[sdiy] Which opamp pins wiring is best for CV out ?? A or B ??

[Simon Brouwer]

The output resistor on the opamp is not only for protection but also to
keep the circuit stable if it has to drive a load with a capacitive
component, such as a patch cable.

That doesn't work if you connect the feedback to the other side of the
output resistor.

But if the load resistance dependent attenuation is a problem, it is an
option, as long as you also provide a direct feedback path for high
frequencies, by adding a capacitor from the opamp's output to its
inverting input.

See e.g.
http://www.ecircuitcenter.com/Circuits/op_cload/op_cload.htm




David Brown schreef:
> If the output resistor is in series with the feedback resistor then
> the output voltage is constant regardless of the load.
>
> With a separate output protection resistor, you will have different
> voltages if the load is 10K, 50K, 100K, etc.
>
> With the protection resistor in series with the feedback loop, there
> are multiple voltage dividers that offset each other.  Think of it
> this way ... the op amp will generate a voltage slightly higher so
> that at the output connection node the voltage will defined by
> -Rf/Ri.  It's compensating for the drop in the series resistor and
> the load. - Dave
>
> At 05:36 PM 2/26/2009, Tom Bugs wrote:
>>I think it is a non-inverting opamp buffer
>>- signal into non-inverting input
>>- there is a resitor from the output pin (100r ? 1k)
>>The question seems to be (and I've wondered this too) - does the
>>feedback to the inverting input come before or after the output resitor
>>- I've always used the 'pre' method (a) but have seen the 'post' method
>> (b)
>>Puzzled me too.
>
> _______________________________________________
> Synth-diy mailing list
> Synth-diy at dropmix.xs4all.nl
> http://dropmix.xs4all.nl/mailman/listinfo/synth-diy
>
>


-- 
Vriendelijke groet,

Simon Brouwer
-*- nl.openoffice.org -*- http://www.opentaal.org -*-