CHAPTER 10 VOLTAGE AMPLIFIERS

Example 10-1, Page 322

In [1]:
re=22.7               #Ac resistance as per example 9-5(Ohm)
RC=3.6                #Collector Resistance(KOhm)
RL=10                 #Load Resistance(KOhm)
Vin=2                 #Input voltage(mV)

rc=RC*RL/(RC+RL)            #AC collector resistance(Ohm)
Av=(rc/re)*1000             #Voltage gain
Vout=Av*Vin                 #Output voltage(mV)

print 'Voltage gain Av = ',round(Av,2)
print 'Output voltage Vout = ',round(Vout,2),'mV'

Voltage gain Av =  116.61
Output voltage Vout =  233.22 mV

Example 10-2, Page 323

In [2]:
RC=3.6                #Collector Resistance(KOhm)
RL=2.2                #Load Resistance(KOhm)
Vin=5                 #Input voltage(mV)
VEE=9                 #collector voltage(V)
RE=10                 #Emitter resistance(KOhm)
VBE=0.7               #Base-emitter voltage drop(V)

rc=RC*RL/(RC+RL)            #AC collector resistance(Ohm)
IE=(VEE-VBE)/RE             #emitter current(mA)
re=25/IE                    #AC resistance(Ohm)
Av=(rc/re)*1000             #Voltage gain
Vout=Av*Vin                 #Output voltage(mV)

print 'Emitter current IE = ',IE,'mA'
print 'Voltage gain Av = ',round(Av,2)
print 'Output voltage Vout = ',round(Vout,2),'mV'

Emitter current IE =  0.83 mA
Voltage gain Av =  45.34
Output voltage Vout =  226.68 mV

Example 10-3, Page 325

In [3]:
re=22.7               #Ac resistance as per example 9-5(Ohm)
B=300                 #current gain
R1=10                 #Base resistance1 (KOhm)
R2=2.2                #Base resistance2 (KOhm)
Rs=0.6                #internal resistance of source(KOhm)
Av=117                #Voltage gain as per example 10-1
Vs=2                  #ac voltage supply(mV)

Zin_base=B*re/1000                                #input impedance of base(KOhm)
Zin_stage=((R1**-1)+(Zin_base**-1)+(R2**-1))**-1  #input impedance of stage(KOhm)
Vin=(Zin_stage/(Rs+Zin_stage))*Vs                 #input voltage(mV)
Vout=Av*Vin                                       #output voltage(mV)

print 'input impedance of stage Zin(stage) = ',round(Zin_stage,2),'KOhm'
print 'Output volatge Vout = ',round(Vout,2),'mV'

input impedance of stage Zin(stage) =  1.43 KOhm
Output volatge Vout =  164.69 mV

Example 10-4, Page 325

In [4]:
re=22.7               #Ac resistance as per example 9-5(Ohm)
B=50                  #current gain
R1=10                 #Base resistance1 (KOhm)
R2=2.2                #Base resistance2 (KOhm)
Rs=0.6                #internal resistance of source(KOhm)
Av=117                #Voltage gain as per example 10-1
Vs=2                  #ac voltage supply(mV)

Zin_base=B*re/1000                                #input impedance of base(KOhm)
Zin_stage=((R1**-1)+(Zin_base**-1)+(R2**-1))**-1  #input impedance of stage(KOhm)
Vin=(Zin_stage/(Rs+Zin_stage))*Vs                 #input voltage(mV)
Vout=Av*Vin                                       #output voltage(mV)

print 'input impedance of stage Zin(stage) = ',round(Zin_stage,2),'KOhm'
print 'Output volatge Vout = ',round(Vout,2),'mV'

input impedance of stage Zin(stage) =  0.7 KOhm
Output volatge Vout =  125.71 mV

Example 10-5, Page 327

In [5]:
re=22.7               #Ac resistance as per example 9-5(Ohm)
B=100                 #current gain
R1=10                 #Base resistance1 (KOhm)
R2=2.2                #Base resistance2 (KOhm)
Rs=0.6                #internal resistance of source(KOhm)
RC=3.6                #colletcor resistance (KOhm)
Vs=1                  #ac voltage supply(mV)
RL=10                 #Load resistance(KOhm)

Zin_base=B*re/1000                                #input impedance of base(KOhm)
Zin_stage1=((R1**-1)+(Zin_base**-1)+(R2**-1))**-1 #input impedance of stage1(KOhm)
Vin=(Zin_stage1/(Rs+Zin_stage1))*Vs               #input voltage(mV)
Zin_stage2=((R1**-1)+(Zin_base**-1)+(R2**-1))**-1 #input impedance of stage2(KOhm)
rc1=(RC*Zin_stage2)/(RC+Zin_stage2)               #AC collector resistance of stage1(KOhm)
Av1=rc1/re                                        #Voltage gain of stage 1
vc=Av1*Vin                                        #AC collector voltage of stage 1(V)
rc2=(RC*RL)/(RC+RL)                               #AC collector resistance of stage2(KOhm)
Av2=rc2/re                                        #Voltage gain of stage 2
Vout=Av2*vc                                       #output voltage(mV)
Av=Av1*Av2                                        #Overall voltage gain
Voutf=Av*Vin                                      #AC output voltage across RL(V)

print 'AC collector voltage of first stage vc = ',round(vc*1000,2),'mV'
print 'AC output voltage across load resistor Vout = ',round(Voutf*1000,2),'V'

