A low-powerlow-voltage slew-rate enhancement circuit for two-stage operational amplifiers

正A novel circuit is presented in order to enhance the slew rate of two-stage operational amplifiers.The enhancer utilizes the class-AB input stage to improve current efficiency,while it works on an open loop with regard to the enhanced amplifier so that it has no effect on the stability of the amplifier.During the slewing period,the enhancer detects input differential voltage of the amplifier,and produces external enhancement currents for the amplifier,driving load capacitors to charge/discharge faster.Simulation results show that,fora large input step,the enhancerreduces settling time by nearly 50%.When the circuit is employed in a sample-and-hold circuit,it greatly improves the spur-free dynamic range by 44.6 dB and the total harmonic distortion by 43.9 dB.The proposed circuit is very suitable to operate under a low voltage(1.2 V or below) with a standby current of 200μA.     

一个低功耗低电压的二级运放压摆率增强电路

本文提出了一个新颖的二级运放压摆率增强电路。该电路采用AB类输入级,提高了电流效率。相对于运放,它完全开环工作,因此不会影响运放的稳定性。当运放处于压摆阶段时,电路检测运放输入差分电压,产生外部的动态电流并注入运放,从而使加快负载电容的充/放电过程。电路仿真结果显示：对于大的输入阶跃信号,该电路可以减少50%的建立时间;将电路运用于采样保持电路时,该电路提高了无杂散动态范围44.6dB,降低了总谐波失真43.9dB。本文提出的电路非常适用于低电压（1.2V或更低）工作,并且只消耗200μA的静态电流。