Audio Power Transistors - Buying in Bulk

There's less information on those devices, hence the low-cost. But the physical chip inside will still be made in the same factories that the branded parts are made in, it's not possible to manufacture semiconductors in lower-quality at a cheaper factory, it's a binary thing.

However, I think if you ask your audio customers which part they would want inside their repair or new product, they will want the branded part every time.

Every time I do an audio-related repair for anyone, I've stopped asking which parts to use.. I simply use branded parts, top-quality (or thereabouts!) ones, and just pass the cost on. No audio customer wants to know that they got the cheaper unbranded parts inside their product.

I agree.

It is so I can keep a large stash on hand for my own stuff and I don't care about the name as long as they work equally well compared to the more expensive ones.

So you're saying one factory makes all the internal chips and then separate factories make the metal casing and stamp their own brand on them, but put those same chips inside?

The internal die (chip) is made in the same factories, i.e. identical quality level, but you won't know which specific transistor that it electrically matches 100% (short of cutting one open, and taking a high-res photo and then comparing with others that might be similar). The wiring (bonding) and encapsulation may well be the same factory too, or may be different (no way to tell that).

Is that a side-by-side of the multicomp and the onsemi MJ15003/MJ15004?

That's a horse of a different color, That's a fake part (the large distributors cannot usually supply fakes unless something goes seriously wrong). A very high percentage of semiconductors from China via AliExpress etc., are fake, but I've never seen a fake from Farnell/Newark (not saying it's never occurred for anyone, but it's exceedingly rare.

By 'fake' I mean that die could say be a deliberately lower-cost one (e.g. smaller and cannot support the same spec as the expected part), or is an old part (possibly faulty).

Do you have access to the Multicomp parts Shibaz? Could you open the metal case and post a pic? That would clear everything up once and for all. The specs sheet of the multicomp MJ15003/004 appear almost the same as the ONSemi part. Otherwise, I'll just have to place an order and open them up myself. Would Newark send me a couple samples for this experiment?

Unfortunately I don't have any : ( I've never received samples from Farnell/Newark, you could try phoning their sales desk, but I don't know if they can provide that or not. If you do manage it, it would be great if you could upload the photos of the internals here to help others too.

Looking at the data sheets for the parts I would sy that there are definite causes for concern:

The features section of the Multicomp data sheet seems to be for a different part.

Multicomp features from data sheet.

The gain is wrong, the specified current range is wrong, what does "diode protection' even mean ?, there is no base emitter resistor in the Motorola/On Semi parts.

The figure for Hfe is specified more reasonably in the data section fo the data sheet:

There is, as Shabaz has pointed out very little information in the Multicomp data sheet (most of the graphs on the Onsemi data sheet are omitted).

So if the data sheet is both brief and self-inconsistent you have very little idea of what you are buying.

On the way home last night I was thinking about the set up needed to test these parts for performance over a reasonable working range ( maybe not needing to go as far as the full specified rang).

You would need a dual channel SMU or equivalent, capable of 10A (@ 2V) and 140V(@1A-pulsed), and most difficult, 5A at 50V

Some way of measuring the thermal resistance - this is challenging - you need to put serious power into the device. keep the case temperature constant and measure the chip temperature.

I guessed it would take a couple of weeks work to set up a rig to do this (non automated and over a limited number of set points) using a suitable lab power supply and standard electronic components with some kind of low power pulse generator and a scope. Or you could just buy the proper gear but expect no change from £50k.

Is this a good use of time ?

I would think that it isn't because the parts are not well enough specified to be sure that you would be getting a consistent product, regardless of the economics.

The real thing from Mouser cost £4.53 if you buy 100, the Multicomp part is £3.26 - so you save £1.27 on each one and as Shabaz says, almost all your customers would rather have the Onsemi parts.

MK