Short notes
Objective questions (Answers are given below)
- For a silicon diode, the value of the forwardbias
voltage typically
(a) must be greater than 0.3 V
(b) must be greater than 0.7 V
(c) depends on the width of the depletion
region
(d) depends on the concentration of majority
carriers. - When forward biased, a diode
(a) blocks current
(b) conducts current
(c) has a high resistance
(d) drops a large voltage - The term bias means
(a) the ratio of majority carriers to minority
carriers
(b) the amount of current across the P-N
junction
(c) a dc voltage applied across the P-N junction
to control its operation
(d) none of the above - To forward-bias a P-N junction, diode,
(a) an external voltage is applied that is
positive at the anode and negative at the
cathode
(b) an external voltage is applied that is
negative at the anode and positive at the
cathode.
(c) an external voltage is applied that is
positive at the P-region and negative at the
N-region
(d) a and c above
- When a P-N junction is forward-biased
(a) the only current is the hole current
(b) the only current is the electron current
(c) the only currentis produced by majority
carriers
(d) the current is produced by both holes and
electrons. - A P-N junction diode’s dynamic conductance
is directly proportional to
(a) the applied voltage
(b) the temperature
(c) the current
(d) the thermal voltage
(Hint : Conductance is reciprocal of the resistance) - The junction capacitance of a linearly graded
junction varies with the applied reverse bias,
VR as
(a) VR
–1 (b) VR
–1/2
(c) VR
–1/3 (d) VR
1/2
(UPSC Engg. Services 2002) - The diffusion capacitance of a forward biased
P+ N (P+ indicates heavily doped P-region)
junction diode with a steady current I depends
on
(a) width of the depletion region
(b) mean life-time of holes
(c) mean life-time of electrons
(d) junction-area
(UPSC Engg. Services 2002) - The width of depletion layer of a P-N junction
(a) decreases with light doping
(b) increases with heavy doping
(c) is independent of applied voltage
(d) is increased under reverse bias. - At room temperature of 25°C, the barrier potential
for silicon is 0.7 V. Its value at 125°C is
…………….. volt.
(a) 0.5 (b) 0.3
(c) 0.9 (d) 0.7. - Junction breakdown occurs
(a) under high temperature condition
(b) with forward bias
(c) under reverse bias
(d) because of manufacturing defect. - Avalanche breakdown is primarily dependent
on the phenomenon of
(a) collision (b) doping
(c) ionization (d) recombination
- Reverse current in a silicon junction nearly
doubles for every……….. °C rise in temperature.
(a) 10 (b) 2
(c) 6 (d) 5.
- (b) 2. (b) 3. (c) 4. (d) 5. (d) 6. (c) 7. (c) 8.(c) 9. (d) 10. (c) 11. (c) 12. (a) 13. (c)
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