# Anna University Electronic Devices and Circuits Model Test Paper

## SECOND SEMESTER-ELECTRONIC DEVICES AND CIRCUITS

## MECHATRONICS ENGINEERING

Time : Three hours Maximum : 100 marks

Answer ALL questions.

PART A — (10 ´ 2 = 20 marks)

1.Give the value of energy gap for semiconductors and insulators.

2.What is meant by extrinsic semiconductor?

3.Define load line in transistor characteristics.

4.What are the salient features of ‘‘*h*’’ parameters?

5.An amplifier has a voltage gain of 1000 and a feedback ratio of 0.001. Find the gain with feedback.

6.What are the two important conditions for oscillations?

7.Define Slew rate in a Op–Amp.

8.What is meant by virtual ground in an Op–amp?

9.Find the frequency of oscillation of a symmetrical astable multivibrator has and 10 K Ohms.

10.What is meant by Hysterisis voltage in a Schmitt trigger circuit?

PART B — (5 ´ 16 = 80 marks)

11.(i)With neat diagrams explain the formation of PN junction and formation of space charge, field distribution in it. (8)

** (**ii) Explain the phenomenon of rectification in a PN junction. (8)

12.(a) (i) Explain the self bias scheme of establishing stable operating point in transistor under Common emitter configuration. (8)

(ii)For a CE silicon transistor amplifier circuit, the bias is provided by potential divider arrangement (self bias). The parameters are

= 12 V, = 2.7 K Ohms, = 1.8 K Ohms, = 56 K Ohms, = 18 K, = 100. Determine the operating point. (8)

Or

(b)(i)Deduce the H parameter equivalent circuit of a Common Base transistor amplifier and define the parameters. (8)

(ii) Explain the high frequency model for a transistor. (8)

13.(a)Explain the voltage series feedback amplifier with an example. Also derive the expression for voltage gain, input resistance and output resistance.

Or

(b) Explain the operation of a Hartley oscillator and derive the expression for oscillation frequency.

14.(a)(i)What are the characteristics of an ideal operational amplifier. (4) ** ** (ii) Explain the operation of an Op–Amp with a Block diagram. (12)

Or

** **(b)(i)With a neat circuit explain the working of an instrumentation amplifier and hence deduce the expression for gain. (8)

(ii) Explain the Op–Amp integrator with necessary diagrams. (8)

15.(a)With neat circuit diagram and waveforms discuss the operation of a transistor based astable multivibrator.