Chapter 8. Comparators and Converters

Example 8.1

In [26]:
#Example 8.1
#In the circuit of figure 8-4(a), R1=100 ohm,R2=56 kilo Ohm, Vin=V pp sine wave
#and the opamp is type 741 with supply voltages 15 V, -15 V.
#Determine the threshold voltages Vul and Vut and draw the output waveform.

from __future__ import division #to perform decimal division
%matplotlib inline
import math
import array
import numpy as np
#Variable declaration
R1=100
R2=56*10**3
vin=1                        #Input voltage in volt
pos_Vsat=14                  #Positive saturation voltage in volt
neg_Vsat=-14                 #Negative saturation voltage in volt
Vut=(R1/(R1+R2))*(pos_Vsat)  #Upper threshold voltage


#calculation
Vut=(R1/(R1+R2))*(pos_Vsat)  #Upper threshold voltage
Vlt=(R1/(R1+R2))*(neg_Vsat)  #Lower threshold voltage

t=np.arange(0,2*math.pi,0.1)
vut=0.5*np.sin(t)
subplot(211)
plt.plot(t,vut)
plt.ylabel('Vin')
plt.xlabel('t')
plt.title(r'$Input voltage$')

import matplotlib.pyplot as plt
t1=math.asin(0.025/0.5)
t2=math.pi-math.asin(-0.025/0.5)
t3=2*math.pi
x=[0,t1,t2,t3]
y=[-14,14,-14,14]
plt.subplot(212)
plt.step(x,y)                #Plotting square wave
plt.title('Output Waveform')
plt.xlabel('t')
plt.ylabel('Vo')

#result
plt.show()

Example 8.2

In [21]:
#Example 8.2
#In the circuit of figure 8-7(a), Vin=500 mV peak 60-Hz sinewave, R=100 ohm.
#IN3826 zener with Vz=5.1 V and the supply voltages= 15 V, -15V.
#Determine the output voltage swing.Assume that the  voltage drop across
#the forward biased zener=0.7V.

%matplotlib inline
from __future__ import division #to perform decimal division
import numpy as np
import matplotlib.pyplot as plt
import math
import array

#Variable declaration
vin=5*10**-3
R=100
Vd1=-0.7   # Output voltage during positive half-cycle of the input
Vd2=5.1    # Output voltage during negative half-cycle of the input

#calculation


t=np.arange(0,2*math.pi,0.1)
vut=0.5*np.sin(t)
subplot(211)
plt.plot(t,vut)
plt.ylabel('Vin')
plt.xlabel('t')
plt.title(r'$Input voltage$')




t1=math.pi
t2=2*math.pi
x=[0,t1,t2]
y=[-0.7,-0.7,5.1]
subplot(2,1,2)
plt.step(x,y)
plt.title('Output Waveform')
plt.xlabel('t')
plt.ylabel('Vo')

#result
print "#Since zener diode is forward biased"
print "Output voltage during positive half-cycle of the input is",Vd1,"V"
print "Output voltage during negative half-cycle of the input is",Vd2,"V" 
plt.show()

#Since zener diode is forward biased
Output voltage during positive half-cycle of the input is -0.7 V
Output voltage during negative half-cycle of the input is 5.1 V

Example 8.3

In [28]:
#Example 8.3
#The V..F converter of figure 8-12 is initially adjusted for a 10 kHz full scale
#output frequency.Determine the output frequencies Fo and Fo/2 if the output
#signal Vin=2 V.
%matplotlib inline
import matplotlib.pyplot as plt
from matplotlib.pyplot import subplot
from __future__ import division #to perform decimal division
import math
import array



#Variable declaration
Vin=2       # Input voltage
Fo1=2*10**3 # Output freq Fo when Vin=2V
Fo2=1*10**3 # Output freq Fo/2 when Vin=2V

#calculation
import array
v=array.array('i',(0 for i in range(0,50)))


count=1
for i in range(1,50):   #for 5 cycles
 if count<4:
    v[i]=5
 else:
    v[i]=0
 if count<10:
    count=count+1
 else:
    count=1


plt.subplot(211)
plt.plot(v)
plt.title('Output Waveform')
plt.xlabel('t(microsec)')
plt.ylabel('Pulse freq output,Fo(V)')

import matplotlib.pyplot as plt
for i in range(1,50):   #for 5 cycles
 if count<10:
    v[i]=5
 else:
    v[i]=0
 if count<20:
    count=count+1
 else:
    count=1

plt.subplot(2,1,2)
plt.plot(v)
plt.title('Output Waveform')
plt.xlabel('t(microsec)')
plt.ylabel('Pulse freq output,Fo(V)')
plt.show()

#result
print "Output freq Fo is ",Fo1,"Hz"
print "Output freq Fo/2 is",Fo2,"Hz"

Output freq Fo is  2000 Hz
Output freq Fo/2 is 1000 Hz

Example 8.4

In [4]:
#Example 8.4
#The F/V converterof figure 8-14(a) is initially adjusted for Vo=2.8V at Fin max
#of 10 kHz. Determine the output voltage Vo if fin= 1 kHz.

#Variable decclaration
Vo=2.8       #At Finmax of 10kHz

#Calculation
Vo1=Vo/10    #Output voltage at Fin=1kHz

#Result
print "Output voltage is",Vo1,"Volts"

Output voltage is 0.28 Volts

Example 8.5

In [27]:
#Example 8.5
#In the circuit of figure 8-25(a), Vin=200 mV peak to peak sine wave at 100 Hz.
#Briefly describe the operation of the circuit and draw the output waveform.
%matplotlib inline
import matplotlib.pyplot as plt
from __future__ import division #to perform decimal division
import numpy as np
import math
import array


#Variable declaration
Vin=100*10**-3           # Input voltage


#calculation

t=np.arange(0,math.pi,0.1)  #time scale
v=Vin*np.sin(t)

import matplotlib.pyplot as plt
plt.xlim(0,2*math.pi)
plt.ylim(0,0.1)
plt.plot(t,v)
plt.ylabel('Vin')
plt.xlabel('t')
plt.title(r'$Input voltage$')


#result
plt.show()