Electronics & Software – Tips & Guide


Can the drain and source of a MOSFET be interchangable

Can the drain and source of a MOSFET be interchangeable?

In some situations, the source and drain terminals of a FET may be switched. Indeed, when the FET is used as a switch, they can usually be switched.

Even when used as amplifiers, they can sometimes be switched, although some aspects of performance, such as voltage management capability, may be degraded.

For most drain and deaf mosfets are interchangeable due to doping and source size and good drainage.

This property makes the mosfet more useful than bjt because the transmitter and the collector cannot be interchanged due to different zones and doping.

Mosfet packaging can be more efficient. The size of the chip is also reduced.

Mosfet is a symmetric device, however, if in your circuit design you have attached your body to one of the terminals, you would like this terminal to be a source.

One could understand by the fact that source simply means that this terminal is a provider of carriers while the drain terminal is one in which the carriers are drained.

For a device with n channels, the terminal at the potential ive with respect to the other will serve as a drain, because the electrons will be drained through this terminal.

The source and drain are interchangeable in the scheme / layout. But once made of silicon, they will be slightly different because of the angular doping process (not 90 degrees) with respect to the silicon substrate, the two terminals being slightly different.

All the steps of the silicon process for the source and the drain are the same. Silicon processing does not consider the source terminal or drain.

You only need to worry about interchangeability when trying to match two mosfets.

In this case, both mosfets must be arranged in such a way that their source and their drains are in the same direction.

The result of this doping asymmetry is that the source and drain characteristics are asymmetrical, so the choice of the terminal is important.