LM317 and LM337 positive and negative adjustable power modules

# ***1. Rectifier bridge***

![image.png] The 12V (*2) AC power supply is adapted and rectified into DC through four 1N4007 rectifier diodes.
![9.jpg]



# ***2. LM317***

LM317 is a three-terminal adjustable voltage regulator, a positive linear voltage regulator used for voltage regulation. The LM317 is very easy to use because setting the output voltage requires only two external circuits in the LM317 regulator circuit.
LM317 is mainly used for local and on-card regulation, if we connect a fixed resistor between the output and regulation of LM317 regulator, then the LM317 circuit can be used as a precision current regulator.

## LM317 Characteristic Parameters

* Three-terminal positive **voltage regulator**
* **Output voltage** can be set from 1.25V to 37V
* **Output current** is 1.5A
* **Maximum input-output voltage difference** is 40V, 15V recommended
* When the voltage difference is 15V, the maximum output current is 2.2A
* **Operating junction temperature** is 125°C
* To-220, SOT223, TO263 available **Package**
* **Load regulation rate* *Typically 0.1%
* **Line Regulation** Typically 0.01%/V
* **Ripple Suppression** is 80 dB
* ![QQ Screenshot 20230527225521.png]
Output voltage formula:
Vout = 1.25V (1 + R2 /R1)
You can set the R 1 value to 240 Ω (recommended), but it can also be set between 100 and 1000 Ω. You must then enter the R2 value to perform the output voltage calculation. In this case, R2 uses a 50k precision potentiometer for the positive voltage adjustable output.

#***3. LM337***

LM337 is the negative voltage model of LM317, and the [output voltage] of LM337(https://baike.baidu.com/item/%E8%BE%93%E5%87%BA% E7%94%B5%E5%8E%8B/5480610?fromModule=lemma_inlink) range is -1.2V to -37V, [load current](https://baike.baidu.com/item/%E8%B4%9F %E8%BD%BD%E7%94%B5%E6%B5%81/9570816?fromModule=lemma_inlink) The maximum is 0.4~2.2A. It is very simple to use, requiring only two external resistors to set the output voltage. In addition, its linear regulation rate and [load regulation rate](https://baike.baidu.com/item/%E8%B4%9F%E8%BD%BD%E8%B0%83%E6%95%B4% E7%8E%87/8283670?fromModule=lemma_inlink) is also [than standard](https://baike.baidu.com/item/%E6%AF%94%E6%A0%87%E5%87%86/22908463 ?fromModule=lemma_inlink) fixed [voltage regulator](https://baike.baidu.com/item/%E7%A8%B3%E5%8E%8B%E5%99%A8/1414426?fromModule=lemma_inlink) good. LM337 has built-in [overload protection](https://baike.baidu.com/item/%E8%BF%87%E8%BD%BD%E4%BF%9D%E6%8A%A4/7901464?fromModule=lemma_inlink ), safe area protection and other [protection circuits](https://baike.baidu.com/item/%E4%BF%9D%E6%8A%A4%E7%94%B5%E8%B7%AF/ 7901598?fromModule=lemma_inlink).
![image.png]
# ***4. Physical display***

***![1.jpg] ![3.jpg]
***![2.jpg]
# **5. Physical display**

The positive power output function is normal
![5.jpg]
**The negative power output function is normal**
![7.jpg]
# **Sixth, the final adjustable video demonstration**