# Chapter 4 , Junction Diode¶

## Example 4.1 , Page Number 103¶

In :
import math

#Variables

Io = 0.15 * 10**-6                 #Peak reverse biased current (in Ampere)
V = 0.12                           #Voltage (in volts)
VT = 26.0 * 10**-3                 #Volt-equivalent of temperature (in volts)

#Calculation

I = Io * (math.exp(V/VT)-1)        #Current flowing (in Ampere)

#Result

print "Current flowing through Germanium diode is ",round(I * 10**6)," micro-A."

Current flowing through Germanium diode is  15.0  micro-A.


## Example 4.2 , Page Number 103¶

In :
import math

#Variables

I = 10 * 10**-3                    #Forward biased current (in Ampere)
Io = 2.5 * 10**-6                  #Peak reverse biased current (in Ampere)
nVT = 2*26.0 * 10**-3              #Volt-equivalent of temperature (in volts)
n = 2                              #For Silicon

#Calculation

V = nVT*math.log(I/Io + 1)         #Forward Voltage (in volts)

#Result

print "Forward Voltage = ",round(V,2),"V."

Forward Voltage =  0.43 V.


## Example 4.3 , Page Number 103¶

In :
#Variables

ND = 10**21          #Donor concentration (in per cubic meter)
NA = 10**22          #Acceptor concentration (in per cubic meter)
De = 3.4 * 10**-3    #Diffusion constant for electron (in meter square per second)
Dh = 1.2 * 10**-3    #Diffusion constant for holes (in meter square per second)
Le = 7.1 * 10**-4    #Diffusion length for electrons (in meter)
Lh = 3.5 * 10**-4    #Diffusion length for holes (in meter)
ni = 1.6 * 10**16    #intrinsic concentration (in per cubic-meter)
e = 1.6 * 10**-19    #Charge on electron (in Coulomb)

#Calculation

Io_by_A =  (Dh/(Lh*ND) + De/(Le*NA))*e*ni**2     #Reverse saturation current density (in Ampere per meter-square)

#Result

print "Reverse saturation current density is ",round(Io_by_A * 10**6,2),"micro Ampere."

Reverse saturation current density is  0.16 micro Ampere.


## Example 4.4 , Page Number 107¶

In :
#Variables

I = 2 * 10**-3                   #Forward current (in Ampere)
VT = 25 * 10**-3                 #Volt equivalent of temperature (in Volts)
n = 1                            #eeta for the given semiconductor

#Calculation

r = n*VT/I                       #Dynamic resistance (in ohm)

#Result

print "Dynamic resistance = ",r," ohm."

Dynamic resistance =  12.5  ohm.


## Example 4.5 , Page Number 107¶

In :
import math

#Variables

VT = 26.0 * 10**-3             #Volt equivalent of temperature (in Volts)
V = 200 * 10**-3               #Voltage (in volts)
Io = 1.0 * 10**-6              #Reverse saturation current (in Ampere)
n = 1                          #For Germanium

#Calculation

r = n*VT/(Io*math.exp(V/(n*VT)))

#Result

print "A.C. resistance = ",round(r,2),"ohm."

A.C. resistance =  11.86 ohm.


## Example 4.6 , Page Number 108¶

In :
#Variables

Vo = 0.7                  #Barrier potential (in volts)
V = 5                     #Voltage (in volts)
R = 100                   #Resistance (in ohm)

#Calculation

I = (V-Vo)/R              #Current flowing through circuit (in Ampere)

#Result

print "Current flowing through the circuit is ",I,"A."

Current flowing through the circuit is  0.043 A.


## Example 4.7 , Page Number 109¶

In :
#Variables

Vo = 0.7                  #Barrier potential (in volts)
V = 15                    #Voltage (in volts)
R = 7.0 * 10**3           #Resistance (in ohm)

#Calculation

I = (V-2*Vo)/R              #Current (in Ampere)
VA = I * R                #Voltage drop (in volts)

#Result

print "Voltage drop across 7 ohm resistance is ",VA," V."

Voltage drop across 7 ohm resistance is  13.6  V.


## Example 4.8 , Page Number 109¶

In :
#Variables

V = 15                    #Voltage (in volts)
Vo = 0.3                  #Voltage across parallel connection (in volts)

#Calculation

VA = V - Vo               #Voltage drop (in volts)

#Result

print "Voltage drop = ",VA," V."

Voltage drop =  14.7  V.


## Example 4.9 , Page Number 110¶

In :
import math
import numpy
%matplotlib inline
from matplotlib.pyplot import plot,title,xlabel,ylabel,annotate

#Variables

VS = 10.0                   #Supply voltage (in volts)
RL = 160                    #Resistance (in ohm)

#Calculation

I = VS / RL                 #Current (in Ampere)

#Result

print "Current flowing is ",I * 10**3," mA."

#Graph

x = numpy.linspace(0,10)
plot(x,62.5 -62.5/10*x,'b')
title("VI Characteristics")
xlabel("Diode Voltage , v in volts")
ylabel("Diode Forward Current , I in A")

Current flowing is  62.5  mA.

