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 <mag...@rubidium.dyndns.org>
Sender: time-nuts-boun...@febo.com
Date: Fri, 20 Jul 2012 00:15:58
To: <time-nuts@febo.com>
Reply-To: Discussion of precise time and frequency measurement
<time-nuts@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
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