A high slew rate, low voltage CMOS class-AB amplifier

Abstract

A simple low voltage operational amplifier is introduced with an efficient class-AB output stage. Two biasing transistors are present in between common source stage. This amplifier is simulated in 0.18 μm CMOS technology. The proposed class-AB amplifier is designed to operate from ±500 mV supplies. The simulated phase margin of proposed class-AB amplifier is 87° at the load of 10 kΩ∥1 pF. The class-AB amplifier's total compensation capacitance is 5 pF, which is less than 50% of conventional amplifiers. The unity gain frequency of proposed class-AB amplifier is 21.17 MHz, when driving a resistive load from 10 kΩ to 500 kΩ and capacitive loads from 1 pF to 5 pF. The slew rates of modified amplifier are 7.5 V/μs and 8.57 V/μs. This modified amplifier greatly increases the slew rate compared to the conventional circuits.