# 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

Look at what the ham radio guys use for their direct conversion receivers . since the sensitivity of the direct conversion receiver depends on the low noise audio amplifiers that follow the RF mixer that conversts the signal direct to audio . you may find some good recipes there cheers mike ZL1BTB

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