Chapter 7 :Transistor Biasing And Stabilization of Operation Point

Example 7.1 Page No.230

In [21]:
#Given
Vcc=9.0                                      #V, collector bias junction voltage
Rb=300*10**3                              #Ohms, , base resistance
Rc=2*10**3                                #Ohms, collector resistance
Beeta=50.0                                #current gain factor

#Calculation
Ib=(Vcc)/Rb
Ic=Beeta*Ib
Icsat=Vcc/Rc
Vce=Vcc-Ic*Rc

#Result
print "a) Base current is ",Ib,"A"
print "b) collector current is =  ",Ic/10**(-3),"mA"
print "collector saturation  current is =  ",Icsat/10**(-3),"mA"
if Ic < Icsat:
    
    print"Since Ic < Icsat \nSo Transistor is not in saturation" 
else:
    print "Transistor is in saturation"

print "c) The collector to emitter voltage is = ",Vce,"V"

a) Base current is  3e-05 A
b) collector current is =   1.5 mA
collector saturation  current is =   4.5 mA
Since Ic < Icsat 
So Transistor is not in saturation
c) The collector to emitter voltage is =  6.0 V

Example 7.2 Page No.230

In [23]:
Vcc=10.0                          #V, collector bias junction voltage
Rb=100*10**3              #Ohms, base resistance
Rc=1*10**3                  #Ohms, collector resistance
Beeta=60                        #current gain
 
#Calculation
Ib=(Vcc)/Rb                 #A, base current
Ic=Beeta*Ib                 #A, collector current
Icsat=Vcc/Rc               #A, collector saturated current
Vce=Vcc-Ic*Rc            #V, collector emitter voltage

#Result
print "a) Base current is ",Ib*10**6,"microA"
print "b) collector current is ",Ic*10**3,"mA"
print "collector saturation current is ",Icsat*10**3,"mA"
if Ic < Icsat:
    
    print"Since Ic < Icsat \nSo Transistor is not in saturation" 
else:
    print "Transistor is  in saturation"
print "c) The collector emitter voltage is ",Vce,"V"

a) Base current is  100.0 microA
b) collector current is  6.0 mA
collector saturation current is  10.0 mA
Since Ic < Icsat 
So Transistor is not in saturation
c) The collector emitter voltage is  4.0 V

Example 7.3 Page No.231

In [25]:
Vcc=10.0                               #V, collector bias junction voltage
Rb=100*10**3                          #Ohms, Base resistance
Rc=1*10**3                            #Ohms, collector resistance
Beeta=150                             #current gain

#Calculation
Ib=(Vcc)/Rb                     #Base current
Ic=Beeta*Ib                     #collector resistance
Icsat=Vcc/Rc                    #A, collector saturation current
Vce=0                           #V, collector emitter voltage

#Result
print "collector current is Ic = ",Ic/10**(-3),"mA"
print "collector saturated current is ",Icsat*10**3,"mA" 
if Ic < Icsat:
    
    print" Transistor is not in saturation." 
else:
    print "Since Ic > Icsat \n So Transistor is  in saturation"
print "collector emitter voltage is ",Vce,"V"

collector current is Ic =  15.0 mA
collector saturated current is  10.0 mA
Since Ic > Icsat 
 So Transistor is  in saturation
collector emitter voltage is  0 V

Example 7.4 Page No.231

In [40]:
Vcc=6          #V,collector base junction voltage
Vbe=0.3        #V,base emittor voltage
Icbo=.000002   #A,colector leakage current
Ic=.001 #A,collector current
Beeta=20.0

#Calculation
#Case 1: Considering Icbo and Vbe in the calculations
Ib=(Ic-(Beeta+1)*Icbo)/Beeta
print Ib
Rb1=(Vcc-Vbe)/Ib
print "value of base resistance is =",round(Rb1/1000,3),"K ohm"

#Case 2: Neglecting Icbo and Vbe in the calculations
Ib2=Ic/Beeta
Rb2=Vcc/Ib2
#Percentage Error
E=(Rb2-Rb1)/Rb1*100
#Displaying The Results in Command Window
print"The Base Resistance (Neglecting Icbo and Vbe) is ",Rb2/1000,"k ohm"
print" Percentage Error is = ",round(E,3)

#b  Due to rise in temprature
beeta1=25.0
Icbo1=10.0
Ic1=beeta1*Ib+(beeta1+1)*Icbo1*10**-6
print "Now collector current is ",round(Ic1*10**3,2),"mA"

4.79e-05
value of base resistance is = 118.998 K ohm
The Base Resistance (Neglecting Icbo and Vbe) is  120.0 k ohm
 Percentage Error is =  0.842
Now collector current is  1.46 mA

