[time-nuts] SR620/PM66xx/CNT-90 input stages

Bruce Griffiths bruce.griffiths at xtra.co.nz
Wed Jun 21 06:40:11 EDT 2017


Your assumptions about my comment are unfounded. It was just intended as an additional reason as to why direct connection to a comparator input isnt a good idea with a high source impedance. The original post asked why a buffer was needed.

 Bruce

> 
>     On 21 June 2017 at 22:14 Charles Steinmetz <csteinmetz at yandex.com> wrote:
> 
>     Bruce wrote:
> 
>         > > 
> >         If the source impendance at dc is 10k at dc a bias current of a few
> >         microamp produces a dc offset of tens of millivolts which may be an
> >         issue if the signal amplitude is low and has a low slew rate.
> > 
> >     > 
>     Jeez, Bruce, it was nothing but a thought experiment to illustrate why
>     an amplifier's DC input current is not a reliable proxy for input
>     impedance It was not a suggestion for how to design an amplifier input.
>     And that should have been obvious to you -- I'm sure it was to
>     everyone else.
> 
>     Get a life.
> 
>     Charles
> 
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