[sdiy] SMT transistor for white noise?

[mark verbos]

https://www.lavarand.org/
LavaRnd
lavarand.org





> On Dec 14, 2025, at 23:28, Hugh Blemings <hugh at blemings.org> wrote:
> 
> Hi All,
> 
> I'm reminded of "ChaosKey" a design that Keith Packard and Bdale Garbee put together to create entropy for the random number generator in the Linux kernel.  It's based off a pair of transistors biased up at something like 20V and fully open source.  https://altusmetrum.org/ChaosKey/
> 
> Might be of interest?
> 
> Cheers,
> Hugh
> 
> 
> On 15/12/2025 07:38, Mike Bryant wrote:
>> I think you'll find the LM194 and its clones are the only monolithic ones left now.   There were others a few years ago but most others are now two very well matched but separate die in the same package.
>> From: Synth-diy <synth-diy-bounces at synth-diy.org> <mailto:synth-diy-bounces at synth-diy.org> on behalf of Ian Fritz via Synth-diy <synth-diy at synth-diy.org> <mailto:synth-diy at synth-diy.org>
>> Sent: 13 December 2025 19:53
>> To: Gordonjcp <gordonjcp at gjcp.net> <mailto:gordonjcp at gjcp.net>
>> Cc: synth-diy at synth-diy.org <mailto:synth-diy at synth-diy.org> <synth-diy at synth-diy.org> <mailto:synth-diy at synth-diy.org>
>> Subject: Re: [sdiy] SMT transistor for white noise?
>>  
>> Do they have these in monolithic pair packages?
>> 
>> Ian
>> 
>> > On Dec 13, 2025, at 12:27 PM, Gordonjcp <gordonjcp at gjcp.net> <mailto:gordonjcp at gjcp.net> wrote:
>> > 
>> > On Sat, Dec 13, 2025 at 11:11:54AM +0000, Mike Bryant 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.
>> >> 
>> > 
>> > Many years ago I bought a bag of something like 500 of the cheapest Chinesiest BC548-wannabes from Some Dude In Shenzen On eBay, expecting to maybe hand-match a couple of sets of a dozen reasonably close ones for filters.
>> > 
>> > Nope.
>> > 
>> > Any two you pulled out of the bag at random would have the same Vbe down to *microvolts*.
>> > 
>> > So that was a quicker evening than I anticipated.
>> > 
>> > --
>> > Gordonjcp
>> > 
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> -- 
> I am slowly moving to hugh at blemings.id.au <mailto:hugh at blemings.id.au> as my main email address.
> If you're using hugh at blemings.org <mailto:hugh at blemings.org> please update your address book accordingly.
> Thank you :)
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