KSC3503E v. KSC3503D

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PMI

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#1
I am wondering if there is a source for the 3503E version outside of the usual large distributors like Mouser (who only stock the D graded part).

This is why I ask:

The Fairchild KSC3503 and KSA1381 were originally complementary devices. As of the last year, the only parts which are easily obtainable are the KSA1381E and the KSC3503D. These hardly make a complementary pair any more.

I recently tested 5-6 of each, purchased together from Mouser, and the results were as follows:

KSA1381E , hfe: 180-195
KSA3503D , hfe: 70-78

This means that the E version tests at the high end of the range, and the D version, at the low end of its respective hfe range. In theory the ranges overlap, in practice, not so much.

For comparison, I also tested two pair of original Fairchild 1381E/3503E, which tested quite close around hfe~192 and 185, respectively.

As far as I can tell, assuming there is not a good alternative, the problem is availability of similarly graded devices. I have found some (in repair stock at a manufacturer), but getting them seems like a hassle... accounting and shipping nightmare.

If anyone has any insight, or useful comments I would appreciate it, or if this has been covered before, please post a link. Thanks.
 
#3
mlloyd1 said:
i feel your pain.
🙁
did you try looking for NOS at bdent.com?
they usually aren't cheap, though ...

mlloyd1
Click to expand...
I have not done that, no. I guess I just find it hard to believe that Fairchild would continue to produce two un-matched devices from what was originally a complementary series, while the rest are obsolete/discontinued, but that appears to be the case... 😕
 
#4
PMI said:
I am wondering if there is a source for the 3503E version outside of the usual large distributors like Mouser (who only stock the D graded part).

This is why I ask:

The Fairchild KSC3503 and KSA1381 were originally complementary devices. As of the last year, the only parts which are easily obtainable are the KSA1381E and the KSC3503D. These hardly make a complementary pair any more.

I recently tested 5-6 of each, purchased together from Mouser, and the results were as follows:

KSA1381E , hfe: 180-195
KSA3503D , hfe: 70-78

This means that the E version tests at the high end of the range, and the D version, at the low end of its respective hfe range. In theory the ranges overlap, in practice, not so much.

For comparison, I also tested two pair of original Fairchild 1381E/3503E, which tested quite close around hfe~192 and 185, respectively.

As far as I can tell, assuming there is not a good alternative, the problem is availability of similarly graded devices. I have found some (in repair stock at a manufacturer), but getting them seems like a hassle... accounting and shipping nightmare.

If anyone has any insight, or useful comments I would appreciate it, or if this has been covered before, please post a link. Thanks.
Click to expand...

Hello PMI. If you can get a batch I will split the cost. There are probably others so a GB seems advisable.

See my post on the VSSA thread:

http://www.diyaudio.com/forums/vend...lateral-mosfet-amplifier-226.html#post3608160
 
#8
#9
PMI said:
I have not done that, no. I guess I just find it hard to believe that Fairchild would continue to produce two un-matched devices from what was originally a complementary series, while the rest are obsolete/discontinued, but that appears to be the case... 😕
Click to expand...

Avnet will sell you 1250 pcs at $0.15 each. They come from Rochester Electronics who obviously has a large stash of obsolete devices.

A group buy could be split 10 ways and cost $20 each resulting in 125 devices each. Shipping additional.
 
#10
woofertester said:
Avnet will sell you 1250 pcs at $0.15 each. They come from Rochester Electronics who obviously has a large stash of obsolete devices.

A group buy could be split 10 ways and cost $20 each resulting in 125 devices each. Shipping additional.
Click to expand...
Rochester Electronics web site is offline, but I see the part listed at Avnet, and some other part-finder type sites, too. I do not have an account at Avnet, but that should not be a problem.
 
#15
Matching is an enormous body of work.
Selecting by hFE is much less work, but still considerable if you are to hold Tj and Ie constant, then what Ie and Tj would each user like?

Batching by rudimentary hFE from a suitably equipped DMM, or similar, would be quick.
I would call this selected hFE, NOT matching.
 
#16
AndrewT said:
Matching is an enormous body of work.
Selecting by hFE is much less work, but still considerable if you are to hold Tj and Ie constant, then what Ie and Tj would each user like?

Batching by rudimentary hFE from a suitably equipped DMM, or similar, would be quick.
I would call this selected hFE, NOT matching.
Click to expand...

I am doing my hfe measurement at Vc and Ic of the biased circuit that the transistors will go into. I don't think that it is necessary to have the transistor match at every Ic and Ib for every Vce.

I am awaiting some transistors that will actually match for the VAS. So far no luck matching complements for VAS transistors. BD139/140 transistors on order.
 
#17
I was buy some KSC/2SC3503E from China, they're look not have Pb-Free/RoSH certified. Not nice like KSA1381ESTU from Digikey.

Used KSC3503D and KSA1381E as pre-driver/driver is ok? I'm worrying about their Hfe aren't equal.
But, why Fairchild do it? May be, because between NPN & PNP types are different, they're need imbalanced to balance.
 
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