# Chapter 6 Common-Emitter Approximations¶

## Example 6.2 Page No 153¶

In [2]:
# given data
R1= 10.0##  Ω
R2= 10010##  Ω
V1= 10##  V
# The total voltage across the 10 Ω resistance
V= R1/R2*V1##  V
V= V*10**3##  mV
print "The total voltage across the 10 Ω resistance = %.2f mV is :"%V

The total voltage across the 10 Ω resistance = 9.99 mV is :


## Example 6.3 Page No 156¶

In [3]:
# given data
R= 10*10**3##  Ω
V_CC= 15##  V
V_BE= 0.7##  V
Vt= 25*10**-3##  V
Vp= 1*10**-3##  V
I= (V_CC-V_BE)/R##  A
r_ac= Vt/I##  Ω
# The total current through diode
Ip= Vp/r_ac##  A
Ip= Ip*10**6##  µA
print "The total current through diode = %.2f µA"%Ip

The total current through diode = 57.20 µA


## Example 6.4 Page No 162¶

In [4]:
# given data
R1= 47*10**3##  Ω
R2= 15*10**3##  Ω
R_E= 8.2*10**3##  Ω
R_C= 10*10**3##  Ω
R3= 3.3*10**3##  Ω
bita= 200#
V_CC= 30##  V
V_BE= 0.7##  V
Vin= 5*10**-3##in V
Vt= 25*10**-3##  V
V2= R2*V_CC/(R1+R2)##  V
# DC voltage across emitter
V_E= V2-V_BE##  V
# Emitter current
I_E= V_E/R_E##  A
r_desh_e= Vt/I_E##  Ω
r_L= R_C*R3/(R_C+R3)##in Ω
A= r_L/r_desh_e#
# The output voltage
Vout= A*Vin##  V
Zin_base= bita*r_desh_e##  Ω
# The input impedance of amplifier
Zin= R1*R2*Zin_base/(R2*Zin_base+R1*Zin_base+R1*R2)##  Ω
Vout= Vout*10**3##  mV
Zin= Zin*10**-3##  k ohm
print "The output voltage = %.2f mV"%Vout
print "The input impedance of amplifier = %.2f kΩ"%Zin

The output voltage = 381.26 mV
The input impedance of amplifier = 4.14 kΩ


## Example 6.5 Page No 163¶

In [5]:
# given data
R1= 10*10**3##  Ω
R2= 2.2*10**3##  Ω
R_C= 3.6*10**3##  Ω
V_CC= 10##  V
I_C= 1.1*10**-3##  A
# The base voltage
V_B= R2*V_CC/(R1+R2)##  V
# The collector voltage
V_C= V_CC-I_C*R_C##  V
print "The base voltage = %.2f V"%V_B
print "The collector voltage = %.2f V"%V_C

The base voltage = 1.80 V
The collector voltage = 6.04 V


## Example 6.6 Page No 164¶

In [6]:
# given data
V2= 1.1##  V
Vin= 1*10**-3##  V
Vt= 25*10**-3##  V
R2= 1*10**3##  Ω
R_C= 3.6*10**3##  Ω
I_E= V2/R2##  A
# Emitter diode ac resistance
r_desh_e= Vt/I_E##  Ω
A= R_C/r_desh_e#
# The output voltage
Vout= A*Vin##  V
Vout= Vout*10**3##  mV
print "The output voltage = %.2f mV"%Vout

The output voltage = 158.40 mV


## Example 6.7 Page No 167¶

In [8]:
# given data
R_C= 10*10**3##  Ω
R_L= 82*10**3##  Ω
r_E= 1*10**3##  Ω
r_desh_e_min= 50##  Ω
r_desh_e_max= 100##  Ω
r_L= R_C*R_L/(R_C+R_L)##  Ω
# The minimum voltage gain
A_min= r_L/r_desh_e_max#
# The maximum voltage gain
A_max= r_L/r_desh_e_min#
print "The minimum voltage gain = %.2f"%A_min
print "The maximum voltage gain = %.2f"%A_max

