[sdiy] Buffered question

Veronica Merryfield veronica at merryfield.ca
Tue Dec 29 18:13:48 CET 2020


Not all op-amps are created equal nor the jobs they do.

If you are not not being picky in your design and some generic 741 derivative is being used then likely you can get away with it acting as it’s intended function and buffer.

However, if your intended use has you selecting based on some other parameter for some feature of the design, the output might not be a good buffer.

For instance, a comparator maybe be optimized in the silicon for very fast switching speeds and not a high output current making a poor candidate as a buffer. Or you may require a high gain bandwidth device that lacks output current, or… the list could go on.

Buffering, outside of a general generic 741 derivative type design, is also something you might want to design and select for - output drive, bandwidth, rail-to-rail, load reactance etc etc. A good buffer might be a poor choice for a comparator, summing junction etc.

So, when it starts to really count, the design choices and devices count.


> On Dec 29, 2020, at 10:41 AM, Kristian Blåsol <kristian.borgstedt at gmail.com> wrote:
> Hello,
> A question about opamp buffers or voltage followers. So one of those circuits makes sure that whatever you plug in to the output of the buffer wont affect whatever you have on the input of the buffer... right?
> But there are so many different circuits you can make with an opamp, is there any of those that in itself IS a buffer, or do ALL other opamp circuits need buffering after it for the output to not affect the input?
> For example: a comparator, isnt that already buffered in itself? Since the output is either ground or +v?
> And how about a mixer/summing amplifier, op-amp as an amplifier, high and low pass filters.
> Im thinking so I dont put a buffer on an already buffered signal... :)
> Thanks in advance,
> /Kristian
> -- 
> ---
> Kristian Blåsol
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