[time-nuts] ? phase comparison or other device
Dr Bruce Griffiths
bruce.griffiths at xtra.co.nz
Sat Jun 30 18:27:34 EDT 2007
> ); SAEximRunCond expanded to false
> Errors-To: time-nuts-bounces+bruce.griffiths=xtra.co.nz+bruce.griffiths=xtra.co.nz at febo.com
> 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
> 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.
> Pete Rawson
What about the power supply noise that appears at the amplifier output
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.
An npn plus a pnp resistor ccan also be used to clamp the output of an
opamp whilst still suppressing the noise gain to a very low value and
prevent opamp saturation.
More information about the time-nuts