Wanted: the definitive RF equivalent model for a resistor!
 

On Sun, 27 Jun 2004 01:56:00 +0100, "fellow" wrote:


"Paul Burridge" wrote in message
.. .
Hi guys,

I've seen a lot of stuff on the net about Spice modelling that takes
into account paractics at RF, but they typically turn out to be....

-----inductor-----resistor------inductor--------
| |
| |
-----cap-----|


Or othertimes, the cap is shown as being across the entire network;
ie., at the outer extrameties of the inductors. The difference in
practice between the two examples is *large* in effect so which is
correct if either, and equally importantly, how can the skin effect be
incorporated into the model to give a more complete picture?
--

"What is now proved was once only imagin'd." - William Blake, 1793.

Same equivalent circuit in the book"Noise Reduction Techniques", but the two
Ls combined as one L. Personally, I would have thought that there should be
an additional inductance in series with R, both in parallel to cap but I
suspect it's ignored because R and C dominate.

Absolutely. It's evident from the simulations I've run that having a
generous lead-length doesn't seriously degrade impedance anything like
as much as the size of the parasitic capacitance does. The value of
Cpar is, it appears, of much greater consequence that attempting to
achieve zero lead length, at up to a Gig at any rate.
--

"What is now proved was once only imagin'd." - William Blake, 1793.