[sdiy] dragging down op-amp CV output?

Roman Sowa modular at go2.pl
Sat Jan 15 09:01:39 CET 2022


If you look under "Maximum peak output voltage swing", you'll find 
+/-10V at 2k load, so that's +/-5V clean wave at 1k in your case.
There's also graph "Maximum Peak Output Voltage vs Load Resistance", 
where you can see exactly that and more (figure 6-45 in my datasheet).

Even if it was 100oh, and indeed while inserting a plug you'd short it 
to GND, and everything goes down, it happens just for a blink of an eye, 
not a big deal IMHO. with 1k you'd have to short 2 jacks to GND at the 
same time. I haven't seen anybody patching 2 patchcords at once. So yes, 
that's good, you're safe with good margin.

Roman

W dniu 2022-01-15 o 06:29, Neil Harper via Synth-diy pisze:
> 2022 - the future is now!
>
> a pretty basic question, but I'd like to follow best practices. I have a
> little envelope generator that outputs 0-5V and the output stage is a
> TL074 opamp.
>
> i'd like to send this CV to a few places internally in my project synth
> but also have several external output jacks. so my first intuition was
> to grab all of those outputs at the output of this single opamp cell,
> maybe with a 1K resistor in front of each.
>
> my concern is that if anything unpredictable happens to the external
> outputs (like getting grounded while being plugged into a jack or
> something) then it will drag down the outputs that are also going
> somewhere internally.
>
> i know i can just take the CV and send it through a buffer-follower for
> every output i want and definitely be safe. but the design space is
> getting a bit cramped and i'm also just curious.
>
> if one of the external outputs does get grounded when sourcing the full
> 5V it draws 5mA thru the 1k resistor.. can the TL074 handle that? does
> it pull the other outputs down, or can it eventually overheat and freak
> out? Datasheet suggests that it's meltdown-protected, but I can't see
> how much current it can source and maintain the 5V.
>
> thanks for all of the help everyone, and a happy 2022. this mailing list
> is a rare truly helpful corners of the internet not attempting to
> commodify my attention.
>
> -- 
> /// Neil Harper
> /// Every Wave is New Until it Breaks
>
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