# Low-noise audio-frequency BJT?

I found myself looking for a low-noise PNP transistor the other day.

I couldn't find any parametric searches that listed noise performance. Even from the transistor manufacturers. You can search by beta, $V_{ceo}$, and $I_{c}MAX$. All these searches seem to return a table of every general-purpose part in the manufacturer's portfolio. Not helpful.

This circuit needs to have low-noise at audio frequencies. RF transistors seems to be better characterized for noise, but they aren't necessarily low-noise at audio frequencies.

The best I have found was a forum thread at DIYaudio, but the recommendations tended to be old-school, even obsolete parts. I'm looking for a mass produced transistor in SOT-23 or smaller.

So recommendations are welcome, but I'd really like to see a selection tool or parametric search that includes this information.

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I found these devices with a search on the NXP web site. They seem similar to the BC108 which used to be the low-noise device most people used to use.

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 Leon's link is for BC859 / BC860. Not sure how trustworthy deep links to NXP.com are. – markrages♦ Feb 18 '11 at 19:06

MPS4355 if RS is low -- up to a few hundred ohms

2N4250 is RS a few K ohms

http://www.thatcorp.com/THAT_IC_Selection_Guide.shtml#XsistorArrays

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 Could you explain what 'RS' means please. Your links seems irrelevant as it doesn't contain any of the products mentioned. – trygvis Nov 22 '12 at 13:51