High frequency stuff

Here are a few thoughts.

Say we have:

                 o Vcc/ Vdd etc.
                 |
                 |
                 |
            _____|_____
           | B |
           | L |
           | A |
           | C |
   o-------| K |------o output
 input | |
           | B |
           | O |
           |_____X_____|
                 |
                 |
                 |
                 |
                 o
               Ground (Vss, Vee, etc.)

I think we could identify several potential issues for discussion here:

    1) Assuming that the "insides" of this black box respond
        INSTANTANEOUSLY to changes at the terminals, is the set
        of caps currently in the IBIS model sufficient for modelling
        the AC behavior of the four-terminal device shown above?
        (Answer: No. To be *rigorous*, you need 4 self-capacitances
        and 6 coupling capacitances connected between every pair of
        terminals.) The question in my mind is whether we need this level
        of detail for DIGITAL circuits... It could certainly be important
        for ANALOG microwave circuits, but I don't think IBIS is quite
        "ready for prime time" there.

        Naturally there could also be inductances in series with every
        lead, with mutual inductances coupling every pair.

    2) Presumably the black box is really NONlinear--the capacitance
        values depend upon the operating point. What can we do in this
        case? Provide a table of C-V data points? What do you do with
        these in a simulation? And how are they measured?

    3) If the "guts" of the black box have significant "memory" and
        DON'T respond instantaneously when we wiggle the terminal voltages,
        what can we do? You can talk about "small-signal" impedances
        and admittances, but these are only valid about a quiescent
        DC operating point--not when the device is slewing rapidly
        through different regions of operation. And it's even scarier
        to think about how to use these in a nonlinear large-signal
        simulation. (Note that this case includes the "feedback"
        situation that we've recently been discussing in the forum.)

   Much of this smells like university research to me...but perhaps
we can conquer it?

--Eric
Received on Fri Jan 7 14:38:00 1994