带Class AB输出级的全差分电路仿真SR的时候出现了这种现象，怎么解决？

chf1

总体电路图：

                               
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• The unstable phenomenon with CMFB circuit(both in open     loop and closed loop):+SR:
  

                               
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VON occurs peak value, why? Actually VOP and VON is symmetric, whythis phenomenon occurs?

                               
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-SR: It also occurs unstable phenomenon. But just lasts for a while.

Why VOP and VON are unstable?The problem is in CMFB circuit,but how to solve it?(CMFB characters)

                               
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