# ANNA UNIVERSITY MODEL TEST PAPERS

B.E. DEGREE EXAMINATION

IV Semester CSE

ELECTRONIC CIRCUITS

Time : Three hours                                                                        Maximum : 100 marks

PART A — (10 ´ 2 = 20 marks)

1. Explain the differences between intrinsic and extrinsic semiconductors.

2. When a reverse bias is applied to a germanium diode the revere saturation current at room temperature is 0.3                         A. Determine  the current flowing in the diode when 0.15 V forward bias is applied at room temperature.

3. Draw a common collector amplifier and its equivalent circuit.

4. Prove that negative feedback in amplifiers improves the stability.

5. Draw a BIFET circuit.

6. What are the ideal  characteristics of op–amp?

7. What are the Barkhausen criterions?

8. Define line regulation and load regulation of a voltage regulator.

9. Draw an active integrator and derive its output expression.

19. Explain the application of analog  multiplexer  as phase detector.

PART B — (5 ´ 16 = 80 marks)

11. (i)      Why there is a need for biasing an amplifier?                                          (4)

(ii)     Draw the ac equivalent circuit of the circuit shown. Find the  and .                                             (12)

12. (a)     Compare CE, CB and CC transistor configurations.

(i)      Interms of input impedance, output impedance, current gain  and
voltage gain.                                                                                       (10)
(ii)    Draw the output characteristics of CE configuration and mark its
regions of operation.                                                                           (6)

Or

(b)     (i)      Explain the characteristics of JFET with its structural diagram. (10)

(ii)    A JFET has drain current of 4 mA. Find  if  = 8 mA and
= 6 V.                                                                                               (6)

13. (a)     (i)      Define slew rate of Op–Ap.                                                                (3)

(ii)    Determine the cutoff frequency of OP–amp whose unity gain
bandwidth is 1 MHz and open loop gain is 2 ´ 105.                         (3)

(iii)   Derive the expression for the output of non–inverting amplifier and
inverting amplifier.                                                                           (10)

Or

(b)     (i)      Draw the architecture block diagram of Op–amp.                         (4)

(ii)    Compare the different types of feedback with respect to gain with
feedback,  and . Give an amplifier circuit as an example for each type of feedback.                                                    (12)

14. (a)     With internal block diagram explain the working of NE555 Timer as monostable  multivibrator. Derive its ontime.                    (16)

Or

(b)     (i)      With a neat diagram explain Line and Load regulation of series
voltage regulator.                                                                              (10)

(ii)    Design a Wein bridge oscillator to generate a Sinusoidal Oscillator at 5 KHz with peak to peak output voltage of 30 V. Draw the designed circuit.                                           (6)

15. (a)     (i)      Design a Butterworth LPF with roll off rate of –400db/decade with a cut off frequency of 3 KHz. Draw the designed circuit.                                                       (6)

(ii)    With characteristics explain Butterworth and Chebyshev filter. (10)

Or

(b)     Draw an Electronic analog circuit to solve the following :

(i)      .                                                            (10)

(ii)                                                                                              (6)

—————