Dual FET LS489A SOT-23 6L footprint

Layout Footprints
1

Hi all, where can I find the footprint of a dual FET in SOT-23 6L package, in this case the LSK489A from LInear Systems?

Thank you very much in advance and best regards

paperino204

I hereby certify that I am not simply asking someone else to design a footprint for me.

This is an auto-generated message that is in place on the “footprints” section of the KiCad.info forum. If I remove it and ask for a footprint to be designed anyway, I understand that I will be subject to forum members telling me to go design my own footprint or referring me to a 3rd party footprint site.

2

Just use a SOT-23-6. I don’t see the problem.

3

You will need to make your own symbol as I don’t see a dual jfet in the libraries. Then you use the generic SOT-23-6. This footprint already has a 3D model.

4

You get to choose whether you put two FETs into one “box” or make two units as is commonly done for a dual op amp for example.

5

Have you tried the 2N7002BKS symbol and changing the footprint?

6

My preference would be to create a two part symbol.

From the Device Library, I’d select Q_NJFET_GDS and copy the symbol (because this matches the symbol drawing and pin arrangement of half of the LS489A in the SOT_23 footprint).

Next, I’d “File > New Symbol”.
Name the symbol, give it two units, open Unit A, and Paste the copied drawing onto the grid. That’s Unit A complete.

Next, Open Unit B and Paste the symbol again, but this time change the pins to match the other half of the SOT_23 footprint.

Save and finally assign the SOT_23 footprint to the new symbol.

7

There are indeed not many Jfet’s in KiCad’s libraries. Making a copy of one and modifying is probably the simplest and quickest method.

  1. Make sure you have a personal library. KiCad’s own libraries are read-only, because they are a part of KiCad itself and can be overwritten during KiCad updates.
  2. Open a Jfet in the Symbol Editor. At this stage the only important part is the symbol graphics. The Q_NJFET_GDS that jmk mentioned is indeed just fine for this.
  3. Right click on the Jfet. then Save Copy As.
  4. In the Save Symbol As dialog, select your personal library (00aa_lib in the screenshot) and enter the LSK489A name, and then press the OK button.
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  5. In the Symbol Editor / File / Symbol Properties dialog, set the General / Number of units to 2.
    image
  6. You can also directly set the Footprint link in that same dialog.
  7. By default the All units are interchangeable checkbox is on, and this is good in this case. It keeps the graphics of both units in your symbol the same.
  8. In the edit window of the symbol editor, modify the pin numbers for both the units.
  9. Save your symbol.
8

I deliberately picked Q_NJFET_GDS because these pin numbers match the SOT_23 footprint for Unit A, soooooo,
only the pin numbers for Unit B need modifying. :slightly_smiling_face:

9

Changing pin numbers is trivial. What I do have a bit of a problem with is:

A beginner can search for an hour for those “parts” and not realizing those are called “units” in KiCad.

10

Many thanks to all! You have been very useful! I am trying to follow your tips and advice. I am a newbee with Kicad…

Many thanks again!

paperino204

11

Ah, my brain fade.
Edits made to the original post. Thanks for mentioning the matter.

12

THT JFETs are nearly extinct and there are few SMD parts left, so not much point adding new ones to the libraries now.

13

I agree.
The two slightly different methods described above (Save as & Copy/Paste) show just how easy it is to create new Symbols in Kicad.

My original choice for using Kicad was the ease with which symbols and footprints could be created. This has been made even easier with the vastly improved documentation of recent times.
The recent large increase in graphical functions to aid with the creation of symbols and footprints has been a bit of a double edged sword. Good because creation is even easier, but bad because there are now so many of these functions to remember to use. :rofl:

14

In my engineering career of almost 50 years, I have recently encountered a JFET in my present contract job but I do not remember for certain whether I have before that. In the 1960’s before college, I was an amateur radio operator. My kit transceiver might have had a JFET in the RF section. A JFET is normally ON and needs gate drive to turn it off; sort of an uncommon requirement.

15

It was just an observation from my side. Not criticism.

Exactly. For me too. Libraries are never complete, so creating your own symbols and footprints (or morphing existing ones into new parts) is essential. The fact that the symbol and footprint editors were very much like the schematic and PCB editors was one of the pillars that convinced me to adopt KiCad. I had a list of a bunch of programs to evaluate, and after the evaluation of KiCad, I just stopped the evaluation, because KiCad ticked nearly all the boxes. (Runs on Linux. FOSS, Editors that work well and are also fairly simple, UI is quite consistent over the different editors). When I started with KiCad (V3 or so) Library management was a mess, and that was my only doubt, but I saw that KiCad was in active development and I guessed (rightly so) that this would be fixed in due time.