Does the schematic in the picture work with these powersupplies from China? Both are rated with 5V but one with 20 amperes and the other with 2 amperes.


If it will not work what would make it work or what else would you recommend?

I need just a little current and at least +-2.3V for an op-amp which is R2 in the picture. For R1 I need high current with +5V.

enter image description here

  • 1
    \$\begingroup\$ a) if the documentation on a seller website isn't sufficient, don't buy there. b) not able to answer your question without knowing what your loads R1 and R2 actually are. if they actually are resistors, you want to revisit ohm's law. \$\endgroup\$ May 6, 2020 at 10:42
  • \$\begingroup\$ @MarcusMüller R1 is the powerconnectors of 25 pieces of PAM8403 ICs in parallel and R2 is 2 pieces of OPA1604 power connectors in parallel \$\endgroup\$ May 6, 2020 at 14:23
  • \$\begingroup\$ uh, so dynamic loads? Hard to say with the data given on the aliexpress website thing. \$\endgroup\$ May 6, 2020 at 14:52
  • \$\begingroup\$ I would put a Schottky bypass diode across each in case one power supply starts or stops sooner than the other. \$\endgroup\$
    – winny
    May 7, 2020 at 14:10

1 Answer 1


I don't see a problem with your approach, looking at your description I think it would work just fine.

You are placing two voltage sources in series, which is alright.

The upper voltage source has a significant load connected to it only, which is relevant to these two items ONLY (note that the Thevenin equivalent to the two node circuit comprised by those two items, a voltage source and a resistive load, is the voltage source only). So that's fine too.

The opamp gets a suitable symmetrical supply, okay there.

There's still plenty that could be wrong as your equivalent diagram is very crude (an opamp is not exactly a resistor...), but what you've drawn there is alright.

  • 1
    \$\begingroup\$ A warm welcome to the site. I think you're using 'Answer' on this site like 'Reply' is used on other discussion sites. Although well-intended, this is a comment and not an answer. It will most likely be deleted but you can delete it yourself before any downvotes reduce your Reputation. Thanks. \$\endgroup\$
    – TonyM
    May 6, 2020 at 11:54
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    \$\begingroup\$ Thanks, TonyM. I'm confused, though. The OP is asking whether his circuit will work. I'm saying "yes, I think it will". How's that a "comment" rather than an "answer"? I don't mind at all deleting my answer, of course. \$\endgroup\$
    – Alex Lopez
    May 6, 2020 at 12:02
  • \$\begingroup\$ Hi Alex, as it stands, it's an unsubstantiated observation. Even though it's a literal reply to the question, which invites a one-word answer, you would normally want something that explains to future readers how you reached that decision, what route your mind took. This is to teach the mindset that lets them solve these things themselves in the future. I can see your point of view, though, and it's a reasonable thing to ask :-) Take a look at some of the well-scored answers on the site, might help. I appreciate that your reputation is too low for you to comment instead of answer at present. \$\endgroup\$
    – TonyM
    May 6, 2020 at 14:53
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    \$\begingroup\$ Hey, Tony, thanks for your help. To be honest, yesterday I couldn't think of anything else to say, but today I figured out a few lines. \$\endgroup\$
    – Alex Lopez
    May 7, 2020 at 10:31
  • \$\begingroup\$ Thanks, Alex - much better now and upvoted. Incidentally, I hadn't flagged it for low quality, another user had done that and I just commented, but I hope they also see the improvement. Good to have you aboard :-) \$\endgroup\$
    – TonyM
    May 7, 2020 at 12:25

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