A class A/B floating buffer BiCMOS power op-amp

A class A/B BiCMOS power op-amp designed to drive the L/R load of a disk drive head actuator is presented. The amplifier uses totem pole NMOS outputs instead of bipolar devices to avoid the high collector resistance in the simplified process used. A unique floating buffer technique regulates the quiescent totem pole current of the output devices and provides control for deep triode NMOS operation. The amplifier is capable of driving a load in all four V-I quadrants without a deadband during transition, and achieves a 0.25 A drive capacity into a 7.5-Ω load using a 5-V supply