High Bandwidth Two stages OTA using Positive Feedback and an LHP Zero

In this paper, to achieve a high gain-bandwidthOp-Amp, a new compensation method for a fully differentialtwo-stage operational transconductance amplifier (OTA) ispresented. The proposed technique adds a left half-plane zeroto the first stage of the OTA using a nulling resistor with aseries compensating capacitor, improving the stability of theclosed-loop configuration. Also, positive feedback from thesecond stage to the first stage and Miller capacitors improvesthe stability and gain bandwidth. The simulation wasperformed with ۹۰nm CMOS technology using HSPICE.Considering the ۱.۲V power supply and ۱۰pf load capacitor,the proposed OTA has a ۳db bandwidth of ۲.۶۴۳۴ MHz, wherepower consumption and DC gain are about ۱.۷۶ mW and ۵۰.۲dB, respectively.

Keywords:

high gain bandwidth , compensation techniques , operational transconductance amplifier (OTA) , Millercompensation , two stage amplifier.