a total power of about 175 mW and occupying only 0.007 mm
²
.This design achieved a unity-gain frequency (UGF) 1.18 MGz and a phase margin (PM) of 48° for all drivable load values. The proposed design, implemented in a standard CMOS 130-nm process, can drive a wide range of load capacitors without sacrificing any aspect of performance.