A multistable transistor circuit

Abstract

A NUMBER of bistable configurations are known which use vacuum tubes and transistors. Each of these requires two active elements and has two stable states. Binary coded decimal counters having ten stable states and using eight active elements, can be made with these devices. Point contact transistors, tetrodes and gas tubes (by virtue of internal positive feedback) exhibit bistability with a single active element. A scale of ten counters can be made with these devices with the use of four active elements. In general, either the speed of response of the reliability is inferior to that obtainable with counters using two active elements per trigger. This paper will consider a method of multistable operation which requires only two active elements, theoretically, for any number of statically stable states. These stable states are achieved by using two active elements in a conventional trigger arrangement. The feedback in the circuit is controlled by a nonlinear load which determines whether the net positive feedback makes the circuit stable or unstable. Thus it is possible to divide the operating range of the trigger into a number of alternately stable and unstable regions.