一种高增益、高带宽全差分运算放大器的设计

Design of a High Gain,High Bandwidth,Fully Differential Operational Amplifier

采用增益提升(Gain-boosting)技术,使用2个三输入管的折叠式共源共栅运算放大器(运放)作为辅助运放,设计了一种宽输入共模范围的高增益、高带宽的全差分运算放大器。主运放输入部分由一对NMOS管和一对PMOS管共同构成,其输入跨导提高至由单MOS管构成的运放输入跨导的2倍。主运放输入跨导的提高间接提升了主运放的增益和带宽。而辅助运放在不改变主运放带宽的同时,通过降低主运放的主极点增大输出阻抗,再次提升主运放的增益,达到了高增益、高带宽的目的。该运算放大器采用商用55 nm CMOS工艺设计,经仿真可得,当负载电容为5 pF时,运放低频增益为115 dB,增益带宽积为209 MHz,总功耗为2.8 mW。

A gain-boosting technique is used to design a high gain,high bandwidth,fully differential operational amplifier(op-amp)with a wide input common-mode range,using two folded common source and common gate op-amps with three-input tubes as auxiliary op-amps.The main op-amp input section consists of a pair of NMOS tubes and a pair of PMOS tubes,and the main op-amp input transconductance is increased to twice that of an op-amp consisting of a single MOS tube.The increase in the main op-amp's input transconductance indirectly increases the main op-amp's gain and bandwidth.While the auxiliary op-amps do not change the bandwidth of the main op-amp,and they increase the gain of the main op-amp again by reducing the main op-amp pole to increase the output impedance,achieving the purpose of high gain and high bandwidth.The op-amp is designed using a commercial 55 nm CMOS process,and simulation results show that the op-amp has a low-frequency gain of 115 dB,a gain bandwidth product of 209 MHz,and a total power consumption of 2.8 mW when the load capacitance is 5 pF.