On Thu, Jul 19, 2012 at 3:57 PM, Richard (Rick) Karlquist <rich...@karlquist.com> wrote: > A fast comparator seems like a good idea, and it > is simple, however it is actually the last thing > you want to use. High thermal sensitivity and high jitter.
The comparator will work but you need some positive feedback to create hysteresis. The problem is the hysteresis cause the output square wave to be not quite 50% duty cycle. But maybe you don't care if the goal is to count cycles. or if you only look at (say) raising edges. > > Rick > > On 7/19/2012 1:35 PM, Dan Kemppainen wrote: >> >> Or use a fast comparator such as an ADCMP600 series. Much lower delays, >> and faster rising/falling edges. >> FYI, I've had good luck with this at 30Mhz. You could transformer couple >> this one, or simply couple it through a cap. >> >> Dan >> >> On 7/19/2012 3:47 PM, time-nuts-requ...@febo.com wrote: >>> >>> This is sort of a FAQ: the argument was already discussed here. One of >>> the >>> most interesting idea (in my opinion) is to use an RS485 line receiver >>> like >>> the ST3485, MAX483, ADM485. They are actually transceivers so they >>> must be >>> tied permanently in RX. Since they are differential you can also put a >>> 1:1 >>> (or a 1:4 to raise the level) transformer to isolate the input too. >> >> >> >> >> _______________________________________________ >> time-nuts mailing list -- time-nuts@febo.com >> To unsubscribe, go to >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. >> > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. -- Chris Albertson Redondo Beach, California _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
