The LM**350 voltage regulator** is 3A DC adjustable power supply, high-performance. It can apply voltage output 1.25V to 35V. so have a few components. If you add two diode series with the output to reduce voltage start with 0-volts.

This circuit looks like in **My first Variable DC Power Supply**, But this high current higher than 3-Amp. Therefore they cause you can supply more any load circuit. Which we can buy this IC at many stores but expensive than **LM317**.

**Table of Contents**Show All

### How it works

In Figure 1 you will see that the circuit form same the **My first Variable DC Power Supply**.

When we apply AC220V or **AC110V**(for the USA) by pressing S1 to turn on this power supply. ACV will flow F1 for protection when the overload or too much voltage input.

Then the ACV will flow into a transformer that has the ability to transform voltage and current to lower levels of AC-18V and next to BD1-**bridge diode** to convert AC to DC.

Next, they will through C1-4700uF electrolytic capacitor smooth (filter) the pulsating voltage from a transformer into a steady direct current (DC).

Now we have voltage at this point is 22V to 25V

And then, the current will flow to the input lead of the IC1-LM350 **power supply**.

Which it is an **adjustable regulator** IC that designed for many supplies for **3 Amp output** and adjustable over 1.2V to 33-volts, and with current limiting, thermal shutdown, full protection.

## LM350 datasheet

How to use LM350? Which there is a simple detail to do this:

The LM350 is best for you. Because it is the adjustable three-terminal positive voltage regulator.

Which looks like a popular LM317. We can set the output voltage with only two external resistors. But It can supply the output current over 3.0A, on the voltage range of 1.2 V to 33 V.

In addition, it uses internal current limiting, thermal shutdown, and safe mode.

We can use the LM350 on a wide variety of applications. For example A simple adjustable switching regulator. A programmable output regulator.

A precision current regulator. By connecting a fixed resistor between the adjust and output

### LM350 Pinout

As in the LM350 pinout above. It looks much like the popular LM317. Also, its pin output connects the heatsink surface. Caution!

Since it has high current over 3A, we must mount the LM350 on the large heatsink.

Basic Features

Basic Features

- 3.0 A Output Current
- Output Adjustable Voltage from 1.2 V to 33 V
- Load Regulation Typically 0.1%
- Line Regulation Typically 0.005%/V
- Internal Thermal Overload Protection
- Internal Short Circuit
- Current Limiting Constant with Temperature
- Output Transistor Safe Area Compensation
- Floating Operation for High Voltage Applications

### LM350 VOLTAGE REGULATOR CALCULATOR

We love it because easy to use. You see LM350 circuit below. We use only 2 resistors to control the output voltage. The formula is:

Vout = 1.25 x {1+(R2/R1)}

In normal operation, the LM350 has a nominal 1.25V **reference voltage** (Vref) between the output lead and Adjustable lead (ADJ). This voltage will across R1+R2 (120 ohms+120 ohms = 240 ohms datasheet)

And, since the voltage is constant, a **constant current** then flows through the output set resistor VR1. To adjust voltage output.

### Using the Resistors list (No calculating)

If we do not have a calculator or busy or slow brain like me. Using the resistors list is an easy solution. Just choose the suitable resistors according to the voltage rate.

