On 9/5/06, John Waters <john_fm_waters@hotmail.com> wrote:
>
> Hi All,
>
> For some of the optocoupler chip, e.g. 4N27, there is a pin coming out
> from
> the base of the phototransistor. The phototransistor senses the light
> coming
> from the photodiode to turn itself on or off, so what is the base used
> for?


Controlling speed of response (hang a cap on it) or anything else you'd like
to do.
You could have the transistor turned on by one isolated input, or N
non-isolated inputs through diodes and resistors.
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