[time-nuts] ? phase comparison or other device

Chuck Harris cfharris at erols.com
Sat Jun 30 19:27:18 EDT 2007

Dr Bruce Griffiths wrote:
> ); SAEximRunCond expanded to false
> Errors-To: time-nuts-bounces+cfharris=erols.com+cfharris=erols.com at febo.com
> Pete wrote:
>> ); SAEximRunCond expanded to false
>> Errors-To: time-nuts-bounces+bruce.griffiths=xtra.co.nz+bruce.griffiths=xtra.co.nz at febo.com
>> Magnus,
>> This discussion is why I have allowed the ADA4899-1 to saturate in the ZCD
>> posted earlier. The transition times up & down in the second stage are 350 
>> to
>> 400 ns; thus I believe the <50ns overload recovery doesn't degrade the
>> measured jitter. With 500MHz 'scope bandwidth, the 1KHz squarewave
>> output has <1% over/under shoot & appears noise free at the zero crossing.
>> The output transitions are fast enough for my HP 5370A to  show < 1ns
>> jitter over 1K or 10K samples.
>> Regards,
>> Pete Rawson 
> Pete
> What about the power supply noise that appears at the amplifier output 
> during saturation?
> Power supply noise is almost always much larger than the opamp input noise.
> A simple resistor + diode clamp in addition to the feedback clamp will 
> easily attenuate the output noise of an opamp with diode clamps across 
> its feedback resistor.

The output of an opamp is always referenced to its power supply,
regardless of the configuration.  If the power supply is noisy,
the output is noisy.

-Chuck Harris

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