On Aug 20, 1:55 pm, John Devereux <jdREM...@[EMAIL PROTECTED]
> wrote:
> Paul <energymo...@[EMAIL PROTECTED]
> writes:
> > Hi,
>
> > Does anyone know of inexpensive (less than 30 cents each @[EMAIL PROTECTED]
QTY 1000)
> > high frequency Schottky diodes with no more than 0.01pF per diode?
>
> > The best I can come up with are from Skyworks Inc., which are around
> > 0.1pF, although they have some that are a bit less capacitance, but
> > they're expensive.
>
> Are there are *any* discrete components with capacitance that small?
> The capacitance between its mounting pads would likely be more than
> that.
>
> --
>
> John Devereux
I did a quick hack estimate of capacitance between a couple of 20mil
square pads 40 mils apart on 1/16 inch FR-4, in this way: the
capacitance per inch of a differential microstrip with 20 mil traces
separated by 40 mils is 2.4pF/inch (more or less). So .02 inches of
that would be about .05pF. I would expect fringing fields to add a
bit to that. Putting a package on top of those pads makes things
worse, as does having wires that come from the pads and end up very
close together at their ends. Guess you could shrink the pads
further, though you still end up with wires that come pretty close.
I wonder why the need for such low capacitance...
Cheers,
Tom
|
