A Simple, Bidirectional, Transistor Switch for Sine-Wave Trains

Trains of sine waves of varying duration and frequency are sometimes required in auditory research or in experiments where nerve or muscle preparations are stimulated. One of the problems involved in such work is the need for a stimulus which is symmetrical to ground (pedestal-free) and which has a small rise time, so that the intensity-latency relationship can be correctly evaluated. It is sometimes also important to know the phase angle at which the sine wave has begun. A switch is described which was designed to meet these conditions. It uses a "normal" transistor in which the functions of the emitter and collector are interchanged periodically by a sinewave oscillator. The paper analyzes the behavior of a "normal" transistor as a bidirectional switch and describes how a suitable circuit can be designed.