# Chapter 13 : Amplifier with negative feedback¶

## Example 13.1, Page No 547¶

In [1]:
import math
#initialisation of variables
Av=100000.0
B=1.0/100
print("when Av=100000")

#Calculations
Acl=Av/(1+Av*B)
print("when Av is 150000")
Av=150000
Acl=Av/(1+Av*B)

#Results
print("when Av is 50000")
Av=50000
Acl=Av/(1+Av*B)
print('The value of Acl= %.2f ' %(Acl))

when Av=100000
when Av is 150000
when Av is 50000
The value of Acl= 99.80


## Example 13.2, Page No 549¶

In [2]:
import math

#initialisation of variables
Rf2=560.0
Rf1=56.0*10**3
Av=100000.0
Zb=1.0*10**3
R1=68.0*10**3
R2=33.0*10**3

#Calculations
B=Rf2/(Rf2+Rf1)
Zi=(1+Av*B)*Zb
Zin=(Zi*R1*R2)/(R1*R2+R1*Zi+R2*Zi)

#Results
print("input impedance with negative feedback is %.2f ohm " %(Zin/10**3))

input impedance with negative feedback is 21.73 ohm


## Example 13.3 Page No 552¶

In [3]:
import math

#initialisation of variables

Zb=1.0*10**3
B=1.0/100
Av=5562.0
R1=68.0*10**3
R2=47.0*10**3
hoe=1.0/(50*10**3)
Rc=3.9*10**3

#Calculations
Zi=(1+Av*B)*Zb
Zin=(R1*R2*Zi)/(R1*R2+R2*Zi+R1*Zi)
Zo=(1/hoe)/(1+Av*B)
Zout=(Rc*Zo)/(Rc+Zo)

#Results
print(" circuit output impedance is %.2f ohm " %Zout)

 circuit output impedance is 720.04 ohm


## Example 13.4, Page No 554¶

In [4]:
import math
#initialisation of variables

Zb=1.0*10**3
hoe=1.0/(85*10**3)
Av=58000.0
Rf2=220.0
Rf1=16.2*10**3
R1=120.0*10**3
R2=39.0*10**3
R7=12.0*10**3

#Calculations
B=Rf2/(Rf2+Rf1)
print("voltage gain")
Acl=Av/(1+Av*B)
Zi=Zb*(1+Av*B)
Zin=(Zi*R1*R2)/(Zi*R1+R2*R1+R2*Zi)
Zo=(1/hoe)/(1+Av*B)
Zout=(R7*Zo)/(R7+Zo)

#Results
print("output impedance is %.2f ohm " %Zout)

voltage gain
output impedance is 108.25 ohm


## Example 13.5 Page No 558¶

In [5]:
import math
#initialisation of variables

Rf2=220.0
R4=3.9*10**3
Acl=75.0
f=100.0

#Calculations
Rf1=(Acl-1)*Rf2
Xc2=Rf2
C2=1/(2*3.14*f*Rf2)
Xcf1=Rf1/100
Cf1=1/(2*3.14*f*Xcf1)

#Results
print('The value of Cf1= %.2f mF' %(Cf1*10**6))

The value of Cf1= 9.78 mF


## Example 13.6 Page No 560¶

In [6]:
import math

#initialisation of variables
Acl=300.0
Rf2=220.0
R4=4.7*10**3
f=100.0

#Calculations
Rf1=(Acl-1)*Rf2
xc2=Rf2
C2=1.0/(2*3.14*f*Rf2)

#Results
print('The value of C2= %.2f mf' %(C2*10**6))

The value of C2= 7.24 mf


## Example 13.7, Page No 565¶

In [7]:
import math
#initialisation of variables

hfe=100.0
Vbe=0.7
Ic1=1.0*10**-3

#Calculations
Ic2=Ic1
Ic3=Ic2
Ic4=Ic3
Vee=10.0
Vce=3.0
Acl=33.0
print("different resistor value of circuit")
R1=Vbe/((10*Ic1)/hfe)
R3=(Vee-Vbe)/(Ic1+Ic2)
Vr2=Vee+Vbe-Vce
R4=Vr2/Ic1
R2=R4
R7=(Vr2-Vbe)/(Ic3+Ic4)
R8=Vee/Ic3
R6=6.8*10**3
R5=(Acl-1)*R6

#Results
print('The value of R5= %.2f  kohm' %(R5/1000))

different resistor value of circuit
The value of R5= 217.60  kohm


## Example 13.8 Page No 566¶

In [8]:
import math

#initialisation of variables
Av=25000.0
hie=2.0*10**3
hib=25.0
hoe=1.0/(100*10**3)
R6=6.8*10**3
R5=220.0*10**3
R1=R6

#Calculations
R8=10*10**3
B=R6/(R5+R6)
Acl=Av/(1+Av*B)
Zi=2*hie*(1+Av*B)
Zin=(Zi*R1)/(Zi+R1)
Zo=(1/hoe)/(1+Av*B)
Zout=(R8*Zo)/(R8+Zo)

