A transformer or differential signaling would also have the virtue of allowing easy galvanic isolation to prevent ground loops.
Fiber optic and line receivers often set their switching threshold using a positive and negative peak detector. The same design works very well for analog peak to peak automatic triggering in oscilloscopes. AN47-59, 50 MHz Adaptive Threshold Trigger Circuit: http://www.linear.com/docs/4138 AN61-15, High Speed Adaptive Trigger Circuit: http://www.linear.com/docs/4150 On Thu, 23 Feb 2012 16:01:55 +0100, Azelio Boriani <[email protected]> wrote: >To square a sine 10MHz you can use a 4:1 transformer with the center tap: >connect the tap to GND and use a differential line receiver (ADM485, >MAX485) connected to the differential signal that comes out from the >transformer. The input of the transformer receives the single ended sine >10MHz. > >On Thu, Feb 23, 2012 at 3:51 PM, Azelio Boriani ><[email protected]>wrote: > >> And by using a differential pair is like halving the rise time: when one >> arm rises the other falls, effectively doubling the speed of the crossing >> and the sharpening of the trigger event. Sort of auto_ schmitt_trigger... >> >> >> On Thu, Feb 23, 2012 at 3:45 PM, Azelio Boriani >> <[email protected]>wrote: >> >>> I recommend the differential pair: here the trigger have to sense the >>> crossing of the two signals and this crossing is well definite. >>> >>> >>>> Darn those finite rise times<grin> >>>> I've been bitten more than once by this very phenomenon (which I admit >>>> doesn't say a lot for me.. being bitten once is ok, but since I've had >>>> multiple bites...) >>>> >>>> But this brings up an interesting time-nut problem for the hive mind.. >>>> >>>> If you had to design some scheme for interconnecting "boxes" and wanted >>>> to transmit an accurate time sync, what should it look like, so that you're >>>> insensitive to things like rise time. >>>> >>>> (maybe this harkens back to the discussion about 10 MHz, why sine vs >>>> square wave distribution) >>>> >>>> It has to be a single signal (maybe a differential pair), because >>>> otherwise, don't you have potential for skew between the multiple signals. >>>> >>>> Zerocrossing sort of works, if you take only one direction, but does >>>> asymmetry of the waveform screw you up? (e.g. what's "zero".. is it half >>>> way between peak values + and -?) _______________________________________________ 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.
