I am sooo frustrated - OpAmp power pins

Hi. I am using KiCAD 5.something. I am using an opamp (dual, 8-pin package) as a small part of a much larger circuit. It has power supply rails at ±30V; ±45V and ±15V (for the opamp). The ±15 may be derived from the 45V rails of fed by anoher board’s existing regulated 15 volt split rails.

here’s the catch - the opamp symbols dont have power pins so I cannot assign them. I did a search on missing pins and the suggestion was to “view --> show hidden pins”. They are. I looked at the pin assignment int he library symbol (RC4558) and they clearly show the + and - pins as “power in”.

HELP! I have looked pretty much everywhere and read the top 10 search results…



That opamp is a dual, and the kicad symbol has 3 units: one for each amplifier half, and one for the power pins. You’ll want to add all 3 units to your schematic, with the same base reference designator, e.g. U1A and U1B for the amplifiers and U1C for the power pins.

Symbol browser:

In the schematic:

Note that the power pins (unit C) is drawn so that it can be overlapped with either of the amplifier symbols if you want to combine them:


You so ROCK!. Thanks. Clear as mud in the interface though.

Thanks gkeeth

Hey, I have been using KiCad for years now but I did never notice that the power pins are designed to fit the OP shape ! :flushed:
Nice and clever !


A general comment to any KiCAD devs etc that might monitor this. At east for me, the idea of 3 modules in a dual opamp is mysterious. I think this really needs some kind of visual/logical queue, such as “A”, “B”, “PWR”. Or a note. Or a mouse over. Or anything. Neither Google nor local searches brought joy (of course, maybe i didnt knwo what to search for, but that just makes me normal).

The format is actually convenient in what is otherwise a complicated symbol. It just needs calling out. Maybe even noting in the pin assignment able whcih module each pin is assigned to, A, B, C would do it.



In general, be aware that symbols can have multiple units and you will need to place all of them in order for all of a physical IC’s pins to be represented in the schematic.

You can see all of a symbol’s units in the symbol picker (A), and selecting each unit will show a preview of what it looks like.

You can also change which unit you are editing in the symbol editor using the dropdown at the top.

You’re right that it would be really nice to have the unit shown/editable in the pin table. Sounds like this will be fixed in v7, see here: https://gitlab.com/kicad/code/kicad/-/issues/6513


Gotcha. I must say that “unit C” of a dual opamp just seemed like another KiCAD weirdness/oversight (its not like it would be the first) :slight_smile: But i now know to look for units and that they will all be useful.
Thanks again

I am used to have 2 units in such a case and being able to use ‘De Morgan’ in one of them to have that symbol with power pins. In my library symbols of LVC2G… gates I defined that way.
But the conception of having 3 units is more universal:

  • if you want to have all power supply units accumulated in one schematic area - you can do this,
  • if you want to have power pins at one of opamps you can place it at that amp.

I also didn’t noticed that previously. Now I am considering redefining my LVC2G… symbols to have separate power unit and not use ‘DeMorgan’ for it.
The problem is that my idea is to not change symbols that I have already used somewhere. I just want to have all my projects being compatible with my libraries. So after changing that symbols I will also update all schematics where I used them. May be when moving to V6 will be the good time to take care of it.

I wonder if the power supply was actually called ‘Power’ rather than ‘Unit C’, it might cause less confusion? I see that in 5.99, there is a checkbox for "Place all units’ which is ticked by default so this might help reduce this problem.

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I remember the first time I looked over this programme after a download.
I did a lot of reading and clicking and quite a bit of head scratching… of course cocky me belongs to the brigade of “if all else fails, read the instructions”.

Eventually I explored the libraries.

And there-upon happened my first, truly WTF moment… 5 :sparkler:!!! parts to a four op amp IC… simply amazing!!!
This I had to see :smiley:

Ended up eating my own sarcasm and deciding showing the power pins as a separate unit was a pretty kewl idea, especially as the power pins fitted the op amps so neatly on that 50 grid.

