摘要
This paper presents a three-stage CMOS operational amplifier （opamp） that combines accuracy with stability for a wide range of capacitive loads. A so-called quenching capacitor is added to a multipath nested Miller compensation （MNMC） topology to obtain stability for a wide range of capacitive loads. Theoretical analysis and mathematical formulas are provided to prove the improvement in stability. A prototype of this frequency compen- sation scheme is implemented in a 0.7μm CMOS process. Measurement′s show that the amplifier can drive capaci- tive loads ranging from 100pF to 100/μF with a gain of 90dB and a minimum phase margin of 26°. The amplifier has a unity-gain bandwidth of 1MHz for a 100pF capacitive load. It employs a quenching capacitance of 18pF.
结合精确度和稳定性的要求提出了一种适合宽范围电容负载的CMOS运放.在多径嵌套式密勒补偿结构中加入一个抑制电容得到适合各种电容负载的稳定性.为了证实稳定性的提高对该结构进行了理论分析并计算得出数学表达式.基于这种新的频率补偿结构,利用CMOS0.7μm工艺模型设计了样品芯片.测试结果表明:该运放可以驱动从100pF到100μF负载电容,直流增益为90dB,最小相位裕度为26°;该运放在100pF负载情况下单位增益带宽为1MHz,使用抑制电容仅为18pF.
