# Placement Papers - DRDO

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### DRDO APTITUDE PAPER

Posted By : Radhakanta Rating : +50, -5
Model for ECE:
Direct Theory question:

1. A triangular-square wave generator uses
* A sine wave oscillator and a comparator
* An integrator and a comparator
* A diffrentiator and comparator
* A sine wave oscillator and a clipper

2. An amplifier has two identical cascaded stages. Each stage has a BW of 20KHz. The overall BW
shall be
* 10KHz
* 12.9KHz
* 20KHz
* 28.3HHz

Direct numerical problem:

1. 1. A parabolic dish antenna has a diameter of 1m. the maximum possible ideal gain of the antenna at a wavelength 3.14cm is
* 20 dB
* 30 dB
* 40 dB
* 50 dB

2. 2. The frequency deviation produced in a VHF carrier by a signal of 100Hz is 50KHz. The frequency modulation is

Application based theoretical or numerical problem:

1. Which one of the pulses has the same form in time domain as well as in frequency domain
Rectangular
Exponenetial
Triangular
Gaussian

2. Good voice reproduction via PCM requires 128 quantisation levels. If the BW of voice channel is 4KHz then data rate is
256 Kbps
128 Kbps
56 Kbps
28 Kbps

3. Match the following:
1. List 1 List2
A. Thyristor 1. Second break down
B. MOSFET 2. Large on-state drop
C. IGBT 3. Small on state drop
D. BJT 4. Slow device

Codes:
(a) A-4, B-3, C-2, D-1 (b) A-1, B-2, C-3, D-4
(c) A-4, B-2, C-3, D-1 (d) A-1, B-3, C-2, D-4

4. List 1 List2

A. Free and forced response 1. Discrete time systems
B. Z transform 2. Dirichlet conditions
C. Probability theory 3. Non-homogenous differential equation
d. Fourier series 4. Random process

Codes:

(a) A-1, B-3, C-2, D-4 (b) A-3, B-1, C-2, D-4
(c) A-1, B-3, C-4, D-2 (d) A-3, B-1, C-4, D-2

Assertion and reasoning type:

The following item consists of two statements labeled as Assertion A and the other as Reason R. Use the following codes:
(a) Both A&R are individually true and R is the correct explanation of A
(b) Both A & R are individually true and R is not the correct explanation of A
(c) A is true and R is false
(d) A is false and R is true

5. AEvery materials has a different value of energy band gap except metals which have no band gap
R The energy band gap is decided by the equilibrium lattice constant, which is different in different materials.

6. AOp-amp are commonly used in instrumentation
R Op-amps do not load the circuit due to their very high input impedance

Problem based on circuits and graphs:

Some examples:
For circuits: HW rectifier, voltmeter, RC or RLC or RL transients, feedback systems, clipper, clamper, transistor biasing,555 circits, logic gates, counters, bridges and wattmeters.
Graphs: Frequency response H(s),open loop gain from root loci, Nyquist plot, transfer functions etc