1.43V : R1 = 470Ω, R2 = 68Ω

1.47V : R1 = 470Ω, R2 = 82Ω

1.47V : R1 = 390Ω, R2 = 68Ω

1.51V : R1 = 330Ω, R2 = 68Ω

1.51V : R1 = 390Ω, R2 = 82Ω

1.52V : R1 = 470Ω, R2 = 100Ω

1.53V : R1 = 390Ω, R2 = 82Ω

1.56V : R1 = 330Ω, R2 = 82Ω

1.57V : R1 = 270Ω, R2 = 68Ω

1.57V : R1 = 470Ω, R2 = 120Ω

1.57V : R1 = 390Ω, R2 = 100Ω

1.59V : R1 = 390Ω, R2 = 100Ω

1.60V : R1 = 240Ω, R2 = 68Ω

1.63V : R1 = 330Ω, R2 = 100Ω

1.63V : R1 = 270Ω, R2 = 82Ω

1.64V : R1 = 390Ω, R2 = 120Ω

1.64V : R1 = 220Ω, R2 = 68Ω

1.65V : R1 = 470Ω, R2 = 150Ω

1.66V : R1 = 390Ω, R2 = 120Ω

1.68V : R1 = 240Ω, R2 = 82Ω

1.71V : R1 = 330Ω, R2 = 120Ω

1.71V : R1 = 270Ω, R2 = 100Ω

1.72V : R1 = 220Ω, R2 = 82Ω

1.72V : R1 = 180Ω, R2 = 68Ω

1.73V : R1 = 470Ω, R2 = 180Ω

1.73V : R1 = 390Ω, R2 = 150Ω

1.76V : R1 = 390Ω, R2 = 150Ω

1.77V : R1 = 240Ω, R2 = 100Ω

1.81V : R1 = 270Ω, R2 = 120Ω

1.82V : R1 = 150Ω, R2 = 68Ω

1.82V : R1 = 330Ω, R2 = 150Ω

1.82V : R1 = 180Ω, R2 = 82Ω

1.83V : R1 = 390Ω, R2 = 180Ω

1.84V : R1 = 470Ω, R2 = 220Ω

1.86V : R1 = 390Ω, R2 = 180Ω

1.88V : R1 = 240Ω, R2 = 120Ω

1.89V : R1 = 470Ω, R2 = 240Ω

1.93V : R1 = 330Ω, R2 = 180Ω

1.93V : R1 = 150Ω, R2 = 82Ω

1.94V : R1 = 270Ω, R2 = 150Ω

1.96V : R1 = 390Ω, R2 = 220Ω

1.97V : R1 = 470Ω, R2 = 270Ω

1.99V : R1 = 390Ω, R2 = 220Ω

2.02V : R1 = 390Ω, R2 = 240Ω

2.03V : R1 = 240Ω, R2 = 150Ω

2.06V : R1 = 390Ω, R2 = 240Ω

2.08V : R1 = 330Ω, R2 = 220Ω

2.10V : R1 = 220Ω, R2 = 150Ω

2.12V : R1 = 390Ω, R2 = 270Ω

2.13V : R1 = 470Ω, R2 = 330Ω

2.16V : R1 = 330Ω, R2 = 240Ω

2.16V : R1 = 390Ω, R2 = 270Ω

2.19V : R1 = 240Ω, R2 = 180Ω

2.23V : R1 = 470Ω, R2 = 390Ω

2.25V : R1 = 150Ω, R2 = 120Ω

2.27V : R1 = 270Ω, R2 = 220Ω

2.27V : R1 = 330Ω, R2 = 270Ω

2.29V : R1 = 470Ω, R2 = 390Ω

2.29V : R1 = 180Ω, R2 = 150Ω

2.31V : R1 = 390Ω, R2 = 330Ω

2.36V : R1 = 270Ω, R2 = 240Ω

2.37V : R1 = 390Ω, R2 = 330Ω

2.40V : R1 = 240Ω, R2 = 220Ω

2.44V : R1 = 390Ω, R2 = 390Ω

2.50V : R1 = 470Ω, R2 = 470Ω

2.57V : R1 = 390Ω, R2 = 390Ω

2.61V : R1 = 220Ω, R2 = 240Ω

2.65V : R1 = 330Ω, R2 = 390Ω

2.66V : R1 = 240Ω, R2 = 270Ω

2.73V : R1 = 330Ω, R2 = 390Ω

2.74V : R1 = 470Ω, R2 = 560Ω

2.75V : R1 = 150Ω, R2 = 180Ω

2.76V : R1 = 390Ω, R2 = 470Ω

2.78V : R1 = 270Ω, R2 = 330Ω

2.78V : R1 = 220Ω, R2 = 270Ω

2.84V : R1 = 390Ω, R2 = 470Ω

2.92V : R1 = 180Ω, R2 = 240Ω

2.96V : R1 = 270Ω, R2 = 390Ω

2.97V : R1 = 240Ω, R2 = 330Ω

3.03V : R1 = 330Ω, R2 = 470Ω

3.05V : R1 = 390Ω, R2 = 560Ω

3.06V : R1 = 270Ω, R2 = 390Ω

3.06V : R1 = 470Ω, R2 = 680Ω

3.08V : R1 = 150Ω, R2 = 220Ω

3.13V : R1 = 220Ω, R2 = 330Ω

3.14V : R1 = 390Ω, R2 = 560Ω

3.18V : R1 = 240Ω, R2 = 390Ω

3.25V : R1 = 150Ω, R2 = 240Ω

3.28V : R1 = 240Ω, R2 = 390Ω

3.35V : R1 = 220Ω, R2 = 390Ω

3.37V : R1 = 330Ω, R2 = 560Ω

3.43V : R1 = 270Ω, R2 = 470Ω

3.43V : R1 = 390Ω, R2 = 680Ω

3.43V : R1 = 470Ω, R2 = 820Ω

3.47V : R1 = 220Ω, R2 = 390Ω

3.50V : R1 = 150Ω, R2 = 270Ω

3.54V : R1 = 180Ω, R2 = 330Ω

3.55V : R1 = 390Ω, R2 = 680Ω

3.70V : R1 = 240Ω, R2 = 470Ω

3.82V : R1 = 180Ω, R2 = 390Ω

3.83V : R1 = 330Ω, R2 = 680Ω

