CHAPTER 9 AC MODELS

Example 9-1, Page 289

In [8]:
import math

f=20                  #frequency(Hz)
R=2                   #Resistance(KOhm)

XC=0.1*R                     #Capacitive reactance(Ohm)
C=(1/(2*math.pi*f*XC))*1000     #Capacitance(uF)

print 'Capacitance C = ',round(C,2),'uF'

Capacitance C =  39.79 uF

Example 9-2, Page 293

In [7]:
import math

f=1                      #frequency(KHz)
R1=600                   #Resistance1(Ohm)
R2=1000                  #Resistance2(Ohm)


RTH=R1*R2/(R1+R2)            #Thevenin resistance(Ohm)
XC=0.1*RTH                   #Capacitive reactance(Ohm)
C=(1/(2*math.pi*f*XC))*1000     #Capacitance(uF)

print 'Capacitance C = ',round(C,2),'uF'

Capacitance C =  4.24 uF

Example 9-3, Page 297

In [6]:
VCC=10                  #collector voltage(V)
RE=1                    #Emitter resistance(KOhm)
VBE=0.7                 #Base-emitter voltage drop(V)
VEE=2                   #Emitter supply voltage(V)

IEQ=(VEE-VBE)/RE        #Q point emitter current(mA)
iepp=0.1*IEQ*1000       #small signal emitter current(uA) 

print 'Q point emitter current IEQ = ',IEQ,'mA'
print 'Small signal emitter current iepp = ',iepp,'uApp'

Q point emitter current IEQ =  1.3 mA
Small signal emitter current iepp =  130.0 uApp

Example 9-4, Page 301

In [3]:
VCC=30                  #Supply voltage(V)
RC=5                    #Collector resistance (KOhm)
RL=100                  #Emitter resistance (KOhm)
RB=1                    #Base resistance (MOhm)
VBE=0.7                 #Base-emitter voltage drop(V)
Bdc=100                 #current gain

IB=(VCC-VBE)/RB         #Base current(mA)
IE=Bdc*IB/1000          #Emitter current(mA)
re=25/IE                #AC resistance(Ohm)

print 'Emitter current IE = ',IE,'mA'
print 'AC resistance re\' = ',round(re,2),'Ohm'

Emitter current IE =  2.93 mA
AC resistance re' =  8.53 Ohm

Example 9-5, Page 302

In [4]:
VCC=10                  #collector voltage(V)
RC=3.6                  #Collector resistance (KOhm)
RE=1                    #Emitter resistance (KOhm)
R1=10                   #Base resistance1 (KOhm)
R2=2.2                  #Base resistance2 (KOhm)
VBE=0.7                 #Base-emitter voltage drop(V)

VBB=(R2/(R1+R2))*VCC    #Base voltage(V)
VE=VBB-VBE              #Emitter voltage(V)
IE=VE/RE                #Emitter current(mA)
re=25/IE                #AC resistance(Ohm)

print 'Emitter current IE = ',round(IE,2),'mA'
print 'AC resistance re\' = ',round(re,2),'Ohm'

Emitter current IE =  1.1 mA
AC resistance re' =  22.66 Ohm

Example 9-6, Page 302

In [5]:
VCC=10                  #collector voltage(V)
RC=3.6                  #Collector resistance (KOhm)
RE=1                    #Emitter resistance (KOhm)
RB=2.7                  #Base resistance (KOhm)
VBE=0.7                 #Base-emitter voltage drop(V)
VEE=2                   #emitter voltage(V)

VE=VEE-VBE              #Emitter to ground voltage(V)
IE=VE/RE                #Emitter current(mA)
re=25/IE                #AC resistance(Ohm)

print 'Emitter current IE = ',IE,'mA'
print 'AC resistance re\' = ',round(re,2),'Ohm'

Emitter current IE =  1.3 mA
AC resistance re' =  19.23 Ohm
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