On 9/6/06, David VanHorn <dvanhorn@microbrix.com> wrote:
> 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.

  Like inproving the sensitivity at the same LED current, by
pre-polarisation of the phototransistor.

Vasile
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