Q.Write a note on opto couplers.

Opto-couplers are the optical isolators used to drive MOSFET/IGBT gates with no direct electrical link. …

[!TLDR]

A light-based isolator (LED + phototransistor in one package) that couples a gate signal to a MOSFET/IGBT while electrically isolating control and power sides.

Some circuits, such as inverters, need the triggering gate signal to be transferred from the control circuit to the MOSFET/IGBT gate without any direct ohmic (electrical) connection, because the control and power sides are often at very different voltage levels (for example a 5 V microcontroller controlling IGBTs switching a much higher voltage in a UPS); the link must be isolated to protect the controller. An opto-coupler does this: it consists of an infrared LED optically aligned with a phototransistor in the same package. When the input gate signal is high, the LED conducts and its light falls on the phototransistor, which conducts so the output goes high; when the input is low, the LED is off, the phototransistor does not conduct and the output goes low. The isolated output drives the gate and source/e …