Out:
<matplotlib.text.Annotation at 0x4deeef0> ## Example 4.11 , Page Number 120¶

In :
#Variables

V25 = 5                  #Initial voltage at 25 degree celsius (in volts)
V100 = 4.8               #Voltage at 100 degree celsius (in volts)
t1 = 25                  #Temperature (in celsius)
t2 = 100                 #Temperature (in celsius)

#Calculation

dVZ = V100 - V25         #Change in zener voltage (in volts)
dt = t2 - t1             #Change in temperature (in celsius)
tc = dVZ/(V25*dt)        #Temperature coefficient

#Result

print "Temperature coefficient is ",round(tc*100,4),"%."

Temperature coefficient is  -0.0533 %.


## Example 4.12 , Page Number 123¶

In :
#Variables

Vs = 12                         #Source voltage (in volts)
Vout = VZ = 8                   #Output voltage (in volts)
VRs = VS - Vout                 #Voltage across resistance in series (in volts)
RL = 10 * 10**3                 #Load resistance (in ohm)
Rs = 5 * 10**3                  #Resistance in series (in ohm)

#Calculation

IL = Vout/RL                    #Load current (in Ampere)
Is = (Vs-Vout)/Rs               #Current through series resistance (in Ampere)
IZ = Is - IL                    #Current through zener diode (in Ampere)

#Result

print "Output Voltage = ",Vout," V."
print "Voltage across Rs = ",Vs," V."
print "Current through series resistance = ",IZ," A."

Output Voltage =  8  V.
Voltage across Rs =  12  V.
Current through series resistance =  0  A.


## Example 4.13 , Page Number 123¶

In :
#Variables

Vout = VZ = 50              #Output voltage (in volts)
RL = 10.0 * 10**3           #Load resistance (in ohm)
VSmax = 120                 #Maximum voltage (in volts)
RS = 5.0 * 10**3            #Resistance in series (in ohm)
VSmin = 80                  #Minimum voltage (in volts)

#Calculation

IL = Vout / RL              #Load current (in Ampere)
ISmax = (VSmax - Vout)/RS   #Maximum series current (in Ampere)
IZmax = ISmax - IL          #Maximum zener current (in Ampere)
ISmin = (VSmin - Vout)/RS   #Minumum series current (in Ampere)
IZmin = ISmin - IL          #Minimum zener current (in Ampere)

#Result

print "Maximum value of zener diode current is ",IZmax * 10**3," mA.\nMinimum value of zener diode current is ",IZmin * 10**3," mA."

Maximum value of zener diode current is  9.0  mA.
Minimum value of zener diode current is  1.0  mA.


## Example 4.14 , Page Number 123¶

In :
#Variables

IZK = 6 * 10**-3               #Minimum zener current (in Ampere)
ILmax = 20.0 * 10**-3          #Maximum load current (in Ampere)
VS = 20                        #Source voltage (in volts)
Vout = 15                      #Output voltage (in volts)

#Calculation

RS = (VS - Vout)/(IZK + ILmax) #Series resistance (in ohm)

#Result

print "Series resistance is ",round(RS,1)," ohm."
print "When the load current will decrease and become 10 mA, the zener current will increase and become 6 + 10 i.e. 16 mA. Thus the current through the series resistance RS will remain unchanged as 6 + 20 i.e. 26 mA. Thus voltage drop in series resistance RS will remain constant. Consequently the output voltage (Vout = VS - IS*RS) will also remain constant."

Series resistance is  192.3  ohm.
When the load current will decrease and become 10 mA, the zener current will increase and become 6 + 10 i.e. 16 mA. Thus the current through the series resistance RS will remain unchanged as 6 + 20 i.e. 26 mA. Thus voltage drop in series resistance RS will remain constant. Consequently the output voltage (Vout = VS - IS*RS) will also remain constant.


## Example 4.15 , Page Number 124¶

In :
#Variables

VL = VZ = 50.0              #Output voltage (in volts)
VS = 120.0                  #Source voltage (in volts)
RL = 10.0 * 10**3           #Load resistance (in ohm)
RS = 5.0 * 10**3            #Resistance in series (in ohm)

#Calculation

VRS = VS - VZ               #Voltage across resistance in series (in volts)
IL = VL/RL                  #Load current (in Ampere)
IS = VRS / RS               #Current through resistance in series (in Ampere)
IZ = IS - IL                #Current through zener diode (in Ampere)

#Result

print "The output voltage is ",VL," V."
print "Voltage drop across RS is ",VRS," V."
print "Current through zener is ",IZ * 10**3," mA."

The output voltage is  50.0  V.
Voltage drop across RS is  70.0  V.
Current through zener is  9.0  mA.


