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VCA821: AGC应用。Vg脚的反馈电压问题

Part Number: VCA821
Other Parts Discussed in Thread: OPA695, OPA820

输入是100Khz,Vpp=0.2V.

VCA821配置的是最大增益Vgainmax =2

OPA695的增益是5

想让sin波形稳定在1V,所以,OPA820的正端参考电压给1V

示波器显示的结果很奇怪,尤其是Vg脚电压,按照手册芯片工作Vg电压是0~2V,仿真示波器看 >4V,AGC环路没有工作。

仿真文件在附件VCA821_AGC仿真.TSC