[time-nuts] What is a Time-Nut grade Zero Crossing Circuit?

Bruce Griffiths bruce.griffiths at xtra.co.nz
Wed Jul 30 23:05:04 EDT 2008

SAIDJACK at aol.com wrote:
> Hi Bob,
> since the sine wave is symmetric, you can use a simple LVC type CMOS  
> inverter with 1M Ohm resistor from input to output, and a 100nF cap (or the  largest 
> COG cap you can find) from the input of the inverter to the sine wave  output.
> You may also want to load the sine wave output with 50 Ohms, as required by  
> the source.
> This works very well. Don't use a schmitt trigger inverter  though.
> bye,
> Said

Noise is lower if you use a pair of resistor to bias the inverter input 
at the threshold rather than the feedback resistor.
A feedback circuit can be added to stabilise the output duty cycle.

If you want subpicosecond jitter you need to use a different 
device/logic family.


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