A Two-Emitter Transistor with a High Adjustable Alpha

The current amplification, α, of a point contact transistor can be increased to values in excess of 20 by the addition of a third point contact which is biased so as to act as an emitter. The amount of increase in α can be adjusted by varying the second emitter current. A qualitative explanation of the α enhancement is discussed which involves an internal positive feedback action that varies the hole transport factor, ß, associated with the second emitter as the first emitter current is changed. The effect of varying the second emitter-to-collector spacing is discussed and experimental results are given.