Вивчення термінології за темою модуля. Exercise 1. Draw Simple amplifying circuit on either transistor or vacuum tube and explain its action

Exercise 1. Draw simple amplifying circuit on either transistor or vacuum tube and explain its action.

Exercise 2. Skim during 5-7 minutes the text below and answer the questions about it content.

The earliest type of the transistor is the bipolar one invented in 1948 as a replacement for the triode vacuum tube. It consists of three layers of doped material, forming two p-n (bipolar) junctions with configurations of p-n-p or n-p-n. One junction is connected to a battery so as to allow current flow (forward bias), and the other junction has a battery connected in the opposite direction (reverse bias). If the current in the forward-biased junction is varied by the addition of a signal, the current in the reverse-biased junction of the transistor will vary accordingly. The principle can be used to construct amplifiers in which a small signal applied to the forward-biased junction causes a large change in current in the reverse-biased junction.

Another type of transistor is the field-effect transistor (FET). Such a transistor operates on the principle of repulsion or attraction of charges due to a superimposed electric field. So they are voltage rather than current controlled, and the base, collector, and emitter functions of the bipolar junction transistor are replaced by the so-called gate, drain, and source terminals, respectively. The control voltage is applied at right angles to the current to be controlled. In contrast to bipolar transistors the function of the field-effect transistors involves only one type of current carriers (electrons or holes), so sometimes they are considered as unipolar type. Different types of field effect transistors include the junction-gate field effect transistor (JFET), the metal-oxide-semiconductor field effect transistor (MOSFET), and the insulated-gate field effect transistor (IGFET). The smallest MOSFET is 1/75,000 as wide as a human hair. The MOSFET has for the most part replaced the bipolar junction transistor in computer memory chips. Usually a memory unit consists of two metal-oxide semiconductor field effect transistors, one N-type and one P-type, integrated on a single silicon chip. Field-effect transistors operate more efficiently than bipolar types, because a large signal can be controlled by a very small amount of energy. These devices have very high speed and extremely low power consumption. They are, however, easily damaged by static electricity.

1) What types of transistor do you know?

2) When was the earliest type of transistor invented?

3) What are the advantages of the field effect transistors over the bipolar ones?

4) Why field effect transistors are considered as unipolar type?

5) How big are the contemporary transistors?

Exercise 3. Find words in Exercise 2 that have an opposite meaning to:

Date: 2016-06-09; view: 464; Нарушение авторских прав