[sdiy] Voltage Feedback Resistors and Circuit Stability

ben gebhardt benjamin_gebhardt at yahoo.com
Fri Nov 13 22:48:53 CET 2020


 (first time poster!)
Hi Ian,
Usually in my experience one would scale down resistors around an opamp to generally lower the johnson noise contribution.  Additionally there is something to be said for high impedance nodes and coupling in radiated noise from external sources but usually that's only problematic over 1M.  
As to why it's commonplace, I'm not sure which schematics you are referring to, but as mentioned, 100k shows up a lot in eurorack circuits since it's the defacto input impedance.

There are a ton of other factors in the decision of this resistor, it's hard to generalize rationale w/o the context of the circuit and design intentions.  Happy to comment on something more specific.
Ben.
    On Friday, November 13, 2020, 04:16:17 PM EST, Mattias Rickardsson <mr at analogue.org> wrote:  
 
 Mattias Rickardsson <mr at analogue.org> skrev:


And perhaps 10k-22k for TL06x.

I should have written 22k-47k.
/mr


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