A gain-enhanced two-stage fully-differential CMOS op amp with high unity-gain bandwidth

This paper presents a gain-enhanced two-stage fully differential CMOS op amp. A very high dc gain is achieved together along with a very high unity-gain bandwidth and low power dissipation. The pole-zero doublet arising from the gain-enhancement is analyzed in detail. The side effects of the gain-enhancement circuit are minimized. The frequency responses indicate that more than 120 dB open loop dc gain and 500 MHz unity-gain bandwidth are obtained. The simulated settling behavior shows that it only takes 13.5 ns to reach more than 120 dB settling accuracy. To date, this is one of the best high-performance op amps that have been reported.