Am 13.04.2016 um 07:03 schrieb Bill Byrom:
I agree with earlier comments that the Analog Devices SiGe voltage comparators appear to be a good choice, with 37 ps typical rise/fall (20%/80%): http://www.analog.com/media/en/technical-documentation/data-sheets/ADCMP580_581_582.pdf The evaluation board single unit price is about $299: http://www.analog.com/media/en/technical-documentation/evaluation-documentation/310187823ADCMP572_3_80_1_2EB_0.pdf
If that is too much, you can do it in the style of my home-etched quickie: 18 * 14 mm, 0.5mm thick FR4. The trick is to get from chip output into the semi-rigid coax as quickly as possible. The CML outputs have an integrated 50 Ohms back termination. SMA launchers will probably complicate things.
This is what has generated the waveforms in my previous post. Note that the 20 GHz sampler is already close to its own risetime limit, so what you see is probably worse than reality. I should have used the 50 GHz plug in with its 9 ps risetime but then I usually avoid that because I don't want to put it in jeopardy. If one wants more voltage, an alternative might be a driver for 10 GBPS DFB laser diodes. 5V in 35 ps seems possible. ADN2525 or so. Hittite is now AD. That is a good thing. Mouser or Digikey and no longer prices and old data sheets under NDA. If you think at Potato Semi chips, watch the loading conditions. Buffers that can barely drive a 0.6 pF FET probe are a bad joke. regards, Gerhard
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