# Chapter 4 - Biolar junction & Field Effect Transistors¶

## Exa 4.1 page 195¶

In [1]:
#given data :
VGS=10 #in Volt
IG=0.001 #in uAmpere
IG=IG*10**-6 #in Ampere
RGS=VGS/IG #in Ohm
print "Resistance between gate and source = %0.2f Mohm "%(RGS*10**-6)

Resistance between gate and source = 10000.00 Mohm


## Exa 4.2 page 195¶

In [2]:
#given data :
delVDS=1.5 #in Volt
delID=120 #in uAmpere
delID=delID*10**-6 #in Ampere
rd=delVDS/delID #in Ohm
print "AC drain Resistance of JFET = %0.2f kohm"%(rd*10**-3)

AC drain Resistance of JFET = 12.50 kohm


## Exa 4.3 page 195¶

In [3]:
#given data :
ID2=1.5 #in mAmpere
ID1=1.2 #in mAmpere
delID=ID2-ID1 #in Ampere
VGS1=-4.25 #in Volt
VGS2=-4.10 #in Volt
delVGS=VGS2-VGS1 #in Volt
gm=delID/delVGS #in Ohm
print "Transconductance = %0.2f mA/V "%gm
print "Transconductance = %0.2f uS "%(gm*10**3)

Transconductance = 2.00 mA/V
Transconductance = 2000.00 uS


## Exa 4.4 page 195¶

In [4]:
#given data :
VDS1=5 #in Volt
VDS2=12 #in Volt
VDS3=12 #in Volt
VGS1=0 #in Volt
VGS2=0 #in Volt
VGS3=-0.25 #in Volt
ID1=8 #in mAmpere
ID2=8.2 #in mAmpere
ID3=7.5 #in mAmpere
#AC drain resistance
delVDS=VDS2-VDS1 #in Volt
delID=ID2-ID1 #in mAmpere
rd=delVDS/delID #in Kohm
print "AC Drain resistance = %0.2f kohm "%(rd)
#Transconductance
delID=ID3-ID2 #in mAmpere
delVGS=VGS3-VGS2 #in Volt
gm=delID/delVGS #in mA/V or mS
print "Transconductance = %0.2f mA/V  "%gm
#Amplification Factor
meu=rd*1000*gm*10**-3 #unitless
print "Amplification Factor : " ,meu

AC Drain resistance = 35.00 kohm
Transconductance = 2.80 mA/V
Amplification Factor :  98.0


## Exa 4.5 page 196¶

In [5]:
from math import sqrt
#given data :
VP=-4.5 #in Volt
IDSS=10 #in mAmpere
IDS=2.5 #in mAmpere
#Formula : IDS=IDSS*[1-VGS/VP]**2
VGS=VP*(1-sqrt(IDS/IDSS)) #in Volt
gm=(-2*IDSS*10**-3)*(1-VGS/VP)/VP #in mA/V or mS
print "Transconductance = %0.2f mA/V "%(gm*1000)

Transconductance = 2.22 mA/V


## Exa 4.6 page 196¶

In [6]:
#given data :
gm=10 #in mS
gm=gm*10**-3 #in S
IDSS=10 #in uAmpere
IDSS=IDSS*10**-6 #in Ampere
#VGS(OFF):VGS=VP
#Formula : gm=gmo=-2*IDSS/VP=-2*IDSS/VG(Off)
VGS_OFF=-2*IDSS/gm #in Volt
print "VGS(OFF) = %0.2f mV "%(VGS_OFF*1000)

VGS(OFF) = -2.00 mV


## Exa 4.7 page 196¶

In [7]:
from __future__ import division
#given data :
VP=-4 #in Volt
VGS=-2 #in Volt
IDSS=10 #in mAmpere
IDSS=IDSS*10**-3 #in Ampere
#Formula : ID=IDSS*[1-VGS/VP]**2
ID=IDSS*(1-VGS/VP)**2 #in Ampere
print "Drain Current = %0.2f mA "%(ID*1000)
print "The minimum value of VDS for pinch-off region is equal to VP. Thus the minimum value of VDS : VDS(min) =",VP,"V"

Drain Current = 2.50 mA
The minimum value of VDS for pinch-off region is equal to VP. Thus the minimum value of VDS : VDS(min) = -4 V


## Exa 4.8 page 197¶

In [8]:
#given data :
IDSS=8.7 #in mAmpere
IDSS=IDSS*10**-3 #in Ampere
VP=-3 #in Volt
VGS=-1 #in Volt
#ID
ID=IDSS*(1-VGS/VP)**2
print "Drain current ID = %0.4f mA "%(ID*1000)
#gmo
gmo=-2*IDSS/VP #in S
print "Transconductance for VGS=0V = %0.2f mA/V or mS"%(gmo*1000)
#gm
gm=gmo*(1-VGS/VP) #in S
print "Transconductance = %0.3f mA/V or mS"%(gm*1000)

Drain current ID = 3.8667 mA
Transconductance for VGS=0V = 5.80 mA/V or mS
Transconductance = 3.867 mA/V or mS


## Exa 4.9 page 197¶

In [9]:

#given data :
IDSS=8.4 #in mAmpere
IDSS=IDSS*10**-3 #in Ampere
VP=-3 #in Volt
VGS=-1.5 #in Volt
#ID
ID=IDSS*(1-VGS/VP)**2
print "Drain current ID = %0.2f mA "%(ID*1000)
#gmo
gmo=-2*IDSS/VP #in S
print "Transconductance for VGS=0V = %0.2f mA/V or mS "%(gmo*1000)
gm=gmo*(1-VGS/VP) #in S
print "Transconductance = %0.2f mA/V or mS "%(gm*1000)

Drain current ID = 2.10 mA
Transconductance for VGS=0V = 5.60 mA/V or mS
Transconductance = 2.80 mA/V or mS


## Exa 4.10 page 197¶

In [10]:
#given data :
VP=-4.5 #in Volt
IDSS=9 #in mAmpere
IDSS=IDSS*10**-3 #in Ampere
IDS=3 #in mAmpere
IDS=IDS*10**-3 #in Ampere
#Formula : IDS=IDSS*[1-VGS/VP]**2
VGS=VP*(1-sqrt(IDS/IDSS)) #in Volt
print "ID=3mA at VGS = %0.3f Volt "%(VGS)
gm=(-2*IDSS)*(1-VGS/VP)/VP #in mA/V or mS
print "Transconductance = %0.2f mA/V or mS "%(gm*1000)

ID=3mA at VGS = -1.902 Volt
Transconductance = 2.31 mA/V or mS


## Exa 4.11 page 197¶

In [11]:
from __future__ import division
#given data :
ID_on=5 #in mAmpere
VGS_on=8 #in Volt
VGS=6 #in Volt
VGST=4 #in Volt
k=ID_on/(VGS_on-VGST)**2 #in mA/V**2
ID=k*(VGS-VGST)**2 #in mA
print "Drain current = %0.2f mA "%ID

Drain current = 1.25 mA