How do you LP wo/caps?

[Harry Bissell]

Hi Y'all...

I guess the buffer capacitance is only about 1-5pF.  I surmise the value by
adding another cap and halving the output frequency... I'm sure that the
buffer can account for 'that much' capacitance....

Some have noted this might not be repeatable. I was only able to tune down to
about 1KHz in the simulation... so who knows ???

And sometimes simulations don't work as advertised anyway...

H^) harry

patchell wrote:

> tomg wrote:
>
> > Harry says the simulation works! and that it's buffer
> > capacitance. I'm inclined to agree. Removing the
> > buffers turns it into a 2 stage vca. Why it's working
> > on buffer capacitance is another question.
> >
>
>     I am surprised too...the input capacitance in a BJT follower is pretty well
> boot strapped, and there would be no miller capacitance to speak of...course, it
> has been a while since I have had to think about such things.
>
> >
> > cya Friday...
> >
> > Tom
> >
> > > > > I don't know if you are into SPICE but this wd solve the
> > > > > question of how useful spice is or is not ;-)
> > > >
> > > > Eh, rather, how able he is to use spice for something....
> > > >
> > > > ;)
> > >
> > > I sent it to Harry..Let him figure it out...;-) ( if he has time that
> > is..)
> > >
> > > > Anyways, most likely are you toying around with the dominant poles...
> > > which is
> > > > not a bad thing but I bet my horse (I don't own one, so thats fine) that
> > > you
> > > > should really go into individual trimming on this one, so I would not
> > make
> > > use
> > > > of it in a commercial product... have you tested temperature stability
> > of
> > > > frequency/Q ? Power-supply stability? Do you ever test that BTW?
> > >
> > > Y-Yes I do..;-)
> > >
> > > > I would not
> > > > be supprised if you would find it more sensitive than normal filters.
> > > > Good or bad, well, thats another plate...
> > > >
> > > > Cheers,
> > > > Magnus
> > >
> > > Me ether!
> > >
> > > Tom
> > >
> > >
> > >
>
> --
>  -Jim
> ------------------------------------------------
> * Visit:http://www.silcom.com/~patchell/
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> * You didn't pay enough!
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