ELECTRONIC COMPONENTS AND DEVICES 1

11. The depletion region or space charge region or transition region in a semiconductor P-N junction diode has
a) electron and holes.
b) positive ions and electrons.
c) positive ions and negative ions.
d) no ions, electron or holes.
ans. c

12. In a p+ n junction diode under reverse bias, the magnitude of electric field is maximum at
a) the edge of the depletion region on the p-side.
b) the edge of the depletion region on the n-side.
c) the p+n junction.
d) the centre of the depletion region on the n-side.
ans. c

13. A p-n junction has a built-in potential of 0.8 V. The depletion layer width at a reverse bias of 1.2V is the 2 micrometer. For a reverse bias of 7.2V , the depletion layer width will be
a) 4 micrometer
b) 4.9 micrometer
c) 8 micrometer
d) 12 micrometer
ans. a

14. At 300 K for a diode current of 1mA , a certain germanium diode requires a forward bias of 0.1435 V, whereas a certain silicon diode requires a forward bias of 0.718 V, Under the conditions stated above , the closest approximation of the ratio of reverse saturation current in germanium diode to that in silicon diode is
a) 1
b) 5
c) 4 x 10³
d) 8 x 10³
ans. c

15. A silicon PN junction at a temperature of 20⁰C has a reverse saturation current of 10 pico-Amperes (pA). The reverse saturation current at 40⁰C for same bias is approximately
a) 30 pA
b) 40 pA
c) 50 pA
d) 60 pA
ans. b

16. Which of the following is not associated with a p-n junction ?
a) Junction Capacitance
b) Charge Storage-Capacitance
c) Depletion Capacitance
d) Channel Length Modulation.
ans. d

17. As the temperature is increased, the voltage across a diode carrying a constant current
a) increases
b) decreases
c) remains constant.
d) may increase or decrease depending on the doping levels in the junction.
ans. b

18. Choose proper substitutes of X and Y to make the following statement correct. Tunnel diode and Avalanche diode are operated in X bias and Y bias respectively
a) X- reverse ,Y-reverse
b) X-reverse, Y -forward
c) X-forward, Y- reverse
d) X-forward, Y-forward
ans. c

19. Consider the following assertions.
S1- For zener effect to occur, a very abrupt junction is required.
S2- For quantum tunneling to occur , a very narrow energy barrier is required.
which of the following is correct?
a) Only S2 is true.
b) S1 and S2 are both true but S2 is not a reason for S1
c) S1 and S2 are both true and S2 is a reason for S1.
d) Both S1 and S2 are false.
ans. a

20. A dc power supply has a no-load voltage of 30 V, and a full-load voltage of 25 V at a full load-current of 1A. Its output resistance and load regulation , respectively are
a) 5 ohm and 20 %
b) 25 ohm and 20%
c) 5 ohm and 16.7%
d) 25 ohm and 16.7 %
ans. b

ELECTRONIC COMPONENTS AND DEVICES

1. The color code of a 1 kiloohm resistance is
a) black , brown , red
b) red, brown, brown
c) brown, black, red
d) black, black , red
ans. c

2. An electron with velocity u is placed in an electric field E and magnetic field B. The force experienced by the electron is given by
a) -eE
b) -eu X B
c) -e(u X E + B)
d) -e(E + u X B)
ans. d

3. The primary reason for the widespread use of Silicon semiconductor device technology is
a) abundance of Silicon on the surface of Earth.
b) larger bandgap of Silicon in comparison to Germanium.
c) favourable properties of Silicon-dioxide (Sio2).
d) lower melting point.
ans. a

4. A Silicon wafer has 100 nm of oxide on it and is inserted in a furnace at a temperature above 1000 degree centigrade for further oxidation in dry oxygen. The oxidation rate is
a) independent of current , oxide thickness and temperature.
b) independent of current, oxide thickness but depends on temperature.
c) slows down as the oxide grows.
d) zero as the existing oxide prevents further oxidations.
ans. d

5. The band gap of silicon at room temperature is
a) 1.3 eV
b) 0.7 eV
c) 1.1 eV
d) 1.4 eV
ans. c

6. n-type silicon is obtained by doping silicon with
a) Germanium
b) Aluminium
c) Boron
d) Phosporous
ans. d

7. Which of the following is true ?
a) A silicon wafer heavily doped with boron is a p+ substrate.
b) A silicon wafer lightly doped with boron is a p+ substrate.
c) A silicon wafer heavily doped with Arsenic is a p+ substrate.
d) A silicon wafer lightly doped with Arsenic is a p+ substrate.
ans. a

8. The concentration of minority carriers in an extrinsic semiconductor under equilibrium is
a) directly proportional to the doping concentration.
b) inversely proportional to the doping concentration.
c) directly proportional to the intrinsic concentration.
d) inversely proportional to the intrinsic concentration.
ans. b

9. Under low level injection assumption, the injected minority carrier current for an extrinsic semiconductor is essentially the
a) diffusion current
b) drift current
c) recombination current
d) induced current
ans. a

10. The majority carriers in an n-type semiconductor have an average drift velocity in a direction perpendicular to a uniform magnetic field B. The electric field E induced due to Hall effect acts in the direction .
a) v X B
b) B X v
c) along v
d) opposite to v
ans. b