CBSE Physics Semi-Conductor Devices Expected Questions : Unit XI
(Derivation/Numerical Type Questions-3 Marks Questions)
1. What is p —n junction ? Explain, with the help of a diagram, how depletion layer is formed near the junction. Explain also what happens to this layer when junction is (i) forward biased and (ii) reverse biased.
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2. For an exterinsic semiconductor, indicate the energy band diagram for donor and acceptor level.
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3. How is depletion region formed in ap-n junction ?
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4. Find the conentration of germanium atoms in an extremely pure crystal of germanium from the following date given below:
Atomic weighs of Ge = 72. 6 ; density = 5.32 x 103 be m-3 ;
Avogadro’s number = 6 02x1023 . Also calculate the concentration of Ge atoms relative to
electron hole pairs if intrinsic carrier density is 2. 4 X 1019 m -3 at room temperature.
5. Pure Si at 300 K has equal electron (ne) and holes (nh) concentration of 1-5 x 1016 m-3. Doping by indium increases nh to 4-5 X 1022 m-3 . Calculate nh in the doped semiconductor.
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6. Write (2375)1o in binary ?
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7. What (110 11011)2 equal to ?
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8. Prove that (A + B). (A.B) = A.B + A . B.
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9. Find the output X in the given circuit symbol.
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