The output waveform of the LM8640

I use the amplifer LM8640 to sence the inductor current in the Buck converter, I chose the gain as 20, and sense resister 5m. Buck converter : input voltage: 12V; output voltage: 3.3V; output currrent:10A.

I found the output waveform of LM8640 was strange, following is the waveform of the comparision between the inductor waveform and the output waveform of LM8640.  Dose anyone have any clue why there will be a drop in the output waveform when the switch is turned off and on?

Kailyn Chen：

Hello, I didn't find LM8640 in our website, do you mean LMP8640?If yes, please attach your circuit for analysis.