# Chapter-17 PNPN and Other Devices¶

## Example-17.1(a) Page Number-854¶

In [76]:
#for the given circuit:
R1=50             #in Kohm
R2=0.1            #in Kohm
C=0.1             #in pF(capacitance)
V=12              #in volts
Ie=0              #in ampere
n=0.6              #intrinsic stand-off ratio
Rbb=5              #in Kohm

#we know, intrinsic stand-off ratio(n)=(Rb1/(Rbb))
Rb1=0.6*Rbb
Rb2=Rbb-Rb1

print"Value of Rb1 at Ie=0A is=",Rb1,"Kohm"
print"Value of Rb2 at Ie=0A is=",Rb2,"Kohm"

Value of Rb1 at Ie=0A is= 3.0 Kohm
Value of Rb2 at Ie=0A is= 2.0 Kohm


## Example-17.1(b) Page Number-854¶

In [75]:
#for the given circuit:
R1=50             #in Kohm
R2=0.1            #in Kohm
C=0.1             #in pF(capacitance)
V=12              #in volts
Ie=0              #in ampere
n=0.6              #intrinsic stand-off ratio
Rbb=5.0           #in Kohm

#The emitter firing potential Vp:
Vp=0.7+(((Rb1+R2)*12)/(Rbb+R2))

print "The emitter firing potential=",round(Vp,1),"V"

The emitter firing potential= 1.2 V


## Example-17.1(c) Page Number-854¶

In [74]:
V=12                    #in volts
Vv=1                    #in volts
Iv=10*(10**-3)          #in ampere
Ip=10*(10**-6)          #in ampere
Vp=8.0                    #in volts

limit1=(V-Vv)/Iv
limit2=(V-Vp)/Ip

if(R1>limit1,R1<limit2):
print "R1 is within the permissible range of values"
else:
print "R1 is not within the permissible range of values"

R1 is within the permissible range of values


## Example-17.1(d) Page Number-854¶

In [73]:
import math
#for the given circuit:
R1=50             #in Kohm
R2=0.1            #in Kohm
C=0.1             #in pF(capacitance)
V=12.0            #in volts
Rbb=5              #in Kohm
Rb1=100*(10**-3)    #in Kohm
Vp=8.0             #in volts

X=(V-Vv)/(V-Vp)             #temporary variable
T1=R1*C*(math.log(X))

T2=(Rb1+R2)*C*(math.log(Vp/Vv))
#Time period T:
T=T1+T2

#frequency of Oscillation F:
F=(1/T)*1000        #to convert the result in Hz
print "frequency of Oscillation=",round(F,1),"Hz"

frequency of Oscillation= 196.1 Hz


## Example-17.1(f) Page Number-854¶

In [72]:
#for the given circuit:
R2=0.1            #in Kohm
C=0.1             #in pF(capacitance)
V=12.0            #in volts
Rbb=5              #in Kohm
Rb1=100*(10**-3)    #in Kohm
Vp=8.0             #in volts

#During charging phase:
Vr2=(R2*V)/(R2+Rbb)
print "the value of Vr1 (during charging phase) is =",round(Vr2,2),"V"

#When Vc=Vp:
Vr2=(R2*(Vp-0.7))/(R2+Rb1)
print "the value of Vr2 (at Vc=Vp) is =",Vr2,"V"

the value of Vr1 (during charging phase) is = 0.24 V
the value of Vr2 (at Vc=Vp) is = 3.65 V


## Example-17.2 Page Number-862¶

In [71]:
#for the silicon PUT:
n=0.8
Vp=10.3              #in volts
Rb2=5                #in Kohm
Vd=0.7               #in volts
#we know, n=Rb2/(Rb1+Rb2)

Rb1=0.8*Rb2/0.2
print "The required value of Rb1=",round(Rb1,1),"Kohm"

#we know, Vp=n*Vbb+Vd
Vbb=(Vp-Vd)/n
print "The required value of Vbb=",Vbb,"V"

The required value of Rb1= 20.0 Kohm
The required value of Vbb= 12.0 V


## Example-17.3(a) Page Number-864¶

In [70]:
Vbb=12             #in volts
Rk=100             #in ohm
Rb1=10.0           #in Kohm
Rb2=5.0            #in Kohm
Vd=0.7             #in volts
#we know,
n=Rb1/(Rb1+Rb2)
Vp=n*Vbb+Vd

print "The required value of Vp=",Vp,"V"

The required value of Vp= 8.7 V


## Example-17.3(b) Page Number-864¶

In [69]:
#from the parameters given in the quesion:
Vbb=12             #in volts
Ip=100*(10**-6)    #in ampere
Vv=1               #in volts
Iv=5.5             #in mA
#calculating maximum value of Resistance R
Rmax=(Vbb-Vp)/Ip
print "The required value of Rmax=",Rmax/1000,"Kohm"

#calculating minimum value of Resistance R
Rmin=(Vbb-Vv)/Iv
print "The required value of Rmin=",Rmin,"Kohm"

The required value of Rmax= 33.0 Kohm
The required value of Rmin= 2.0 Kohm


## Example-17.3(c) Page Number-864¶

In [68]:
import math
#from the parameters given in the quesion:
R=20             #in Kohm
C=1              #in microF
Vbb=12           #in volts

x=Vbb/(Vbb-Vp)
#The reqired Timeperiod T:
T=R*C*round(math.log(x),2)

print "Time period of Oscillation=",T,"ms"
#The required Frequency F:
F=1/T
F=F*1000            #converting result into Hz
print "Frequency of Oscillation=",round(F,1),"Hz"

Time period of Oscillation= 25.8 ms
Frequency of Oscillation= 38.8 Hz