Chapter 8: Voltage Regulators

Example No. 8.1 Page No:362

In [1]:
#Variable Declaration:
Vo=15.0                 #Output voltage in volt
Vr=2.0                  #Ripple voltage in volt

#Calculations:
Vimin=Vo+3.0            #Calculating minimum input voltage  

Vi=Vimin + Vr/2.0       #Calculating input voltage

Vz=Vi/2.0               #Calculating zener voltage

Vz=10.0                 #Volatge in volt
Iz=20.0*10**-3          #Current in ampere

R1=(Vi-Vz)/Iz           #Calculating resistance value
 
I2=50.0*10**-6          #Current ampere
R2=(Vo-Vz)/I2           #Calculating Resistance value
R2=R2/1000.0            #Calculating resistance value

R3=Vz/I2                #Calculating resistance value
R3=R3/1000.0            #Calculating resistance value

Vcemax=Vi+Vr/2          #Calculating volatge

IE=50.0*10**-6          #Current in ampere
IL=50.0*10**-6          #Current in ampere

P=(Vi-Vo)*IL            #Calculating power           
P1=P*1000000.0          #Calculating power


#Results:
print('As Vz=%.1f, use Zener diode 1N758 for 10V'%Vz)
print('\nR1= %d ohm'%R1)
print('\nR2= %.1f kohm'%R2)
print('\nR3= %d kohm'%R3)
print('\nSelect C1= 50uF')
print('\nP= %.1f mW'%P1)
print('\nUse the transstor 2N718 for Q1')

As Vz=10.0, use Zener diode 1N758 for 10V

R1= 450 ohm

R2= 100.0 kohm

R3= 200 kohm

Select C1= 50uF

P= 200.0 mW

Use the transstor 2N718 for Q1

Example No. 8.2, Page No: 366

In [2]:
#Variable Declaration:
IL=0.25                #Current in ampere
Vr=5.0                 #Ripple voltage in volt

#Calculations:
R=Vr/IL                #Calculating value of resistance 
RL=10.0                #Calculating value of resistance
VL=IL*RL               #Calculating voltage

Vo=Vr+VL               #Calculating output voltage
Vdrop=2.0              #Voltage drop in volt
Vi=Vo+Vdrop            #Calculating voltage

#Results:
print('R= %d ohm'%R)
print('\nVo= %.1f V'%Vo)
print('\nVo= %.1f V'%Vi)

R= 20 ohm

Vo= 7.5 V

Vo= 9.5 V

Example No. 8.3, Page No: 368

In [1]:
#Variable Declaration:
VL=5.0                 #Voltage in volt
RL=100.0               #Resistance in ohm

#Calculations:
IL=VL/RL               #Calculating current 
IL1=IL*1000.0          #Calculating current
#Part A
R1=7.0                 #Resistance in ohm        
VR1=IL*R1              #Calculaing voltage drop across R1
VR1x=VR1*1000.0        #Calculatingvoltage drop across R1

#Part B
VLb=5.0                #Voltage in volt
RLb=2.0                #Resistance in ohm

ILb=VLb/RLb            #Calculating current

R1=7.0                 #Resistance in ohm           
VR1=ILb*R1             #Calculating voltage drop accross R1

Io=0.147               #Current in ampere     
Ic=ILb-Io              #Calculating current

#Results:
print('Part A')
print('\nLoad Current IL= %d mA'% IL1)
print('\nVoltage accross R1= %d mV'%VR1x)
print('\nAs voltage < 0.7V, Q1 is OFF')
print('\nHence IL=Io=Ii=50 mA')
print('\n\nPart B')
print('\nLoad Current IL= %.1f A'%ILb)
print('\nVoltage accross R1= %.1f V'%VR1)
print('\nAs voltage > 0.7V, Q1 is ON')
print('\nHence Ic= %.3f A'%Ic)

Part A

Load Current IL= 50 mA

Voltage accross R1= 350 mV

As voltage < 0.7V, Q1 is OFF

Hence IL=Io=Ii=50 mA


Part B

Load Current IL= 2.5 A

Voltage accross R1= 17.5 V

As voltage > 0.7V, Q1 is ON

Hence Ic= 2.353 A

Example No. 8.4, Page No: 371

In [4]:
#Variable Declaration:
R1=240.0                #Resistance in ohm
R2=2000.0               #Resistance in ohm
Iadj=50.0*10**-6        #Current in ampere
Vref=1.25               #Reference voltage in volt   

