Field-Effect Optocoupler

EE 58 February 1987 FIELD-EFFECT OPTOCOUPLER by W Teder In this article we will examine a number of possible applications of a recently introduced optocoupler incorporating an infra-red light-emitting diode and a phototransistor made in field effect technology. In spite of its many interesting applications in the field of audio engineering, the Type H11F3 FET optocoupler from General Electric (GE) has so far passed unnoticed to many hobbyists and professional de- signers eager to experiment with new semiconductors. Apart from its use as a fast, elec- trically isolated switch (solid- state relay), the H11F3 is emi- nently suitable for quite a num- ber of applications having to do with AF signal processing. Table 1 shows the maximum ratings of the FET optocoupler, while Fig. 1 shows its pin assignment and its equivalent circuit diagram. The field-effect element in the H11F3 is a non- polarized, photo-sensitive semi- conductor layer, comparable to a drain-source junction. This semico...