3.84V : R1 = 270Ω, R2 = 560Ω

3.88V : R1 = 390Ω, R2 = 820Ω

3.91V : R1 = 470Ω, R2 = 1K

3.92V : R1 = 220Ω, R2 = 470Ω

3.96V : R1 = 180Ω, R2 = 390Ω

4.00V : R1 = 150Ω, R2 = 330Ω

4.02V : R1 = 390Ω, R2 = 820Ω

4.17V : R1 = 240Ω, R2 = 560Ω

4.33V : R1 = 150Ω, R2 = 390Ω

4.36V : R1 = 330Ω, R2 = 820Ω

4.40V : R1 = 270Ω, R2 = 680Ω

4.43V : R1 = 220Ω, R2 = 560Ω

4.44V : R1 = 470Ω, R2 = 1.2K

4.46V : R1 = 390Ω, R2 = 1K

4.50V : R1 = 150Ω, R2 = 390Ω

4.51V : R1 = 180Ω, R2 = 470Ω

4.63V : R1 = 390Ω, R2 = 1K

4.79V : R1 = 240Ω, R2 = 680

5.04V : R1 = 330Ω, R2 = 1K

5.05V : R1 = 270Ω, R2 = 820Ω

5.10V : R1 = 390Ω, R2 = 1.2K

5.11V : R1 = 220Ω, R2 = 680Ω

5.14V : R1 = 180Ω, R2 = 560Ω

5.17V : R1 = 150Ω, R2 = 470Ω

5.24V : R1 = 470Ω, R2 = 1.5K

5.30V : R1 = 390Ω, R2 = 1.2K

5.52V : R1 = 240Ω, R2 = 820Ω

5.80V : R1 = 330Ω, R2 = 1.2K

5.88V : R1 = 270Ω, R2 = 1K

5.91V : R1 = 220Ω, R2 = 820Ω

5.92V : R1 = 150Ω, R2 = 560Ω

5.97V : R1 = 180Ω, R2 = 680Ω

6.04V : R1 = 470Ω, R2 = 1.8K

6.06V : R1 = 390Ω, R2 = 1.5K

6.32V : R1 = 390Ω, R2 = 1.5K

6.46V : R1 = 240Ω, R2 = 1K

6.81V : R1 = 270Ω, R2 = 1.2K

6.92V : R1 = 150Ω, R2 = 680Ω

6.93V : R1 = 330Ω, R2 = 1.5K

6.94V : R1 = 180Ω, R2 = 820Ω

7.02V : R1 = 390Ω, R2 = 1.8K

7.10V : R1 = 470Ω, R2 = 2.2K

7.33V : R1 = 390Ω, R2 = 1.8K

7.50V : R1 = 240Ω, R2 = 1.2K

8.07V : R1 = 330Ω, R2 = 1.8K

8.08V : R1 = 150Ω, R2 = 820Ω

8.19V : R1 = 270Ω, R2 = 1.5K

8.30V : R1 = 390Ω, R2 = 2.2K

8.43V : R1 = 470Ω, R2 = 2.7K

8.68V : R1 = 390Ω, R2 = 2.2K

9.06V : R1 = 240Ω, R2 = 1.5K

9.58V : R1 = 330Ω, R2 = 2.2K

9.77V : R1 = 220Ω, R2 = 1.5K

9.90V : R1 = 390Ω, R2 = 2.7K

10.03V : R1 = 470Ω, R2 = 3.3K

10.37V : R1 = 390Ω, R2 = 2.7K

10.63V : R1 = 240Ω, R2 = 1.8K

11.25V : R1 = 150Ω, R2 = 1.2K

11.44V : R1 = 270Ω, R2 = 2.2K

11.48V : R1 = 330Ω, R2 = 2.7K

11.67V : R1 = 180Ω, R2 = 1.5K

11.83V : R1 = 390Ω, R2 = 3.3K

12.40V : R1 = 390Ω, R2 = 3.3K

12.71V : R1 = 240Ω, R2 = 2.2K

13.75V : R1 = 330Ω, R2 = 3.3K

15.31V : R1 = 240Ω, R2 = 2.7K

16.25V : R1 = 150Ω, R2 = 1.8K

16.53V : R1 = 270Ω, R2 = 3.3K

16.59V : R1 = 220Ω, R2 = 2.7K

18.44V : R1 = 240Ω, R2 = 3.3K

19.58V : R1 = 150Ω, R2 = 2.2K

20.00V : R1 = 220Ω, R2 = 3.3K

23.75V : R1 = 150Ω, R2 = 2.7K

24.17V : R1 = 180Ω, R2 = 3.3K

28.75V : R1 = 150Ω, R2 = 3.3K

For example, you need 20V 5A power supply. You look at 5.00V. We can see at 5.04V or 5.05V rate.

I look at 5.05V because I have R1=270 ohms. Then I use R2 is 820 ohms. Is it easy?

### Capacitor filters

- Both C1 and C4-0.1uF are input bypass capacitor. It needs if devices (IC1) more than 6 inches from filter capacitors.
- C3-47uF is a bypass capacitor that prevents 86dB ripple rejection.
- C5- 100uF is used to improves transient response. Output capacitor in the range of 1uF to 1000uF of tantalum electrolytic is commonly used to provide improved output impedance and rejection of transients.

**Protection Diodes**

When external capacitors are used with any **IC regulators.** Sometimes necessary to add protection diode to prevent the capacitors from discharging through low current point into the regulator.