## Example 4.16 , Page Number 124¶

In :
#Variables

VS = 16.0                   #Source voltage (in volts)
RL = 1.2 * 10**3            #Load resistance (in ohm)
RS = 1.0 * 10**3            #Resistance in series (in ohm)

#Calculation

VL = VS * RL/(RS + RL)      #Voltage across load (in volts)
IZ = 0                      #Current through zener diode (in Ampere)
PZ = VZ*IZ                  #Power across zener diode (in Ampere)

#Result

print "VL = ",round(VL,2)," V."
print "IZ = ",IZ," A."
print "PZ = ",PZ," W."

VL =  8.73  V.
IZ =  0  A.
PZ =  0.0  W.


## Example 4.17 , Page Number 124¶

In :
#Variables

Vin = 20                   #input voltage (in volts)
RS = 220.0                 #Series resistance (in ohm)
VZ = 10                    #Zener voltage (in volts)
RL1 = 200                  #Load resistance1 (in ohm)
RL2 = 50                   #Load resistance2 (in ohm)
PZmax = 400 * 10**-3       #Power (in watt)

#Calculation

VL1 = Vin*RL1/(RS + RL1)   #Voltage across load1 (in volts)
IL1 =IR=Vin/(RS + RL1)     #Load1 current (in Ampere)
IZ1 = 0                    #Zener current 1 (in Ampere)
VL2 = Vin*RL2/(RS + RL2)   #Voltage across load2 (in volts)
IL2 =IR=Vin/(RS + RL2)     #Load2 current (in Ampere)
IZ2 = 0                    #Zener current 2 (in Ampere)

#Result

print "VL1 = ",round(V,2)," V."
print "IL1 = ",round(IL1*10**3,2),""
print "IZ1 = ",IZ1," A."
print "IR1 = ",round(IL1*10**3,2)," A."

print "VL2 = ",round(VL2,1)," V."
print "IL2 = ",round(IL2*10**3,2)," A."
print "IZ2 = ",IZ2," A."
print "IR2 = ",round(IL2*10**3,2)," A."

VL1 =  15.0  V.
IL1 =  47.62
IZ1 =  0  A.
IR1 =  47.62  A.
VL2 =  3.7  V.
IL2 =  74.07  A.
IZ2 =  0  A.
IR2 =  74.07  A.


## Example 4.18 , Page Number 125¶

In :
#Variables

VS = 100              #Source voltage (in volts)
VL = VZ = 50          #Voltage across load (in volts)
V = 10.0/(10 + 5)     #Voltage (in volts)

#Calculation

VR = VS - VL          #Voltage across resistance using KVL (in volts)

#Result

print "Voltage drop across 5 kilo-ohm resistor is ",VR," V."

Voltage drop across 5 kilo-ohm resistor is  50  V.


## Example 4.19 , Page Number 125¶

In :
#Variables

V = 12                 #Voltage (in volts)
R = 120                #Resistance (in ohm)
VDCmin = 15            #Minimum dc voltage (in volts)
VZ = 12                #Zener voltage (in volts)
VDCmax = 19.5          #Maximum dc voltage (in volts)
IZmin = 20 * 10**-3    #Minimum current through zener (in Ampere)
IL = 100 * 10**-3      #Current through load (in Ampere)
IZmax = 200 * 10**-3   #Maximum current through zener (in Ampere)

#Calculation

VSmin = VDCmin - VZ    #Minimum voltage across Ri (in volts)
VSmax = VDCmax - VZ    #Maximum voltage across Ri (in volts)
ISmin = IZmin + IL     #Minimum current through Ri (in Ampere)
Rimin = VSmin/ISmin    #Resistance Ri1 (in ohm)
ISmax = IZmax + IL     #Minimum current through Ri (in Ampere)
Rimax =VSmax/ISmax     #Resistance Ri2 (in ohm)

#Result

print "Ri for minimum voltage is ",Rimin," ohm."
print "Ri for maximum voltage is ",Rimax," ohm."

Ri for minimum voltage is  25.0  ohm.
Ri for maximum voltage is  25.0  ohm.


## Example 4.20 , Page Number 126¶

In :
#Variables

Vi = 50.0                #Voltage (in volts)
R = 1.0 * 10**3          #Resistance (in ohm)
VZ = 10.0                 #Voltage across zener (in volts)
IZmax = 32.0 * 10**-3    #Maximum current across zener (in Ampere)
IZmin = 0.0              #Minimum current across zener (in Ampere)

#Calculation

IR = (Vi - VZ)/R         #Supply current (in Ampere)
ILmax = IR - IZmin       #Maximum load current (in Ampere)
RLmin = VZ/ILmax         #Minimum corresponding load resistance (in ohm)
ILmin = IR - IZmax       #Minimum load current (in Ampere)
RLmax = VZ/ILmin         #Maximum corresponding load resistance (in ohm)

#Result

print "Range of RL : From ",RLmin,"ohm to ",RLmax*10**-3," kilo-ohm."
print "Range of IL : From ",ILmin* 10**3," mA to ",ILmax*10**3," mA."

Range of RL : From  250.0 ohm to  1.25  kilo-ohm.
Range of IL : From  8.0  mA to  40.0  mA.