matched transistors

araven · 14th August 2006, 10:02 PM

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

Nelson Pass · 14th August 2006, 10:17 PM

IMHO, no. I think that it's more important to verify good
current gain at higher currents.

AndrewT · 15th August 2006, 07:31 AM

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.

araven · 15th August 2006, 09:00 AM

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

jacco vermeulen · 15th August 2006, 10:38 AM

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.

AndrewT · 15th August 2006, 11:25 AM

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.

14th August 2006, 10:02 PM	#1
araven diyAudio Member Join Date: Aug 2006	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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14th August 2006, 10:17 PM	#2
Nelson Pass The one and only Join Date: Mar 2001	IMHO, no. I think that it's more important to verify good current gain at higher currents.

15th August 2006, 07:31 AM	#3
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	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.

15th August 2006, 09:00 AM	#4
araven diyAudio Member Join Date: Aug 2006	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

15th August 2006, 10:38 AM	#5
jacco vermeulen diyAudio Member Join Date: Oct 2004 Location: At the sea front, Rotterdam or Curaçao	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.

15th August 2006, 11:25 AM	#6
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	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.