LM337 Negative Voltage Regulator Circuits – DIY & Pinout Guide

The LM337 is an adjustable negative voltage regulator. As the name suggests, it can supply an adjustable negative voltage from -1.2V to -37V at a current of 1.5A or more. It also comes with many protection features, such as thermal and short-circuit protections.

This chip can be used to build a fixed negative voltage regulator with the addition of a couple of components or an adjustable negative voltage regulator employing a potentiometer. The LM337 regulator is available in a TO-220, TO-03 metal can, SOT-223 SMD package, and more.

Features

• Adjustable output voltage range from -1.2V to -37V
• Typical output current of 1.5A
• Internal short-circuit and over-temperature protection
• Line regulation typically 0.01%/V
• Load regulation typically 0.3%
• Excellent thermal regulation, 0.002%/W
• 77 dB ripple rejection
• Excellent rejection of thermal transients
• 50 ppm/˚C temperature coefficient
• P + Product Enhancement tested
• Standard 3-lead transistor package

Pinouts

Buy LM337 at Amazon.com here (affiliated link)

Example LM337 Circuits

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Using the LM337 is quite simple, but how can we design a circuit that fully utilizes its capabilities? Let’s look at some example circuits below.

Basic LM337 Adjustable Negative Voltage Regulator Circuit

Let’s first look at the basic adjustable negative voltage regulator configuration for the LM337. We would also get to learn how to calculate the output voltage and the basic circuit structure.

To find the Vout for this circuit, we need to use the following formula.

Vout = Vref (1+ R2/R1) + (I_ADJR2)

The LM337 keeps the reference voltage (Vref) between the Adjust and Vout pins at -1.25V and limits the IAdj to a constant 100μA. The main factors for the output voltage are R1 and R2. R1 is recommended to be 120Ω to maintain the aforementioned Vref. R2 may be a 5kΩ potentiometer so that we can adjust the output voltage.

Conclusion 

The LM337 may often be a forgotten regulator IC because of its specific usage. But it was relatively good at its job as a negative voltage regulator. If you happen to have the LM337 in your storage, consider revisiting it. For instance, try increasing its output current by using an amplifier transistor or adapt it to other uses. In the future, we might explore more of this chip’s usages in greater detail.

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