The Load Line and Dynamic Characteristic

Author: E.E. Kimberly

Figs. 27-10 and 27-11 represent the static characteristics of a 6C5 which will now be used to develop the dynamic characteristic in conjunction with a circuit. In Fig. 27-13 is shown the circuit to be used as an amplifying device for alternating voltage. By Kirchhoff 's Law,

or

This is the equation of a straight line called the load line. If eb across the triode were zero, all of the voltage Ebb would appear across RL', and the current ib would be

If the voltage eb were 400 volts, no voltage would be left for RL; so 4 would be zero. With these intercepts known, the load line is drawn in Fig. 27-11.

Fig. 27-13. Triode Amplifier Circuit

Intersections of the load line and the plate characteristics of Fig. 27-11 represent points for which the plate current is such that the sum of the voltage across the triode and the voltage drop across RL is equal to the plate battery voltage Ebb. If all such points are transferred to the mutual characteristic graph of Fig. 27-10, the resulting locus is a tube-and-circuit characteristic called the dynamic characteristic.