[sdiy] Buffered question
David G Dixon
dixon at mail.ubc.ca
Wed Dec 30 18:16:59 CET 2020
"Opamp buffer circuits aren't just for supplying current, they are also for
providing low output impedances."
It's not always the circuit. Some opamps - such as low power varieties -
have weak current outputs.
On 12/29/20, David G Dixon <dixon at mail.ubc.ca> wrote:
> Most of the common opamp circuit configurations also act as buffers.
> What that means is that the opamp will supply as much current as is
> required to maintain the desired voltage regardless of the downstream
> However, if there is something like a diode inbetween the opamp's
> output and the destination, then you have to be very careful. For
> example, the classic two-diode opamp rectifier does not buffer, and
> must be followed with a buffer generally. This is one of those areas
> where it is easy to make a design mistake, and then when your design
> doesn't do exactly what it is supposed to, you have a
> forehead-slapping moment when you realize that you have
> inappropriately taken opamps for granted.
> From: Synth-diy [mailto:synth-diy-bounces at synth-diy.org] On Behalf Of
> Kristian Blåsol
> Sent: Tuesday, December 29, 2020 6:41 AM
> To: synth-diy mailing list
> Subject: [sdiy] Buffered question
> [CAUTION: Non-UBC Email]
> 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
> 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 Blåsol
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