Cascode Amplifier Example - Fall 2000RPxy,()xy.xyFunction for calculating parallel resistors.R1390000 R2200000 R356000 R4100RC20000 RE4300 RS1000 RL10000Vp65 Vm0 VBE0.65 VT0.025β199α0.995rx20 r050000vs1With vs = 1, the voltage gain is equal to vo.1DC Bias SolutionVBB1VpR3.VmR1R2.R1R2R3αIE1.1βR1R1R2R3.R3.IE1RBB1RPR1R2R3,VBB1VmIE11βRBB1VBEIE1RE.VBB1VmIE1IE1Solve these to obtain.IE1VpR3.VmR1R2.R1R2R3VmVBERBB11βREα1βR1R3.R1R2R3.IE11.0552 103=re1VTIE1re123.6922=2IE2αIE1.IE21.0499 103=re2VTIE2re223.8113=Checks for active mode.VB1VBEIE1RE.VmVB15.1874=VB2VpR2R3.VmR1.R1R2R3IE21βRPR1R2R3,.VB224.9472=VC1VB2VBEVC124.2972=VCB1VC1VB1VCB119.1098=Active mode.VC2VpαIE2.RC.VC244.1065=VCB2VC2VB2VCB219.1594=Active mode.AC Solution 3vtb1vsRPR2R3,RSRPR2R3,.vtb10.9777=Rtb1RPRSRPR2R3,,Rtb1977.6536=Rte1RPRER4,Rte197.7273=rie1Rtb1rx1βre1rie128.6805=rie2rx1βre2rie223.9113=4ric1r0RPrie1Rte1,1αRte1.rie1Rte1ric12.1678 105=ic1scvtb1rie1RPRte1r0,αRte1Rte1r0.ic1sc7.692 103=vte2ic1scric1.vte21.6674 103=Rte2ric1Rte22.1678 105=5Rtc2RPRCRL,Rtc26.6667 103=ic2scvte2Rte2RPrie2r0,αr0.Rtc2r0Rtc2.ic2sc7.6572 103=ric2r0RPrie2Rte2,1αRte2.rie2Rte2ric29.7899 106=voic2scRPric2Rtc2,.vo51.0132=AvvoAv51.0132=This is the voltage gain.routRPRCric2,rout1.9959 104=6rieo2rie2r0Rtc2rie2r0Rtc21β.rieo227.0685=Rtc1rieo2Rtc127.0685=rib1rx1β()re1RPRte1r0Rtc1,.βRte1.Rtc1.Rtc1r0Rte1rib12.4255 104=rinRPrib1RPR1R2R3,,rin1.6453 104=The following solution is based on the r0 approximations for Q2 . ic2scαic1sc.ric1rie2ric1.ic2sc7.6527 103=The ric1rie2ric1 is a current divider.voic2scRPRtc2ric2,.vo50.983=AvvoAv50.983=This is the voltage gain.routRPric2RC,rout1.9959 104=rib1rx1β()re1Rte1.rib12.4304 104=rinRPrib1RPR3R2,,rin1.5624
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