Question
Why are optoisolators often used in conjunction with solid-state circuits that control 120 VAC circuits?
Answer Options
- A) Optoisolators provide a low-impedance link between a control circuit and a power circuit
- B) Optoisolators provide impedance matching between the control circuit and power circuit
- C) Optoisolators provide an electrical isolation between a control circuit and the circuit being switched
- D) Optoisolators eliminate the effects of reflected light in the control circuit
Correct Answer: C
Explanation
When using low-voltage, sensitive control circuits (like microprocessors or digital logic) to switch high-voltage, high-power circuits (like 120 \text{ VAC} or transmitter power supplies), safety and noise immunity are critical concerns. A failure in the high-voltage side could destroy the low-voltage side or create a shock hazard for the operator.
Optoisolators are used precisely for this safety function: Optoisolators provide an electrical isolation between a control circuit and the circuit being switched. Since the signal is passed via light across a gap, there is no direct electrical connection, providing a barrier that protects the sensitive control electronics from high-voltage spikes and transient noise originating in the power circuit.
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