Chapter02:The 741 IC OP-AMP

Ex2.1:Pg-80

In [4]:
#Ex 2.1

# data from fig of Ex2.1
VCC=5.0;#V
IS=10**-14.0;#A
RS=39*1000.0;#ohm
VBE12=0.7;#V(Assumed)
VBE11=0.7;#V(Assumed)
VEE=-5;#V
IREF=(VCC-VBE12-VBE11-VEE)/RS*10**6;#micro A
print "Estimated input reference current , IREF(micro A)",round(IREF,2)
VT=25*10**-3;#V(Thermal Voltage)
VBE=VT*log(IREF*10**-6/IS);#V
IREF=(VCC-VBE-VBE-VEE)/RS*10**6;#micro A
print "More precise value of reference current , IREF(micro A)",round(IREF,2)
#Replacing Vcc by 15 V in the original design
VCC2=15.0;#V
VEE2=-15.0;#V
IREF=(VCC2-VBE-VBE-VEE2)/RS*10**6;#micro A
VBE=VT*log(IREF*10**-6/IS);#V
R5=(VCC-VBE-VBE-VEE)/(IREF*10**-6);#ohm
R5=round(R5/1000);#kohm
print "Value of R5(kohm) : ",R5

Estimated input reference current , IREF(micro A) 220.51
More precise value of reference current , IREF(micro A) 225.88
Value of R5(kohm) :  12.0

Ex2.2:Pg-81

In [5]:
#Ex 2.2
import math
# data from fig of Ex2.2
IC10=20*10**-6;#A
IREF=0.5*10**-3;#A
IS=10**-14;#A
VT=25*10**-3;#V(Thermal Voltage)
R4=VT/IC10*math.log(IREF/IC10);#ohm
print "For Widlar current source design, the value of R4(kohm) : ",round(R4/1000,2)

For Widlar current source design, the value of R4(kohm) :  4.02

Ex2.3:Pg-82

In [7]:
#Ex 2.3

import math
# given data
Gm1=10.0;#mA/V
Gm1=Gm1/1000;#A/V
Cc=50.0;#pF
Cc=Cc*10**-12;#F
Rt=10**8;#ohm(Shunting resistance with Cc)
 # solution
Ao=Gm1*Rt;#unitless
fp=1/(2*math.pi*Rt*Cc);#Hz
ft=Gm1/(2*math.pi*Cc)/10**6;#MHz
print "Frequency at which gain is maximum, fp in Hz",round(fp,1)
print "Unit gain frequency, ft(MHz)",round(ft,1)
#Bode plot can not be plotted with the given data in the question by using python functions. 

Frequency at which gain is maximum, fp in Hz 31.8
Unit gain frequency, ft(MHz) 31.8

Ex2.4:Pg-83

In [10]:
#Ex 2.4

import math
# given data
SR=10.0/10**-6;#V/s
Vout=10.0;#V(magnitude of output voltage)
fm=SR/(2*math.pi*Vout)/1000;#kHz
print "Full power bandwidth(kHz)",round(fm,1)
VT=25.0/1000;#V(Thermal voltage)
ft=SR/(2*math.pi*4*VT)/10.0**6;#MHz
print "Unity gain bandwidth(MHz)",round(ft,1)

Full power bandwidth(kHz) 159.2
Unity gain bandwidth(MHz) 15.9

Ex2.5:Pg-84

In [11]:
#Ex 2.5

VCC=5;#V
VEE=-5;#V
VBE=0.6;#V
VCE23=0.6;#V
VCE_sat=0.2;#V
Vo_max=VCC-VCE_sat-VBE;#V
Vo_min=VEE+VCE_sat+VBE+VCE23;#V
print "Maximum output voltage(V)",round(Vo_max,2)
print "Minimum output voltage(V)",round(Vo_min,2)

Maximum output voltage(V) 4.2
Minimum output voltage(V) -3.6