8/17/2019 Compre Part B 2014

1/2

BIRLA INSTITUTE OF TECHNOLOGY AND SCIENCE, PILANI

Hyderabad Campus

Second Semester 2013-14

Analog ElectronicsECEF341/ EEEF341/EEE C364)

Comprehensive Exam-Part-B (Closed Book)

Time : 130min. Date: 5/5/2014

Max Marks : 90 Day: Monday

1. 

a) In the circuit shown in fig 1a, the output voltage  follows the equationof the form

 

    Find a, b and . (12M) 

-

+

R

R

C

-

+

R

R

C

-

+

R

R

R

C

v  x 

v y 

v 

et

 

Fig.1a

 b)  A capacitive motion transducer circuit is shown in fig.1b . The gap ‘d’ 

 between the parallel plates of the capacitor is varied as

d(t) = 10-3[1 + 0.1sin(1000πt)] mtrs. If the value of the capacitance is 2pF

at t=0ms, what is the output voltage V0 at t=2ms? (8M) 

Fig.1b

2.  Derive the transfer function of the circuit shown in the fig 2 below

assuming the opamp to be ideal. Show that the circuit realizes a high pass

filter. What is the high frequency gain of the circuit? What are the values

of R 3 and R 4  for maximally flat response with a 3-dB frequency of 103 

rad/s. Use C1=C2=10nF (Hint: For a maximally flat response Q=(√ )and ω3db = ω0 and the standard transfer function of a second order HPF is

  , where a2= High-freq. gain) (10M) 

-

+

R3

R4

C1

C2

Vi

+

-

V0

+

-

 

Fig.2 

b) An amplifier has a slew rate of 60V/µs. What is the highest frequency at

which a 20-V peak to peak sine wave can be produced at the output?

(5M)

3.  a) M1, M2 and M3 in the circuit shown in fig.3a are matched N channel

enhancement mode MOSFETS operating in saturation mode, forward

voltage drop of each diode is 0.7V, reverse leakage current of each diode

is negligible and the opamp is ideal. Find the values of Is and V0. (5M) 

Fig.3a 

8/17/2019 Compre Part B 2014

2/2

 b) The transfer characteristic for the precision rectifier circuit is shown in fig .3b

Assume ideal diodes and opamps. What are the values of Vx and Vy? (8M) 

Fig.3b 

4.  a) For the circuit shown in the fig 4a, find the loop gain L(jω), the frequency

for zero loop phase and R 2/R 1 that results in oscillations.

(12M)

-

+

R1   R2

C

CR

R

V0

Va

 

Fig.4a 

b) For the circuit shown in the fig 4b, calculate the threshold levels andoutput levels and label them on the transfer characteristics (V0 (vs )Vi). The

diodes are assumed to have a constant 0.7V while conducting and the opamp

saturates at + 12V. (8M) 

-

+

Vi

+

-

V0

+

-

10kΩ

R2=60kΩ

R1=10kΩ

 

Fig.4b 

5.  a) Explain in brief about the three types of sensor arrangement in

 pressure sensors with neat diagrams. (6M) 

 b)  Explain the two basic modes of operation of ultrasonic sensors with

diagrams. (6M) 

c)  Design a negative voltage regulator as shown in the fig 5, the load

current varies in the range of 0-1A, and the unregulated DC input varies

from 12-18V for all line and load changes. The 8.5V zener diode requires

at least 1mA of current to stay in its regulation region. Assume β=50. 

(10M)

(i) Determine the value of R S for proper circuit operation.

(ii) Determine the maximum power dissipation of R S, D1 and Q1..

Fig.5