Download dmt 121/3 electronic i

DMT121-Electronic I
Sem II_2009/2010
DMT 121/3 ELECTRONIC I
TUTORIAL 1
INTRODUCTION TO SEMICONDUCTOR
OBJECTIVE QUESTIONS:
1. A semiconductor is a crystalline material with:
a) Many free electrons held by the attraction of positive ions.
b) Strong covalent bond between neighboring atoms.
c) Only one electron in its outer shell
d) A filled valence shell.
2. A metallic conductor has
a) Many free electrons held by the attraction of positive ions.
b) Strong covalent bond between neighboring atoms.
c) Only one electron in its outer shell
d) A filled valence shell.
3. In a semiconductor, the concept of an energy gap is used to show the difference between
the energies of the
a) nucleus and outer shell electrons
b) nucleus and the free electrons
c) conduction band electrons and valence electrons
d) core electrons and valence electrons
4. An impurity such as Antimony (Sb) has 5 electrons in its outer shell. When silicon has Sb
impurities,
a) an n material is formed
b) the crystal will be negatively charged
c) both of the above
d) none of the above
5. Compared to a p-material, the energy levels in an n-material are
a) the same
b) greater
c) lower
6. When a pn junction is formed, the electrons move across the junction and fill holes in the
p-region. The filled hole is a
a) neutral atom
b) minority carrier
c) positive ion
d) negative ion
7. The forward biased knee voltage in a semiconductor diode is approximately equal to the
a) bias supply voltage
b) breakdown voltage
c) output voltage
d) barrier potential
8. Using the ideal diode model, the current in the circuit shown is
a) 0.73 mA
b) 0.80 mA
c) 0.87 mA
d) 1.2 mA
DMT121-Electronic I
Sem II_2009/2010
9. Using the
a)
b)
c)
d)
practical diode model, current in the circuit shown is
0.73 mA
0.80 mA
0.87 mA
1.2 mA
10. The diode model which includes the large reverse resistance is the
a) Ideal model
b) Practical model
c) Complete model
d) All of the above
11. To forward-bias a diode,
a) An external voltage is applied that is positive at anode and negative at
cathode.
b) An external voltage is applied that is negative at anode and positive at
cathode.
c) An external voltage is applied that is positive at the p region and negative at n
region.
d) Answer (a) and (c).
12. When a diode is forward-biased,
a) The only current is hole current.
b) The only current is electron current.
c) The only current is produced by majority carrier.
d) The current is produced by both holes & acceleration.
SUBJECTIVE QUESTIONS:
1. List 2 semiconductor material.
2. If the atomic number of neutral atom is 14, how many electrons do the atom is have?
How many protons? Sketch the atomic structure.
3. Explain the difference between conductors, semiconductor and insulators.
4. Why does a semiconductor have fewer free electrons than a conductor?
5. What is different between intrinsic and extrinsic semiconductor?
6. Describe the difference between n-type and p-type semiconductor materials.
7. Describe the difference between donor and acceptors impurities.
8. Describe the difference between majority and minority carriers.
DMT121-Electronic I
Sem II_2009/2010
9. Determine whether each silicon diode in Figure 1 is forward-biased or reverse-biased.
10. Determine the voltage across each diode in Figure 1 by using the practical model.
11. Determine the voltage across each diode in Figure 1 by using the ideal model.
12. Determine the voltage across each diode in Figure 1 by using the complete diode
model with r’d = 10 Ω and r’D = 100 M Ω.
Figure 1