[sdiy] Buffered question

[David G Dixon]

"Not when connected to multiple loads."

Why not?  Multiple loads are just impedances in parallel.  A low output
impedance just means that the desired voltage is maintained even when the
current output is high.  To me, that's essentially all it means.  Of course,
I'm a chemical engineer who does electronics for fun, so maybe my
understanding is lacking, but that's how I understand it.

MC

On 12/30/20, David G Dixon <dixon at mail.ubc.ca> wrote:
> "Opamp buffer circuits aren't just for supplying current, they are 
> also for providing low output impedances."
>
> Same dif?
>
>
>
>
>
> 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
>>
>>
>
>