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Simulators >> Circuit Simulators >> strange results for phase response
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Message started by dimita on Sep 11^th, 2008, 12:44am

Title: strange results for phase response
Post by dimita on Sep 11^th, 2008, 12:44am

Hi,
I run AC simulation of some opamp in unity gain buffer configuration(open loop response), the open loop gain seems to be usual response with dominant pole at low frequencies, but the phase starts from -180 degree and rising. There is no invertion at DC, can anyone explain such phase behaviour?

Title: Re: strange results for phase response
Post by dimita on Sep 11^th, 2008, 12:46am

For some reason I can not upload the attachment with waveform :(

Title: Re: strange results for phase response
Post by tempora on Sep 16^th, 2008, 4:48am

Hi,

Maybe your setup is wrong. Try this;
- connect Vdc (reference) to in_positive
- connect vsin acmag=1 to in_negative (feedback loop branch)
- run dc with closed loop
- run ac with opened loop

You should get a good results then.

L.S.