Why isolation is required in ?

Question

why isolation is required in gate drive circuits? ?

Answer 1

Gate of a FET? In general, isolation is not required, although some applications may need it.

Gate of a SCR? same answer applies, it depends on the application.

Answer 2

It is not always required (I assume you are referring to FETs).

To best answer your question, it would be best to have a specific example of what you are referring to.

For instance, when using MOSFETs in a switching power supply, it is imperative that isolation be employed so that the output voltage can stand alone from the input.  Especially, when a transformer is used in the power supply, the feedback to the FET driver is the only electrical connection between the input and the output.  The simple act of isolating this path makes a huge difference in the applicability of the entire device.