For beginners: regulated linear regulator

If you need simple regulated power supply, you can build it using typical old chip LM317 (LM117). Here is the abstract from datasheet: The LM317/117 series of adjustable 3-terminal positive voltage regulators is capable of supplying in excess of 1.5A over a 1.2V to 37V output range. They are exceptionally easy to use and require only two external resistors to set the output voltage. Further, both line and load regulation are better than standard fixed regulators. Also, the LM117 is packaged in standard transistor packages which are easily mounted and handled.
In addition to higher performance than fixed regulators, the LM117 series offers full overload protection available only in IC’s. Included on the chip are current limit, thermal overload protection and safe area protection. All overload protection circuitry remains fully functional even if the adjustment terminal is disconnected.
Normally, no capacitors are needed unless the device is situated more than 6 inches from the input filter capacitors in which case an input bypass is needed. An optional output capacitor can be added to improve transient response. The adjustment terminal can be bypassed to achieve very high ripple rejection ratios which are difficult to achieve with standard 3-terminal regulators.
Besides replacing fixed regulators, the LM117 is useful in a wide variety of other applications. Since the regulator is “floating” and sees only the input-to-output differential voltage, supplies of several hundred volts can be regulated as long as the maximum input to output differential is not exceeded, i.e., avoid short-circuiting the output. (end of abstract)

I only can add, that the power dissipation rule as mentioned in older post about linear regulator is working here too.

LM317 regulator schematics

LM317 is usually made in TO220, transistor package. There is difference in pinout compared to 78XX series regulators. The output of the regulator is connected to the screw tab. There are also other types of package. SMD packages are made too.

LM317 regulator circuit diagram

This is typical circuit from the datasheet. Theoretical output voltage is from 1.2V to max about 28V. Using floating regulator trick, the output can be higher. Max current with TO-220 case is about 1.5A (you max calculate power dissipation and select proper heat sink).

LM317 regulators

I connected circuit on the breadboard. I used trimmer instead of resistors. I think, it is possible to use any trimmer form 3K to ? kilo-ohms. Somehow I didn’t managed to get 1.2V output even when I connected regulating pin to ground…

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