Advantages and disadvantages of optocoupler (opto-isolator)

An optocoupler (optoelectronic coupler/optoisolator) is basically an interface between two circuits that operate at (usually) different voltage levels. With an optocoupler, the only contact between the input and the output is a beam of light. Although optocoupler has many advantages, it has disadvantages too. Let’s check them one by one.

Advantages of Optocoupler

Following are the benefits of optocoupler:

• The key advantage of an optocoupler is the electrical isolation between the input and output circuits.
• Optocoupler can be employed in any situation where a signal must be passed between two circuits that are isolated from each other.
• It is possible to have an insulation resistance between the two circuits in the thousands of megohms.
• It is useful in high voltage applications where the potentials of two circuits may differ by several thousand volts.
• The most common industrial use of the optocouplers (or optically-coupled isolators) is as a signal converter between high-voltage pitot devices (limit switches etc.) and low voltage solid-state logic circuits.
• Complete electrical isolation between two circuits is often necessary to prevent noise generated in one circuit from being passed to the other circuit. This is especially necessary for the coupling between high-voltage information-gathering circuits and low-voltage digital logic circuits.
• The optocoupler eliminates the need for a relay-controlled contact or an isolating transformer, which are traditional methods of providing electrical isolation between circuits.
• The optocoupler works well on either AC or DC high-voltage signals.
• It is also used in a number of sensor applications to sense the presence of physical objects.
• The lifetime of optocouplers can exceed several decades.
• It offers a very good response at lower frequencies. It works very fast.
• No contact bounce, no interference caused by arcs, wear the circuitry.
• It is compact and lightweight.
• It is cheap. (Check price on Amazon)
• It consumes less power.
• It has a high switching frequency due to short switch-on and switch-off times.

Disadvantages of Optocoupler

Following are the drawbacks of optocoupler:

• Optocoupler needs external biasing voltage for its operation.
• The High-frequency response is poor.
• Optocoupler is not capable to handle high current.
• Optocouplers using phototransistors do not have such as good a linear relationship between the changes in light input and output current as photodiode types

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