1.
Calculate built in potential of a germanium PN
junction at 300

^{o}K, if P-side is doped with 5 x 10^{16}acceptors/cm^{3}and N-side with 5 x 10^{14}donors/cm^{3}.
2.
The resistivites of the two sides of an abrupt
silicon PN junction are 9.6 Ω-cm on P-side and 100 Ω-cm on N-side. Find contact
potential at room temperature.

3.
For what voltage, will the reverse current in a
PN junction silicon diode reach 95% of its saturation value at room
temperature?

4.
What is the ratio of currents for a forward bias
of 0.1 volt to the current for the same magnitude of reverse bias of silicon PN
junction at room temperature?

5.
If the reverse saturation current in a silicon
PN junction is 1 nA. Find the applied voltage for a forward current of 0.5 µA?

6.
A silicon diode at room temperature conducts 5
mA at 0.7 volts. If the voltage increases to 0.8 volts, find the diode current.

7.
What is the change in voltage at 300

^{o}K for a tenfold increase in current for a silicon diode operating in the conducting region?
8.
For a silicon diode operating under conducting
region at room temperature, if the voltage is increased by 0.24 volts, then the
current flowing through it increases by _______ number of times.

9.
Calculate the factor by which the reverse
saturation current of a germanium diode is multiplied, when the temperature is
increased from 20 to 100

^{o}C.
10.
What increase in temperature would result in a
reverse saturation current, which is 50 times its value at room temperature?

11.
A silicon diode operates at a forward voltage of
0.7 volts. Calculate the factor by which the current will be multiplied, when
the temperature is decreased from 25

^{o}C to – 55^{o}C.
12.
For a silicon P

^{+}N junction, N_{D}= 10^{15}atoms/cm^{3}and the built in potential of 0.5 volts. If the applied reverse voltage is 10 volts, find the value of electric field at the junction.
13.
Calculate the width of depletion region of a PN
junction under open circuit, when doped equally on both sides with 10

^{21}atoms/m^{3}. Assume built in potential of 0.2 volts and ε_{r}= 10.
14.
Find the magnitude of the electric field at the
center of depletion region of silicon PN junction with N

_{A}= N_{D}= 10^{21}atoms per m^{3}and built in potential of 0.6 volts.
15.
If the reverse saturation current of diode is 30
nA, then voltage across the diode is ___________________

16.
The zero voltage barrier height of an alloy
silicon PN

^{+}junction is 0.6 volts, given N_{A}= 5 x 10^{16}atoms/cm^{3}. Calculate the width of depletion layer for an applied reverse voltage of 5.6 volts.
17.
The zero voltage barrier height of an alloy
silicon P

^{+}N junction is 0.6 volts, given N_{D}= 5 x 10^{16}per cm^{3}. Calculate the width of depletion layer for an applied forward voltage of 0.5 volts.
18.
A silicon PN junction is formed from P material
doped with 10

^{22}acceptors/m^{3}and N material doped with 1.2 x 10^{21}donors/m^{3}. Find the thermal voltage and barrier voltage at 27^{o}C.
19.
A silicon diode has a saturation current of 0.1
pA at 20

^{o}C. Find its current when it is forward biased by 0.55 volts. Find the current in the same diode when the temperature rises to 100^{o}C.
20.
A silicon PN junction is formed from N material
doped with 2.5 x 10

^{21}donors/m^{3}and P material doped to have the same impurity density. Assume n_{i}= 1.5 x 10^{16}/m^{3}and is temperature independent.
a.
Find thermal voltage and barrier voltage at 40

^{o}C.
b.
To what temperature would the junction have to
be raised (in

^{o}C) in order that the thermal voltage be 30 mV? What would be the barrier voltage at that temperature?
21.
A silicon PN junction has a saturation current
of 1.8 x 10

^{-14}A. Assuming that η=1 and the temperature is 27^{o}C.
a.
Find the current in the junction when the
forward biasing voltage is 0.6 volts .

b.
Repeat (a) when forward biasing voltage is 0.65
volts.

22.
The forward current in a PN junction is 1.5 mA
at 27

^{o}C. If I_{o}= 2.4 x 10^{-14}A and η = 1. What is the forward biasing voltage across the junction?
23.
The forward current in a PN junction is 22 mA,
when the forward biasing voltage is 0.64 volts. If the thermal voltage is 26 mV
and η = 1, find the reverse saturation current?

24.
A bar of silicon is doped so that one side (side
A) has 1.85 x 10

^{22}electrons/m^{3}and the other side (side B) has 2.66 x 10^{10}electrons/m^{3}. If the bar is to be used as a junction diode, which side should be the anode and which side is cathode?
25.
The reverse breakdown voltage of a certain diode
is 150 volts and its reverse saturation current is 0.1 pA. What is the current
in the diode, when the reverse bias voltage is 149.95 volts? Assume constant n
= 2.

26.
For a certain diode, a reverse current of 9.3 nA
was measured when the reverse voltage across the diode was 349.99 volts. If the
breakdown voltage is 350 volts and reverse saturation current is 0.1 pA, find
the value of the constant ‘n’?

27.
A diode has its maximum power dissipation rating
as 0.1 watts and its reverse breakdown voltage as 200 volts. What maximum
reverse current does it sustain at breakdown without damage?

28.
A diode has a reverse breakdown voltage of 100
volts and a saturation current of 0.05 pA. How much power does it dissipate
when the reverse voltage is 99.99 volts? Assume constant n = 2.5.

29.
A diode has a reverse saturation current of 45
pA at a temperature of 373

^{o}K. What is the approximate value of Io at 273^{o}K?
30.
When the voltage across a forward biased diode
at T = 10

^{o}C is 0.621 volts and the current is 4.3 mA. If the current is held constant, what is the voltage at T = 40^{o}C and T= - 30^{o}C.