[sdiy] Buffered question

[Michael E Caloroso]

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.

MC

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 impedance.
>
> 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]
> 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
>
>