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Building a PNP CE AMP

@crake
6 years ago
https://everycircuit.com/circuit/5297268912291840
Two main steps. Set up the DC circuit and the AC circuit. See below. This is not the only way to build an Amp. Have fun with Electronic! _________________________________ 1st DC Circuit: ==> Chosen: IC ~= 1mA ==> Calculated: IB ~= IC/Beta = 1mA/100 = 10uA ==> Chosen: Current through the voltage divider is chosen to be 10*IB = 10*10uA = 100uA ==> Chosen: VE ~= Vcc - 1V = 12V - 1V = 11V ==> Calculated: VB ~= VE - Vbe = 11V - 0.7V = 10.3V ==> Calculated: R1 = (Vcc - VB)/(10*IB) = (12V - 10.3V)/100uA = 17kohm ==> Calculated: R2 = (VB - Vgnd)/(10*IB) = (10.3V - 0V)/100uA = 103kOhm ==> Calculated: RE = (Vcc - VE)/IE = (12V - 11V)/1mA = 1kOhm ==> Chosen: VC ~= Vcc/2 = 12V/2 = 6V ==> Calculated: RC = (Vcc/2 - Vgnd)/IC = (6V - 0V)/1mA = 6kOhm *Assuming one may be using 5% metal-film resistors, we'll round these to the nearest available value. R1 = 17kOhm ==> 16kOhm R2 = 103kOhm ==> 100kOhm RE = 1kOhm RC = 6kOhm ==> 6.2kOhm _________________________________ 2nd AC Circuit: ==> Chosen: Gain = 10 ==> Chosen: Rload ~= 10*RC = 10*6kOhm = 60kOhm ==> Calculated: Re = V_thermal/IE = 25mV/1mA = 25Ohm ==> Since we want Gain = 10 and Gain ~= RC/(RE_un-bypassed + Re) = 6kOhm/(RE_un-bypassed + 25Ohm) ==> Solving for RE_un-bypassed = (RC - 10*Re)/10 = (6kOhm - 10*25Ohm)/10 = 575Ohm ==> In order to NOT disturb the DC bias we carefully set up, and we already know what we wanted RE to be for IE = 1mA, the new RE is split into two resistors, one is AC bypassed, the other is not, but their sum is 1kOhm. Therefore, RE_bypassed = RE_DC_BIAS - RE_un-bypassed = 1kOhm - 575Ohm = 425Ohm Rload = 60kOhm ==> 62kOhm RE_bypassed = 425Ohm ==> 430Ohm RE_un-bypassed 575Ohm ==> 560Ohm _________________________________ Equation ==> Rin = R1||R2||RE', where RE' = RE*(Beta + 1) ==> Vo = (Vi')*Gain, where Vi' = Vi*(Rin/(Rin + RS)) and RS = 50Ohm in this case, and Gain = R_load-equivalent/(RE + Re), where R_load-equivalent = RC||Rload ==> Putting it all together: Vo = Vi*[(R1||R2||RE*(Beta + 1))/(R1||R2||RE*(Beta + 1) + RS)]*[R_load-equivalent/(RE + Re)] = Vi*0.995511*9.63481. Let Vi = 500mV, we have: Vo = 500mV*0.995511*9.63481= 4.79578V ~= 4.8V
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