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Posts: 1
Registered: ‎08-06-2015

EFM32LG880F64 opamp2 clips lower half signal in a cascaded PGA configuration

Hi, I use EFM32LG880F64’s on-chip opamps in a cascaded PGA configuration: with opamp2 as the last stage. The signal has a 1.25V DC offset. halfbias and bias were all set as default. I found that when opamp2 gain is higher, the lower half of the signal is clipped. When I remove halfbias and increase bias, the signal clipping went away. This problem only exists in some boards, while most of the boards function as expected. Are there any differences between mcu parts? Why clipping only happens at high gain? Could register default values vary from part to part? Thanks for your helps!

Posts: 2,321
Registered: ‎10-14-2014

Re: EFM32LG880F64 opamp2 clips lower half signal in a cascaded PGA configuration

[ Edited ]

@wave_rider1

Could you reproduce this on our STK board? If yes could you upload a code that could reproduce this issue. How about the swing range of the input signal?

Do you mind uploading the captured signal here if you have?

 

WeiguoLu