A high-speed operational amplifier with gain boosting and slew rate enhancement circuits

Abstract

A high-speed and high-slew-rate operational amplifier (OPA) is presented in this paper. The gain boosting circuit is embedded in the circuit in order to improve the open-loop DC gain, which significantly improves the overall gain without adding additional stages and ensures high performance under low supply voltage conditions. In order to meet the demand for fast response in high-speed applications, the slew rate enhancement circuits are proposed to reduce the large signal build-up time of this OPA. Meanwhile, the operational amplifier employs the Ahuja compensation method to improve the phase margin (PM) of the circuit and is able to achieve a higher unit gain bandwidth with a smaller compensation capacitance. The proposed operational amplifier is designed based on TSMC 0.18µm CMOS process with a chip area of 0.468mm². Post-simulation results show that the op-amp has an open-loop gain of 111dB, a unit gain bandwidth of 240 MHz, and a phase margin of 62°. The measured quiescent current is 3.1mA under the 5V supply voltage, and the slew rates are 403V/µs and 386V/µs with the help of the slew rate enhancement circuits.