基于GSMC 0.13μm工艺的低失调运算放大器设计

Design of an ultra-low offset operational amplifier based on GSMC 0.13μm process

针对斩波调制导致的输出纹波和带宽受限的问题,采用复合路径结构,将运放分为高频低增益的主路径和低频高增益的辅助路径,主路径决定带宽,辅助路径决定失调,斩波调制位于辅助路径,解除了带宽限制;将Ping-pong自动调零与斩波调制相结合,减小了运放的失调和斩波调制导致的纹波;采用复合路径混合嵌套米勒补偿的方法来进行频率补偿,保证了多级运放的稳定性。低失调运放的设计基于华虹宏力(GSMC)0.13μm CMOS工艺,经Spectre仿真得到,运放的单位增益带宽为3.53 MHz,输入等效失调电压小于15.8μV,纹波等效到输入小于175μV,满足低频微弱信号的放大需求。

To reduce output ripples and release bandwidth limitation caused by chopping modulation,multipath structures were used to divide up the op amp into a high-frequency low-gain path and a low-frequency high-gain path,which determined the bandwidth and offset respectively.The chopping modulation was in the low-frequency high-gain path,which removed the bandwidth limitation of the operational amplifier.The Ping-pong auto-zeroing and chopping modulation were combined to reduce the offset and output ripples.The hybrid nested Miller compensation was used to compensate the frequency and ensure the stability of the multistage op amp.The design of the op amp chip was based upon GSMC 0.13μm CMOS process.Spectre simulation shows that the unity gain bandwidth of the low-offset op amp is 3.53 MHz,the maximum offset is less than 15.8μV,and the maximum input equivalent ripple is 175μV.