Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!uwm.edu!bionet!agate!ucbvax!tut.cis.ohio-state.edu!sei.cmu.edu!fs7.ece.cmu.edu!o.gp.cs.cmu.edu!andrew.cmu.edu!cl2n+ From: cl2n+@andrew.cmu.edu (Christopher Fleming Lane) Newsgroups: sci.electronics Subject: Re: MOSFET Puzzle Message-ID: Date: 10 Apr 91 17:45:04 GMT References: <1285@tusun2.mcs.utulsa.edu> Distribution: na Organization: Class of '92, Carnegie Mellon, Pittsburgh, PA Lines: 29 In-Reply-To: <1285@tusun2.mcs.utulsa.edu> Hi, I have a clue as how to do this. First you must realize that a MOSFET is a 4 terminal device with the small signal equivilent below: Gate --------------- --------------------- Drain Vgs GmVgs GmbVbs Ro Source ----------------------------------------------------- Vbs Bulk --------------- Where Vgs is the gate to source Voltage, Vbs is the bulk to source Voltage, GmVgs is the transconductance of the Gate-Source, GmbVgs is the transconductance os the Bulk-Source, and Ro is the output impedance. Gm is large the Gmb. If it is set up like Gate --------- Drain - - - - Source ------- Source with source and bulk tied together, an input Vo would result in an output of -GmVoRo, which will hopefully be bigger than Vo. I hope this answers the question. I may be wrong (no guarantees). Later, Chris Lane cl2n@andrew.cmu.edu