> i would recommend you to use 1N5817 - 1N5819
> shottky barrier diodes.
> this have a drop of 0.6V at 1A current flow.
> so if your current flow is some 100mA definitely you will be getting some
> voltage drop below 0.2V

Unfortunately, forward voltage drop does not decrease anything like linearly 
with falling current.
You'll probably see 300 mV+ at 100 mA with a 1N5817.

The lower voltage (20V) 1N5817 has a lower drop than the 30V 1N5819. About 
0.1V in practice, which can be useful. I alsways specifiy 20 Volt parts 
rather than 30V in locations where I want lowest drop if the circuit can 
tolerate it. The difference can represent a ~5% efficiency gain in low 
voltage (eg single NimH cell) systems.

As noted before - an opamp or comparator and FET will give you close to zero 
volt drop if it matters enough to you.


          Russell McMahon 

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