1
GATE ECE 1993
MCQ (More than One Correct Answer)
+2
-0.6
The built-in potential (Diffusion Potential) in a p-n junction
A
is equal to the difference in the Fermi level of the two sides, expressed in volts.
B
increases with the increase in the doping levels of the two sides.
C
increases with the increase in temperature.
D
is equal to the average of the Fermi levels of the two sides.
2
GATE ECE 1992
+2
-0.6
The 6 V 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 V is:
A
1.2 kΩ
B
50 Ω
C
80 Ω
D
0 Ω
3
GATE ECE 1991
+2
-0.6
The small signal capacitances of an abrupt P+−N junction is 1 nF at zero bias. If the built-in voltage is 1 volt, the capacitance at a reverse bias voltage of 99 volts is equal to
A
100
B
0.1
C
0.01
D
10
4
GATE ECE 1991
Numerical
+2
-0
Referring to the figure. The switch S is in position 1 initially and steady state conditions exist from time t = 0 to t = t0. At t = t0, the switch is suddenly thrown into position 2. The current I through the 10K resistor as a function of time t, from t = 0 is (in mA) _____________.

(Give the sketch showing the magnitudes of the current at t = 0, t = t0 and t = $$\infty$$ )