1. A semiconductor is irradiated with light such that carriers
are
uniformly generated throughout its volume. The semiconductor
is n-type with
ND = 1019 per cm3. If the excess electron
concentration in the steady state is ∆n = 1015 per cm3
and
if τp
= 10 µsec
(minority carrier life time), the generation rate
due to irradiation is
Ans : (a)
2. A PN junction with a 100 Ω resistor, is forward biased
so that a
current of 100 mA flows. If the voltage across this combination
is
instantaneously reversed to 10 volts at t = 0, the reverse
current that flows
through the diode at t=0 is approximately
given by
(a) 0 mA (b) 100 mA
(c) 200 mA (d) 50 mA
Ans : (b)
3. An infrared LED is usually fabricated from
(a) Ge (b) Si
(c) GaAs (d) Ga As P
Ans : (C)
4. In a transistor having finite β, the forward bias across the
base
emitter junction is kept constant and the reverse bias across the
collector base junction is increased. Neglecting the leakage
across the
collector base junction and the depletion region
generating current, the base
current will ________.
(increase / decrease / remain constant).
Ans : Decreases
5. An n-channel JFET has a pinch off voltage of VP =
-5volts,
VDS(max) = 20 volts, and gm = 2 mA/V. the minimum
ON
resistance is achieved in the JFET for
Ans : (b)
6. The JFET in the circuit shown in figure has an IDSS
= 10 mA
and VP = 5 volts. The value of the resistance RS for
a drain
current IDS of 6.4 mA is ______________
(select the nearest value)
Ans : (a)
7. If the transistors in figure, have high values of β
and
a VBE of 0.65 volt, the current I, flowing through
the 2 KΩ
resistance will be ________________________
(a) 1 mA (b) 2 mA (c) 3 mA (d) 4 mA
Ans : (a)
8. The 6 volts zener diode shown in figure has zero zener
resistance
and a knee current of 5 mA. The minimum value of R so that
the
voltage across it does not fall below 6 volts is :
Ans : (b)
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