Although the surge is **short**, there is enough energy to damage parts of the IC.

- When negative voltage or 20A spikes flow backward the output it will be absorbed voltage with D3-diode.
- Then D2 to
**protect**Out and Adj lead. - D1 is protected
**voltage spikes**to Input and output lead.

**Learn more:**

Gel cell battery charger circuit

0-30V 0-5A regulated variable power supply

12V to 5V converter step down

## Components list

IC1: LM350T 3 terminal **positive voltage regulator 3Amp**

C1: 4700uF 35V_Electrolytic

C3_47uF 35V_Electrolytic

C5_100uF 50V_Electrolytic

C2,C4_0.1uF 50V_ ceramic capacitors

BD1_4A 200V brigde diode

D1-D3_1N4007___1A 1000V Diode

R1,R2_120Ω 0.5W **resistors**

VR1_Variable Resistors_5K(B)

S1_On-Off or SPST switch

F1_0.5A Fuse

T1_3A 18V to 21V transformer

Heatsink, PCB, wires, and others

## Make LM350 power supply

The circuit has a few parts you can assemble devices on perforated Board and wiring as Figure 2

The IC1-LM350 power supply must be mounted to a big size heatsink because at work times it is very hot.

**We assemble and wiring parts on perforated board.**

## Testing

Before check circuit and wiring for error. Then adjust VR1 to a minimum. Next, we test this project with apply voltage output is 1.2V. You can watch the video below. Then adjust the voltage to **12V**.

And next, I try to use the 12V 50W **lamp** as the load. The voltage will must not lower than 12V and I measure the current of the lamp of 3.5A.

This project is good as we need to. We are happy. Thank you for watching.

## Increasing Performance

Also, we can increase the performance of this project as follows.

**add voltmeter to display a level voltage**.**add potentiometer**for fine adjusting like an LM317 power supply.**High current**—When actually using, we should use a soldering iron to increase the size of the conductor wire. Because the current flows through input, output and ground are too much.- While it is running. It is so hot. We should add a cooling fan.

Then, We assembled this project on the ABS Plastic Electronic Project Junction Box in Enclosure Case.

Because the drill is easy to install as an electrical insulator And cheap too.

Look at! We finished the LM350 adjustable voltage Regulator project.

Buy it here: LM350 Linear Voltage Regulators

LM350 – Voltage Regulators – Linear

## We recommend other circuits using LM350

**12V to 6A 3A DC converter**—you can reduce 12V to 6V for any the circuit. Using 6V regulator.

**24V 3A Regulator**—We love it, and you?

**0-12V 3A Variable power supply**—LM350 can start voltage at zero voltags. And can protect load of wrong polarity.

**High power pulse generator up to 3A max**—It may to control Motor or lamp with pulse. Low current using! It is good learning too.

OR…What is more? it is not enough!

Look:

## LM338 Adjustable Power Supply 5A and 10A

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I always try to make Electronics **Learning Easy**.