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Posted By: kishore Member Level: Gold Posted Date: 06 Jun 2008
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2007 Jawaharlal Nehru Technological University B.Tech Electronics & Communications Engineering ELECTRONIC DEVICES & CIRCUITS Question paper
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1. (a) Derive the expression for the electro static deflection sensitivity in the case of
CRT.
(b) Compare electro static and electro-magnetic deflection sensitivity in all re-
spects. [8+8]
2. (a) Explain about various current components in a forward biased p-n junction
diode.
(b) Find the value of D.C. resistance and A.C resistance of a Germanium junction
diode at 250 C with Io = 25µA and at an applied voltage of 0.2V across the
diode. [8+8]
3. (a) Define the following terms of a half wave rectifier with resistive load.
i. Ripple factor.
ii. Peak inverse voltage.
iii. Rectification efficiency.
(b) A 230 V, 60Hz voltage is applied to the primary of a 5:1 step down, center
tapped transformer used in a full wave rectifier having a load of 900
.If the
diode resistance and the secondary coil resistance together has a resistance of
100
, determine [6+10]
i. dc voltage across the load.
ii. dc current flowing through the load.
iii. dc power delivered to the load.
iv. PIV across each diode
v. Ripple voltage and its frequency.
4. (a) What are the different configurations of BJT?
(b) Derive the relation between and .
(c) Calculate the collector current and emitter current for a transistor with dc =
0.99 and ICBO = 50 µ A when the base current is 20µ A. [6+6+4]
5. (a) Define the different parameters of FET.
(b) What are special semiconductor devices? Give explanation for any two devices.
[8+8]
6. (a) Draw the circuit diagram of emitter follower circuit using n-p-n transistor and
derive expressions for AI ,AV ,Ri,R0 using hybrid model
(b) Derive expressions for the lower and upper cut off frequencies of an n stage
amplifier. [8+8]
7. (a) Prove that the upper cutoff frequency with feedback is ( 1 + A ) times upper
cutoff frequency with out feedback.
(b) For the given circuit(as shown in figure1), calculate Avf , Rif and Rof . The
transistor h-parameters are hie= 2 K, hfe= 100, hre=0. [8+8]
8. (a) Draw the circuit diagram of a RC phases shift oscillator using BJT. Derive
the expression for frequency of oscillators.
(b) Classify different type of oscillators based on frequency range.
(c) Why RC oscillators are not suitable for high frequency applications. [8+4+4]
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