Load-Line Analysis of NMOS AmplifierIt is a graphical analysis
similar to load-line analysis of pn diode.SchematicCircuit
Analysis:Input loopOutput loopLoad linevGSvDSWe look for the
operating point
Load-Line Analysis of NMOS AmplifierExercise:
Draw the Load lineRD= 1 kW
Load-Line Analysis of NMOS AmplifierLoad lineTaking iD=0 or
vDS=0 we find out the load lane and the quiescent operating point Q
for VGS=4VThe quiescent valuesvin(t)=0 then iDQ=9 mAvGSQ=4V and
vDSQ=11VPoints A & B intersection of curve and the load-line
for the maximum and the minimum gate voltage
Input signalLoad-Line Analysis of NMOS Amplifier(peak-to-peak
amplitude is 2V)12V peak-to-peakInverse operationThe positive peak
of the input occurs at the same time as the min. value of vDS. The
output is not a symmetrical sinusoid! (nonlinear
distortion)vDS(t)vin(t)2V peak-to-peak
Self Bias CircuitsAnalysis of amplifier circuits is often
undertaken in two steps:(1) The dc circuit analysis to determine
the Q point. It involves the nonlinear equation or the load-line
method. This is called bias analysisThe fixed-plus self-bias
circuitExercise: Find VG voltage as a function of VDD, R1 and
R2
Self Bias CircuitsAnalysis of amplifier circuits is often
undertaken in two steps:(1) The dc circuit analysis to determine
the Q point. It involves the nonlinear equation or the load-line
method. This is called bias analysisThe fixed-plus self-bias
circuit
Self Bias CircuitsAnalysis of amplifier circuits is often
undertaken in two steps:(1) The dc circuit analysis to determine
the Q point. It involves the nonlinear equation or the load-line
method. This is called bias analysis(2) Use a linear small-signal
equivalent circuit to determine circuit parametersEquivalent
circuitAnalysisvGSvDSfind vGS
Self Bias CircuitsPlot ofandDisregarded root for vGS
Self Bias CircuitsAnalysis of amplifier circuits is often
undertaken in two steps:(1) The dc circuit analysis to determine
the Q point. It involves the nonlinear equation or the load-line
method. This is called bias analysis(2) Use a linear small-signal
equivalent circuit to determine circuit parametersEquivalent
circuitAnalysisvGSvDSFor saturation regionfind iD
Self Bias CircuitsAnalyze the self-bias circuit shown. The
transistor has KP=50mA/V2, Vto=2V, L=10mm, and W=400mmfind vGSfind
iDExercise 12.5find vDS
FlexibleField Effect TransistorsEE314
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