2.3 Part 3

1. Remember pronunciation of the following words

parameter, ratio, analyse, symbolize, microhm, sufficient, quantity, maintain, maintenance.

2. Read the words, pay attention to stress shift

analyse — analysis; define —definition; maintain — maintenance; specify — specification.

3. Find Russian equivalents to the English words

particular a	постоянный
quantity n	значение
internal a	определять
define v	частный, особенный
value n	внутренний
constant a	существовать
control v	случай
sufficient a	количество
quality n	управлять
case n	достаточный
exist v	качество

2.3.4 Find the sentences with the Independent Participle Construction in paragraphs 4 and 5. Translate the sentences

TUBE PARAMETERS OR CHARACTERISTICS

1. Three important ratios, obtainable from either set of curves, are helpful in analysing tube performance. These are the amplification factor, the mutual conductance, and theinternal plate resistance. They are called the tube parameters or characteristics.

2. The amplification factor, symbolized by the Greek letter (i (pronounced "mu"), is defined as the ratio of plate-voltage change to grid-voltage change, when plate current is maintained constant. It is a measure of the relative effectiveness of the grid as compared with the plate in controlling flow of plate current. In Figure 5 the plate currents at A and B are the same and by the above definition

ju=AB/AE_c

where AE_C represents the difference between the grid potentials of the two curves through A and B. In triodes, |i ranges in value from 2 to 1000, with most tubes included in the range 10 to 40. For any particular triode, the amplification factor is almost constant for all operating conditions, except at very low plate currents.

3. Mutual conductance, G_m, is the ratio of plate-current change to grid-voltage change, when plate voltage is held constant. It is a measure of the effectiveness of the grid in controlling plate current. In Fig. 5

G_m=BC/AE_c..

4. Mutual conductance is stated in microhms, and for most tubes it has a value of a few thousand. It is nearly so - constant as the amplification factor, its size depending mainly on the amount of plate current.

5. Internal plate resistance, R_p, is given by the ratio of plate-voltage change to plate- current change, grid voltage being held constant. It is measured in ohms, and in Fig.5

R=AB/BC.

6. In the case of triodes, R_p ranges in value between 2,000 and 100,000 ohms. From the above definitions, it can be seen that the following relationship exists between the three parameters:

ju=R_p * G_m .

7. It is thus sufficient to specify any pair of these quantities, since the third may be computed from them.

2.3.5 Translate the word-combinations

1. amplification factor, mutual conductance, internal plate resistance, tube parameters, plate - voltage change;

2. as compared with; in the case of triodes; from the above definitions; in terms of these quantities.

6. Answer the questions

1 What is called the tube parameters or characteristics? 2. How is the amplification factor defined? 3. What is mutual conductance? 4. What does the size of mutual conductance depend on? 5. In what units is internal plate resistance measured?

6. Read these symbols

v —

A + B = C;J4;Ohm's Law: R = —; aⁿ = 4a"; dy

6. Translate the words, pay attention to negative suffixes

unknown, unusual, unnecessary, unavailable; disconnect, disadvantage, discharge; inexact, independent, inefficient.

6. Identify parts of speech

particular, mainly, definition, sufficient, specify, nearly, effectiveness, obtainable, helpful, relationship, internal, amplify.

6. Form nouns from these verbs with the help of suffixes -ence, -ance, -

tion

differ, conduct, perform, operate, define, resist. 2.4 Part 4

1. Remember the pronunciation of these words

component, averagel, instance, instantaneous, load.

2. Read the words, pay attention to stress shift:

determine—determination; apply — application; fluctuate — fluctuation; combine — combination.

3. Find Russian equivalents to the English words

component n средний

average а внешний

compose v мгновенный

instance n составная часть

external а объединять(ся)

instantaneous а нагрузка

corresponding а составлять

load а пример

combine v соответствующий

4. Find synonyms, translate them

determine v, apply v, to take place, instantaneous a, compute v, maintain v, occur v, support v, immediate a, calculate v, define v, use v.

2.4.5 Find a sentence with the word "one", define its function (paragraph 1); sentences with should, define its function and translate into Russian (paragraph2) ; identify parts of speech and functions of the words with the suffix -ing (paragraph 4)

COMPONENTS OF CURRENTS AND VOLTAGES

1.In most tube applications the plate current, grid voltage, and plate voltage are not constant but vary with time between maximum values, as shown in Figure 6.

2. It is helpful to consider that such a current or voltage is composed of a D.C. or average component together with an A.C. or varying component of peak value or effective value. In all but a ew cases the A.C. component is the one which is of certain interest, but it should be noted that the D.C. component is necessary, since this ermines the portion of the tube characteristics in which the operation takes place. It should also be noted that the average value may change when a signal is applied.

3. A typical instance is given in Figure 7, which shows a triode tube with external resistance R in its plate circuit. E is an alternating voltage, the signal, which causes the instantaneous grid potential to fluctuate up and down about its average value. The plate current will vary correspondingly.

4. 

   hi

   0

   «H

   This current in flowing through the load resistance R produces varying amounts of IR drop, and corresponding variations in plate potential will take place. It should be noted that the average or D.C. component of plate potential is less than the B-supply voltage E by the D.C. component of drop in the load resistor R. Then A.C. components of plate current and plate potential combine to give the useful output of the iube.

Figure 6-Compontnts of Plate Current Figure 7-Triode wiht Resistanse Load 2.4.6 Translate the word-combinations

1. tube application, peak value, load resistor;

2. in all but a few cases; in all but few cases; it should be noted; the plate current will vary correspondingly.

2.4.7 Answer the questions

Are the plate current, grid voltage, and plate voltage constant in most tube applications? 2. Why is the D.C. component necessary? 3. What a typical instance does Fig. 7 show?