ISRO Scientist or Engineer Electronics 2018


For the following questions answer them individually

Question 1

The circuit shown in the fig. below is a:

($$A_1 \& A_2$$ are ideal op-amps)

Video Solution

Question 2

Determine the change in collector current, $$\triangle I_c$$ due to change in base emitter voltage $$V_{BE}$$ from $$25^\circ C$$ to $$100^\circ C$$ for a Silicon Transistor in Fixed Bias Configuration having $$\beta = 100$$.
$$($$Consider following variation in Silicon transistor parameters with temperature - At $$T = 25^\circ C, V_{BE} = 0.65 V$$ and At $$T = 100^\circ C. V_{BE} = 0.5 V)$$

Video Solution

Question 3

An antenna is fed with $$200 \pi W$$ power. The efficiency of the antenna is 75%. If the radiation pattern of the antenna is
$$P(\theta, \phi) = \sin^2 \theta \times \sin^2 \phi$$ for $$0 \leq \phi \leq \pi$$ (elevation angle).
= 0 elsewhere
Find the radiation intensity in the direction of maximum radiation

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Question 4

A reflex klystron is oscillating at 10GHz when operated in $$2\frac{3}{4}$$ mode. find the transit time of the electron in repeller space in nano seconds (ns).

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Question 5

Identify A and B current limiting techniques in a.c. to d.c. power supplies respectively, in the graph below.

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Question 6

A Gold cavity resonator resonating at 10 GHz is fully coated using $$2 \mu m$$ YBCO (Yttrium Barium Copper Oxide) material and operating at boiling temperature of liquid nitrogen.
What is the Skin Depth of RF at this frequency?
Assume $$\sigma_{A \mu} = 4e 7$$ Siemens/meter at cavity operating temperature.

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Question 7

A steady state is achieved in following Network at t = 0, find the time when $$V_{c(t)}$$ will be maximum

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Question 8

Y-parameter for following network is given as

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Question 9

A satellite transmits signals at a frequency of 6 GHz to a user 40000 km away. The free space pathloss incurredby the signal is nearly :

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Question 10

The satellite communication link between two point is established with uplink carrier-tonoise ratio of 20 dB and downlinkcarrier to noise ratio of 14 dB. The overall C/N is close to:

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