John Ackermann N8UR wrote: > 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. > > John
One could also use a PECL to TTL level translator. JPL have used ECL dividers throughout to produce 10MHz, 1MHz and 100KHz outputs from the 100MHz signal derived from a Hydrogen maser: http://tmo.jpl.nasa.gov/progress_report2/42-30/30I.PDF Where TTL outputs are required an ECL to TTl translator followed by a discrete amplifier to drive TTL levels in a 50 ohm load was used. Bruce _______________________________________________ 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.
