Hal Murray wrote: >> Start with a buffer amp and then a decent Schmidt trigger. > > If you have a clean input signal, a Schmitt trigger doesn't solve any > problems. It does help if you have a slowly rising signal such that noise > might be significant while the signal is near threshold. A 10 MHz sine wave > is slow relative to AC logic. > > Since we were recently speaking of LPROs, their user manual has a section on > how to convert 10 MHz sine waves into TTL signals. None of their suggestions > used Schmitt triggers. > > This feels like the sort of thing that should have been hashed out here by > now. Is it time to start a FAQ?
The TADD-2 uses an input circuit published by Wenzel in their "Waveform Conversion" document at http://www.wenzel.com/documents/waveform.html. I haven't measured its standalone jitter, but its input sensitivity is great -- it will reliably trigger a CMOS gate from an input at least down to -10 dBm, maybe lower (I don't recall the exact limits I found when I tested). If you build this, note one thing -- with the 100 ohm emitter resistor specified, the square wave output is more like 6V than 5V p-p. I use 120 ohms instead to get a 5 volt output. While the Wenzel circuit requires a modest handful of discrete components, I think it's the most useful solution by a pretty clear margin for our typical requirement of driving a single-ended logic gate from an HF source. John _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