I suppose my comments really amount to: Read, digest and explore everything on the page. It is amazing what you can find: perhaps even a holy grail lurking in an unkempt corner of a dusty page. :slightly_smiling_face:

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This is more of a librarian consideration than a Kicad specific thing. What is more important is consistency and right now there are three methods in Kicad. when you have inconsistent schemas that a team of libraries follow, you end up with inconsistent schematics (yes I have this with Mentor :frowning: )

  1. one of the unit’s has the PSU pins (typically unit #1)
  2. an additional unit is dedicated to the PSU pins - my personal preference as I put the decoupling in a corner
  3. a global label is hidden - REALLY hate this, looking at you 74xx series… so glad this finally got resolved https://github.com/KiCad/kicad-library/issues/605

What would be handy would be some form of ECR that flags an error if there are an multi-part that does not have all parts on the sheet. unused unit should be terminated correctly to stop noise, overheating etc…

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Thats what I thought when I dicovered this the first time.

On the other hand, there might be devices with various units that have totally different meanings - or just several different power supplies.
This would mean the components would need user defined names for every unit. Comfortable but also additional work for the SW designers.

The KiCad-keep-it-simple-and-universal-approach with UNITx may be not so bad to cover every device …

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What’s really frustrating me in this case is that I can’t find a shortcut that lets me place the other units one after another when adding a part that has multiple units. Eagle was super clear and let you put all units.
I’d say from my experience, that the default case (only place Unit A, then stop) is the most unusual; I almost always want to continue placing the other ones as well in one go. Instead, there’s lots of right-click-submenu-diving in Kicad, which is totally unnecessary.

You must have different KiCad than me :slight_smile:

  1. To place Unit A I press ‘a’ and then select it from my libraries.
  2. To place Unit B I press ‘a’ and then I select Unit B of that element from ‘-- Recently Used --’ list at the beginning of libraries list.

It looks for me enough simple.

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I usually take the first unit of the first symbol from the library (also use the a shortcut key instead of a mouse click to add a symbol).

For the following symbols I just hover over a symbol that’s already on the scyhematic and press c for copy. For multi-unit symbols you still have to change the unit (and do the annotation) though.

Often you quite early know in your design what size of resistors and capacitors you’re going to use. If you assign a footprint to the first resistor and capacitor, then the footprint info is also copied, which saves some mouse clicks later on.

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Well, that’s true, but why isn’t there a “next-unit” hotkey? Or a ‘Shift-A’ add that behaves the same as ‘a’ but performs an integrated ‘c’ and lets you place parts and units until you right-click or hit ESC. It’s still clicky-clicky now.

:wink: My example came from an earlier approach where I used c (clone key) instead of another a (add) to rapidly multiply parts as needed. From time to time, I still do it this way, with setting up all units and cloning them, but in some cases I still want to quickly rearrange which units do what in PCB design phase.
Another factor of complexity one has to manage comes when annotating afterwards, and units you meant to be in one part are put into different ones.
But I didn’t mean to get too off-topic here.

Maybe I’ll just hand-in a small pull-request that will add two or thee new keys to be assigned for people who appreciate a bit of additional comfort.


Maybe I’ll just hand-in a small pull-request that will add two or thee new keys to be assigned for people who appreciate a bit of additional comfort.

which kicad-version do you use? The actual nightly v5.99 already has a switch to “place all units” at the standard “choose symbol” (Add symbol) dialog.


It would be handy to be able to have a special “dump all unused units” function to place all these spares on an extra sheet.
When you are have placed a unit and want place another, it would be good if a variant of Copy could offer the next unit from the package rather than another Unit A

In KiCad-nightly V5.99 a similar feature is already implemented.
I just placed a TL074 on a schematic, and after placement, unit B is automatically attached to the cursor, etc. until all 5 units are placed.
At least when the “Place all units” checkbox is checked.



How great! Thanks for pointing this out!
I’m on KiCad 5.1.9 ATM, currently sticking to Ubuntu 21.04’s repository as I prefer kinda stable releases; but possibly will reconsider upgrading. :wink: