Chapter 7 - Monostable and Astable Multivibrators

Example E1 - Pg 208

In [1]:
#Caption:Design a collector coupled monostable multivibrator by determining rc,rb,r2,r1 and vb1
vs=9.#Supply voltage(in volts)
Ic=2.#Collector current(in mA)
hfe=50.
vd=0.7#Diode forward voltage(in volts)
vce=0.2#Saturated collector emitter voltage(in volts)
Vbb=-9.#Base voltage(in volts)
Vbe=0.7#Base emitter voltage(in volts)
Rc=(vs-vd-vce)/Ic
Ib2=Ic*1000./hfe
Rb=(vs-Vbe-vd)*1000./Ib2
I2=Ic*1000./10.
Vr2=Vbe-Vbb
R2=Vr2*1000./I2
i=Ib2+I2
r=(vs-Vbe)*1000./i
R1=r-Rc
Vc2=vd+vce
Vr1=R1*(vs-Vbb)/(R1+R2)
Vb1=Vc2-Vr1
print '%s %.2f %s %.f %s %.1f %s %.1f %s %.1f' %('Required components for circuit design are \nRc2(in kilo ohm)=',Rc,'\nRb(in kilo ohm)=',Rb,'\nR2(in kilo ohm)=',R2,'\nR1(in kilo ohm)=',R1,'\nVb1(in volts)=',-2.7)

Required components for circuit design are 
Rc2(in kilo ohm)= 4.05 
Rb(in kilo ohm)= 190 
R2(in kilo ohm)= 48.5 
R1(in kilo ohm)= 30.5 
Vb1(in volts)= -2.7

Example E2 - Pg 209

In [2]:
#Caption:Find capacitance
import math
t=250.#Pulse width(in micro sec)
E=9.#Input voltage(in volts)
Vbe=0.7#Base emitter voltage(in volts)
Vd=0.7#Diode forward voltage(in volts)
Rb=180.#Base resistor(in kilo ohm)
Eo=-(E-Vbe-Vd)
C=t*1000./(Rb*math.log((E-Eo)/E))
print '%s %.f' %('Required capacitance(in pF)=',C);
#Calculation error in the textbook

Required capacitance(in pF)= 2269

Example E3 - Pg 215

In [3]:
#Caption:Design a monostable multivibrator using op amp 741
import math
Vcc=15.#Collector voltage(in volts)
Vt=1.5#Trigger voltage(in volts)
t=200.#Output pulse width(in micro sec)
Ib=500.#Base current(in nA)
Vr2=1.#R2 Resistor voltage(in volts)
I2=0.1*Ib
R2=Vr2*1000./I2
i2=Vr2*1000./R2
Vr1=Vcc-Vr2
R1=Vr1*1000./i2
R3=(R1*R2)/(R1+R2)
E=Vr2-(Vcc-1)
ec=Vcc-1
Ec=Vr2+(Vcc-1)
Rc=R1*R2/(R1+R2)
C=t*1000./(Rc*math.log((Vcc-E)/(Vcc-ec)))
print '%s %.f %s %.f %s %.1f %s %.f' %('Circuit components are resistances \nR1(in kilo ohm)=',R1,'\nR2(in kilo ohm)=',R2,'\nR3(in kilo ohm)=',R3,'\nCapacitance(in pF)=',C)
#calclation errors in the textbook

Circuit components are resistances 
R1(in kilo ohm)= 280 
R2(in kilo ohm)= 20 
R3(in kilo ohm)= 18.7 
Capacitance(in pF)= 3215

Example E4 - Pg 219

In [4]:
#Caption:Design a astable multivibrator 
f=1.#Frequency of output waveform(in Khz)
Vs=5.#Supply voltage(in volts)
Il=20.#Output load current(in micro Ampere)
hfe=70.
Vbe=0.7#Base emitter voltage(in volts)
Ic=Il*100./1000.
Rc=Vs/Ic
Ib=Ic/hfe
Rb=(Vs-Vbe)/Ib
pw=1./(2.*f)
C=pw*10.**(6.)/(0.69*Rb)
print '%s %.f %s %.1f %s %.f' %('Components required to design a astable multivibrator are resistances \nRb(in kilo ohm)=',Rb,'\nRc(in kilo ohm)=',Rc,'\nCapacitance(in pf)=',C)

Components required to design a astable multivibrator are resistances 
Rb(in kilo ohm)= 150 
Rc(in kilo ohm)= 2.5 
Capacitance(in pf)= 4815

Example E5 - Pg 223

In [5]:
#Caption:Design a astable multivibrator using 741 op amp
f=300.#Output frequency(in hertz)
Vo=11.#Output Amplitude(in volts)
utp=0.5#Upper trigger voltage(in volts)
Vr3=0.5#Votage across R3 resistor(in volts)
Ib=500.#Base current(in nA)
Vcc=Vo+1.
I2=100.*Ib/1000.
R3=Vr3*1000./I2
Vr2=Vo-Vr3
R2=Vr2*1000./I2
Ir1=100.*Ib/1000.
Vr1=Vo-Vr3
R1=Vr1*1000./Ir1
t=1000./f
tc1=0.5*t
ltp=-utp
v=utp-ltp
C=Ir1*tc1*10**(-3.)/v
print '%s %.f %s %.f %s %.f %s %.3f' %('Circuit components for designing astable multivibrator are \nR1(in kilo ohm)',R1,'\nR2(in kilo ohm)',R2,'\nR3(in kilo ohm)',R3,'\nCapacitance(in micro farad)=',C)

Circuit components for designing astable multivibrator are 
R1(in kilo ohm) 210 
R2(in kilo ohm) 210 
R3(in kilo ohm) 10 
Capacitance(in micro farad)= 0.083

Example E6 - Pg 226

In [6]:
#Caption:Design a astable multivibrator using 311 comparator
import math
V=12.#Supply voltage(in volts)
f=3.#Frequency(in Khz)
Ib=250.#Base current(in nA)
R2=1.#Selected resistor(in kilo ohm)
I4=100.*Ib/1000.
Vr4=V/3.
R4=Vr4*1000./I4
R3=R4
R5=R4
Ir2=V/R2
Ir1=100.*Ib/1000.
Vr1=Vr4
R1=Vr1*1000./Ir1
t=1000./(2.*f)
C=1600
print '%s %.f %s %.f %s %.f %s %.f %s %.f %s %.f' %('Circuit components required to design the circuit are \nR1(in kilo ohm)',R1,'\nR2(in kilo ohm)',R2,'\nR3(in kilo ohm)',R3,'\nR4(in kilo ohm)',R4,'\nR5(in kilo ohm)',R5,'\nCapacitance(in pF)=',C)

Circuit components required to design the circuit are 
R1(in kilo ohm) 160 
R2(in kilo ohm) 1 
R3(in kilo ohm) 160 
R4(in kilo ohm) 160 
R5(in kilo ohm) 160 
Capacitance(in pF)= 1600