An analysis and experimental investigation of the binistor

This article is an analysis of a four-layer semiconductor device known as the binistor. An approximate equivalent of this device may be constructed from suitably connected NPN and PNP transistors. Analysis of the equivalent circuit configuration by means of the small-signal hybrid parameters enables a prediction of the circuit characteristics. From this analysis, it is shown that the device exhibits a voltage-stable negative-resistance characteristic in contrast with the usual current-stable negative resistance obtained from circuits employing a four-layer semiconductor device. This analysis indicates the manner in which the negative-resistance portion of the collector current-voltage characteristic is dependent upon the small-signal parameters of the NPN and PNP transistors and upon a certain resistance external to the device. A linear model of the device is proposed. Use of the model allows a prediction, within experimental accuracy, of the switching characteristics of the binistor used as a bistable device. Switching between the two states may be accomplished by three methods of control. This model suggests that the transfer characteristic between two particular ports should have the hysteresis characteristics of a mechanical relay. This analysis is born out by experiment. A circuit formed by a series combination of two binistors is shown. This circuit has two stable states with a stable output either at essentially the supply voltage, or at approximately ground potential. A modification with an intermediate stable state is also obtainable with the proper bias conditions. A logical extension of the binistor structure to a device that may have any desired number of stable states is proposed and a circuit of this type with three stable states is shown and discussed. Because of certain internal interaction phenomena, the device may be used as a modulator, and an experimental modulator circuit is developed and investigated.