electronics-and-communication-engineering-exam-question-papers Related Question Answers

1. In the circuit shown, in switch S is open for a long time and is closed at t = 0. The current i(t) for t ≥ 0+ is





2. In a semiconductor material. The hole concentration is found to be 2 x 2.5 x 1015 cm-3. If mobility of carriers is 0.13 m2/ v-s. Then find the current density if electric field intensity is 3.62 x 10-19





3. Consider the system with and where p and q are arbitrary real numbers. Which of the following statements about the controllability of the system is true?





4. A MOSFET has a threshold voltage of 1 V and oxide thickness of 500 x 10-8 [εr = 3.9; ε0 = 8.85 x 10-14 F/cm, q = 1.6 x 10-19 c]. The region under the gate is ion implanted for threshold voltage tailoring. The base and type of impant required to shift threshold voltage to - 1 V are __________ .





5. What is the propagation constant for air filled wave guide with dimensions a = 1.59" and b = 0.795" at 4.95 GHz?





6. Radiation resistance of an antenna is 54 Ω and loss resistance is 6 Ω. If antenna has power gain of 10, then directivity is:





7. The inverse of given Laplace transform is





8. Consider the amplitude modulated (AM) signal Ac cos ωct + 2 cos ωmt cos ωct For demodulating the signal using envelope detector, the minimum value of Ac should be





9. In a 4 bit weighted resistor D/A converter, the resistor value corresponding to LSB is 32 kΩ. The resistor value corresponding to MSB will be





10. Find 'X' in the circuit below : f1(A, B, C, D) = Σ(6, 7, 13, 14); f2(A, B, C, D) = Σ(3, 6, 7); f3(A, B, C, D) = Σ(5, 6, 7, 14, 15)





11. Suppose that the modulating signal is m(t) = 2cos (2p fmt) and the carrier signal is xC(t) = AC cos(2p fct), which one of the following is a conventional AM signal without over modulation?




12. What are the values of Emax and Emin displayed on the oscilloscope, when a 1 kV P-P carries is modulated to 50%?





13. Consider the common emitter amplifier shown below with the following circuit parameters: β = 100, gm = 0.3861 A/V, r0 = ∞ rp = 259 Ω, Rs = 1 kΩ, RB = 93 kΩ, RC = 250 Ω, RL = 1 kW, C1 = ∞ and C2 = 4.7mF. The resistance seen by the source Vs is





14. As the temperature increases the mobility of electrons __________ .





15. Consider the following Maximum energy of electrons liberated photoelectrically is independent of light intensityMaximum energy of electrons liberated photoelectrically varies nonlinearly with frequency of incident light.





16. When phase-lag compensation is used in a system, then gain cross over frequency, bandwidth and undamped frequency are respectively





17. The equivalent form of the logical expression A BC + A B C + ABC + ABC + AB C is





18. The gradient of any scalar field always yields __________ .





19. In a flash type ADC, employing 15 comparators resolution with 10 volts reference; is expected to be :





20. During transmission over a communicate channel, bit errors occur independently with probability . If a block of 3 bits are transmitted, the probability of at most one bit error is equal to


21. If x1[n] x1(z) with ROC = R1 and x2[n] x2(z) with ROC = R2 then ROC for x1[n] + x2[n] will be __________ (where Ri → Region of convergence and x1[n] and x2[n] are causal).





22. Consider a unity feedback control system with open-loop transfer function The steady state error of the system due to a unity step input is :





23. The analog signal given below is sampled at 1200 samples per second. m(t) = 2 sin 120 p t + 3 sin 240 p t + 4 sin 360 p t + 5 sin 480 p t + 6 sin 600 p t + 7 sin 720 p t. The folding (maximum) frequency is __________ .





24. If the system T.F. is The differential equation representing the system is


25. The antenna current of an AM transmitter is 8 A, when only the carrier is sent, but it increases to 8.93 A when the carrier is modulated by a single sine wave. Determine the antenna current when the percent of modulation changes to 0.8





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