# CHAPTER08:BJT CIRCUITS¶

## Example E01 : Pg 410¶

In [1]:
# Ex_8_1
# given data :
Beta=100.;# unitless
Rc=2.;# kohm
Rb=100.;# kohm
Vcc=10.;# V
VBE=0.7;# V

# Part (a)
IB=(Vcc-VBE)/(Beta*Rc+Rc+Rb);# mA
print"IB(mA)",IB
IC=Beta*IB;# mA
print"IC(mA)",IC
VCE=Vcc-(IB+IC)*Rc;# V
print"VCE(V)",VCE

# Part (b)
VCE=7;# V
ICB=(Vcc-VCE)/Rc;# mA(ICB=IC+IB)
IB=ICB/(1+Beta);# mA
IC=ICB*Beta;# mA
Rb=(Vcc-VBE-Rc*ICB)/IB;# kohm
print"Value of Rb(kohm)",Rb

IB(mA) 0.0307947019868
IC(mA) 3.07947019868
VCE(V) 3.77947019868
Value of Rb(kohm) 424.2


## Example E04 : Pg 411¶

In [2]:
# Ex_8_4
# given data :
Beta=50.;# unitless
VBE=0.7;# V
VCC=22.5;# V
Rc=5.6;# kohm
VCE=12.;# V
IC=1.5;# mA
S=3.;# Stability factor(S<=3)
Rec=(VCC-VCE)/IC;# kohm(Rec=Re+Rc)
Re=Rec-Rc;# kohm
RbBYRe=(S-1)/(1-S/(1+Beta))
Rb=RbBYRe*Re;# kohm
IB=IC/Beta;# mA
V=IB*Rb+VBE+(IB/1000+IC)*Re;# V
R1=Rb*VCC/V;# kohm
R2=R1*V/(VCC-V);# kohm
print"Value of Re(kohm)",Re
print"Value of R1(kohm)",R1
print"Value of R2(kohm)",R2
# Answer in the book is wrong for R1.

Value of Re(kohm) 1.4
Value of R1(kohm) 23.1674403279
Value of R2(kohm) 3.41331378755


## Example E05 : Pg 414¶

In [3]:
# Ex_8_5
# given data :
VCC=20.;# V
Rc=1.5;# kohm
VCE=8.;# V
IC=4.;# mA
Beta=50.;# unitless\
VBE=0.2;# V
print"Part (a)"
S=12.;# Stability factor
IB=IC/Beta;# mA
Re=(VCC-VCE-IC*Rc)/(IB+IC);# kohm
RbBYRe=(S-1)/(1-S/(1+Beta))
Rb=RbBYRe*Re;# kohm
IE=IB+IC;# mA
VBN=VBE+IE*Re;# V
V=VBN+IB*Rb;# V
R1=Rb*VCC/V;# kohm
IR1=(VCC-VBN)/R1;# mA
IR2=IR1-IB;# mA
R2=VBN/IR2;# kohm
print"Value of R1(kohm)",R1
print"Value of R2(kohm)",R2
print"Value of Re(kohm)",Re
print"Part (b)"
S=3.;# Stability factor
IB=IC/Beta;# mA
Re=(VCC-VCE-IC*Rc)/(IB+IC);# kohm
RbBYRe=(S-1)/(1-S/(1+Beta))
Rb=RbBYRe*Re;# kohm
IE=IB+IC;# mA
VBN=VBE+IE*Re;# V
V=VBN+IB*Rb;# V
R1=Rb*VCC/V;# kohm
IR1=(VCC-VBN)/R1;# mA
IR2=IR1-IB;# mA
R2=VBN/IR2;# kohm
print"Value of R1(kohm)",R1
print"Value of R2(kohm)",R2
print"Value of Re(kohm)",Re
print"Value of Rb(kohm)",Rb
# Answer in the book is wrong.

Part (a)
Value of R1(kohm) 53.6062378168
Value of R2(kohm) 34.9428208386
Value of Re(kohm) 1.47058823529
Part (b)
Value of R1(kohm) 9.68992248062
Value of R2(kohm) 4.61254612546
Value of Re(kohm) 1.47058823529
Value of Rb(kohm) 3.125


## Example E06 : Pg 415¶

In [4]:
# Ex_8_6
# given data :
VBE=0.7;# V
Beta=50.;# unitless
VCE=4.;# V
VCC=12.;# V
Rc=4.3;# kohm
VEE=-6.;# V
IC=1.5;# mA
S=3.;# Stability factor(S<=3)
Rec=(VCC-VCE)/IC;# kohm(Rec=Re+Rc)
Re=Rec-Rc;# kohm
RbBYRe=(S-1)/(1-S/(1+Beta))
Rb=RbBYRe*Re;# kohm
IB=IC/Beta;# mA
V=IB*Rb+VBE+(IB/1000+IC)*Re;# V
R1=Rb*VCC/V;# kohm
R2=R1*V/(VCC-V);# kohm
print"Value of Re(kohm)",Re
print"Value of R1(kohm)",R1
print"Value of R2(kohm)",R2
# Answer in the book is wrong for R1.

Value of Re(kohm) 1.03333333333
Value of R1(kohm) 11.3778365789
Value of R2(kohm) 2.72095665325