kiCad dual opamp problem - Page 1
Forum section: electronics / general

author: multime
author_rank: Regular Contributor
timestamp: May 29, 2025, 02:49:51 pm
content: I am trying to learn how to use KiCad 8 and when i select Lm358 dual opamp to add to the schematic kiCad display it with just 3 pins. How can i work with that.

author: tooki
author_rank: Super Contributor
timestamp: May 29, 2025, 02:58:31 pm
content: Well you’re not done yet. You need to add the remaining units of themulti-unit symbol. (That’s the keyword to search for.)

author: themadhippy
author_rank: Super Contributor
timestamp: May 29, 2025, 03:27:11 pm
content: reslect the symbol click the > by it and a drop down list will apear showing part A part B and part C ,the other option at the bottom of the symbol select window is a tick box for "place all units" with that ticked you place the first part of a component and the next part is automatically picked for you once youve place the first part.

author: multime
author_rank: Regular Contributor
timestamp: May 30, 2025, 02:01:02 pm
content: Thanks for the help all sorted now. Bit of a long winded procedure but its a free program and looks like it does a decent job.

author: julian1
author_rank: Frequent Contributor
timestamp: May 30, 2025, 10:07:57 pm
content: The non-laborious way is hotkey 'a' to add new component, then select the dual op-amp unit A from dialog.Then just tap the mouse to the schematic three times - once for unit A, again for unit B/second op-amp, and finally the unit C/ supply symbol.Kicad will change/update the symbol under the mouse pointer as a prompt, each mouse-click, so you know what your getting.

author: Doctorandus_P
author_rank: Super Contributor
timestamp: May 31, 2025, 03:24:39 pm
content: Quote from: multime on May 30, 2025, 02:01:02 pmWhat do you mean by that? It's just normal procedure with all PCB design programs I've used ever since the late '80-ies.I have seen a few designs where a schematic symbol for a dual opamp is a rectangle with 8 pins in the same orientation as the DIP (or SMT) package. That is so horrible that I usually immediately disregard it. If people show such a schematic on a forum, my usual response is to redraw the schematic before I go further into it.

author: eugene
author_rank: Frequent Contributor
timestamp: May 31, 2025, 04:09:50 pm
content: Quote from: multime on May 30, 2025, 02:01:02 pmI'm not sure what you would prefer, but you are free to make new schematic symbols with the power pins on one of the two opamps.And, the fact that KiCad is free doesn't have much to do with it; all of the big-money EDA tools that I have used do it the same way. I just don't want you to feel as though things would be different if you bought a Altium or Cadence license.

author: Doctorandus_P
author_rank: Super Contributor
timestamp: May 31, 2025, 07:27:30 pm
content: In addition, the power pins (Unit C in a dual opamp) in KiCad is designed in such a way that you can place it on top of one of the opamps themselves, or put it in an another area, for example in the power distribution section.

author: multime
author_rank: Regular Contributor
timestamp: May 31, 2025, 09:26:47 pm
content: Doctorandus -pit may be normal procedure to yourself and you may have used other progs over the years I on the other hand haven't. I am a total beginner and the very thing you dislike is what i expected to pop up. What came up instead was something i would expect to see in a circuit diagram not a schematic.Thanks julian 1eugene with that statement i was simply following the saying " Never look a gift horse in the mouth " , And have no fear or concern i wont be purchasing any of the paid for progs.

author: tooki
author_rank: Super Contributor
timestamp: May 31, 2025, 10:35:43 pm
content: Quote from: multime on May 31, 2025, 09:26:47 pmUmmm… what? A circuit diagram and schematic are two names for the same thing. (Unlike, for example, a block diagram.)

author: John B
author_rank: Frequent Contributor
timestamp: May 31, 2025, 11:33:40 pm
content: Maybe everyone can appreciate that the free piece of software gives you choice as to whether you'd prefer to use 3 separate symbols, a monolithic 8 pin block or even make your own 8x individual pin multi part symbol in different hierarchical sheets for some eldritch horror of a schematic.

author: multime
author_rank: Regular Contributor
timestamp: June 01, 2025, 12:49:53 pm
content: tookiOKJohn B, ooh that latter part sounds good, just the type of thing i like. Please supply more detail

author: Doctorandus_P
author_rank: Super Contributor
timestamp: June 01, 2025, 02:40:34 pm
content: Do you want to organize the obfuscated schematic diagram contest?

author: multime
author_rank: Regular Contributor
timestamp: June 02, 2025, 12:37:45 pm
content: Doctorandus_PIf i hadn't been so busy i would have jumped at that offer

author: bson
author_rank: Unknown
timestamp: June 06, 2025, 10:01:29 pm
content: I must be totally broken, because I find it exceedingly annoying when IC symbols mix signals and power in the same unit. 74AHC1G04 comes to mind... Routing signals around power symbols and decoupling caps, which then gets increasingly more annoying when flipped or rotated... grrr. <= pet peeve

author: Doctorandus_P
author_rank: Super Contributor
timestamp: June 06, 2025, 10:47:07 pm
content: Nah, don't annoy yourself with that. Life's too short.Different peoples have different idiosyncrasies. Some people really do insist of keeping each decoupling capacitor near to the IC pin that it connects to. Others draw the power supply and a whole bunch of decoupling capacitors on a separate sheet. I do this second approach. Usually draw too many decoupling capacitors, and throw the left overs away when the PCB is nearly finished.Another such idiosyncrasy is the modern craze of putting (often dotted) rectangles around each and every trivial circuit section.The snippet below is from AxxSolder. It's a quite nice project overall, but the whole schematic is as crammed full on one sheet as this snippet suggests. I'm quite certain that just arranging the boxes and drawing them took several hours out of someone's life.These days I only draw trivial schematics on a single sheet. But I never let that sheet get crammed full. Before it gets there I take a step back and take five minutes to add some organization into it. Quite often I end up with two sheets, and the secondary sheet has all the power conditioning. From voltage regulators to decoupling capacitors. This stuff is necessary to make a working product, but it's not interesting for understanding how the project works.