[time-nuts] Distribution amps and slew rate

David Hooke dhooke at gmail.com
Sat Nov 3 17:44:09 EDT 2012


Given that slew rate is so critical, why do we distribute sine waves and 
perform the zero-crossing detection at every target instrument?


> Trigger jitter is the noise at the trigger point. it's a combination 
> of thermal noise and the slew-rate at the trigger points. It is often 
> that trigger jitter is dominated by slew-rate, but there is also 
> internal sources of trigger jitter. The slope dependent trigger jitter 
> follows the formula:
> t_jitter = v_noise / s_slew
> t_jitter is the trigger jitter (s)
> v_noise is the noise power (V)
> s_slew is the slew rate (V/s)
> When the time-span of a measurement is long, long-term stability comes 
> in as well as systematic drifts. Also, systematic noise such as hum 
> also becomes important.
> To see how much you depend on slew-rate limitation, you can reduce the 
> amplitude, and as this reduces the slew-rate you can separate the 
> slew-rate dependent jitter from the intrinsic jitter of the input. It 
> also helps you to identify if you need to work on the slew-rate limit 
> rather than anything else.

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