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https://designers-guide.org/forum/YaBB.pl Design >> Analog Design >> body effect decreases output impedance in source followers? https://designers-guide.org/forum/YaBB.pl?num=1305707851 Message started by surreyian on May 18th, 2011, 1:37am |
Title: body effect decreases output impedance in source followers? Post by surreyian on May 18th, 2011, 1:37am Hello all, In razavi's design of analog CMOS integrated circuit, chapter 3, it states/shows that body effect decrease the output resistance. But I find it puzzling. I bias the NMOS source with a certain voltage, eg 0.3V. Setup 1: Base and Source are connected together to 0.3V bias. (No body effect) Setup 2. Source is connected to 0.3V whilst base is connect to ground. (with Body effect) Id=(Vgd-Vth)^2K. Based on the equation, setup 2 Vth will be greater than setup 1, hence reducing Id, hence increase output resistance. Am I right in the analysis? If that is the case how does body effect reduces output impedance? |
Title: Re: body effect decreases output impedance in source followers? Post by raja.cedt on May 19th, 2011, 11:57am hello..this is small signal o/p impedance and expression is 1/(gm+gmb), so it decrease. but you are arguing from large signal and that to some mistake is there in that equation. Thanks. |
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