The Beam Power Tube

Author: E.E. Kimberly

Fig. 27-23. Elements of the Beam Power Tube

The effects of secondary emission may be eliminated by means other than a suppressor grid. In the beam power tube shown in Fig. 27-23, the beam-confining plates or shields are at cathode potential and by their repelling action confine the cathode electron flow in two concentrated beams. These beams, while still producing secondary emission at the plate, act like a space charge and repel the emitted electrons back to the plate. In the resulting characteristics of Fig. 27-24 the linear region extends over a wider range of plate voltage and the knee Is more sharply defined than in those of a pentode.

Fig. 27-24. Average Plate Characteristics for Type 6L6 Beam Power Tube

The beam power tube is specially desirable where a maximum of power with a minimum of distortion is needed. If the screen grid of a beam power tube is connected to the plate instead of to the cathode, the plate characteristics become those in Fig. 27-25.

Fig. 27-25. Average Plate Characteristics for Type 6L6 Beam Power Tube Connected as a Triode (Screen Is Connected to Plate Instead of to Cathode)