Example 7.5 Page No.235

In [3]:
Vcc=10.0      #V,collectoe base junction voltage
Rc=500.0      #Ohms,colector resistance
Rb=500000  #Ohms,base resistance
Beeta=100.0   #current gain
#Calculation
Ib=Vcc/(Rb+Beeta*Rc) #emittor currenr
Ic=Beeta*Ib
Ie=Ic
Vce=Vcc-Ic*Rc
Vc=Vce

# Results 
print "emittor current is ",round(Ie*1000,1),"mA"
print"The collector voltage is ",round(Vc,1),"V"

emittor current is  1.8 mA
The collector voltage is  9.1 V

Example 7.6 Page No.235

In [2]:
#Given Circuit Data
Vcc=20.0     #V,collector base voltage
Rc=2000.0    #Ohms.collector resistance
Rb=200000.0   #Ohms,base resistance
Beeta1=50.0   #current gain factor
Beeta2=200.0

#Calculation CASE-1: Minimum Collector Current
#from fig 7.14
Ibmin=Vcc/(Rb+Beeta1*Rc)
Icmin=Beeta1*Ibmin
#result
print "minimum    base curent    is ",round(Ibmin,6),"A"
print "minimum collector current is ",round(Icmin*1000,3),"mA"
#Calculation CASE-2: Maximum Collector Current
Ibmax=Vcc/(Rb+Beeta2*Rc)
Icmax=Beeta2*Ibmax

#Results 
print"The maximum    base   current =  ",round(Ibmax/10**(-3),6),"A"
print"The Maximum Collector Current = ",round(Icmax/10**(-3),2),"mA"

minimum    base curent    is  6.7e-05 A
minimum collector current is  3.333 mA
The maximum    base   current =   0.033333 A
The Maximum Collector Current =  6.67 mA

Example 7.7 Page No.238

In [1]:
Vcc=10.0    #V collector junction voltage
Rc=2000.0    #Ohms collector resistane
Rb=1000000.0 #Ohms,base resistance
Re=1000.0    #Ohms emittor resstance
Beeta=100.0  #current gain

#Calculation
Ib=Vcc/(Rb+(Beeta+1)*Re)
Ic=Beeta*Ib
Ie=Ic+Ib
#Results 
print " The Collector Current Ic =  ",round(Ic*1000,3),"mA"
print " The Base Current Ib  .",round(Ib*1000000,2),"microA"
print " The Emitter Current Ie = ",round(Ie*1000,3),"mA"

 The Collector Current Ic =   0.908 mA
 The Base Current Ib  . 9.08 microA
 The Emitter Current Ie =  0.917 mA

Example 7.8 Page No.239

In [4]:
Vcc=6        #V,collector bias junction volage
Vbe=0.3      #V base emittor voltage
Rc=50        #Ohms collector resistance
Rb=10*10**3  #Ohms base resistance
Re=100       #Ohms emittor resistance
Beeta1=50    # gain factor
Beeta2=200

#Calculation CASE-1: Minimum Emitter Current & corresponding Vce
Iemin=(Vcc-Vbe)*(Beeta1+1)/(Rb+(Beeta1+1)*Re)
Vcemin=Vcc-(Rc+Re)*Iemin
#Calculatioen CASE-2: Maximum Emitter Current & corresponding Vce
Iemax=(Vcc-Vbe)*(Beeta2+1)/(Rb+(Beeta2+1)*Re)
Vcemax=Vcc-(Rc+Re)*Iemax

#Results 
print"The Minimum Emitter Current Ie(min) is",round(Iemin*1000,2),"mA"
print "The Corresponding Vce =  V .",round(Vcemin,1),"v"
print "The Maximum Emitter Current Ie(max) = .",round(Iemax*1000,1),"mA"
print "The Corresponding Vce =  V .",round(Vcemax,1),"v"

The Minimum Emitter Current Ie(min) is 19.25 mA
The Corresponding Vce =  V . 3.1 v
The Maximum Emitter Current Ie(max) = . 38.1 mA
The Corresponding Vce =  V . 0.3 v

Example 7.9 Page No. 240

In [48]:
Vcc=6.0                         #V, collector bias junction voltage
Vbe=0.3                         #V, base emitter voltage
Rc=1*10**3                   #Ohms, collector resistance
Rb=10*10**3                 #Ohms, base resistance
Re=100.0                        #Ohms, emitter resistance
Beeta1=50                       #current gain factor
Beeta2=200
Ie1=19.25*10**(-3)                     #A,for beeta=50,  from example 7.8 
Ie2=38.2*10**(-3)                       #A,for beeta=200, from example 7.8

#Calculation  (i)

