On 3/12/2010 10:49 AM, Spehro Pefhany wrote:
>
> Not exactly practical in most cases (not much output current available,
> requires high input voltage&  power), but there's this simple&  cheap one:
>
>
>                 +12VDC              eg. 2N4401
>                    +       E    C
>                    |  ___
>                     -|___|- -   -  output (-300 ~ -400mV)
>                              ^ /
>                       1K     ---
>                               |
>                               |
>                              ===
>                              GND
>
>
> Don't bother trying to SPICE it.

That rings a bell... I saw this many years ago. Just tried it and got 
open circuit voltage of -419mV and a short circuit current of 900nA.

It's easy to explain: when the emitter-base zeners, the collector makes 
a negative voltage because of [???]
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