3. Match these words to their definitions.

1. abundance a. a piece of wire or other material used for increasing electrical resistance.

2. density b. large enough in amount or number to be noticeable or to have an important effect.

3. linear c. a large quantity of something

4. sufficient d. the opposite order to what is usual.

5. resistor e. a simple substance that is not a metal, and exists naturally in large quantities combined with other metals, minerals.

6. substantial f. the relationship between mass and size.

7. reverse g. as much as is needed for a particular purpose; enough.

8. silicon h. consisting of lines or in the form of a straight line.

4. Give the Russian equivalents of the following expressions.

A tunnel diode, a two-terminal negative resistance device, depletion region, a pn-junction, charge carriers, filled levels, energy levels, the barrier potential, electron flow, heavily doped with holes, a shortage of electrons, valence band, an abundance of electrons, a shortage of electrons, tunneling through the barrier.

5. Are the following sentences True or False?

   1. A tunnel diode is a device which can be employed as a resistor.

   2. A tunnel diode is a low-frequency component.

   3. The width of the depletion region at a pn-junction depends upon the doping density of the conductor material.

   4. When semiconductor material is lightly doped, there is an abundance of electrons.

   5. Electrons fill the valence band and create a layer of filled levels at the top of the conduction band.

   6. No tunneling occurs because there are no empty lower levels to which electrons from either side might cross the depletion region.

   7. The p-side lost negative charges and the n-side gained them.

   8. The electrons tunnel through the banner from the lower-energy levels on the p-side to the higher levels on the n-side.

   9. Despite the fact that the junction is reverse biased low current flows.

   10. With decreasing reverse bias less electrons tunnel from the p-side to the n-side.

6. Answer the questions.

   1. What is a tunnel diode?

   2. Are there any differences between tunnel diodes and other electronic devices?

   3. What can give charge carriers sufficient energy to cross the depletion region?

   4. Is there a shortage of electrons when semiconductor material is heavily doped?

   5. Why are the filled levels on the n-side exactly opposite those on the n-side?

   6. What side lost negative charges?

   7. How do the electrons tunnel through the banner?

   8. What is the reverse characteristic of a tunnel diode?

7. Complete the following sentences.

1. A tunnel diode is a … … … which can be employed as an amplifier.

2. A tunnel diode is a … component.

3. The … … is an insulator since it lacks charge carriers.

4. A small forward or reverse bias can give charge carriers … … to cross the depletion region.

5. When semiconductor material is very heavily doped with holes, there is a … of … .

6. Electrons fill the … … and create a layer of filled levels.

7. No … occurs because there are no lower … … to which electrons might cross the … ….

8. Despite the fact that the junction is reverse biased … … flows.