Design approach for high-bandwidth low-power three-stage operational amplifiers

A new design approach to optimize the frequency compensation network of three-stage operational amplifiers (op-amps) is presented. The proposed criterion is aimed at maximizing the bandwidth of well-established three-stage opamps using Nested-Miller Compensation with feedforward tranconductance stage and nulling resistor (NMCFNR). As shown by design examples in a commercial 0.35-mu m CMOS technology, the proposed approach allows the amplifier bandwidth to be enhanced significantly with respect to that resulting from using existing design strategies for NMCFNR op-amps. It is also demonstrated that NMCFNR op-amps, designed according to the proposed method, even guarantee larger values of the gain-bandwidth product than three-stage amplifiers using more complicated frequency compensation techniques, such as AC boosting compensation or damping-factor control frequency compensation. Copyright (C) 2010 John Wiley & Sons, Ltd.