What I would like to accomplish: I am trying to add current regulators into a home built dual rail linear regulated power supply. I previously asked this question about transformer fusing and received useful responses from the EE Community. The supply is mostly complete now and I also added a current source using the following schematic off the LM317 datasheet:

Current Source using LM317

I adjusted the resistor values though to ensure that the current source stays well below my max current (.35Amps on each secondary of the transformer).

I would like to also build a current regulator on the negative rail using either Figure 12 or Figure 15 from the LM337 datasheet:

Example from LM337 Datasheet Example from LM337 Datasheet

Problem: I may not understand exactly what is going on with the LM337 schematics, but I cannot figure out how to connect this circuit up correctly, especially after the LM317 current regulator was straight forward.

Where do I place the load? I think this is supposed to be a Current Source where the load goes between V-in and V--. I appreciate any help you can provide in understanding how the LM337 current regulator configurations are supposed to work.

  • \$\begingroup\$ The LM317 circuit, after you put the resistor in, is just a two-terminal limiter. It will work in series with a load regardless of whether the series connetion is (+)-load-regulator-(-) or (+)-regulator-load-(-), and regardless o f whether (+) or (-) is ground. So, there's no reason to do an LM337 variant. \$\endgroup\$
    – Whit3rd
    Commented Mar 3, 2017 at 22:30

1 Answer 1


Use them exactly as you used the 317, -ve supply input to Vin, load between ground and ADJ, resistor between ADJ and VOUT. As shown in the schematic below:


simulate this circuit – Schematic created using CircuitLab

They are shown the way they are shown in the data sheet because current flows from ground, out of Vin and into your -ve power supply pin - remember conventionally we say that current flows from +ve to -ve

  • \$\begingroup\$ I just tried placing the load between ADJ and Gnd and it worked. To make sure I understand what's going on, is this current regulator operating as a current sink? \$\endgroup\$ Commented Dec 15, 2015 at 16:18
  • \$\begingroup\$ Yes (ish) that's not really a useful way of looking at it. The load and regulator components together are a current sink, the regulator (and associated resistor) is really acting as a variable resistance that will get higher when the current limit is reached. \$\endgroup\$
    – Icy
    Commented Dec 15, 2015 at 16:26
  • 1
    \$\begingroup\$ @DaveG - but also note that you should not do this as an add-on current limiter for a voltage supply. Adding this circuit will cause very considerable voltage losses at the load. At the least, you have the drop across the resistor, plus the dropout voltage (~1.5 to 2 volts). \$\endgroup\$ Commented Dec 15, 2015 at 17:21
  • \$\begingroup\$ Thanks @WhatRoughBeast, definitely don't plan to make this a current limiting device, rather a way to control current regardless (for the most part) of voltage. \$\endgroup\$ Commented Dec 15, 2015 at 18:06

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.