Some Phototube Circuits

Author: J.B. Hoag

Two simple phototube amplifier circuits are shown in Fig. 20 G.

Fig. 20 G. Simple phototube amplifying circuits. (From E. & N. P.)

The one on the left can be used when the incident light is of constant intensity or changes at a slow rate. The circuit on the right is useful when the light intensity changes more rapidly.

Fig. 20 H. The B battery serves both the photoelectric and the amplifier tube

Figure 20 H shows a circuit in which a common battery B is used for both the phototube and the amplifier tube. A useful a.c.-operated phototube circuit is shown in Fig. 20 I.

Fig. 20 I. A practical phototube circuit

A gas-filled tetrode (2051) is used to supply sufficient power to operate a relay directly. The lamp serves the double purpose of providing a beam of light for operation of the phototube and to lower the supply voltage to a value suitable for the filament of the 2051 tube.