#Calculation:
Vo=(Vref*(1+R2/R1))+(Iadj*R2)  #Calculating output voltage

#Result:
print('Vo= %.2f V'%Vo)

Vo= 11.77 V

Example No. 8.5, Page NO:371

In [5]:
#Variable Declaration:
Iadjmax=100.0*10**-6          #Current in ampere
R1=240.0                      #Resistance in ohm
Vref=1.25                     #Reference voltage in volt 
 
#Calculations:
#First case: Vo=4
Vo=4.0                              #Voltage in volt
R2a1=(Vo-Vref)/(Vref/R1 + Iadjmax)  #Calculating value of resistance
R2a=R2a1/1000.0                     #Calculating value of resistance

#First case: Vo=12
Vo=12.0                             #Voltage in volt
R2b1=(Vo-Vref)/(Vref/R1 + Iadjmax)  #Calculating value of resistance
R2b=R2b1/1000.0                     #Calculating value of resistance

#Results:
print('\nR2= %.2f kohm'%R2a)
print('\nR2= %.2f kohm'%R2b)

R2= 0.52 kohm

R2= 2.03 kohm

Example No.8.6, Page No: 377

In [2]:
#Variable Declaration:
ILmax=0.5                 #Current in ampere

#Calculations:
#Part 1
Rsc=0.7/ILmax             #Calculting value of resistance

#Part 2
RL=100.0                  #Resistance in ohm
Vo=20.0                   #Voltage in volt

IL1=Vo/RL                  #Calculating current

#Part 3
RLn=10.0                 #Resistance in ohm

IL2=Vo/RLn                #Calculating current
Von=RLn*ILmax            #Calculating voltage

#Results:
print('Rsc= %.1f ohm'%Rsc)
print('\nIL= %.1f A'%IL1)
print('\nIL= %.1f A'%IL2)
print('\nSince IL > ILmax of 0.5A, current limiting will happen')
print('\nVo= %.1f V'%Von)

Rsc= 1.4 ohm

IL= 0.2 A

IL= 2.0 A

Since IL > ILmax of 0.5A, current limiting will happen

Vo= 5.0 V

Example No. 8.7, Page No: 378

In [3]:
#Variable Declaration:
R2=10000.0                #Resistance in ohm 
Vo=12.0                   #Output voltage in volt
Vref=7.15                 #Reference voltage

#Calculations:
R1=(Vo/Vref)*R2 - R2      #Calculating resistance value
R1a=R1/1000.0             #Calculating resistance value

#Result:
print('\nR1= %.2f kohm'%R1a)

R1= 6.78 kohm

Example No.8.8, Page NO: 380

In [4]:
#Variable Declaration:
Vref=7.15                #Reference voltage in volt
Vo=5.0                   #Output voltage in volt

#Calculations:
k=Vref/Vo                
k1=k-1

#For min voltage of 2V
Vom=2.0                  
km=Vref/Vom
km1=km-1.43

R1a=10000.0                #Resistance in ohm
R1b=2000.0                 #Resistance in ohm
 
R2=R1a/2.145               #Calculating resistance value
R2n=R2/1000.0              #Calculating resistance value

R1=6000.0                  #Resistance in ohm
R3=(R1*R2)/(R1+R2)         #Calculating resistance value
R3n=R3/1000.0              #Calculating resistance value

#Results:
print('(R1b+R2)/R2= %.2f'%k)
print('\nR1 = %.2f * R2'%k1)
print('\n(R1a+R1b+R2)/R2= %.3f'%km)
print('\nR1a = %.3f * R2'%km1)
print('\nR2= %.2f kohm'%R2n)
print('\nR3= %.2f kohm'%R3n)

(R1b+R2)/R2= 1.43

R1 = 0.43 * R2

(R1a+R1b+R2)/R2= 3.575

R1a = 2.145 * R2

R2= 4.66 kohm

R3= 2.62 kohm
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