Hi guys,
Someone warned me recently about picking too small of resistor values to put into op amp buffer circuits. He cautioned against "loading" the op amp.
I don't know what that means. What would the effects of that translate to in an audio circuit? Increased THD, clipping or something like that?
Someone warned me recently about picking too small of resistor values to put into op amp buffer circuits. He cautioned against "loading" the op amp.
I don't know what that means. What would the effects of that translate to in an audio circuit? Increased THD, clipping or something like that?
^ As the replies above.
You have to remember that the feedback network is driven by the opamp. Like most things, its a compromise. An LM4562 (for example) is OK down to 600 ohm loading and so it makes sense to keep the networks low-ish to minimise noise contribution (thermal and stray pickup). So values in the 2 to 5k range would be ideal. Use a more weedy device like a TL072 and values around 10k make more sense. Any higher and you run into issues with noise and stray pickup.
The short circuit current should not be used as a "maximum current" guide.
Instead look at the plot of: output voltage vs output load. You will see a kink where the available maximum output voltage drops off as the output load reduces.
That gives a very good guide to the maximum usable output current.
Instead look at the plot of: output voltage vs output load. You will see a kink where the available maximum output voltage drops off as the output load reduces.
That gives a very good guide to the maximum usable output current.
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