# Electronics and Communication Engineering - Exam Questions Papers

41.

For a message signal m(t) = cos (2pfmt) and the carrier frequency fc, which of the following represents a single side band (SSB) signal?

 A. cos (2pfmt) cos (2pfct) B. cos (2pfct) C. cos [2p(fc + fm) t] D. [1 + cos (2pfmt) cos (2pfct)]

Explanation:

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42.

In the circuit shown below, the op-amp is ideal, the transistor has VBE = 0.6 V and β = 150. Decide whether the feedback in the circuit is positive or negative and determine the voltage V at the output of the op-amp A. Positive feedback, V = 10 V B. Positive feedback, V = 0 V C. Negative feedback, V = 5 V D. Negative feedback, V = 2 V

Explanation:

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43.

Which of the following addressing modes is used in the instruction PUSH B?

 A. Direct B. Register C. Register Indirect D. Immediate

Explanation:

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44.

Consider a silicon p-n junction at room temperature having the following parameters:
Doping on the n-side = 1 x 1017 cm-3
Depletion width on the n-side = 0.1 μm
Depletion width on the p-side = 1.0 μm
Intrinsic carrier concentration = 1.4 x 1014F. cm-1.
Thermal voltage = 26mV
Permittivity of free space = 8.85 x 10-14F. cm-1.
Dielectric constant of silicon = 12. The peak electric field in the device is

 A. 0.15 MV.com-1, directed from p-region to n-region B. 0.15 MV.com-1, directed from n-region to p-region C. 1.80 MV.com-1, directed from p-region to n-region D. 1.80 MV.com-1, directed from n-region to p-region

Explanation:

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45.

A single turn loop is situated in air, with a uniform magnetic field normal to its plane. The area of the loop is 5 m2 and the rate of change of flux density is 2 Wb/m2/s. What is the emf appearing at the terminals of the loop?

 A. -5 V B. -2 V C. -0.4 V D. 0 V