I have a 12 V, 1.25 A supply and want to make it 4 V, 2 A using a voltage divider design. What method should I use for this design?

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    \$\begingroup\$ You should not use a voltage divider at all. Useful link: XYproblem.info \$\endgroup\$
    – winny
    Jan 27 at 15:02
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    \$\begingroup\$ Use a buck regulator and not a voltage divider. \$\endgroup\$
    – Andy aka
    Jan 27 at 15:06
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    \$\begingroup\$ Even if a voltage divider would work, it definitely can't increase current. You can't increase the current of a DC supply by any linear method. \$\endgroup\$
    – Hearth
    Jan 27 at 15:39
  • \$\begingroup\$ Why voltage dividers don't work as power supplies. \$\endgroup\$
    – Matt S
    Jan 27 at 15:45
  • \$\begingroup\$ A voltage divider will give you the voltage for a fixed current. Bigger problem is you want 2A from a 1.25A supply. Investigate buck convertors. \$\endgroup\$ Jan 27 at 16:51

2 Answers 2


I assume the term "voltage divider" is a vocabulary mismatch, what you need is a buck DC-DC converter to get 4V at good efficiency.

Here is a list of candidates (I filtered on current and voltage).

Here's a nice cheap one.

I picked one with adjustable output because 4V is not a common output voltage, so it is not available in fixed output voltage version.

You can design one if you want but if you only need one to solve a problem, readymade ones are faster to implement.


That won't work.

Voltage dividers reduce predictably the voltage of signals, not the voltage of power supplies.

You need a switching DC-DC converter (step-down a.k.a. buck regulator) instead.

See When would I use a voltage regulator vs voltage divider?

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    \$\begingroup\$ The difference is that a voltage divider reduces the voltage of a signal predictably. It reduces a power supply voltage unpredictably. \$\endgroup\$ Jan 27 at 16:28
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    \$\begingroup\$ @GodJihyo the difference is that a "signal" wire is something that carries a quite small current whereas a "power supply" wire carries a relatively large and sometimes unpredictable current. \$\endgroup\$
    – user253751
    Jan 27 at 16:32
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    \$\begingroup\$ Specifically, voltage dividers work when the next stage's input is high impedance (relative to the divider impedances); most power supplies by necessity need to have very low-impedance outputs. \$\endgroup\$
    – Matt S
    Jan 27 at 16:37

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