Analogue multiplication with the space-charge-limited surface-channel triode

It is shown that the space-charge-limited surface-channel triode can be operated so as to give a current-voltage characteristic described by i = 4PV1V2, where P is perveance, V1is gate voltage and V2 is drain voltage. The accurate analogue multiplication of two voltages with a cadmium sulphide thin-film triode is described. Materials and design problems are briefly discussed and it is concluded that by using a silicon triode it should be possible to achieve accurate multiplication at frequencies up to several Mc/s with a dynamic range of about two orders of magnitude for each input signal.