Peter Onion wrote:
>
> On 16-Jan-02 Peter Onion wrote:
>
> > I assume you mean by putting a suitable resistor between the o/p and i/p of
> > the
> > gate ?  I did think about this, but since I'm using a schmitt trigger
> > (because
> > I have a spare gate in a 74HC14 that is used for other things) I didn't try
> > it
> > as I don't think you can bias schmitt trigger gates into a "linear" region,
> > but
> > I may be wrong.
> >
> > I'll give it a try tonight and let you know if it works or not.
>
> Well I spent a few hours playing with this idea last night.
>
> It seems that is it impossible to get a 74HC11 inverter into it's linear region
> without it oscillating at some high frequency.  I tried all sorts of things to
> calm it down, higher and lower feedback resistors, small and large C, ferrite
> beads etc etc etc...

That's why you use a schmidt trigger inverter
like a 74HC14, the hysteresis lets you bias it
with 2 resistors between the input thresholds,
and you can drive it hi/low with the smallest
AC signal that the threshold delta allows.
1.2v AC should be do-able.
I did suggest this a couple posts back. :o)
-Roman

>
> In the end I gave up and went back to using the x2 bipolar amp infront of a
> schmitt trigger.

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