Jawaharlal Nehru Technological University Hyderabad 2005 B.E Computer Science ELECTRONIC DEVICES & CIRCUITS I B.TechRegular s, set 4 - Question Paper

Code No: RR10205 Set No.4
I B.Tech. Regular Examinations, June 2005
ELECTRONIC DEVICES & CIRCUITS
( Common to Electrical & Electronic Engineering, Electronics &
Communication Engineering, Computer Science & Engineering, Electronics
& Instrumentation Engineering, BioMedical
Engineering, info
Technology, Electronics & Control Engineering, Computer Science &
Systems Engineering, Electronics & Telematics, Electronics & Computer
Engineering and Instrumentation & Control Engineering)
Time: three hours Max Marks: 80
ans any 5 ques.
All ques. carry equal marks
? ? ? ? ?
1. (a) Derive the expression for transit time _ (tow) and final velocity V in the case
of an electron traversing in uniform electric field E
(b) An electron with a velocity of three × 105ms-1 enters an electric field of 910 v/m
making an angle of 600 with the positive direction. The direction of the electric
field is in the positive Y direction. compute the time needed to reach its
maximum height.[8+8]
2. (a) elaborate general specifications of PN junction diode.
(b) The voltage across a silicon diode at room temperature (300 0 k) is 0.7 volts
when 2mA current flows through it. If the voltage increases to 0.75V compute
the diode current (assume VT = 26mA).[8+8]
3. (a) A 15015
Volts (rms) ideal transformer is used with a full wave rectifier
circuit with diodes having forward drop of 1volt. The load is a resistance of
100ohm and a capacitor of 10,000µf is used as a filter across the load resistance
compute the dc load current and voltage.
(b) Draw the circuit diagram of a bridge rectifier circuit with Psection
followed
by Lsection
filter and discuss its operation.[8+8]
4. (a) Draw the circuit and discuss the output characteristics of CB transistor Configuration?
(b) Derive the expression for the collector current without neglecting the leakage
current.[8+8]
5. (a) Briefly explain about the subsequent opto electric devices.
i. Photo diode
ii. Photo transistor
(b) List out various kinds of MOSFETS and compare their salient features.[8+8]
6. (a) What is meant by thermal runaway briefly explain?
(b) What is the condition for thermal stability?
(c) An npn
transistor if b =50 is used in common emitter circuit with VCC=10V
and RC=2K. The bias is found by connecting 100K resistance from collector
to base.[4+4+8]
obtain the quiescent point and stability factor S.
7. (a) Classify the amplifiers based as feedback topology and provide their block diagram.
How the input and output impendence are effected in every case.
(b) Draw the circuit diagram of a current feed back circuit and derive Expressions
for Voltage gain and output resistance, and input resistance.[8+8]
8. (a) Show that the gain of Wien bridge oscillator using BJT amplifier must be at
lowest three for the oscillations to occur.
(b) In a transistorized Hartley oscillator the 2 inductances are 2mH and 20µH
while the frequency is to be changed from 950KHZ to 2050KHZ. compute the
range over which the capacitor is to be varied.[8+8]

Earning:   Approval pending.