# Chapter 4- DC Biasing - BJTs¶

## Example-4.1 Page No-165¶

In [4]:
#from the given data:
Vcc=12.0                   #supply voltage in volts
Vbe=0.7                    #base emitter voltage in volts
Rb=240.0                   #base Resistance in kohm
B=50
Rc=2.2                     #collector resistance in kohm

#Calculation:
Ib=(Vcc-Vbe)/Rb            #base current in microA
Ic=B*Ib                    #collector current in mA
Vce=Vcc-Ic*Rc              #collector-emitter voltage in volts
Vb=Vbe                     #base volate in volts
Vc=Vce                     #collector voltage in volts
Vbc=Vb-Vc                  #bse-collector voltage in volts

print "a.Base current Ibq=",round(Ib*1000,2),"microA and Collector current Icq=",round(Ic,2),"mA"
print "b.Collector-Emitter voltage Vceq=",round(Vce,2),"V"
print "c.Base voltage Vb=",Vb,"V and Collector Voltage Vc=",round(Vc,2),"V"
print "d.Base-Collector voltage Vbcq=",round(Vbc,2),"V"

a.Base current Ibq= 47.08 microA and Collector current Icq= 2.35 mA
b.Collector-Emitter voltage Vceq= 6.82 V
c.Base voltage Vb= 0.7 V and Collector Voltage Vc= 6.82 V
d.Base-Collector voltage Vbcq= -6.12 V


## Example-4.2 Page No-167¶

In [2]:
#from the given data:
Vcc=12.0                   #supply voltage in volts
Rc=2.2                     #collector resistance in kohm

Icsat= Vcc/Rc              #saturation level
print "The current saturation level=",round(Icsat,2),"mA"

The current saturation level= 5.45 mA


## Example-4.3 Page No-170¶

In [10]:
#from the given figure:
Vcc=Vce=20.0               #supply anmd collector emitter voltage in volts
Ic=10                      #collector current in mA at Vce=0V
Vbe=0.7                    #base emitter voltage in Volts
Ib=0.025                   #base current in mA
#calculations:
Rc=Vcc/Ic
Rb=(Vcc-Vbe)/(Ib)
print "Collector Resistance=",Rc,"Kohm"
print "Base Resistance=",Rb,"Kohm"

Collector Resistance= 2.0 Kohm
Base Resistance= 772.0 Kohm


## Example-4.4 Page No-172¶

In [20]:
#from the given figure:
Vcc=20.0                   #supply voltage in volts
Rb=430.0                   #base Resistance in kohm
B=50
Rc=2.0                     #collector resistance in kohm
Re=1.0                     #emitter resistance in kohm

#calculation:

Ib=(Vcc-Vbe)/(Rb+(B+1)*Re)
Ic=B*Ib
Vce=Vcc-(Rc+Re)*Ic
Vc=Vcc-Ic*Rc
Ve=Vc-Vce
Vb=Vbe+Ve
Vbc=Vb-Vc

print "Base Current=",round(Ib*1000,2),"microA"
print "collector Current=",round(Ic,2),"mA"
print "Collector Emitter voltage=",round(Vce,2),"V"
print "Collector voltage=",round(Vc,2),"V"
print "emitter voltage=",round(Ve,2),"V"
print "Base voltage=",round(Vb,2),"V"
print "Base Collector voltage=",round(Vbc,2),"V"

Base Current= 40.12 microA
collector Current= 2.01 mA
Collector Emitter voltage= 13.98 V
Collector voltage= 15.99 V
emitter voltage= 2.01 V
Base voltage= 2.71 V
Base Collector voltage= -13.28 V


## Example-4.6 Page No-174¶

In [19]:
#from the given figure:
Vcc=20.0                   #supply voltage in volts
Rc=2.0                     #collector resistance in kohm
Re=1.0                     #emitter resistance in kohm

Icsat= Vcc/(Rc+Re)        #saturation level
print "The current saturation level=",round(Icsat,2),"mA"