#Results
print("output impedance is %.2f ohm " %Zout)

output impedance is 131.48 ohm


## Example 13.9 Page No 568¶

In [9]:
import math
#initialisation of variables

hic=2.0*10**3
hie=hic
hfe=100.0
hfc=100.0
Av=25000.0
B=1.0/33.4

#Calculations
R8=10*10**3
R5=R8
Ze=(hic+R8)/hfc
Zo=Ze/(1+Av*B)
Zout=(R5*Zo)/(R5+Zo)

#Results
print("output impedance is %.2fohm " %Zout)

output impedance is 0.16ohm


## Example 13.10 Page No 570¶

In [10]:
import math

#initialisation of variables
hfemin=100.0
hfemax=400.0
hiemin=2.0*10**3
hiemax=5.0*10**3
Rc=12.0*10**3
Rl=120.0*10**3
Re1=150.0

#Calculations
print(" voltage gain at extreme value ")
Avmax=(hfemax*((Rc*Rl)/(Rc+Rl)))/(hiemax+Re1*(1+hfemax))
Avmin=(hfemin*((Rc*Rl)/(Rc+Rl)))/(hiemin+Re1*(1+hfemin))

#Results
print("approximate voltage gain")
Av=((Rc*Rl)/(Rc+Rl))/Re1

 voltage gain at extreme value
approximate voltage gain


## Example 13.11, Page No 571¶

In [11]:
import math

#initialisation of variables
Av=70.0
f=100.0
rs=600.0
Rc=12.0*10**3
Rl=120*10**3
Re2=3.9*10**3
hie=2.0*10**3
hfe=100.0
R1=Rl
R2=39.0*10**3
Re1=150.0

#Calculations
Zb=hie+Re1*(1+hfe)
Zin=(R1*R2*Zb)/(R1*R2+R1*Zb+R2*Zb)
C1=1/(2*3.14*f*((Zin+rs)/10))
C2=1/(2*3.14*f*Re1)

#Results
print('The value of C2= %.2f mF ' %(C2*10**6))

The value of C2= 10.62 mF


## Example 13.12, Page No 573¶

In [12]:
import math
#initialisation of variables

Av=1000.0
f=100.0
hie=2.0*10**3
hfe=100.0
R8=12.0*10**3
Rl=120*10**3
R10=3.9*10**3
R6=Rl
R7=39.0*10**3

#Calculations
R3=R8
Av1=math.sqrt(Av)
Av2=Av1
R9=((R8*Rl)/(R8+Rl))/Av2
R9=330#use standard value
Av2=((R8*Rl)/(R8+Rl))/R9
Av1=Av/Av2
Zb=hie+R9*(1+hfe)
Zin=(R6*R7*Zb)/(R6*R7+R6*Zb+R7*Zb)
R4=((R3*Zin)/(R3+Zin))/Av1
R5=R10-R4

#Results
print('The value of R5= %.2f ' %(R5/1000))

The value of R5= 3.67


## Example 13.13, Page No 574¶

In [13]:
import math
#initialisation of variables

f=100.0
hie=2.0*10**3
hfe=100.0
R8=12.0*10**3
Rl=120.0*10**3
R10=3.9*10**3
R6=Rl
R7=39.0*10**3
R3=R8
R4=220.0
rs=600.0
Zin2=16.0*10**3
R9=330.0

#Calculations
Zb=hie+R4*(1+hfe)
Zin=(R1*R2*Zb)/(R1*R2+R1*Zb+R2*Zb)
C1=1.0/(2*3.14*f*((Zin+rs)/10))
Xc2=0.65*R4
C2=1.0/(2*3.14*f*Xc2)
C3=1.0/(2*3.14*f*((Zin2+R3)/10))
C4=1.0/(2*3.14*f*.65*R9)
C5=1.0/(2*3.14*f*((R8+Rl)/10))

#Results
print('The value of C5= %.2f mF ' %(C5*10**6))

The value of C5= 0.12 mF


## Example 13.14, Page No 580¶

In [14]:
import math
#initialisation of variables

hfe=100.0
hie=2.0*10**3
R4=100.0
R1=5.6*10**3
R6=2.2*10**3

#Calculations
Zi=hie+(1+hfe)*R4
print("open loop current gain")
Ai=(hfe*hfe*R1)/(R1+Zi)
B=R4/(R4+R6)
print("closed loop gain")
Acl=Ai/(1+Ai*B)
Zi=hie/(1+Ai*B)

#Results
print('The value of Zi= %.2f ohm ' %(Zi))

open loop current gain
closed loop gain
The value of Zi= 14.43 ohm


## Example 13.15, Page No 585¶

In [15]:
import math
#initialisation of variables

Av=60000.0
Acl=300.0
f1=15.0*10**3
B=1.0/300

#Calculations
f2=(Av*f1)/Acl
print("% distortion with NFB")
NFB=(.1/(1+Av*B))*100.0

#Results
print(" percenatge  distortion with NFB is %.3f percent " %NFB)

% distortion with NFB
percenatge  distortion with NFB is 0.050 percent