I found a very nice diode array which seems perfectly suited for a fast sampling oscilloscope front-end. The Skyworks SMS3923-081LF has four fast Schottky diodes in a dual series pair arrangement. It comes in a tiny 6-lead SC-88 case, and the datasheet has a model for the package parasitics as well as SPICE parameters. I made an LTspice component from it.

At first I forgot to add the "p" to the CJO parameter, making it 0.9 Farads instead of pico-farads. This did not simulate well.

The only thing I don't particularly like about these diodes is the diffusion transit time (TT SPICE parameter) of 80 ps. I wish it were smaller, but the truth is that I'm not going to get strobe pulses anywhere near that short, at least in the near future.

Other than that, it looks like a winner.

I'm still playing with some simulations of this part. I'll update the log with results soon.