[sdiy] SMT transistor for white noise?

[Paul Perry]

Is it possible to simply amplify the thermal noise in a high value resistor?
paul perry Melbourne Australia

On Sat, Dec 13, 2025 at 10:15 PM Mike Bryant <mbryant at futurehorizons.com>
wrote:

> Too true 🙂   A large percentage of the world's small signal transistors
> now come from a huge fab in Chongqing and they just brand them to whatever
> their client wants.
>
> Small power devices may be your best bet for more consistent noise as they
> are larger area and so will have a few more defects in them.
> ------------------------------
> *From:* Synth-diy <synth-diy-bounces at synth-diy.org> on behalf of
> Gordonjcp <gordonjcp at gjcp.net>
> *Sent:* 13 December 2025 10:32
> *To:* synth-diy at synth-diy.org <synth-diy at synth-diy.org>
> *Subject:* Re: [sdiy] SMT transistor for white noise?
>
> On Sat, Dec 13, 2025 at 12:55:30AM -0500, Mike Beauchamp wrote:
> > I'm noticing my latest batch of MMBT3904 by ONSEMI are barely creating
> any
> > white noise, requiring about 8000x gain to get up to +/- 5V.
> >
> > Previous batches of the MMBT3904 only required about 500x gain to get up
> to
> > +/- 5V. When I was using TH 2N3904, I think the gain required was only
> about
> > 200x.
>
> I'm guessing you've got cheap Chinese ones this time round. They're far
> too high quality to use as noise sources.
>
> You need to pay a bit extra to get American-made dodgy counterfeit
> components for this.
>
> --
> Gordonjcp
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