[time-nuts] reference oscillator input circuit

Magnus Danielson magnus at rubidium.dyndns.org
Wed Dec 8 20:50:12 UTC 2010


On 12/08/2010 09:13 PM, Rick Karlquist wrote:
> Yes, and thus if you are going to use a comparator or line
> receiver (not recommended), then you should use the SLOWEST
> one that still works, if you want to optimize jitter.
> This is because the noise bandwidth is less.

For optimum result you need to balance the slew-rate gain (essentially 
gain of the transition slew-rate) and the amount of added noise. You 
need a certain amount of bandwidth for a certain amount of output 
slew-rate, but higher bandwidth also gives more noise. A multi-stage 
setup use moderate gain and bandwidth in the initial stages, but it 
increases down the line.

A few links:
http://www.ko4bb.com/~bruce/CLKSHPR.html
http://www.ko4bb.com/~bruce/ZeroCrossingDetectors.html

As for transformer isolation, for most uses I find it fairly useless, 
but an RF-choke to isolate the front-end and the electronics RF-wise in 
common mode sense is more useful IMHO.

Cheers,
Magnus




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