Ie1=19.25*10**(-3)                       #A,for beeta=50,  from example 7.8                       
Vce=Vcc-(Rc+Re)*Ie1                       #V, collector emitter voltage
Icsat1=Vcc/(Rc+Re)                       #collector saturated current
Vcesat1=0
print "The collector voltage is Vcc ",Vcc,"V"
print "The collector emitter voltage is Vce",Vce,"V"
print "Because Collector voltage is greater than collector emitter voltage so Transistor is  in saturation "
print "collector saturated current is ",round(Icsat1*10**3,2),"mA"
print "collector emitter satirated voltage is",Vcesat1,"V"

# ii
Icsat2=Icsat1
Vcesat2=Vcesat1
print "(ii) collector saturated current is ",round(Icsat2*10**3,3),"mA"
print "collector emitter satirated voltage is",Vcesat2,"V"

The collector voltage is Vcc  6.0 V
The collector emitter voltage is Vce -15.175 V
Because Collector voltage is greater than collector emitter voltage so Transistor is  in saturation 
collector saturated current is  5.45 mA
collector emitter satirated voltage is 0 V
(ii) collector saturated current is  5.455 mA
collector emitter satirated voltage is 0 V

Example 7.10 Page No.240

In [5]:
Vcc=9       #V,collector bias junction voltge
Vce=3       #V,collector emittor voltage
Re=500      #Ohms,emittor resistance
Ic=8*10**(-3) #A,collector current
Beeta=80
#Calculation
Ib=Ic/Beeta
Rb=(Vcc-(Beeta+1)*Ib*Re)/Ib
#Displaying The Results in Command Window
print"The Base Resistance is :",round(Rb/1000,5),"kohm"

The Base Resistance is : 49.5 kohm

Example 7.11 Page No.242

In [6]:
Vcc=12.0    #V collector bias junction voltage
Vbe=0.3     #V base emitter junction voltage
R1=40000.0    #Ohms resistance
R2=5000.0     #Ohms resistance
Re=1000.0     #Ohms emitter reistance
Rc=5000.0     #Ohms collector resistance
Beeta=60

#Calculation
Vb=(R2/(R1+R2))*Vcc
Ve=Vb-Vbe
Ie=Ve/Re
Ic=Ie
Vc=Vcc-Ic*Rc
Vce=Vc-Ve
# Results 
print" V2= Vb ",round(Vb,1),"v"
print" Ve =  ",round(Ve,1),"v"
print" Ie =  ",round(Ie/10**(-3),1),"mA"
print" Ic =  ",round(Ic/10**(-3),1),"mA"
print" Vc =  ",round(Vc,0),"v"
print" Vce = ",round(Vce,0),"v"

 V2= Vb  1.3 v
 Ve =   1.0 v
 Ie =   1.0 mA
 Ic =   1.0 mA
 Vc =   7.0 v
 Vce =  6.0 v

Example 7.12 Page No.243

In [7]:
Vcc=15.0 #V collector bias junction voltage
R1=200.0 #Ohms resistor 1
R2=100.0 #Ohms resistor 2
Rc=20.0  #Ohms collector resistace
Ic=.1    #A collector current

#Calculation
Ie=Ic
Vb=(R2/(R1+R2))*Vcc
Ve=Vb  # Neglecting Vbe
Re=Ve/Ie
Vce=Vcc-(Rc+Re)*Ic
# Results
print" The Emitter Resistance is Re =  .",Re,"ohm"
print" The Collector to Emitter Voltage is Vce =  ",Vce,"v"

 The Emitter Resistance is Re =  . 50.0 ohm
 The Collector to Emitter Voltage is Vce =   8.0 v

Example 7.13 Page No.246

In [8]:
Vcc=12.0     #V collector bias junction voltage
Vbe=0.3     #V base emitter voltage
R1=40000.0  #Ohms given resistance
R2=5000.0   #Ohms
Re=1000.9   #Ohms emitter resistance
Rc=5000.0   #Ohms collector resistance
Beeta=60
#Calculation
Vth=(R2/(R1+R2))*Vcc
Rth=R1*R2/(R1+R2)
Ib=(Vth-Vbe)/(Rth+Beeta*Re)
Ic=Beeta*Ib
Vce=Vcc-Ic*(Rc+Re)

# Results 
print "collector current is ",round(Ic*1000,2),"mA"
print "collector to emitter voltage =  ",round(Vce,2),"v"

collector current is  0.96 mA
collector to emitter voltage =   6.23 v

Example 7.14 Page No.248

In [9]:
Vcc=12      #V collector bias junction voltage
Vee=15.0     #V emittor bias junction voltage
Rc=5000.0   #Ohms collector resistance
Re=10000.0  #Ohms emitter resistance
Rb=10000.0  #Ohms base resistance
Beeta=100

#Calculation
Ie=Vee/Re
Ic=Ie
Vce=Vcc-Ic*Rc
#Displaying The Results in Command Window
print" Ic =  ",Ic/10**(-3),"mA"
print" Vce = ",Vce,"v"

 Ic =   1.5 mA
 Vce =  4.5 v