A class-AB high-speed low-power operational amplifier in BiCMOS technology

A BiCMOS op-amp is described which exploits BiCMOS technology to obtain very high transconductance, slew-rate, and fast small-signal-settling response. The absence of vertical PNP transistor requires the op-amp to use a wideband, composite PMOS-vertical-NPN structure as a substitute for PNP transistors to realize a class-AB input stage of an op-amp. The AC small-signal equivalent circuit of the input stage is analyzed and methods for optimizing the nondominant pole positions to obtain fast settling are given. Measurements in the unity-gain buffer configuration indicate maximum slew-rates of 150 V//spl mu/s (rising) and 280 V//spl mu/s (falling) and a transconductance of 20 mS at a quiescent power of 20 mW from 5 V supply using a 0.8-/spl mu/m BiCMOS process with peak f/sub T/ of 11 GHz.