Transistor 2-terminal switches

A 2-terminal self-biased memory-type switching device is an electronic bistable switch which has only two accessible terminals to all voltage and current sources. Such a switch can be realized with a single multiterminal semiconductor device exhibiting negative resistance, if advantage is taken of the "blocking voltage" concept. The blocking voltage is defined here as the forward voltage at a P-N junction at which the incremental conductance is a hundredfold greater than the incremental conductance at zero voltage. By proper circuit connections, the blocking voltage may be utilized to block injection of minority carriers in a semiconductor device until the voltage applied to the device exceeds a peak value. Such a device may exhibit low or negative a-c resistance after the peak value is exceeded. It is shown in the following discussion how the blocking-voltage concept may be applied to obtain negative resistance behavior from a junction transistor, a point-contact transistor, a modified double-base diode, or a modified tetrode. A few applications, mainly in the telephone field, are also indicated.