0
3.7kviews
Design a single stage CE amplifier to give voltage gain of 40 and the output voltage of 4V(peak) and temperature stability factor S=10 Use transistor 2N525

enter image description here

1 Answer
0
110views

The specifications of transistor 2N525 are

PD(max)=225mW

hfe=45(typ)

hc=1.4KΩ    hre=3.2×104,       hoe=25μmho

i)Calculation of RC

The voltage gain is given as

Av=hfeRchfe+ΔhRc

and Δh=hiehoehfehre

=(1.4k×25μ=mho)(45×3.2×104)

Δh=0.0206

40=45×Rc1.4k+0.0206×RC

RC=1.25KΩ

select RC=1.3kΩ

ii)Selection of Q-point

VCEQVp+VCE(gat)

4V+0.3V

4.3V

Select VCEQ=6V,VRC7.5V,VRE=1.5VandVCC=15V

Ic=VRcRC=7.5V1.3kΩ

=5.77mA(Select I_{C}=6mA)

Q-point will be (6V.6mA) .........(ii)

iii)Calcualtion of RE

As IE=IC=6mA

RE=VREIC=1.5V6mA=250Ω

Select RE=270Ω      ........(iii)

iv)Selection of R1andR2

If S=10 then

RB=9RE=9×2700=2430Ω

VB=VE+VBE=1.5+0.7=2.2V

Ri=RBVCCVB2430×15V2.2V=16.6kΩ

and RB=R1||R2 substituting values of R_{B} and R_{1} in this equation we get R2=2.874kΩ

Select R1=16kΩ and R2=3kΩ     .......(iv)

v)Calculation of by-pass capacitor CE

The XCE should be very much less than RE so as to bypass the dc signal to the ground

XCE=RE10=270Ω10=27Ω

CE=12πfXCE

As lower cutoff frequency is not given let us take f=20HZ

=12π20Hz27Ω=295μF

Select CE=330μF     .........(v)

vi) Calculation of coupling capacitor, Cc

The coupling capacitor is used to allow only ac signal to go to next stage and to block all dc

The output impedance of first stage is

R01=RL=RC=1.3kΩ

and the input impedance of second stage

Rin1=RB||Rin2=0.888kΩ

The capacitace reactance

XCC=R01+Rin2

=1.3k+0.888k=2.188kΩ

CC=12πfXCC=12π×20Hz×2.188kΩ=3.63μF

Select CC=10μF    ........(vi)

Please log in to add an answer.