Electronic – FET device parameters explaination

fet

I'm looking for a FET device to use as ON/OFF switch.

I've found for example this device:
http://www.vishay.com/docs/62903/sis990dn.pdf

I need to find a device that can handle on Source-Drain up to 5V-5A and a gate where is enought 3.3v or 5v to enable it.

But I looked at this datasheet and I don't know which values I need to looking for. Can you indicate me which parameters I should look at?

Best Answer

It can be a minefield. Take a look at this graph: -

enter image description here

This graph tells me it is the wrong device for your application. With an applied gate-source voltage of 5V and 5A being taken from drain to source, the volt drop from drain to source is 2V i.e. a power dissipation of 10 watts.

At higher gate drive voltages (say 6V) the characteristic improves; for 5A, the volt drop is probably about 0.5V i.e. a dissipation of 2.5 watts (getting better).

You don't have a 6V (or higher) gate drive so it's no-good for your use. As a starter tip, search for devices that are maybe rated no-more than that 30V Vds. The Si990 is 100 v rated and immediately I saw that I thought it might be be tailored for your application.

All FETs have this graph in their data sheet.

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