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Better op-amp buffer configuration?

Hi All,

I realize that using a single-supply op-amp as a buffer may be one of the easiest circuit configurations in the world; just tie the chip's output back to the inverting input, and insert the signal into its non-inverting input. That's how the books show it anyway, but are their any real-life op-amp issues that I have to look out for with this basic circuit? Anything I can do to make this circuit operate better under temperature, along with the unavoidable op-amp variations? Perhaps to help with any stability or voltage offset issues? Or is this circuit simply the way op-amp buffers are done, even in real life?

Thank You,

Bill

Cross posted to sci.electronics.design and sci.electronics.basics

Reply to
billcalley
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Such simple buffers are used by the millions. Most opamp data sheets show tweaks to make the amp handle more capacitive load without ringing.

Reply to
John Popelish

If you want just a buffer, there are specialized circuits with fixed voltage gain(1 or 2) and with a lot of current output capability.

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Or this specialized audio circuit
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These buffers have the gain setting resistors built-in and usually are trimmed for accuracy. Otherwise any opamp which is stable at the gain of 1 can be used, as you wrote. Stability depends on the opamp design and on the load characteristic. Here are a few remedies:

1) Capacitive loads can be isolated with a 220 ohms series resistor on the output. 2) You can increase the phase margin by throwing away some bandwidth with a R-C series combination between +in and -in. 3) Instead of connecting directly the -in to the output, you can use a resistor with a parallel capacitor (1k + 100p). 4) A Zobel network on the output. A buffer is actually the most demanding application, stability wise. Keep away from certain opamps, especially high-speed parts, that exhibit a bag of stability problems if the trace on the circuit board is longer than an inch... 
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ciao Ban
Bordighera, Italy
Reply to
Ban

Thanks for all of your help guys!

Cheers,

Bill

Reply to
billcalley

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