An Optoelectronic Switch for Low-Level Analog Applications

This paper discusses characteristics and applications of an analog switch based upon the back-to-back connection of two light-emitter/phototransistor assemblies, with an original method of zeroing the offset voltage. The resulting device is thoroughly analyzed, and it is shown how this solid-state switch is comparable in accuracy with electromechanical relays, but it has much higher repetition-rate capabilities. Two applications are then introduced, namely an analog commutator and a low-level multiplexer, where the performances of the switch find their best exploitation.