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I am fairly new to electronics. I am using the MAX7219 to control an led matrix and the data sheet for the MAX7219 says that the maximum current each light can get is 40mA, but for my purpose I need 70mA for each light. I am using an Arduino to control the leds and the max pin output is also 40mA. The basic schematic for how I have the matrix set up is here: enter image description here

Is there an easy way using transistors or something that I can get the higher current leds working with the lower current control?

Jared Cohen
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    You probably could, but it would be a reasonably big hassle, requiring like 16 transistors plus passives. Why not just find a higher current version? – BeB00 Mar 30 '20 at 01:44
  • @BeB00 I have thought about using transistors to do it, but I do not know how. I have tried looking for higher current versions but I can't seem to find any. If you know of one then I will definitely get one – Jared Cohen Mar 30 '20 at 01:45
  • How big is your matrix? – BeB00 Mar 30 '20 at 01:52
  • @BeB00 my matrix right now is just one led hooked up for testing. But for the future purposes I am planning on daisy chaining a bunch of these to have a much larger matrix. If I were to take a guess now I would say its 16x16 or possibly larger – Jared Cohen Mar 30 '20 at 01:55
  • I think that might be non trivial, because you have to limit current to all of those LEDs. I'm not sure you could accomplish that without more complex current limiting than just passives (which is what I was thinking before) – BeB00 Mar 30 '20 at 02:01
  • @BeB00 sorry I meant 2x2 of these 8x8 grids. for some reason I brainfarted and typed 16x16 – Jared Cohen Mar 30 '20 at 02:02
  • I think even with an 8x8 it might be pretty hard, hopefully someone will be along with more input soon – BeB00 Mar 30 '20 at 02:03
  • @BeB00 ok thank you. What do you mean by current limiting? Sorry I am new to this – Jared Cohen Mar 30 '20 at 02:04
  • https://www.waveformlighting.com/pcb-designs/when-and-why-do-leds-need-current-limiting-resistors – BeB00 Mar 30 '20 at 02:08
  • @BeB00 thank you I was misunderstanding – Jared Cohen Mar 30 '20 at 02:16
  • Hi, I have the same problem, did you find any solution? It's definitely possible as it's explained here https://www.maximintegrated.com/en/design/technical-documents/app-notes/1/1196.html but I am struggling to know what transistor to buy or how it is going to work without negative voltage with the PFET solution. – Maxime Jul 06 '21 at 17:23

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