Gain-Enhanced Feedforward Path Compensation Technique for Pole-Zero Cancellation at Heavy Capacitive Loads

摘要

An improved frequency compensation technique is presented in this paper. It is based on a cascade of a voltage amplifier and a transconductor to form a composite gain-enhanced feedforward stage in a two-stage amplifier so as to broaden the gain bandwidth via low-frequency pole-zero cancellation at heavy capacitive loads, but yet without increasing substantial power consumption. The technique has been confirmed by the experimental results. An operational amplifier has been designed to drive a capacitive load of 300 pF. The amplifier exhibits a dc gain of 87 dB, a gain bandwidth of 10.4 MHz at 63.7° phase margin, an average slew rate of 3.5 V/μs, a compensation capacitor of only 6 pF while consuming 2.45 mW at a 3-V supply in a standard 0.6-μm CMOS technology.