Operational amplifier circuit with slew rate enhancement

摘要

A low power operational amplifier adjusts its output slew rate by providing additional bias current to its differential amplifier stage when the amplitude of the differential input signal exceeds a given threshold. The additional bias current provides an enhanced current for charging or discharging an internal compensating feedback capacitor of the operational amplifier. The power dissipation of the operational amplifier is kept low by employing FET transistors for the basic operational amplifier functions and by minimally biasing the slew rate enhancement circuitry associated with monitoring the amplitude of the differential input signal as well as providing the additional current to the differential amplifier stage when the amplitude of the differential input signal exceeds the given threshold. The given threshold for the differential input signal is determined according to the bias currents and the width-to-length ratios of the FETs of the differential input stage and the FETs of the monitoring and adjustment circuitry.