## Tuesday, 11 June 2013

### Video Solutions for GATE 1992 ECE : One Mark Questions ( Electron Devices )

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

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)