My speciality. Овчинникова Т.Е - 16 стр.

compared with the plate in controlling flow of plate current. In Figure 5 the plate
currents at A and В are the same and by the above definition
                                         µ=AB/∆Ec
where ∆Ec represents the difference between the grid potentials of the two curves
through A and B. In triodes, µ 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, Gm, 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
                                       Gm=BC/∆Ec..
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, Rp, 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, Rp 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:
                                        µ= Rp * Gm .
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.




      2.3.6 Answer the questions

1What 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?

      2.3.7 Read these symbols
                                        m
                              V
A + B = C ; 4 ; Ohm’s Law: R = ; a n = n a ′′′ ;
                              I
dy