6: Semiconductors

Example number 6.1, Page number 133

In [4]:
#importing modules
import math
from __future__ import division

#Variable declaration
V1=1.4;       #voltage1(V)
V2=1.5;       #voltage2(V)
I1=60;        #forward current for 1.4V(mA)
I2=85;        #forward current for 1.5V(mA)

#Calculation
I1=I1*10**-3;      #forward current for 1.4V(A)
I2=I2*10**-3;      #forward current for 1.5V(A)
Rs1=V1/I1;         #static resistance for 1.4V(ohm)
Rs2=V2/I2;         #static resistance for 1.5V(ohm) 
dV=V2-V1;          #change in voltage(V)
dI=I2-I1;          #change in current(A)
Rd=dV/dI;          #dynamic resistance(ohm)

#Result
print "static resistance for 1.4V is",round(Rs1,1),"ohm"
print "static resistance for 1.5V is",round(Rs2,1),"ohm"
print "dynamic resistance is",Rd,"ohm"
print "answer for dynamic resistance given in the book is wrong"

static resistance for 1.4V is 23.3 ohm
static resistance for 1.5V is 17.6 ohm
dynamic resistance is 4.0 ohm
answer for dynamic resistance given in the book is wrong

Example number 6.2, Page number 134

In [1]:
#importing modules
import math
from __future__ import division

#Variable declaration
IE=1;       #emitter current(mA)
IB=0.02;     #base current(mA)

#Calculation
IC=IE-IB;      #collector current(mA)
beta=IC/IB;       #value of beta
alpha=IC/IE;      #value of alpha

#Result
print "value of beta is",beta
print "value of alpha is",alpha

value of beta is 49.0
value of alpha is 0.98

Example number 6.3, Page number 134

In [2]:
#importing modules
import math
from __future__ import division

#Variable declaration
alpha=0.99;        #value of alpha
I_CBO=0.5;         #value of ICBO(micro A)

#Calculation
beta=alpha/(1-alpha);         #value of beta
ICEO=1/(1-alpha)*I_CBO;      #value of ICEO(micro A)

#Result
print "value of beta is",beta
print "value of ICEO is",ICEO,"micro A"

value of beta is 99.0
value of ICEO is 50.0 micro A

Example number 6.4, Page number 134

In [3]:
#importing modules
import math
from __future__ import division

#Variable declaration
delta_Ic=4.5-2;         #change in collector current(mA)
delta_Ib=80-40;         #change in base current(microA)

#Calculation
delta_Ic=delta_Ic*10**-3;        #change in collector current(A)
delta_Ib=delta_Ib*10**-6;        #change in base current(A)
beta_AC=delta_Ic/delta_Ib;       #value of beta
alpha_AC=beta_AC/(1+beta_AC);    #value of alpha

#Result
print "value of beta is",beta_AC
print "value of alpha is",round(alpha_AC,4)

value of beta is 62.5
value of alpha is 0.9843

Example number 6.5, Page number 134

In [4]:
#importing modules
import math
from __future__ import division

#Variable declaration
IE=1;          #emitter current(mA)
Oc=0.04;       #output current(mA)

#Calculation
IC=1-Oc;       #collector current(mA)
alpha=IC/IE;      #value of alpha

#Result
print "current gain is",alpha

current gain is 0.96

Example number 6.6, Page number 134

In [5]:
#importing modules
import math
from __future__ import division

#Variable declaration
alpha=0.96;         #current gain
R=1;          #resistance(K ohm)
V=1.5;              #voltage drop(V)

#Calculation
IC=V/R;        #collector current(mA)
IE=IC/alpha;      #emitter current(mA)
IB=IE-IC;         #base current(mA)

#Result
print "base current is",IB,"mA"

base current is 0.0625 mA