The minimum voltage gain = 89.00
The maximum voltage gain = 178.00


## Example 6.8 Page No 169¶

In [9]:
# given data
bita= 200#
R1= 47*10**3##  Ω
R2= 15*10**3##  Ω
r_E=  1*10**3##  Ω
r_desh_e= 50##  Ω
Zin_base= bita*(r_E+r_desh_e)##  Ω
# The input impedance of the amplifier
Zin= R1*R2*Zin_base/(R1*R2+R1*Zin_base+R2*Zin_base)##  Ω
Zin= Zin*10**-3##  k ohm
print "The input impedance of the amplifier = %.2f kΩ"%Zin

The input impedance of the amplifier = 10.79 kΩ


## Example 6.9 Page No 171¶

In [10]:
# given data
bita= 150#
R1= 10*10**3##  Ω
R2= 2.2*10**3##  Ω
R_E= 1*10**3##  Ω
V_CC= 10##  V
V_BE= 0.7##  V
Vt= 25*10**-3##  V
V_B= R2*V_CC/(R1+R2)##  V
V_E= V_B-V_BE##  V
# The emitter current,
I_E= V_E/R_E##  A
r_desh_e= Vt/I_E##  Ω
Zin_base= bita*r_desh_e##  Ω
# The input impedance of each stage
Zin= R1*R2*Zin_base/(R1*R2+R1*Zin_base+R2*Zin_base)##  Ω
Zin= Zin*10**-3##  k ohm
print "The input impedance of each stage = %.2f kΩ"%Zin

The input impedance of each stage = 1.18 kΩ


## Example 6.10 Page No 172¶

In [11]:
# given data
bita= 150#
R1= 10*10**3##  Ω
R2= 2.2*10**3##  Ω
R_E= 1*10**3##  Ω
Rs= 1*10**3##  Ω
R_C= 3.6*10**3##  Ω
R_L= 1.5*10**3##  Ω
V_CC= 10##  V
V_BE= 0.7##  V
Vt= 25*10**-3##  V
Vin= 1*10**-3##  V
V_B= R2*V_CC/(R1+R2)##  V
V_E= V_B-V_BE##  V
I_E= V_E/R_E##  A
r_desh_e= Vt/I_E##  Ω
Zin_base= bita*r_desh_e##  Ω
Zin= R1*R2*Zin_base/(R1*R2+R1*Zin_base+R2*Zin_base)##  Ω
Vb1= Zin*Vin/(Rs+Zin)##  V
r_L= R_C*Zin/(R_C+Zin)##  Ω
V_B= R2*V_CC/(R1+R2)##  V
V_E= V_B-V_BE##  V
I_E= V_E/R_E##  A
r_desh_e= Vt/I_E##  Ω
A1= r_L/r_desh_e#
Vb2= A1*Vb1##  V
r_L= R_C*R_L/(R_C+R_L)##  Ω
A2= r_L/r_desh_e#
# The ac output voltage across the final load resistor
Vout= A2*Vb2##  V
A= A1*A2#
Vout= A*Vb1##  V
print "The ac output voltage across the final load resistor = %.2f volts"%Vout

The ac output voltage across the final load resistor = 0.99 volts


## Example 6.11 Page No 173¶

In [12]:
# given data
bita= 150#
R1= 10*10**3##  Ω
R2= 2.2*10**3##  Ω
R_C= 3.6*10**3##  Ω
Rs= 1*10**3##  Ω
R_L= 1.5*10**3##  Ω
r_E= 180##  Ω
R_E= 1*10**3##  Ω
V_CC= 10##  V
V_BE= 0.7##  V
Vt= 25*10**-3##  V
Vin= 1*10**-3##  V
V_B= R2*V_CC/(R1+R2)##  V
V_E= V_B-V_BE##  V
I_E= V_E/R_E##  A
r_desh_e= Vt/I_E##  Ω
Zin_base= bita*(r_desh_e+r_E)##  Ω
Zin= R1*R2*Zin_base/(R1*R2+R1*Zin_base+R2*Zin_base)##  Ω
r_L= R_C*Zin/(R_C+Zin)##  Ω
A1= r_L/(r_E+r_desh_e)#
r_L= R_C*R_L/(R_C+R_L)##  Ω
A2= r_L/(r_desh_e+r_E)#
A= A1*A2#
Vb1= Zin*Vin/(Rs+Zin)##  V
# The ac voltage at the final output
Vout= A*Vb1##  V
Vout= Vout*10**3##  mV
print "The ac voltage at the final output = %.2f mV"%Vout

The ac voltage at the final output = 18.77 mV