Lecture 21

Rg is large compared to 1gm so that the acve inductor

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Unformatted text preview: re 21 – Slide 18 CGD + C SB gm Prof. Ming C. Wu 9 Example vout vin a= RS [CGD1CGS1 + (CGD1 + CGS1 )(CSB1 + CGD 2 + CDB 2 )] g m1 b = RS CGD1 + EE105, Fall 2013 CGS gm = 2 a( jω ) + b( jω ) + 1 1 + ( jω ) CGD1 + CSB1 +C GD 2 +C DB 2 g m1 Lecture 21 – Slide 19 Prof. Ming C. Wu Source Follower: Input Capacitance §༊  Recall that the voltage gain of a source follower is Av = 1 gm Follower stage with MOSFET capacitances shown λ =0 + RS •  CXY can be decomposed into CX and CY at the input and output nodes, respectively: C X = (1 − Av )CGS = Cin = CGD + EE105, Fall 2013 RS Lecture 21 – Slide 20 CGS 1 + g m RS CGS 1 + g m RS Prof. Ming C. Wu 10 Example λ≠0 Cin = CGD1 + EE105, Fall 2013 1 CGS1 1 + g m1 (rO1 || rO 2 ) Lecture 21 – Slide 21 Prof. Ming C. Wu Source Follower: Output Impedance λ =0 •  The output impedance of a source follower can be obtained by direct AC analysis of small-signal model, similarly as for the emitter follower jωRG CGS + 1 vX = iX j...
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