Tag Archives: LM317

Circuit adds foldback-current protection

Use-an-LM317-as-0-to-3V-adjustable-regulator-fig-1 by Rafael Garcia-Gil @ edn.com:

For many applications that require power-supply currents of a few amperes or less, three-terminal adjustable-output linear voltage regulators, such as National Semiconductor’s LM317, offer ease of use, low cost, and full on-chip overload protection. The addition of a few components can provide a three-terminal regulator with high-speed short-circuit current limiting for improved reliability. The current limiter protects the regulator from damage by holding the maximum output current at a constant level, IMAX, that doesn’t damage the regulator (Reference 1).

Circuit adds foldback-current protection – [Link]

Use an LM317 as 0 to 3V adjustable regulator


by Vladimir Rentyuk @ edn.com:

Most engineers know that they can use an inexpensive, three-terminal adjustable regulator, such as Fairchild Semiconductor’s LM317, as an adjustable regulator to only some necessary value of voltage, such as 36 or 3V. This value cannot be less than 1.25V without employing other approaches, however. The devices’ inner reference voltage is 1.25V, and their output voltage accordingly cannot be less than this value without potential bias (Reference 1). One way to solve this problem is to use a reference-voltage source based on two diodes (Reference 2).

Use an LM317 as 0 to 3V adjustable regulator – [Link]

PICkit Project Power Supply

Enhance the power supply capabilities of the PICkit with this external 3.3V/5V supply.  The standard supply in the PICkit will only supply 1.8-5V and 30 mA when using the USB connection, while this external supply is selectable between 3.3V/5V, and the LM317 regulator can supply 1.5A.  This can be handy if you have more than a few LEDs in your project.  The input voltage can vary quite a bit, but must be greater than 6.5V to achieve 5V out.  The input capacitor must also be rated for your input V if you choose to use higher V

PICkit Project Power Supply – [Link]

Op-Amp based linear regulators


Warren Young of Tangentsoft writes:

Experienced audio DIYers are familiar with monolithic linear regulators like the 78xx series and the LM317. Here’s a simplified block diagram of a standard linear regulator, from National Semiconductor’s Application Note 1148

Let’s see… We have an op-amp, a couple of transistors, a voltage reference, and a few resistors. Can we build a linear regulator from these individual components? Yes, we can!


Op-Amp based linear regulators – [Link]

Dual Adjustable Power Supply


This project is a solution to power up most of devices or projects requiring dual (+/-) adjustable power supply. The circuit is based on LM317 positive and LM337 negative voltage regulators. LM317 series of adjustable 3 terminal regulator is capable of supplying in excess of 1.5A over a 1.2V to 30V DC output range, due to TO3 package of IC and large heat sink the power supply can handle maximum load current.

Dual Adjustable Power Supply – [Link]

Temperature Controlled PC FAN


This project is a temperature controller for a PC FAN. It regulates the speed of the FAN attached to it according to measured temperature. Temperature is sensed using a simple NTC thermistor.

In most PCs the fan runs constantly, which may not be necessary. A simple circuit can regulate the fan speed according to temperature. This not only saves energy, it also reduces fan noise. Only three components are needed to allow the fan speed to be controlled according to the actual temperature: one adjustable voltage regulator (LM317T) and two resistors that form a voltage divider. One of the resistors is a NTC thermistor (temperature-sensitive resistor), while the other is a normal resistor.

Temperature Controlled PC FAN – [Link]

Control an LM317T with a PWM signal


by Aruna Rubasinghe:

The LM317T from National Semiconductor is a popular adjustable-voltage regulator that provides output voltages of 1.25 to 37V with maximum 1.5A current. You can adjust the output voltage with a potentiometer. The circuit in Figure 1 replaces the potentiometer with an analog voltage that you can control from a PWM (pulse-width-modulation) signal. You control this signal with a microcontroller or any other digital circuit. You can use the same microcontroller to dynamically monitor the output and adjust the LM317T.

Control an LM317T with a PWM signal – [Link]

1.25V to 15V Simple Dual Symmetrical Power Supply


manekinen @ mdiy.pl builds a simple symmetrical power supply based on LM317 and LM337. Design is Eagle and includes PCB so you can build it your own.

This time, simple project that i made from simple need. Simple, cheap and functional regulated power supply 1,25V to 15V, two separately regulated positive lines and two negative. This power supply uses LM317 and LM337 integrated circuit stabilizers – or their stronger versions. Galvanically separated lines can be connected in various configurations.

1.25V to 15V Simple Dual Symmetrical Power Supply – [Link]

Variable 0..30V 20A Regulated Power supply using LM317

Radu Motisan  writes:

Having a regulated power supply that can output precise voltages in the 0 .. 30Volts interval is a great add-on for any electronics lab. Especially when it’s a high power supply.

For this article, I’m going to show my supply, built from scratch, the design I’ve used (schematics) and a few safety tips.

First thing we need is a high power transformer. I’ve ordered a custom toroidal unit, with a primary for 220V mains, and two secondaries one of 24Volts, 10Amps max and another one of 12V, 0.5Amps max. It’s very heavy it it was quite expensive. I’ve also purchased a rectifier bridge, capable of handling 400V at 35A max.

Variable 0..30V 20A Regulated Power supply using LM317 – [Link]