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Old 14th August 2006, 10:02 PM   #1
araven is offline araven  United Kingdom
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Default matched transistors

Hi all,

For this amplifier I'm building, I need 4 2SJ162s and 4 2SK1058 output transistors. I can get these for about $40, or I can get these as "quad matched pairs" for $88.
My question is it worth the extra cash for them to be matched? I don't know enough about amplifiers to realise how much difference there could possible be using individual transistors, some of which may vary compared to others.

Many thanks,
Alex
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Old 14th August 2006, 10:17 PM   #2
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IMHO, no. I think that it's more important to verify good
current gain at higher currents.
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Old 15th August 2006, 07:31 AM   #3
AndrewT is offline AndrewT  Scotland
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Hi,
I hope you mean $40 (£25) for the set of eight.
If you are only buying 4pair you will have little opportunity to match.
I bought 16pair for 4 projects and was left with one (out of the 32) that had a significant Vds mismatch. The current in this FET is measurably greater than it's partners. I suspect it runs at a higher temperature, both Tc and Tj. I hope I cannot hear it.
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Old 15th August 2006, 09:00 AM   #4
araven is offline araven  United Kingdom
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Hi, thanks for the replies.

Yes I do mean $40 for eight ($88 for a set of eight that are all matched). The online site i was looking at to get the matched 4 pairs is http://www.tech-diy.com/LATFET.htm . They also stock other matched transistors that i need too.

It's hard to find a source for these chips, there are a few people selling them on ebay at £4 each, but I had a bad feeling these might be mixed and matched and badly matched.

If i went for the $40 for eight, would it be worth me getting an extra pair just incase one had a significant Vds mismatch like you encountered? It would be handy to have a spare pair for any failures I suppose.

Lastly, I'm assuming these are pretty good output transistors if you bought 16 pairs of them

Many thanks,
Andy
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Old 15th August 2006, 10:38 AM   #5
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Buy 8, and if there's anything wrong with them harass this guy =>

http://www.diyaudio.com/forums/membe...fo&userid=1925

Jack has pretty neat measuring gear, he's bound to deliver you nicely matched specimens.
(don't mind his odd avatar, he's from New Jersey)
Idea : you could ask Jack if he's able/willing to match the Renesas/Hitachi devices at a specified drain current.


On the other hand, if someone who's likely to have designed more amplifier circuits than any other tells you not to bother ?
In church you have to sit on your knees and wait for lightning to strike as a sign. Overhere, you just yank the Pass chain at the right moment.
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Old 15th August 2006, 11:25 AM   #6
AndrewT is offline AndrewT  Scotland
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Hi,
Rapid sell them and they recently reduced their price. I announced it on a thread.

Their service is good, delivery is generally next day, prices are very competitive. Free delivery if over £25.
www.rapidonline.com if you don't have a catalogue.
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