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https://designers-guide.org/forum/YaBB.pl Design >> Analog Design >> Diffamp https://designers-guide.org/forum/YaBB.pl?num=1253896888 Message started by raja.cedt on Sep 25th, 2009, 9:41am |
Title: Diffamp Post by raja.cedt on Sep 25th, 2009, 9:41am hi, while reading differential amplifiers i found 4 gains (differential to differential, common mode to differential, common mode to common mode,differential to common mode)..i didn't understand theoretically how differential mode will be converted into common mode Thanks, Rajasekhar. |
Title: Re: Diffamp Post by cczhang on Sep 27th, 2009, 2:02am HI,generally speaking, differential opamp has common mode feedback circuit, and there will be mismatch between mosfets, so there will be four gains |
Title: Re: Diffamp Post by raja.cedt on Sep 27th, 2009, 8:49am hi, could you please explain clearly.. Thanks Rajasekhar. |
Title: Re: Diffamp Post by thechopper on Sep 27th, 2009, 9:07am Hi Rajasekhar, Itīs simple: just imagine a resistive loaded diff pair with a purely differential signal, and assume a mismatch on the load resistor. The single ended output signals will not be perfectly centered around the nominal CM since both are different (non-symmetrical) due to the resistorīs mismatch. Thus you generated a CM output signal by ONLY applying a differential signal. Regards Tosei |
Title: Re: Diffamp Post by raja.cedt on Sep 28th, 2009, 9:49pm hi, thanks for your ans, i have understand your ans like the following. Due to mismatch in resistor output voltages are not perfect differential, so you can divide them into differential and common mode. Correct me if am wrong. Thanks, rajasekhar. |
Title: Re: Diffamp Post by cczhang on Sep 29th, 2009, 12:26am raja.cedt wrote on Sep 28th, 2009, 9:49pm:
Hi,maybe this paper will help you understand the gains. |
Title: Re: Diffamp Post by raja.cedt on Sep 29th, 2009, 1:13am hi cczhang, thank you very much for the paper. Thanks, Rajasekhar |
Title: Re: Diffamp Post by thechopper on Sep 29th, 2009, 7:12pm raja.cedt wrote on Sep 28th, 2009, 9:49pm:
That's correct Rajasekhar. Regards Tosei |
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