For most transistors it takes around 7 volts to break down the reverse
emitter/base junction so this circuit may not work at 5 volts. Maybe you
can substitute a low voltage zener for the transistor.
Maris


At 09:13 AM 9/1/99 +0200, you wrote:
>Hi,
>as more people wished, here is the true h/w random number generator:
>
> White noise generator, design by dr. Imre Bartfai, 8/30/1999
>
> +--------------------------------------------------------------------- Vdd
> |                           220k                    220k               5V
> |                       +---\/\/\---+           +---\/\/\---+------+
> |                       |           |           |           |      |
> | Ge                    |    |\     |           |    +------+      \
> | EFT317 PNP      +-----+----|- \   |           |    |             / 220k
> |      C          |     |    |    >-+----| |----+    |     |\      \
> |   |/            \  +-------|+ /        47n    |    +-----|- \    |
> +--B|        220k /  |  |    |/                 |    |     |    >--+
>     |\            \  |  |  1/2 LM358            +----------|+ /    |
>       |E          |  |  |                       |    |     |/      \
>       +----| |----+--+  +                       +    +             /  47k
>       |    47n    |     |                       |    | 1/2 LM358   \
>       \           \     \                       \    \             |
>  4k7  /        1M /     / 2k2                1M /    / 2k2         + out
>       \           \     \                       \    \
>       |           |     |                       |    |
>       +-----------+-----+-----------------------+----+---------------- Vss
>
> Standard TTL can not be driven, but CMOS (and maybe LS) are o.k.
> The power supply must be filtered thoroughly due to the high gain!
>
>Regards,
>Imre
>
>