mosfet datasheets

[woodford]

what values do i need to check on mosfet datasheets to check for alternatives if the original part number is not available?am i right to assume if the alternative has the same internal diagram as the original then it will be ok? there are things listed on datasheets like thermal resistance etc....does everything have to match? thanks.

[jetadm123]

Re: mosfet datasheets

what values do i need to check on mosfet datasheets to check for alternatives if the original part number is not available?am i right to assume if the alternative has the same internal diagram as the original then it will be ok? there are things listed on datasheets like thermal resistance etc....does everything have to match? thanks.

A lot of people go by the voltage, current and Rds(on) values. As you have probably guessed, there's more to it that meets the eye.

There are several ways you can approach this:

1) Go to digikey.com and enter "mosfet" in the search window. Select FET-single. You can enter the parameters of the original mosfet and their database will search for an equivalent. This is very time consuming with no guarantee of a match.

2) Go to websites like like Fairchild Semiconductor or International Rectifier and try out their semiconductor cross-reference search. The thinking been done for you and all you have to do enter the original part number.

3) If the above fails, try contacting technical support of the original manufacturer or Fairchild, IR, etc. for help in selecting a substitute. Be sure you send a copy of the spec sheet of the mosfet in question when you submit your request.

[Longbow]

Re: mosfet datasheets

I've had good luck matching 2 specific values. These are the safe reverse voltage rating, and the safe forward current rating. Usually the data sheets will also indicate switching application and a forward resistance value for a saturated device. Watch for devices that contain internal protection diodes and go with a similar substitute.