The current saturation level= 6.67 mA


## Example-4.8 Page No-178¶

In [23]:
#from the given figure:
Vcc=22.0                   #supply voltage in volts
R1=39.0                    #base Resistance in kohm
R2=3.9                     #base Resistance in kohm
B=100
Rc=10.0                     #collector resistance in kohm
Re=1.5                      #emitter resistance in kohm
Vbe=0.7                    #base emitter voltage in Volts

#calculation:
Rth=(R1*R2)/(R1+R2)         #Thevenin resistance in kohm
Eth=(R2*Vcc)/(R1+R2)        #Thevenin voltage in Volts
Ib=(Eth-Vbe)/(Rth+(B+1)*Re)  #base current in microA
Ic=B*Ib                      #collector current in mA
Vce=Vcc-Ic*(Rc+Re)           #collector emitter voltage in Volts

print "collector Current=",round(Ic,2),"mA"
print "Collector Emitter voltage=",round(Vce,2),"V"

collector Current= 0.84 mA
Collector Emitter voltage= 12.36 V


## Example-4.10 Page No-180¶

In [24]:
#from the given figure:
Vcc=22.0                   #supply voltage in volts
R1=39.0                    #base Resistance in kohm
R2=3.9                     #base Resistance in kohm
B=50
Rc=10.0                     #collector resistance in kohm
Re=1.5                      #emitter resistance in kohm
Vbe=0.7                    #base emitter voltage in Volts

#calculation:
Rth=(R1*R2)/(R1+R2)         #Thevenin resistance in kohm
Eth=(R2*Vcc)/(R1+R2)        #Thevenin voltage in Volts
Ib=(Eth-Vbe)/(Rth+(B+1)*Re)  #base current in microA
Ic=B*Ib                      #collector current in mA
Vce=Vcc-Ic*(Rc+Re)           #collector emitter voltage in Volts

print "collector Current=",round(Ic,2),"mA"
print "Collector Emitter voltage=",round(Vce,2),"V"

collector Current= 0.81 mA
Collector Emitter voltage= 12.66 V


## Example-4.11 Page No-181¶

In [47]:
#from the given figure:
#EXACT ANALYSIS
Vcc=18.0                   #supply voltage in volts
R1=82.0                    #base Resistance in kohm
R2=22                      #base Resistance in kohm
B=50
Rc=5.6                      #collector resistance in kohm
Re=1.2                      #emitter resistance in kohm
Vbe=0.7                     #base emitter voltage in Volts

#calculation:
Rth=(R1*R2)/(R1+R2)         #Thevenin resistance in kohm
Eth=(R2*Vcc)/(R1+R2)        #Thevenin voltage in Volts
Ib=(Eth-Vbe)/(Rth+(B+1)*Re)  #base current in microA
Ic=B*Ib                      #collector current in mA
Vce=Vcc-Ic*(Rc+Re)           #collector emitter voltage in Volts

print "Exact Analysis:"
print "collector Current=",round(Ic,2),"mA"
print "Collector Emitter voltage=",round(Vce,2),"V\n"

print "Approximate Analysis:"
Vb=Eth=3.81                 #base voltage in volts
Vbe=0.7                     #base emitter voltage in Volts
Rc=5.6                      #collector resistance in kohm
Re=1.2                      #emitter resistance in kohm
Vcc=18.0                    #supply voltage in volts

#calculation:
Ve=Vb-Vbe                   #emitter voltage in volts
Ic=Ve/Re                    #collector current in mA
Vce=Vcc-((Ic*(Rc+Re)))      #collector emitter voltage in Volts

print "collector Current=",round(Ic,2),"mA"
print "Collector Emitter voltage=",round(Vce*10,2),"V"

Exact Analysis:
collector Current= 1.98 mA
Collector Emitter voltage= 4.55 V

Approximate Analysis:
collector Current= 2.59 mA
Collector Emitter voltage= 3.77 V


## Example-4.12 Page No-184¶

In [31]:
#from the given figure:
Vcc=10.0                   #supply voltage in volts
Rb=250                     #base Resistance in kohm
B=90
Rc=4.7                      #collector resistance in kohm
Re=1.2                      #emitter resistance in kohm
Vbe=0.7                     #base emitter voltage in Volts

