[time-nuts] ? phase comparison or other device

Dr Bruce Griffiths bruce.griffiths at xtra.co.nz
Fri Jun 29 03:52:22 EDT 2007

Ulrich Bangert wrote:
> Enrico,
> you are right: Both of these articles should be read with Collins's
> perhaps the better (and newer!) one. 
> There is however one question remaining for me: When I learned
> electronics it was generally considered bad design to let an amplifier
> run into limiting due to supply limitations. If limiting was needed, so
> was the rule, then it should be accomplished by planned feedback, say an
> pair of antiparallel diodes in the feedback path. Can you give some
> comments on whether this also applies to ZCDs or if really supply based
> limiting is necessary?
> Best regards
> Ulrich Bangert 

Diode clamps are usually essential particularly with opamps as in most 
cases their recovery from input overdrive is otherwise too slow to be 
useful in such circuits.
The Collins paper also indicates, as I suspected, that the -5v and +5V 
clamp levels used in the JPL ZCD are somewhat arbitrary and lower clamp 
levels can be used.


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