Kurukshetra University 2009 B.Tech Electronics and Communications Engineering Semiconductor Devices and Circuits (SDC) - Question Paper

BT-3/D09
SEMICONDUCTOR DEVICES AND CIRCUITS
Paper: ECE-201(E)
Time: 3 Hours
Maximum Marks:100

Note: Attempt 5 questions, selecting at lowest 1 ques. from every unit.

UNIT-I

1. (a)Explain the photoelectric effect. elaborate different devices based on this principle ? discuss the working of photo-voltaic cell. [10]

(b) discuss the working of a full wave bridge rectifier with suitable waveforms. [10]

2. (a) A half wave rectifier uses a transformer ratio 2: 1. The load resistance is 500 ohms. If the primary voltage is 240 V (rms), obtain the d.c. output voltage and peak inverse voltage. [10]

(b) elaborate the different parameters to design a power supply. discuss the working principle of SMPS with suitable diagrams. [10]

UNIT-II

3. discuss the following:
(a) Operating point of transistor. [5]
(b) Comparsion of transistor action in CB, CC and CE configurations. [5]
(c) Biasing of transistor. [5]
(d) Emitter follower. [5]

4. (a) elaborate the different limitations for BJT to operate a high frequencies ? How these can be eliminated ? [10]

(b) A transistor is operating in CE configuration, in whici Vcc = eight V, and voltage drop across resistance R connected in collector circuit is 0.5 V The value of Rc = 800 ohms.If alpha = 0.96, determine the (i) collector emitter voltage, and (ii) base current.

UNIT-III

5. (a) Why feedback is needed in amplifiers ? What is the effect of feedback on bandwidth, input and output resistance. Derive the relations. [14]

(b) Draw and discuss the circuit of phase shift oscillator .What is the frequency of oscillations ? [14]

6. (a) discuss and compare different feedback topologies used.

(b) elaborate the different power amplifiers ? Classify ther and compare their characteristics. [10]

UNIT-IV

7. (a) Compare JFET with BJT. [10]

(b) In an n-channel JFET biased by potential divide method, it is desired to get ID = 2.5 mA and VDS = eight V.If VDD = one M ohms and R2 = 500 k ohms, obtain the value of RS. The parameters of JFET are IDSS = 10 mA an Vp = -5 V. [10]

8. Write short notes on the following:

(a) V-MOSFET. [10]

(b) MOSFET in Enhancement modes. [10]

Earning:   Approval pending.