#calculation:
Ib=(Vcc-Vbe)/(Rb+(Rc+Re)*B)  #base current in microA
Ic=B*Ib                      #collector current in mA
Vce=Vcc-Ic*(Rc+Re)           #collector emitter voltage in Volts

print "Collector Current=",round(Ic,2),"mA"
print "Collector Emitter voltage=",round(Vce,2),"V"

Collector Current= 1.07 mA
Collector Emitter voltage= 3.68 V


## Example-4.13 Page No-185¶

In [48]:
#from the given figure:
Vcc=10.0                   #supply voltage in volts
Rb=250                     #base Resistance in kohm
B=135
Rc=4.7                      #collector resistance in kohm
Re=1.2                      #emitter resistance in kohm
Vbe=0.7                     #base emitter voltage in Volts

#calculation:
Ib=(Vcc-Vbe)/(Rb+(Rc+Re)*B)  #base current in microA
Ic=B*Ib                      #collector current in mA
Vce=Vcc-Ic*(Rc+Re)           #collector emitter voltage in Volts

print "Collector Current=",round(Ic,2),"mA"
print "Collector Emitter voltage=",round(Vce,2),"V"

Collector Current= 1.2 mA
Collector Emitter voltage= 2.92 V


## Example-4.14 Page No-186¶

In [57]:
#from the given figure:
Vcc=18.0                   #supply voltage in volts
R1=91.0                   #base Resistance in kohm
R2=110.0                   #base Resistance in kohm
Rc=3.3                      #collector resistance in kohm
Re=0.51                    #emitter resistance in kohm
Vbe=0.7                     #base emitter voltage in Volts
B=75.0

#calculation:
Rb=R1+R2
Ib=(Vcc-Vbe)/(Rb+(Rc+Re)*B)  #base current in microA
Ic=B*Ib                      #collector current in mA
Vc=Vcc-Ic*(Rc)               #collector voltage in Volts

print "Base Current=",round(Ib*1000,2),"microA"
print "Collector voltage=",round(Vc,2),"V"

Base Current= 35.54 microA
Collector voltage= 9.2 V


## Example-4.16 Page No-188¶

In [65]:
#from the given figure:
Vee=20.0                   #emitter voltage in volts
Rb=240.0                   #base Resistance in kohm
Re=2.0                     #emitter resistance in kohm
Vbe=0.7                     #base emitter voltage in Volts
B=90.0

#calculation:
Ib=(Vee-Vbe)/(Rb+(B+1)*Re)  #base current in microA
Ie=(B+1)*Ib                 #emitter current in mA
Vce=Vee-Ie*Re               #collector emitter voltage in Volts

print "Base Current=",round(Ib*1000,2),"microA"
print "Collector voltage=",round(Vce,2),"V"

Base Current= 45.73 microA
Collector voltage= 11.68 V


## Example-4.17 Page No-190¶

In [86]:
#from the given figure:
Vcc=10.0                   #collector voltage in volts
Vee=4                      #emitter voltage in volts
B=60
Rc=2.4                     #collector resistance in kohm
Re=1.2                     #emitter resistance in kohm

#calculation:
Ie=(Vee-Vbe)/Re             #emitter current in mA
Ib=Ie/(B+1)                 #base current in microA
Vce=Vee+Vcc-Ie*(Rc+Re)      #collector emitter voltage in Volts
Vcb=Vcc-B*Ib*Rc              #collector base voltage in Volts

print "Emitter Current=",round(Ie,2),"mA"
print "Base Current=",round(Ib*1000,2),"microA"
print "Collector Emitter voltage=",round(Vce,2),"V"
print "Collector Base voltage=",round(Vcb,2),"V"

Emitter Current= 2.75 mA
Base Current= 45.08 microA
Collector Emitter voltage= 4.1 V
Collector Base voltage= 3.51 V


## Example-4.18 Page No-190¶

In [73]:
#from the given figure:
Vcc=20.0                   #supply voltage in volts
Rb=680.0                   #base Resistance in kohm
Rc=4.7                     #collector resistance in kohm
Vbe=0.7                     #base emitter voltage in Volts
B=120.0

