I am about to order the IRFP240 and 9240 with 610 and 9610 I just wanted to know that in the reel of 100 how many of them are matching in how many sets? just to order the quantity.
How tightly are you matching them, and what is the group size?
For .1v Vgs and pairs, it will be nearly all of them.
😎
For .1v Vgs and pairs, it will be nearly all of them.
😎
it would be a set of 7 but tolerances... I believe Nelson sir you should tell us how good it has to be how many millivolts
Are you after 7 matches ? Seems like an odd number.
In the Pass amps only the MOSFETs in one leg need to be matched, not one leg to another.
Unless you are building an Aleph X which is a different kettle of fish.
In the Pass amps only the MOSFETs in one leg need to be matched, not one leg to another.
Unless you are building an Aleph X which is a different kettle of fish.
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It is rare that anyone bothers to try to match P to N's. In an output
stage the big thing is to get DC current sharing so that no one device
hogs the current.
😎
stage the big thing is to get DC current sharing so that no one device
hogs the current.
😎
I just went through this exercise with just the 240's for an Aleph X build. I was shooting for quads within 0.010V of each other or better and was able to get matches for about 80% of them. There were a few that were pretty far off for whatever reason (edge of the die?) and a few that were grouped tightly for 3 or a pair, but not four.
i mean not for the n and p type match but for each channel n or p...
the group size can be 6 so how many of such groups can be achieved is the question... let me try....
I think just for one pair of output since n and p need not be matched i think we can just use one n and one p for small power amp..
the group size can be 6 so how many of such groups can be achieved is the question... let me try....
I think just for one pair of output since n and p need not be matched i think we can just use one n and one p for small power amp..
It largely depends on whether you can get your hands on fets that come from the same batch (same lot-code). For these matching is much more effective and has the added bonus that the other fet-properties are very similar as well.
In a pass MOSFET amp, what emitter Rs are you talking about? The concensous here, I agree with regarding Source Resistors. You need to match your pairs, quads etc., of the same sex, attached to one rail. It is extremely difficult and expensive to match the other sex with the other rail. IE; N-N-N match's and P-P-P match's is all that is ussually attempted. No N-P match's are easy. It is possible to match P-N but you need alot of outlying Vgs etc. parts to find matches. It is not really designed or intended to be a complementary device. You are lucky if you find matches. 😀
Match as closely to your intended use as you can. For the Aleph X, I did 22V at .75A for 45 seconds. IIRC, the rationale for the current and time is so that the FET doesn't heat up too much since it's not sinked during matching. If you were really hard core, you would sink it sufficiently and wait for steady state. 🙂
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