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b gilbert 2nd May 2009 07:27 PM

Best transistors to have on hand
Hi All... I'm new here, with a fairly basic question, but hopefully not TOO stupid...

I have a small, but reasonable collection of transistors, (for example, 2n2907, 2n2222, NTE123, NTE123AP, NTE159, etc) but whenever I look at a circuit, I never seem to have the ones I need. I'd like to go ahead and buy some of the more popular and useful transistors to keep on hand.

Has anyone developed a list of transistors that everybody should have on their bench? Or do you have a few favorites that you always seem to see in a circuit? (I'm talking about audio freq stuff here, of course.)

Another reason I want to do this is because of availability... who knows when the supplies of these things are going to dry up and all we can get are SMDs.

I realize this might be an impossible question to answer... everything depends on the circuit, of course, and there are MILLIONS of transistors out there... I'm just wondering if there are some good, basic, common components that I should be looking for for audio circuits. (and if you have any good surplus sources in the US, you might mention that, too!)

Thanks for your thoughts

Mr Evil 2nd May 2009 08:02 PM

There are too many different BJTs in common use to suggest any one type. I tend to keep a stock of various BC5xx (especially BC550/BC560 for low noise, and BC546/BC556 for the higher voltage rating); most audio circuits are not too picky about the exact transistors used and these will usually work. There are SMD equivalents of all of these too (BC8xx).

For JFETs you will almost always see 2SK170/2SJ74.

Also very useful is 2N7002. This is a common MOSFET for switching, and can be pressed into service for audio too.

Geek 3rd May 2009 01:04 AM

BC's are expensive and hard to find this side of the pond in most cases.

To that collection, I'd add 2N5088 and the PNP counterpart.. pretty low noise and decent sounding.

2N4401/4403 as well, they're a better sounding transistor than the typical 3904/3906 and about as inexpensive.


b gilbert 3rd May 2009 02:12 PM

Thanks, folks.... this is exactly what I needed.

Best, BG

keantoken 4th May 2009 11:07 PM

How about you try these...

BC556B/546B (if you need different Hfe's, also get the BCxxxA and BCxxxC ones)
2N5089/5088, and 5210 for higher voltages
2N4124/4126 (general purpose, I prefer these to the 390x)
MPSA18 (good, fast, high-gain, used in amplifiers alot in the LTP)
2N3904/3906 (of course... but I don't like these very much, I think they're used so often mostly because they've simply been the standard transistor for what, 20 years?)

From what I know, these will substitute almost any component you find well enough, unless maybe something uses Japanese parts (which seems to be getting more and more likely) or if it has rails above, say 40V.

People on this forum say to stay away from NTE parts, and buy from Mouser, Onsemi etc. instead. NTE is apparently known for putting out counterfeits.

Also, you might wish to have some higher power ones on hand as well, such as:

MJE340/350 (though some say these don't compare with the BD139/140 and others)

As for diodes, the 1N4148 is the standard, I see the BAT54 being used in audio (though according to simulation model this diode has extra low voltage drop and so you might want to consider that when designing). As for rectifier diodes, it shouldn't be hard to look at the DIY PSU schematics and see what people like to use. You might try looking through the model libraries of LTSpice, as they have most of the non-japanese popular transistors.

If I made a mistake hopefully someone will point it out.

I understand what you're going through. The confusion cleared up for me when I found a selection of transistors I liked and began to understand a lot about each transistor's function in a circuit. If you know well why the specific transistor is needed, it is often trivial to select a substitute.

Hope this helps,
- keantoken

Mr Evil 5th May 2009 12:07 AM


Originally posted by keantoken
...I see the BAT54 being used in audio (though according to simulation model this diode has extra low voltage drop and so you might want to consider that when designing)...
It has a low forward voltage drop because it is a Schottky diode. There are a few places where these are useful, e.g. precision rectifiers. I like to make sure I have some small-signal Schottky diodes on hand, but I only very rarely use any.

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