A low-voltage high-gain wide-bandwidth class-AB differential difference amplifier

This paper presents a CMOS low-voltage high gain and wide bandwidth differential difference amplifier (DDA). It is based on a robust two-stage class-AB amplifier with cascode Miller compensation. The first stage is a folded-cascode OTA with improved wide swing biasing circuit and the second stage is class-AB output stage biased with translinear circuit. The two input pairs can be either NMOS or PMOS pair. It achieves a DC open loop gain of 80 dB and unity-gain bandwidth of 20 MHz with 380 μA current drawn from a single 1.5V power supply in 0.13 μm CMOS. Its application for current feedback instrumentation amplifier is discussed.