Andhra University 2007 B.E ELECTRONICS - I - Question Paper

I Year B.E./B.Tech Degree exams

ELECTRONICS - I

(Common to EEE & ECE Branches)

Time : 3 hours Maximum : 75 Marks

ques. one is compulsory

ans any 4 from ques. two to 8

All ques. carry marks

19

b) A silicon diode operates at a forward voltage of 0.35V.

compute the factor by which the current will be multiplied


when the temperature is increased from 200 to 1400 C.

(7m)

3. a) Draw the V-I characteristics of Zener diode and discuss its


operation. (7m)

b) Draw the equivalent circuit of a tunnel diode and discuss its

operation. List out the applications of tunnel diode.


(8m)

4. a) elaborate the factors which reason in shift of operating point

in a transistor circuit. discuss thermal runaway. (5m)

b) Design a self bias (emitter bias) circuit for a silicon transistor

having b=60,VBE=0.6Vwith operating point (5V, 1mA).


presume 3.3 , 10 LR= KS£ and 10 . CC V = V (5m)

c) elaborate the regions of operation of a Transistor? discuss.

(5m)

5. a) describe the h-parameters of a transistor and derive the


expressions for 1, , V i A A Rand 0 R for CE transistor amplifier

using h-parameters. (8m)

b) A single stage CE amplifier having, 1500 50, ie fe h= Wh =

2.5 104 re h = ´ - and 25 oe h = m mhos. compute 1, , V A A

iR, 0


,

IS R

A and VS A

when 1

S

R

=


K

W

and 2

.


L

R

=

K

W


.

(7m)

6. a) explain the influence of coupling capacitance C C on the low

frequency response of RC couped amplifier. (5m)

20

b) Draw the hybrid-II model of BJT in CE connection and

derive the formula for short circuit current gain. (5m)

c) A BJT has hie=5KWhfe=150atIC=1mA with

Tf =MHz and ' 12 . b c C = PF Determine i) ' , ' , m be bb g r r


and b'e C at room temperature and a collector current of

1mA. (5m)

7. a) discuss the operation of depletion mode MOSFET and

enhancement kind MOSFET with the help of neat sketches.

(5m)

b) A FET has a driven current of 4mA. If eight DSS I =mA and

( ) six . GS off V = -V obtain the values of GS V and . P V (5m)

c) discuss how a FET is used as a voltage variable resistor.

(5m)

8. a) discuss the operation of full wave rectifier with necessary


circuit and waveforms. Derive the expressions for , , DC DC I V

, rms I dcoutput power and efficiency of the identical rectifier.

(10m)

b) A full-wave rectifier has a centre-tap transformer of 100-0-

100V and every 1 of the diodes is rated at max I =400ma

and 150 . avI = mA Neglecting the voltage drop across the


diodes, determine i) the value of load resistor that provide the

largest d.c power output, ii) d.c load voltage and current

and iii) PIV of every diode. (5m)

Earning:   Approval pending.