PN Junction · Electronic Devices and VLSI · GATE ECE
Marks 1
1
A region of negative differential resistance is observed in the current voltage characteristics
of a silicon PN junction if
GATE ECE 2015 Set 1
2
In the circuit shown below, the Zener diode is ideal and the Zener voltage is 6V. The output
voltage V0 (in volts) is ________.
GATE ECE 2015 Set 1
3
When the optical power incident on a photodiode is 10μW and the responsivity is 0.8 A/W,
the photocurrent generated (in μA) is ________.
GATE ECE 2014 Set 1
4
In a forward biased P-N junction diode, the sequence of events that best describes
the mechanism of current flow is
GATE ECE 2013
5
Which of the following is NOT associated with a P-N junction?
GATE ECE 2008
6
In the following limiter circuit, an input voltage $${\mathrm V}_\mathrm i\;=\;10\sin\left(100\mathrm{πt}\right)$$ applied. Assume
that the diode drop is 0.7V when it is forward biased. The Zener breakdown
voltage is 6.8V.
The maximum and minimum values of the output voltage respectively are
GATE ECE 2008
7
In a p+n junction diode under reverse bias, the magnitude of electric field is
maximum at
GATE ECE 2007
8
In the figure, a silicon diode is carrying a constant current of 1 mA. When the
temperature of the diode is 20°C, VD is found to be 700 mV. If the temperature
rises to 40°C, VD becomes approximately equal to
GATE ECE 2002
9
For small signal a.c. operation, a practical forward biased diode can be modeled
as
GATE ECE 1998
10
The static characteristic of an adequately forward biased p-n junction is a straight
line, if the plot is of
GATE ECE 1998
11
The depletion capacitance,
CJ, of an abrupt P-N junction with constant doping on
either side varies with reverse bias, VR , as
GATE ECE 1995
12
The diffusion potential across a P-N junction
GATE ECE 1995
13
A zener diode works on the principle of
GATE ECE 1995
14
In a junction diode
GATE ECE 1990
Marks 2
1
The photocurrent of a PN junction diode solar cell is 1 mA. The voltage corresponding to its maximum power point is 0.3 V. If the thermal voltage is 30 mV, the reverse saturation current of the diode (in nA, rounded off to two decimal places) is _____.
GATE ECE 2024
2
A p-type semiconductor with zero electric field is under illumination (low level injection) in steady state condition. Excess minority carrier density is zero at x = $$\pm$$ 2ln, where ln = 10$$-$$4 cm is the diffusion length of electrons. Assume electronic charge, q = $$-$$1.6 $$\times$$ 10$$-$$19 C. The profiles of photo-generation rate of carriers and the recombination rate of excess minority carriers (R) are shown. Under these conditions, the magnitude of the current density due to the photo-generated electrons at x = +2ln is ___________ mA/cm2 (rounded off to two decimal places).
GATE ECE 2022
3
For a particular intensity of incident light on a silicon pn junction solar cell, the photocurrent
density (JL) is 2.5 mA/cm2
and the open-circuit voltage (V$$_{oc}$$) is 0.451 V. consider thermal
voltage (V$$_T$$) to be 25 mV. If the intensity of the incident light is increased by 20 times,
assuming that the temperature remains unchanged. V$$_{oc}$$ (in volts) will be ______.
GATE ECE 2017 Set 2
4
Consider the charge profile shown in the figure. The resultant potential distribution is best
described by
GATE ECE 2016 Set 3
5
Consider a region of silicon devoid of electrons and holes, with an ionized donor density of
$${\mathrm N}_\mathrm d^+=10^{17}\;\mathrm{cm}^{-3}$$. The electric field at x = 0 is 0 V/cm and the electric field at x = L is
50 kV/cm in the positive x direction. Assume that the electric field is zero in the y and z directions
at all points.
Given q = 1.6 × 10−19 coulomb, $$\varepsilon$$0 = 8.85 × 10−14 F/cm, $$\varepsilon$$r = 11.7 for silicon, the value of L in nm is ________.
GATE ECE 2016 Set 2
6
The electric field profile in the depletion region of a p-n junction in equilibrium is shown
in the figure. Which one of the following statements is NOT TRUE?
GATE ECE 2015 Set 3
7
The built-in potential of an abrupt p-n junction is 0.75V. If its junction capacitance
(CJ) at a reverse bias (VR) of 1.25V is 5pF, the value of
CJ (in pF) when VR = 7.25V is ___________.
GATE ECE 2015 Set 1
8
Consider an abrupt PN junction (at T = 300 K) shown in the figure. The depletion region width Xn
on the N-side of the junction is 0.2 µm and the permittivity of silicon (εsi) is 1.044×10-12 F/cm. At
the junction, the approximate value of the peak electric field (in kV/cm) is _________.
GATE ECE 2014 Set 2
9
In the circuit shown below, the knee current of the ideal Zener diode is 10 mA. To
maintain 5V across RL, the minimum value of RL
in Ω and the minimum power
rating of the Zener diode in mW, respectively, are
GATE ECE 2013
10
In the circuit below, the diode is ideal. The voltage V is given by
GATE ECE 2009
11
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 2 µm. For a reverse bias of 7.2 V, the depletion layer
width will be:
GATE ECE 2007
12
The Zener diode in the regulator circuit shown in figure has a Zener voltage of
5.8 Volts and a Zener knee current of 0.5 mA. The maximum load current drawn
from this circuit ensuring proper functioning over the input voltage range
between 20 and 30 Volts, is
GATE ECE 2005
13
A Silicon PN junction diode under reverse bias has depletion region of width 10
µm. The relative permittivity of Silicon, ɛr = 11.7 and the permittivity of free space ɛ0 = 8.854 × 10-12 F/m.The depletion capacitance of the diode per square meter is
GATE ECE 2005
14
At 300 K, for a diode current of 1 mA, a certain germanium diode requires a
forward bias of 0.1435 V. Where as 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
GATE ECE 2003
15
Choose proper substitutes for X and Y to make the following statement correct
Tunnel diode and Avalanche photodiode are operated in X bias and Y bias
respectively.
GATE ECE 2003
16
The built-in potential (Diffusion Potential) in a p-n junction
GATE ECE 1993
17
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:
GATE ECE 1992
18
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 = $$\infty$$ )
GATE ECE 1991
19
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
GATE ECE 1991
20
The diffusion capacitance of a P-N junction
GATE ECE 1987