AC collector voltage of first stage vc =  21.67 mV
AC output voltage across load resistor Vout =  2.53 V

Example 10-6, Page 331

In [6]:
VCC=10                  #collector voltage(V)
RC=3.6                  #Collector resistance (KOhm)
re=0.18                 #Emitter resistance (KOhm)
R1=10                   #Base resistance1 (KOhm)
R2=2.2                  #Base resistance2 (KOhm)
Rs=0.6                  #internal resistance of source(KOhm)
VBE=0.7                 #Base-emitter voltage drop(V)
Vs=50                   #ac voltage supply(mV)
RL=10                   #Load resistance(KOhm)
B=200                   #current gain 

Zin_base=B*re                                     #input impedance of base(KOhm)
Zin_stage=((R1**-1)+(Zin_base**-1)+(R2**-1))**-1  #input impedance of stage(KOhm)
Vin=(Zin_stage/(Rs+Zin_stage))*Vs                 #input voltage(mV)
rc=(RC*RL)/(RC+RL)                                #AC collector resistance of stage(KOhm)
Av=rc/re                                          #Voltage gain of stage
Vout=Av*Vin                                       #output voltage(mV)

print 'input impedance of stage Zin(stage) = ',round(Zin_stage,2),'KOhm'
print 'Output volatge Vout = ',round(Vout,2),'mV'

input impedance of stage Zin(stage) =  1.72 KOhm
Output volatge Vout =  544.91 mV

Example 10-7, Page 332

In [7]:
VCC=10                  #collector voltage(V)
RC=3.6                  #Collector resistance (KOhm)
re=0.18                 #Emitter resistance (KOhm)
re1=0.0227              #Ac resistance as per example 9-5(KOhm)
R1=10                   #Base resistance1 (KOhm)
R2=2.2                  #Base resistance2 (KOhm)
Rs=0.6                  #internal resistance of source(KOhm)
VBE=0.7                 #Base-emitter voltage drop(V)
Vs=50                   #ac voltage supply(mV)
RL=10                   #Load resistance(KOhm)
B=200                   #current gain 

Zin_base=B*(re+re1)                               #input impedance of base(KOhm)
Zin_stage=((R1**-1)+(Zin_base**-1)+(R2**-1))**-1  #input impedance of stage(KOhm)
Vin=(Zin_stage/(Rs+Zin_stage))*Vs                 #input voltage(mV)
rc=(RC*RL)/(RC+RL)                                #AC collector resistance of stage(KOhm)
Av=rc/(re+re1)                                    #Voltage gain of stage
Vout=Av*Vin                                       #output voltage(mV)

print 'input impedance of stage Zin(stage) = ',round(Zin_stage,2),'KOhm'
print 'Output volatge Vout = ',round(Vout,2),'mV'

input impedance of stage Zin(stage) =  1.73 KOhm
Output volatge Vout =  484.55 mV

Example 10-8, Page 333

In [8]:
re=0.18               #emitter reistance(Ohm)
B=200                 #current gain
R1=10                 #Base resistance1 (KOhm)
R2=2.2                #Base resistance2 (KOhm)
Rs=0.6                #internal resistance of source(KOhm)
RC=3.6                #colletcor resistance (KOhm)
Vs=1                  #ac voltage supply(mV)
RL=10                 #Load resistance(KOhm)

Zin_base=B*re                                     #input impedance of base(KOhm)
Zin_stage1=((R1**-1)+(Zin_base**-1)+(R2**-1))**-1 #input impedance of stage1(KOhm)
Vin=(Zin_stage1/(Rs+Zin_stage1))*Vs               #input voltage(mV)
Zin_stage2=((R1**-1)+(Zin_base**-1)+(R2**-1))**-1 #input impedance of stage2(KOhm)
rc1=(RC*Zin_stage2)/(RC+Zin_stage2)               #AC collector resistance of stage1(KOhm)
Av1=rc1/re                                        #Voltage gain of stage 1
vc=Av1*Vin                                        #AC collector voltage of stage 1(V)
rc2=(RC*RL)/(RC+RL)                               #AC collector resistance of stage2(KOhm)
Av2=rc2/re                                        #Voltage gain of stage 2
Vout=Av2*vc                                       #output voltage(mV)
Av=Av1*Av2                                        #Overall voltage gain
Voutf=Av*Vin                                      #AC output voltage across RL(V)

print 'AC collector voltage of first stage vc = ',round(vc,2),'mV'
print 'AC output voltage across load resistor Vout = ',round(Voutf,2),'mV'

AC collector voltage of first stage vc =  4.79 mV
AC output voltage across load resistor Vout =  70.39 mV

Example 10-9, Page 335

In [44]:
RV_min=0                #minimum variable resistance (KOhm)
RV_max=10               #maximum variable resistance (KOhm)
re=0.1                  #Emitter resistance (KOhm)

rf_min=RV_min+1         #minimum feedback resistance(KOhm)
rf_max=RV_max+1         #maximum feedback resistance(KOhm)
Av_min=rf_min/re        #minimum voltage gain
Av_max=rf_max/re        #maximum voltage gain

print 'minimum voltage gain Av(min)= ',Av_min
print 'minimum voltage gain Av(max)= ',Av_max

minimum voltage gain Av(min)=  10.0
minimum voltage gain Av(max)=  110.0
In [ ]: