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

[SAIDJACK at aol.com]

Hi Bruce,
 
that would work too. We get <330fs jitter rms with this circuit using  the 
Fairchild UHS LVC family, that's pretty much the noise floor of the  OCXO :)
 
If you use a bias network, you won't get 50% symmetry since it will never  
perfectly match the inverter's inflection point (which changes with temp etc),  
and you may insert noise from the power supply. With the feedback resistor it  
will operation at the inversion point without adding power  supply noise.
 
bye,
Said
 
 
In a message dated 7/30/2008 20:06:12 Pacific Daylight Time,  
bruce.griffiths at xtra.co.nz writes:

>   
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.

Bruce




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