how many of IRFP240 will match in one batch of 100 units?

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..
 

flg

Member
2005-07-06 1:13 am
North East
Not in a Pass MOSFET amp. Emitter resistors yes,

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. :D
 
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. :)