CIRCUIT WITH AN OPTOCOUPLER

摘要

An optocoupler driver circuit comprises an optocoupler (OC) with a light-emitting device (D) and a photosensitive device (T). A current source (CS) supplies a current (Is) to both the light-emitting device (D) and an impedance (Z). The ratio of the current (Id) through the light-emitting device (D) and the resulting current (Ic) through the photosensitive device (T) decreases if the temperature increases. The voltage (Vd) across the light-emitting device (D) also decreases if the temperature increases. The decrease of the voltage (Vd) across the light-emitting device (D) causes the current (Iz) through the impedance (Z) to decrease. Consequently, the current (Id) through the light-emitting device (D) increases and counteracts the decreasing ratio.