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High Amperage Power MOSFETs

Aaron Cameron

Sep 19, 2014
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When you see a datasheet for a power MOSFET that says a continuous drain current max of 25 A. What voltage is that talking about? 25 A at 1V is different than 25A at 100v. Could it be at the max Drain to Source voltage?

Please help

Aaron
 

KrisBlueNZ

Sadly passed away in 2015
Nov 28, 2011
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Hi Aaron and welcome to Electronics Point :)

The maximum continuous drain current relates to when the MOSFET is saturated, i.e. VDS is very low. As soon as VDS starts to rise, power dissipation in the MOSFET starts to rise very quickly. It's only because MOSFETs have such a low RDS(on) that they can achieve such high ID(max) specifications, because the low ON-resistance means that VDS can be very low and threfore the power dissipation is very low.
 

Arouse1973

Adam
Dec 18, 2013
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Also the data sheet will normally give the conditions for this max current. It might say with a VGS of 10 Volts and then there should be an on state resistance also with a VGS of 10 Volts and possibly a pulsed current of some value. This would indicate as Kris has said the transistor is fully on. For me a more useful parameter is the power rating because you might not always be able to drive the circuit in the same way they have done to test it. So it's sometimes better to keep an eye on the power dissipation rather than just the current.
Adam
 
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