TL431 Calculator

Last Updated on 04/20/2024 by

TL431 Calculator

TL431 Calculator

When you use a TL431 calculator, you’re figuring out how to make a circuit work the way you want it to. The TL431 is a special component that helps control things in the circuit. To set up the circuit right, you need to know a few important things.

Firstly, you’ll want to decide what voltage and current you need in your circuit. Think of voltage as the power level, and current as the flow of electricity.

These are like the settings on your gadget – you need to get them just right.

The TL431 has a special voltage called the reference voltage. It’s like a starting point or a guide for the circuit.

Knowing this reference voltage helps you calculate the values of other parts in the circuit so everything works smoothly.

So, in simple terms, using a TL431 calculator means figuring out the right settings for your circuit by understanding how much power you want, how much electricity should flow, and using the TL431’s reference voltage as a guide.

It’s like tuning a radio to get the best signal for your favorite station!

What is TL431?

The TL431A is like a smart electronic tool with three parts that can control electrical circuits.

It pays attention to what voltage you want, a special starting voltage it has, and the values of some other electronic parts.

Imagine it as a mini electric guide that can be set to work with different voltages. You tell it what voltage you need in your circuit (could be between 2.5 to 36 volts), and it uses that starting voltage it comes with, along with two other electronic parts (resistors), to make things work just the way you want.

This special tool is good for handling up to 100 mA of electricity. So, TL431A is like a little wizard that helps you easily control and set up voltages in your electrical gadgets.

TL431 Circuit Formula

Vout = Vref × (1 + R2 / R1)


  • Vout: This is the voltage you want as the result, the output voltage. It’s what you’re aiming for in your electronic circuit.
  • Vref: This is the reference voltage of the TL431. Think of it as a starting point or a base voltage. Typically, it’s around 2.5V for the TL431.
  • R1: This is the value of the resistor connected between the REF (Reference) and cathode pins of the TL431. It’s one of the external resistors you use in your circuit.
  • R2: This is the value of the resistor connected between the cathode and anode pins of the TL431. It’s the other external resistor in your circuit.


Let’s say you want an output voltage (Vout​) of 10 volts using a TL431 where the reference voltage (Vref​) is approximately 2.5 volts. Now, you have to choose values for R1 and R2 to achieve this desired output.

The formula is-

Vout = Vref ×(1 + R2 / R1)

Substitute the known values


Now, let’s solve for the ratio




Now, you can choose specific resistor values that satisfy this ratio. For example, you could set R1=1kΩ and R2=3kΩ. Plug these values into the formula to check:




So, in this example, if you use R1=1kΩ and R2=3kΩ, the output voltage (Vout​)

should be 10 volts according to the TL431 formula.

TL431 Voltage Reference

The TL431 is a three-terminal adjustable precision shunt regulator. It’s often used as a voltage reference in electronic circuits. Here’s a breakdown of its role as a voltage reference:

Reference Voltage (Vref​)

The TL431 has a built-in reference voltage, typically around 2.5 volts. This voltage is stable over temperature changes and is used as a reference point for other voltages in a circuit.

Adjustable Output Voltage

The TL431 can be used to generate a stable output voltage that is adjustable. By connecting external resistors (usually labeled as R1 and R2) to the device, you can set the output voltage to a desired level.

The formula for the output voltage (Vout​) in terms of Vref​, R1, and R2 is often given as Vout = Vref ×(1 + R2 / R1). This allows for flexibility in configuring the circuit for different voltage requirements.

Shunt Regulator

The TL431 maintains a stable voltage by “shunting” excess current away from the load. It adjusts its resistance to keep the voltage across it constant, making it useful as a regulator.

TL431 Voltage Regulator Circuit

Components Needed.

TL431 (the voltage regulator itself)

Resistors (R1 and R2) for setting the desired output voltage

Input voltage source (Vin)

Output load (Vout)

Capacitors for stability (optional but recommended)

Circuit Description.

Setting the Output Voltage.

Connect the REF pin of the TL431 to the junction of R1 and R2. Connect R1 between the REF pin and cathode pin of the TL431.

Connect R2 between the cathode pin and ground. The output voltage (Vout​) is determined by the values of R1 and R2 according to the formula Vout = Vref ×(1 + R2 / R1)

Choose the values of R1 and R2 to obtain the desired output voltage.

Connecting Input and Output

Connect Vin to the anode pin of the TL431.

Connect Vout to the cathode pin of the TL431.

Stability Considerations

Adding capacitors (typically an input capacitor and an output capacitor) can enhance the stability and transient response of the regulator.

How it Works

The TL431 regulates the voltage by adjusting its internal resistance to maintain a constant voltage between the REF and cathode pins. This stabilizes the output voltage.

The values of R1 and R2 determine the desired output voltage according to the formula provided earlier.

If the output voltage tends to deviate, the TL431 takes corrective action, adjusting its resistance to bring the voltage back to the set point.

This basic TL431 voltage regulator circuit provides a simple yet effective way to control and stabilize the output voltage in electronic applications.

How to Use Our TL431 Calculator for Voltage Regulation?

To use the TL431 calculator provided in the HTML script code:

Open the TL431 Calculator

Enter Values

You will see input fields for “Reference Voltage (Vref),” “Resistor R1 (kΩ),” and “Resistor R2 (kΩ).”

Enter the known values for your circuit into these fields. For example:

Reference Voltage (Vref​): The typical value for TL431 is around 2.5V.

Resistor R1 (R1): The resistor value between REF and cathode pins.

Resistor R2 (R2): The resistor value between cathode and anode pins.

Click “Calculate Output Voltage”

After entering the values, click the “Calculate Output Voltage” button.

View Results

The calculated output voltage (Vout​) will be displayed below the button.

FAQ. (Frequently Asked Questions)

What is a TL431 voltage regulator?

The TL431 is a three-terminal adjustable precision shunt regulator commonly used in electronic circuits. It serves as a voltage reference and can be configured to regulate output voltages.

What is the reference voltage (Vref​) of the TL431?

The reference voltage (Vref​) of the TL431 is typically around 2.5 volts. It serves as a stable starting point for calculating the desired output voltage.

How do I use the TL431 calculator?

Enter the reference voltage (Vref​), resistor R1, and resistor R2 values into the corresponding input fields. Click the “Calculate Output Voltage” button, and the calculated output voltage will be displayed.

Can I use the TL431 calculator for any voltage regulator circuit?

The TL431 calculator is specifically designed for circuits using the TL431 voltage regulator. It helps determine the output voltage based on the TL431 formula. Different voltage regulators may require different calculations.

Are there any limitations to the TL431 calculator?

The TL431 calculator assumes valid numerical inputs and does not account for certain factors like tolerances in resistor values.

It’s important to use accurate values and ensure the compatibility of the calculated output with your specific circuit requirements.

What should I do if I encounter issues with the TL431 calculator?

Check your input values, ensure they are valid numbers, and be mindful of units (e.g., volts for voltages, and kilohms for resistors).

If issues persist, consider consulting additional resources or seeking assistance from experts in electronics.

Gregory Dcosta is an entrepreneur and software developer known for creating a popular tool website. Born and raised in Mumbai India, showed an early interest in technology.After graduation, Gregory worked in various tech companies, gaining experience and honing their skills. However, they always had a desire to create something of their own. This led them to start their own website where they could develop tools to help people solve everyday problems.

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