A high speed fully differential CMOS opamp

A high-speed fully differential folded cascode operational amplifier is presented. The operational amplifier uses fully differential boosting amplifiers to increase the open loop gain of the opamp. The opamp has a CMFB circuit that is made of a switched capacitor circuit and a continuous time CMFB circuit. The boosting amplifiers have continuous time CMFBs. The opamp is designed in TSMC 0.25 u digital CMOS process with 2.5 V power supply and achieved a dc gain of 81 dB with a 680 MHz unity gain frequency and 30 mW power consumption.