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### ECE :: Exam Questions Paper

1. In the following non planar graph number of independent loop equations are 2.  A. 8 B. 12 C. 7 D. 5   3. A transmission line has a characteristic impedance of 50 Ω and a resistance of 0.1 Ω/m, if the line is distortion less, the attenuation constant (in Np/m) is

4.  A. 500 B. 5 C. 0.014 D. 0.002   5. A certain 8 bit uniform quantization PCM system can accommodate a signal ranging from - 1 V to + V. The rms value of the signal is V . The signal to quantization noise ratio is:

6.  A. 30 dB B. 46.91 dB C. 40 dB D. 49.92 dB   7. A rectangular waveguide, in dominant TE mode, has dimensions 10 cm x 15 cm. The cut off frequency is

8.  A. 10 GHz B. 1 GHz C. 15 GHz D. 25 GHz   9. A radar receiver has a noise figure of 10 dB at 300 K having a bandwidth of 2.5 MHz. The minimum power it can receive is

10.  A. 3.45 x 10-15 W B. 1.38 x 10-15 W C. 7.5 x 10-15 W D. 93.15 x 10-15 W   11. 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 12.  A. i(t) = 0.5 - 0.125e-1000t A B. i(t) = 1.5 - 0.125e-1000t A C. i(t) = 0.5 - 0.5e-1000t A D. i(t) = 0.375e-1000t A   13. 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

14.  A. 7.6237 x 10-4 A/cm2 B. 7.6237 x 10-5 A/cm2 C. 7.6237 x 10-3 A/cm2 D. none of these   15. 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?

16.  A. The system is completely state controllable for any non zero values p and q B. Only p = 0 and q = 0 result in controllability C. The system is uncontrollable for all values of p and q D. We cannot conclude about controllability from the given data   17. A MOSFET has a threshold voltage of 1 V and oxide thickness of 500 x 10-8r = 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 __________ .

18.  A. 8.6 x 1011/cm2, p-type B. 8.6 x 1011/cm2, n-type C. 0.86 x 109/cm2, p-type D. 1.02 x 1012/cm2, n-type   19. What is the propagation constant for air filled wave guide with dimensions a = 1.59" and b = 0.795" at 4.95 GHz?

20.  A. 0.6698 B. 0.7698 C. 0.503 D. 0.6598   