Junction Noise

[Martin Czech]

:::>The best noise generator trans I've found are the 2SC828 and 2SC829.
:::
:::I did some tests with the SH09 noise circuit. I got the best results with 
BC140 and BC 141.
:::Note that these are medium power types (To5 package). You shouldn't overlook 
power transistrors!
:::I haven't tried the 2S828 and 829 though.
:::
:::/Jorgen

Again: the individual transistor parameters have a great influence
on noise. There is a lot of variation. Low noise types are often
selected devices. E.g. a 2SC828 may differ in this respect from
manufacturer to manufacturer. Most transistors amd diodes
are not designed to run in avalanche breakdown, there's
no spec for this mode, so I wouldn't expect that a specific
type would always behave the same, if you pick -say- 100
transistors with the same stamp but diffrent supplier.
You have to select, and I think this is the main reason
why shift register noise became fashionable.

btw.: what about scarmbling junction noise with such a
shift register? The spectral density should be fine
as well as distribution, and it should be real random,
not pseudo, since the junction noise sometimes
toggles a bit in the first stage, for example.


m.c.