Exercise :: Exam Questions Papers - Exam Paper 1
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6. | 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 |
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Answer: Option A Explanation: i(f) = 0.5, i(i) = 0.75 i(t) = Vr + (ii - ij)e-1/p = 0.5 - 0.125e-1000t . |
7. | 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 |
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Answer: Option A Explanation: Current density J = σE Where σ = conductivity Given -> μ = 0.13 m2/v-s = 0.13 x 104 cm2/V sec P = 2.25 x 1015/cm3 We have, ∴ ni = 1.5 x 1010 Also n.p. = ∴ n =
= (1.6 x 10-19 x 0.13 x 104 x 2.25 x 1015) x = (0.468) (4.5 x 1015) σ = 2.106 x 1015 μ/cm J = σE ∴ Current density = 2.106 x 1015 x 3.620 x 10-19 = 7.6237 x 10-4 A/m2. |
8. | Consider the system |
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Answer: Option C Explanation: Use the condition of controllability. |
9. | 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 __________ . |
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Answer: Option A Explanation: VT(new) = VT(odd) +
∴ ∴ fB = - 8.6 x 1011 The threshold voltage is always negative for p-channel and hence implant is of p-type. |
10. | What is the propagation constant for air filled wave guide with dimensions a = 1.59" and b = 0.795" at 4.95 GHz? |
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Answer: Option A Explanation: Here, a = 1.59'' = 40.386 mm = 4.04 cm ∴ |