CHAPTER 4:ANALOG ELECTRONIC VOLT-OHM-MILLIAMMETER

Example 4-1, Page Number 88

In [1]:
import math

#Variable Declaration
Vcc=20              #Supply Voltage(V)
Rsm=9.3*10**3       #Rsm=Rs+Rm(ohm)
Im=1*10**-3         #Emitter Current(A)
hfe=100             #Transistor h parameter
Vb1=0.7             #Base Emitter Voltage drop(V)
#Calculation
#To obtain meter current when E=10V
E=10                #Base input voltage(V)
Ve=E-Vb1            #Emitter Voltage(V) found using KVL aclong base loop
Im=Ve/Rsm           #Emitter current 

#With the transistor
Ib=Im/hfe           #Base current is approximately equlat to Ie/hfe
Ri=E/Ib             #Input resistance with transistor

#Without transistor
Ri1=Rsm             #Input resistance without transistor

#Results

print "When E=10 V, meter current is",int(Im*10**3),"mA"
print 
print "Input Impedance,"
print "with transistor=",round(Ri/10**6),"mega ohm"
print "without transistor=",Ri1/10**3,"kilo ohm"

When E=10 V, meter current is 1 mA

Input Impedance,
with transistor= 1.0 mega ohm
without transistor= 9.3 kilo ohm

Example 4-2, Page Number 89

In [2]:
import math

#Variable Declaration

R2=3.9*10**3           #in ohm
R3=3.9*10**3           #in ohm
Vcc=12                 #in V
Vee=-12                #in V 
Vbe=0.7                #Base Emitter voltage in V

#Calculation 

#When E=0
E=0                         
Vr2=E-Vbe-Vee          #KVL 
Vr3=E-Vbe-Vee          #KVL
I2=Vr2/R2              #Ohm's Law
I3=I2               

print "When E=0V, I2=I3=",round(I3*10**3,1),"mA"

#When E=1
E=1                   #in V
Vp=0                  #in V
Ve1=E-Vbe             #KVL
Ve2=Vp-Vbe            #KVL
V=Ve1-Ve2             #KVL
print "When E=1V, meter circuit voltage(V)=",V,"V"

#When E=0.5
E=0.5                 #in V
Vp=0                  #in V
Ve1=E-Vbe             #KVL 
Ve2=Vp-Vbe            #KVL
V=Ve1-Ve2             #KVL  
print "When E=0.5, meter circuit voltage=",V,"V"

When E=0V, I2=I3= 2.9 mA
When E=1V, meter circuit voltage(V)= 1.0 V
When E=0.5, meter circuit voltage= 0.5 V

Example 4-3, Page Number: 93

In [6]:
import math

#Variable Declaration

E=7.5                      #in V
Vgs=-5                     #FET gate source voltage in V
Vp=5                       #in V
Rsm=1*10**3                #Rs+Rm in ohm
Im=1*10**-3                #in A
Ra=800*10**3               #in ohm
Rb=100*10**3               #in ohm
Rc=60*10**3                #in ohm
Rd=40*10**3                #in ohm

Eg=E*(Rc+Rd)/(Ra+Rb+Rc+Rd) #Voltage Divider Rule 
Vs=Eg-Vgs                  #KVL              

Ve1=Vs-Vbe                 #KVL 
Ve2=Vp-Vbe                 #KVL
V=Ve1-Ve2                  #KVL
Im=V/Rsm                   #Ohm's Law

print "Im is",round(Im*10**3,2),"which is",round(Im*10**3,2)*100,"% of full scale"
print "As the meter is in 10V range, 75% of full scale is",10*0.75,"V"

Im is 0.75 which is 75.0 % of full scale
As the meter is in 10V range, 75% of full scale is 7.5 V

Example 4-4, Page Number: 97

In [3]:
import math

#Variable Declaration

Im=100*10**-6            #Full scale current in A
Rm=10*10**3              #Meter resistance in ohm 
Ib=0.2*10**-6            #Op-amp input current in A
E=20*10**-3              #Maximum input in V

#Calculations

I4=1000*Ib               #Since I4>>Ib
Vout=Im*Rm               #Ohm's Law  

R3=E/I4                  #Ohm's Law  
R4=(Vout-E)/I4           #Ohm's Law

#Results

print "R3=",R3,"ohm"
print "R4=",round(R4*10**-3,1),"kilo ohm"

R3= 100.0 ohm
R4= 4.9 kilo ohm

Example 4-5, Page Number: 98

In [4]:
import math

#Variable Declaration
E=1.0                #in V
I=1*10**-3           #in A
Rm=100               #in ohm

R3=E/I               #Ohm's Law
Vo=I*(R3+Rm)         #Maximum Output voltage

print "R3=",R3/1000,"kilo Ohm"
print "Maximum voltage at output terminal=",round(Vo,1),"V"

R3= 1.0 kilo Ohm
Maximum voltage at output terminal= 1.1 V

Example 4-7, Page Number: 107

In [5]:
import math

#Variable Declaration

Iav=1*10**-3                          #in A 
Rm=1.2*10**3                          #in ohm
E=100*10**-3                          #in V

#With half wave rectifiers,
Ip=2*Iav/0.637                        #Using relation between Ip and Iav for HWR

#Peak value of Er3=input peak voltage
Ep=E/0.707                            #Relation between peak voltage and rms 
R3=Ep/Ip                              #in ohm
print "R3=",round(R3),"ohm"

#When E=50mV
E=50*10**-3                           #in V
Ep=E/0.707                            #Peak Voltage in V 
Ip=Ep/R3                              #Peak current in A 

Iav=0.637*Ip/2                        #Average Current in A

print "When input is 50mV, meter deflection is",round(Iav*10**3,1),"mA(half scale)"

R3= 45.0 ohm
When input is 50mV, meter deflection is 0.5 mA(half scale)