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Design >> Mixed-Signal Design >> AC simulation of common-mode feedback in loop...
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Message started by thomasross20 on Oct 6^th, 2008, 4:21am

Title: AC simulation of common-mode feedback in loop...
Post by thomasross20 on Oct 6^th, 2008, 4:21am

Hello,

I've currently got a telescopic amplifier with a differential-difference amplifier for the commno-mode feedback (basically an amp which compares the average of the outputs to a common mode level).

I am having trouble plotting the a.c. response of the common-mode part of the circuit. I want to see the gain and phase from the outputs of the amp to the input off the DDA which feed back to the amp and then to the output.... the system is unstable and I cannot simulate the a.c. to see the poles & zeros.

I have tried placing a large RC low-pass from the outputs of the amp to the input of the DDA, but no luck.

Thanks for any help,

Thomas

Title: Re: AC simulation of common-mode feedback in loop...
Post by thomasross20 on Oct 6^th, 2008, 8:00am

I think I have solved my problem; thanks for those that took the time to read, anyway :)

Title: Re: AC simulation of common-mode feedback in loop...
Post by Frank Wiedmann on Oct 6^th, 2008, 8:40am

You might want to search this forum for "stb analysis".