Apropos of the '5 GHz beads' and 'new kinds of parts' threads, I'm considering doing new small parts of our own, based on magic GHz transistors, but house-trained enough to use in normal boards (with op amps and so on).
Specifically, it looks like a win to make mezzanine-packaged SiGe BJTs with beads, on little crenelated boards. They'd be something like TMB-package LEDs, but without the plastic overmold.
I was playing around in LTspice, using the Infineon and Murata models for the BFP640 and the GHz beads that include the package parasitics, it seems that the main obstacle to getting good stability at high collector current is the pad capacitance right at the transistor.
With pad capacitances below 0.1 pF or so, the beads make them nice and stable at all relevant collector currents, but at 0.5 pF, you have to stay below 3 mA or thereabouts. Series inductance doesn't matter much for stability, or for performance at < 1 GHz, where we mostly live.
So, we're getting some boards made with a whole bunch of 5-mm squares, each containing a fast transistor and two or three of these magic beads.
Dunno yet how we'll get them apart--probably routing and snap tabs, or else V-grooving. And then there's the question of how to use them in production. We'll see!
Cheers
Phil Hobbs