Review exam:ELEC04: Electronic Devices & Circuits 1

Question 1

For a PN-junction we generally have
I. Width of depletion layer
Il. Junction barrier voltage
IlI. Reverse leakage current
Which of the above parameters will decrease when the temperature of the junction rises?

Answer 1

I and II only

Question 2

At absolute zero temperature a semi-conductor behaves as:

Answer 2

Insulator

Question 3

In a semiconductor avalanche breakdown takes place:

Answer 3

Reverse bias exceeds the limiting value

Question 4

Before doping the semiconductor material is generally

Answer 4

Purified

Question 5

What is considered the maximum forward current for silicon diode rectifier?

Answer 5

600 A

Question 6

An electron in the conduction band:

Answer 6

Has higher energy than the electron in the valence band

Question 7

What is considered the maximum peak inverse voltage for silicon diode rectifier?

Answer 7

1000V

Question 8

An electron in the conduction band:

Answer 8

Has higher energy than the electron in the valence band

Question 9

What is considered the maximum peak inverse voltage for silicon diode recrifier?

Answer 9

1000V

Question 10

The ayomic mass unit in grams is the reciprocal of

Answer 10

Avogadro’s number

Question 11

The ayomic mass unit in grams is the reciprocal of

Answer 11

Avogadro’s number

Question 12

At room temperature when a voltage is applied to an intrinsic semi conductor

Answer 12

Electron move towards positive terminal and holes towards negative terminal

Question 13

Which of the following decays decreases the number of both protons and neutrons by two and may result in a stable nucleus?

Answer 13

Alpha Decay

Question 14

Majority carriers in an n-type semiconductor are

Answer 14

Electrons

Question 15

Majority carriers in an n-type semiconductor are

Answer 15

Electrons

Question 16

Calculate the maximum fraction of the volume in a simple cubic crystal occupied by the atoms. Assume that the atoms are closely packed and that they can be treated as hard spheres. This fraction is also called the packing density.

Answer 16

52%

(Volume ka sphere with radius (a/2) over volume ka cube (a^3)

Question 17

What is the other name of negative electron

Answer 17

Negatron

Question 18

In the reverse-bias region the saturation current of a silicon diode is about 0.1uA(T=20degrees). Determine its approximate value if the temperature is increased 40 degrees.

Answer 18

1.6uA

Question 19

In case a PN junction is forward biased

Answer 19

Depletion region decreases

Question 20

Which of the following is the first postulate of Niels Bohr to support his atomic structure theory?

Answer 20

Electron orbits are discrete non-radiating and the electron may not remain between these orbits

Question 21

In a diode, the region near the junction consisting of positive and negative ions is called the

Answer 21

Depletion region

Question 22

Calculate the effective densities of states in the conduction band or germanium at 300 degree K.

Answer 22

1.02x10^25 m^-3

Question 23

What crystalline structure has a coordination number of 12?

Answer 23

Face centered cubic

Question 24

Given Pmax=14mW for each diode, determine the maximum current rating of each diode (using the approximate equivalent model)

Answer 24

20mA

=14mW/0.7

Question 25

Determine the diode current at 20 degrees C for a silicon diode with Is=0.1uA at a reverse-bias potential of -10V.

Answer 25

0.1uA Shockley equation

Question 26

The two types of current in a semiconductor are

Answer 26

Electron current and the whole current

Question 27

Determine the temperature coefficient of a 5V zener diode(rated 25degrees C) if the nominal voltage drops to 4.8V at a temp of 100 degrees C.

Answer 27

0.053%/degrees C

Question 28

A conductor material has a free electron density if 10^24 electrons per cubic meter. When a voltage is applied a constabt drift velocity of 1.5x10^-2 m/s is attained by the electrons. If the cross sectional area of the material is 1 cm^3 , calculate the magnitude of the current. Electron charge is 1.5x10^-19

Answer 28

0.24A

Question 29

EG for silicon is 1.12 eV and for germanium is 0.73eV thus it can be concluded that

Answer 29

Less number of electron whole pairs will be generated in silicon than in germanium at room temperature