[time-nuts] Zero-Crossing Detector Design?

lists at lazygranch.com lists at lazygranch.com
Thu Jul 19 22:34:22 UTC 2012


Are you speaking of slew rate limiting in the strict sense of the word, that is a current starved input stage due to the presence of a compensation cap? Or are you using the term slew more vaguely. 


-----Original Message-----
From: Magnus Danielson <magnus at rubidium.dyndns.org>
Sender: time-nuts-bounces at febo.com
Date: Fri, 20 Jul 2012 00:15:58 
To: <time-nuts at febo.com>
Reply-To: Discussion of precise time and frequency measurement
	<time-nuts at febo.com>
Subject: Re: [time-nuts] Zero-Crossing Detector Design?

On 07/19/2012 11:53 PM, ehydra wrote:
> On the Bruce page there is a table with increasing stage amplification
> from low-level to the output.
> If this is the optimum for low jitter how does it connect to the
> well-known rf design philosophy to have the highest amplification at the
> first stage, not the last stage, to have maximum S/N ?
>
> Any idea?

You balance noise bandwidth with slew-rate gain. Normally you just look 
at the noise of the amplifiers and comes up with the traditional gain 
formula. Here you only want the first amplifier to have the bandwidth 
that supports the slew-rate it will have, in the same way the next 
amplifier's bandwidth and gain is set to optimum. The goal becomes to 
achieve optimum slew-rate gain with least added noise. The formulas in 
the article is derived for same amplifier noise, where as Bruce 
generalized them for the case where the amplifier noises may be different.

So, different design goals makes for different solutions. Makes sense or 
should I go into more detail?

Cheers,
Magnus

_______________________________________________
time-nuts mailing list -- time-nuts at febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.


More information about the time-nuts mailing list