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Aug 18th, 2019, 7:51am
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 Fully differential (differential in - differential out) OpAmp offset simulatoin (Read 387 times)
 7IC7 New Member Offline Posts: 1 Fully differential (differential in - differential out) OpAmp offset simulatoin Apr 02nd, 2019, 12:05pm   Hello everyone,I have a question about the offset simulation of the fully differential amplifiers (differential in - differential out). I am not able to find a good resource that provides an understandable test bench (for offset simulations).The only link that I found is this one which is not complete:https://designers-guide.org/forum/Attachments/offsetFullyDiffopampV1.pdfHave you done this type of simulation before? If yes, please help.Regards, Back to top IP Logged
 Ken Kundert Global Moderator Offline Posts: 2211 Silicon Valley Re: Fully differential (differential in - differential out) OpAmp offset simulatoin Reply #1 - Apr 2nd, 2019, 5:36pm   Generally you just provide some feedback and then measure the difference in voltage between the two inputs.Placing the amplifier in a unity gain configuration works well.You might want to take a look at https://designers-guide.org/analysis/diff.pdf for general information on how to test differential circuits.-Ken Back to top IP Logged
 Salim2019 New Member Offline Posts: 5 Re: Fully differential (differential in - differential out) OpAmp offset simulatoin Reply #2 - Apr 7th, 2019, 2:14pm   Hi,Connect your amplifier as a unity gain buffer, sweep differentially your inputs and record the output.I will assume you are working with single supply operation let say 3.3 V. So use two DC sources with 1.65 at each input with a variable callled X, now sweep X from -1.65 to 1.65,Now you have two output signals, ideally they must intersect at the point of X=0. any shift from this point is your offset voltage. Note I am talking about the x-axsis.Hope I could answered your question Back to top IP Logged
 kabir_fakir Junior Member Offline Posts: 29 Re: Fully differential (differential in - differential out) OpAmp offset simulatoin Reply #3 - May 3rd, 2019, 2:09pm   Salim2019 wrote on Apr 7th, 2019, 2:14pm:Hi,Connect your amplifier as a unity gain buffer, sweep differentially your inputs and record the output.I will assume you are working with single supply operation let say 3.3 V. So use two DC sources with 1.65 at each input with a variable callled X, now sweep X from -1.65 to 1.65,Now you have two output signals, ideally they must intersect at the point of X=0. any shift from this point is your offset voltage. Note I am talking about the x-axsis.Hope I could answered your question Yes SALIM is right. I have done same procedure with fully differential OTA. By the way, I have followed the doc cited by Ken Kudert. Good luck! Back to top Always a learner and will be .   IP Logged
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