#calculation:
Ib=(Vcc-Vbe)/(Rb+(Rc)*B)     #base current in microA
Ic=B*Ib                      #collector current in mA
Vce=Vcc-Ic*(Rc)               #collector emitter voltage in Volts
Vb=Vbe                        #Base voltage in Volts
Vc=Vce                        #collector voltage in Volts
Ve=0                          #emitter voltage in Volts
Vbc=Vb-Vc                     #base collector voltage in Volts

print "Base Current=",round(Ib*1000,2),"microA"
print "Collector Current=",round(Ic,2),"mA"
print "Collector emitter voltage=",round(Vce,2),"V"
print "Base Voltage=",Vb,"V"
print "Collector Voltage=",round(Vc,2),"V"
print "Emitter Voltage=",Ve,"V"
print "Base-collector Voltage=",round(Vbc,2),"V"

Base Current= 15.51 microA
Collector Current= 1.86 mA
Collector emitter voltage= 11.25 V
Base Voltage= 0.7 V
Collector Voltage= 11.25 V
Emitter Voltage= 0 V
Base-collector Voltage= -10.55 V


## Example-4.19 Page No-191¶

In [87]:
#from the given figure:
Vee=9                      #emitter voltage in volts
B=45
Rc=1.2                     #collector resistance in kohm
Rb=100.0                   #Base resistance in kohm

#calculation:
Ib=(Vee-Vbe)/Rb            #base current in microA
Ic=B*Ib                    #collecotr current in mA
Vc=-Ic*Rc                  #collector voltage in Volts
Vb=-Ib*Rb                  #base voltage in Volts

print "Collector voltage=",round(Vc,2),"V"
print "Base voltage=",round(Vb,2),"V"

Collector voltage= -4.48 V
Base voltage= -8.3 V


## Example-4.21 Page No-194¶

In [88]:
#from the given figure:
Vcc=20.0                   #supply voltage in volts
Ic=8.0                     #collector current in mA
Ib=40.0                    #base current in microA
Vbe=0.7                     #base emitter voltage in Volts

#calculation:
Rc=Vcc/Ic                   #Collector resistance in kohm
Rb=(Vcc-Vbe)/(Ib/1000)      #base resistance in kohm

print "Base resistance=",round(Rb,2),"kohm"
print "Collector resistance=",round(Rc,2),"kohm"

Base resistance= 482.5 kohm
Collector resistance= 2.5 kohm


## Example-4.22 Page No-196¶

In [85]:
#from the given figure:
Vcc=18.0                   #supply voltage in volts
R2=18.0                    #base Resistance in kohm
Re=1.2                     #emitter resistance in kohm
Vbe=0.7                     #base emitter voltage in Volts
Ic=2                        #collector current in mA

#calculation:
Ve=Ic*Re                   #emitter voltage in Volts
Vb=Vbe+Ve                  #base voltage in Volts
R1=((R2*Vcc)/(Vb))-R2      #base resistance in kohm
Vc=Vce+Ve                   #collector voltage in Volts
Rc=(Vcc-Vc)/Ic              #collector resistance in kohm

print "R1=",round(R1,2),"Kohm"
print "Rc=",round(Rc,2),"kohm"

2.4
R1= 86.52 Kohm
Rc= 2.18 kohm


## Example-4.26 Page No-201¶

In [90]:
#from the given figure:
Vcc=12                  #supply voltage in volts
Vbe=0.7                 #base emitter voltage in Volts
Rx=1.1                  #resistance in kohm

Ix=(Vcc-Vbe)/Rx
print "Mirrored current I=",round(Ix,2),"mA"

Mirrored current I= 10.27 mA


## Example-4.27 Page No-201¶

In [92]:
#from the given figure:
Vcc=6                   #supply voltage in volts
Vbe=0.7                 #base emitter voltage in Volts
Rx=1.3                  #resistance in kohm

Ix=(Vcc-Vbe)/Rx
print "Current I=",round(Ix,2),"mA"

Current I= 4.08 mA


## Example-4.29 Page No-204¶

In [94]:
#from the given figure:
Vz=6.2                  #diode voltage in volts
Vbe=0.7                 #base emitter voltage in Volts
Re=1.8                  #emitter resistance in kohm

I=(Vz-Vbe)/Re
print "Current I=",round(I,2),"mA"

Current I= 3.06 mA