Electronics > PCB/EDA/CAD

Discussion: Schematic designators: T vs Q (also U vs IC)

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RedLion:
So, in most schematics, transistors are usually designated by Q**, but I see more and more schematics and libraries using T**, especially in Europe or with younger engineers.

Same goes for integrated circuits, using IC** in favor of U**.

I personally adopted the T** and IC** designators since University, before that I just followed the default Altium library.

I wondered, is either one the "correct" way? I don't think there is a broadly accepted standard on this. Also, what do you guys use? Are there any regional differences?

jpanhalt:
Usually, it is pretty easy to answer such questions.  Either the program you are using will give a clue or Google, or god forbid:

https://en.wikipedia.org/wiki/Reference_designator

TimFox:
That wikipedia article agrees with my traditional US usage:
Q for transistor, vs. T for transformer
U for integrated circuit, vs. V for vacuum tube,
etc.

RedLion:

--- Quote from: jpanhalt on July 13, 2021, 09:00:42 pm ---Usually, it is pretty easy to answer such questions.  Either the program you are using will give a clue or Google, or god forbid:

https://en.wikipedia.org/wiki/Reference_designator

--- End quote ---

Well that's what I'm wondering, I use Altium, which is famously Australian, so the (admittedly useless) preinstalled library uses Q and U, but in Germany I see IC and T more often. I took it up since my bachelor's thesis, where I had to work with the institute's library, and have been since then, also because I "stole" a few footprints for myself. I also prefer T for transistors since I use way more of those than transformers.

There is the DIN/EN-norm 81346 I found, but it's really strange and no-one uses it; it defines the function of a part rather than the part itself, so for example Q is defined as "controlled switching or varying of a flow of energy, signal or matter". Certainly an easy to grasp concept  ???

Also are these norms not a bit of a mute point anyway, since the designator is usually next to the symbol so you'd know anyway?

SiliconWizard:
The list in the Wikipedia article looks reasonable to me.

There are a few minor things that I do not exactly follow (and that are frequently not exactly followed.) For instance, I use "X" for crystals or oscillators, but apparently X would be a socket, and Y should be used instead (or XTAL for crystals only.) "X" is very common for that though. Also, "J" apparently should be used only for jack-like connectors, but I use it for all kinds of connectors including headers...

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