Chapter 6 : Voltage Regulators

Example 6.1 Page No.246

In [1]:
# Given data 

Veb = 1.0
beta = 15.0
Vc = 5.0
Io = 1.0   # for 7805 maximum value of I b is 1 Ampere 
R1 = 7.0
# Solution 

# for Load = 100ohms 

Rl = 100.0

Il=Ic=Ii = Vc/Rl
# voltage across R1
V1 = R1*(50*10**-3)
# for load = 5 ohms

Rl1 = 5.0
Il1 = Vc/Rl1
V12 = Il1 * Rl1 # Finding the Voltage drop across R1 when Rl = 5 Ohms 
# Finding the value of Io
Io = (Il1 + (beta*(Veb/R1)))/(beta + 1)
Ic = beta*(Io - (Veb/R1))

# for load = 1 Ohm

Rl2 = 1.0
Il2 = Vc/Rl2
# Finding the value of Io
Io1 = (Il2 + (beta*(Veb/R1)))/(beta + 1)
Ic1 = beta*(Io1 - (Veb/R1))

print " The value of load current when Rl = 100 ohms is =",int(Il*10**3),"mA"
print " The voltage across R1 when load is 100 ohms     =",int(V1*10**3),"mV"
print " The value of load current when Rl = 5 ohms      =",int(Il1),"A"
print " The voltage across R1 when load is 5 Ohms       =",int(V12),"V"
print " The value of output current when load is 5 ohms =",int(Io*10**3),"mA"
print " The value of collector current is               =",int(round(Ic*10**3)),"mA"
print " The value of output current when load is 1 Ohm  =",int(Io1*10**3),"mA"
print " The value of collector current is               =",round(Ic1,2),"A" 

 The value of load current when Rl = 100 ohms is = 50 mA
 The voltage across R1 when load is 100 ohms     = 350 mV
 The value of load current when Rl = 5 ohms      = 1 A
 The voltage across R1 when load is 5 Ohms       = 5 V
 The value of output current when load is 5 ohms = 196 mA
 The value of collector current is               = 804 mA
 The value of output current when load is 1 Ohm  = 446 mA
 The value of collector current is               = 4.55 A

Example 6.2 Page No.247

In [2]:
# Given data

Vo = 7.5
Iq = 4.2*10**-3
Ir1 = 25*10**-3
Vr = 5

# Solution 

R1 = Vr/Ir1
R2 = 2.5/(Ir1 + Iq)

# Displaying the outputs 

print "The value of R1 =",int(R1),"Ohms" 
print "The value of R2 =",int(R2),"Ohms"

The value of R1 = 200 Ohms
The value of R2 = 85 Ohms
In [ ]: