[sdiy] 3.3V regulator ?

[Michael E. Caloroso]

Linium wrote:
> BTW, what is the purpose of the silicon diode before the zener ? If i 
> understand well it will make the voltage drop by 0.6v. So it will produce 
> something like 4.4 V from the 5v power line then this will turned into 3.3v 
> by the zener. Is it to make the zener produce less warmth ? Or may be to 
> protect the CI from an accidental negative voltage ?

The silicon diode is used to raise the zener voltage.  They are wired in
series.  When you measure the voltage drop across the 3.3v zener and the
0.7v silicon diode, the sum is 4.0v.  Very common technique.

MC