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Topic: Favourite Power MOSFET (Read 3861 times) previous topic - next topic

larryd

There will be other components in the circuit that will be much more than .002 ohms so you will never get near 20 watts.


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No technical PMs.
The last thing you did is where you should start looking.

allanhurst

#16
Apr 25, 2017, 03:32 am Last Edit: Apr 25, 2017, 03:42 am by allanhurst
If there's 100A flowing down that wire, however it gets there, it will get hot. But not for long.

If you look at the specs for these amazing devices, their 'continuous' rating is actually for pulses.

Imagine the size of their bondwires!  They fail before the external leads.

When you get it wrong  ( I have) it blows the package to bits.

And emits the infamous magic smoke.

Allan

larryd

Let's say Rds on was .008 ohms at 100 amps.
That would be 80watts, you would need huge heat sinking to keep the package from melting and remember the leads are physically connected and dissipate heat to the device.



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No technical PMs.
The last thing you did is where you should start looking.

allanhurst

#18
Apr 25, 2017, 04:25 am Last Edit: Apr 25, 2017, 04:25 am by allanhurst
They're great devices.. but ...

caveat emptor when it comes to the current ratings...

Allan

larryd

"caveat emptor when it comes to the current ratings..."
Quite true.

I derate by 1/2 or more when high current raises its ugly head.

BTW, I hate heat sinks.

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No technical PMs.
The last thing you did is where you should start looking.

alka

I know it's not though hole but I bought more psmn2r4-30 mosfets than anything else. About 50 cents a peice 2.4mOhm and a 3.3mm package. Takes about the same size on a board as a sot-23.  A very fast recovery diode too for motor driving. Great for small speed controllers.

TomGeorge

#21
Apr 28, 2017, 04:27 pm Last Edit: Apr 28, 2017, 04:28 pm by TomGeorge
Hi,
"RFD3055LE" that almost sounds like its the MOSFET solution to the good old  2N3055 power?? transistor.

2N3055 friend to all those who ventured into  the electronics world of model train control.

In the 60s and 70s, Cyclops toys in Australia had to make a transistor controller for Triang-Hornby model railways that they were the importer for.

The imported controllers, were expensive because they had to be rebuilt to 240Vac spec even on the 15Vac/12Vdc side. The imported units had lighter insulation on the low voltage side, a no no by Australian Electrical Regs.

The local design used the 2N3055 as the transistor of choice.
The controller comprised of apart from a transformer, a SELENIUM rectifier, 1k pot, 1k resistor, 2N3055 and a 21W automotive globe to act as current limit.

Ahh the days of locally built electronics.

RFD3055LE, you wonder about some part numbers don't you, some make sense when you look at the components characteristics, others look like they just ran a random number generator to get a part number.

Tom..... :)
Everything runs on smoke, let the smoke out, it stops running....

allanhurst

Anyone remember the NKT404?

Allan

Henry_Best

Anyone remember the NKT404?
I don't remember that particular one, but I do remember Newmarket Transistors.

allanhurst

They were B* awful.  And so were the transistors. The NKT404 was a TO-3 gemanium power PNP, used in such demanding applications as  power invertors for the HT in PYE's later valve mobile radios, taking over from synchronous vibrators.

It is said that Sinclair's early hobby projects such as his tiny super-regen MW receiver used their reject devices, and led to such sparkling tomes as  '101 things to do with a MAT101'.

They were absorbed into the Philips empire at one point - no idea what happened to them in the end.

Allan

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