Identifying optocouplers (opto-isolators) True or False: An optocoupler is an IC package that contains an LED and a zener diode.

Introduction / Context:
Optocouplers (also called opto-isolators) provide galvanic isolation between an input circuit and an output circuit using light, improving safety and noise immunity. Knowing their internal composition helps you select the correct device and avoid confusing them with unrelated protection components like zener diodes.

Given Data / Assumptions:

• Typical optocoupler packages include a light emitter and a light sensor.
• Common pairings: LED + phototransistor, LED + photodiode, LED + phototriac, or LED + photodarlington.
• No zener breakdown element is part of the essential optocoupler function.

Concept / Approach:

The essence of optical isolation is that an LED on the input side converts electrical current into light, which traverses an internal gap and is detected on the output side by a photosensitive device. This optical path transfers information while maintaining electrical isolation (high isolation voltage). A zener diode is a voltage-clamping device; it is not needed for optical coupling and would not perform the required photodetection.

Step-by-Step Solution:

Verification / Alternative check:

Part examples: 4N25 (LED + phototransistor), PC817 (LED + phototransistor), MOC3021 (LED + phototriac). Datasheets confirm no zener is used for the coupling mechanism.

Why Other Options Are Wrong:

• “True” would misleadingly equate zener devices with photodetectors. While some ICs may add protection diodes, the optocoupling action is not achieved with a zener.

Common Pitfalls:

• Confusing input protection (which might use zeners elsewhere on a board) with opto-isolation internals.
• Assuming any diode paired with an LED forms an optocoupler; it must be a photo-responsive element.

Final Answer:

False