Thermionic valves and the cathode-ray tube

Abstract

The thermionic valve was the first active (amplifying) element in electronics. Although obsolete for most small-scale amplification, the valve still finds a place where high voltages must be handled or high-power high-frequency signals are involved. In addition, the inherent characteristics of valve audio amplifiers are popular with many audiophiles. In particular, the graceful behaviour of the circuits near overload can give a subjectively clean sound at high levels. It is therefore useful for the electronic engineer to have at least a rudimentary knowledge of the valve and its circuitry. This chapter gives a brief account of valve (vacuum tube) circuits, including a description of the one thermionic device which is still extensively used: the cathode-ray tube.