[sdiy] Inverting Amplifier as a Buffer Output.

Antti Huovilainen ajhuovil at cc.hut.fi
Thu Jun 24 00:00:32 CEST 2010

On Wed, 23 Jun 2010, Oscar Salas wrote:

> Thanks all for your replies.
> I forgot to say that my question about these buffer outputs are within 
> the context of a modular synthesizer. So we can expect 100K input 
> impedances and 1K output impedance (A) or near 0 output impedance (B)

1k is a bit of an overkill. 100 ohms will do fine to ensure stability, and 
all opamps you're likely to use will have protection against short 

> In which way could the case B) drive the opamp out of compliance if 
> there is low input impedance. What I should expect?

As far as stability goes, case B is pretty much same as no output resistor 
at all. Opamps really hate uncompensated capacitance at the negative input 
and a normal coaxial audio cable will have perhaps 100 pF / meter 
parasitic capacitance.


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   -- Lt. Cmdr. Ivanova

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