Why are optoisolators often used in conjunction with solid-state circuits that control 120 VAC circuits?
Optoisolators provide a low-impedance link between a control circuit and a power circuit
Optoisolators provide impedance matching between the control circuit and power circuit
Optoisolators provide an electrical isolation between a control circuit and the circuit being switched✓Bonne réponse
Optoisolators eliminate the effects of reflected light in the control circuit
Explication
An optoisolator carries the control signal across as light, so the low-voltage logic and the 120 VAC side share no conductive path and a fault on the mains side cannot reach the control circuit or the operator. It provides high isolation rather than a low-impedance link, and it neither matches impedances nor concerns itself with reflected light.