Electronic Devices

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1.What is the order of energy gap in a conductor, semi conductor, and insulator?.

2.Why does the conductivity of a semi conductor change with the rise in temperature ?

3. Is the number of electrons greater than, less than (or) equal to the number of holes in an
intrinsic semi conductor?

4.Show in a energy band diagram the donor level for an N-type semi conductor.

5.. Draw in a energy band the acceptor level for a P-type semi conductor .

6.what is knee voltage in a junction Diode?

7. In transistor a current controlled or)temperature controlled device?.

8. In a given diagram ,is the diode reverse (or) forward biased?.

9.which gate is represented by the following diagram?.

10.The ratio of number of free electrons to holes ne/nh for two different materials A and B are 1 and <1 respectively. Name the type of semi conductor to which A and B belongs.

11.In half wave rectification , what is the output frequency if the input frequency is 50 hz. What is the output frequency of a full wave rectification for the same input frequency.

12. How can you relate drift velocity and mobility of an electron?

13. Show by the graph how does the current vary with the voltage change for a junction diode.

14. Why do semiconductors obey OHM’S law for only low fields?

15. Mention the factors upon which Tranconductance of a transistor depend.

16. For faster action which transistor is used and why?

17. What are input and output characteristics of a transistor? Draw the graphs.

18. A germanium diode is preferred to a silicon one for rectifying small voltages. Explain why?

19.Express by a truth table the output Y for all possible inputs A and B in the circuit shown below.

20. Write the Boolean equation and truth table for the circuit shown below.What is the output when all the inputs are high?

23. For a common emitter amplifier, current gain = 50. If the emitter current is 6.6mA, calculate collector and base current. Also calculate current gain, when emitter is working as common base amplifier.

24.The base current is 100mA and collector current is 3mA.
a) Calculate the values of b, Ie, and a
b) A change of 20mA in the base current produces a change of 0.5mAin the collector current. Calculate ba.c.

25. In NPN transistor circuit, the collector current is 5mA. If 95% of the electrons emitted reach the collector region, what is the base current?In a transistor circuit shown the figure, the emitter current is 5mA and collector current 4.75 mA. Calculate the base current and the value of Rb.

27.A circuit symbol of a logic gate and two input wave forms A and B are shown

a) Name the logic gate
b) Give the output wave form

28. The diode shown in the figure has a constant voltage drop of 0.5V at all currents and a maximum power rating of 100mW. What should be the value of resistance R connected in series, for maximum current.?

29.For a transistor working as a common base amplifier, current gain is 0.96. If the emitter current is 7.2mA, then calculate the base current. 30. For a common emitter amplifier, the current gain is 70. If the emitter current is 8.8mA, calculate the collector and base current.

31.The base current of a transistor is 105 mA and collector current is 2.05 mA.
a) Deterine the value of β ,Ie , and α
b) A change of 27 μA in the base current produces a change of 0.65 mA in the collector current . Find βa.c.

32. In a silicon transistor, a change of 7.89mA in the emitter current produces a change of 7.8 mA in the collector current. What change in the base current is necessary to produce an equivalent change in the collector current?


CBSE Physics (Chapter Wise With Hint / Solution) Class XII (By Mr. Sreekumaran Nair)