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Comparator for restoring 27MHz clock from sine signal.

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OwO:
Why deal with all these hacks when a PL133-37TC costs $0.5 and can accept 100mV peak to peak input  :-// Really reminds me of that "unnecessary complexity" thread someone mentioned "baroque designs"  :-DD

nick_d:
Can this do it?
http://www.ti.com/product/SN74LVC1G14

The qiuescent current is 10uA, would have to check power draw from switching based on your input frequency and so on.

The amount of hysteresis at 3V (the difference in input thresholds) can be between about 0.4V and 1.0V. Thus you would want an input sine wave of at least 1V (plus margin) peak to peak.

Do you actually need the high pass filter and centre-ing circuit? If so then I suggest to bias the input with a resistive divider, say 1M to +3V and 1M to ground. Biasing it with feedback may be problematic as has been mentioned.

If the input frequency is going to be high enough you won't need the Schmitt and could go for this one:
http://www.ti.com/product/SN74LVC1G04
That would allow a much smaller peak to peak input, if you can bias it accurately.

Finally, whatever you are driving with this clock signal might be able to handle the sine wave input directly, check it!

Edit: whoops just noticed the 100mV peak to peak specification. Yes that would be problematic for the 74LVC1G04 solution. Back to the drawing board. New idea: what about a comparator that compares the signal with the RC filtered low passed version of the signal? Set cutoff to somewhat lower than 27 MHz. Use a slow enough comparator that no hysteresis is needed, the slower slew rate would save power too. The only tricky part is most comparators have open collector output, and the pull-up will waste power.

cheers, Nick

Esmund:
Ok, thank you for all responses. I'll design PCB to test some of concepts that you gave me here. I'll share my results as soon as I finish, maybe it'll be useful for someone else :). To be honest I really like idea to use PL133-37TC, I missed at first that ac coupled input operates from 0.1V.   

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