What is the formula for Regulator Feedback Divider?

The Regulator Feedback Divider formula is Vout = Vref × (1 + R1/R2), where Vout—Regulated output voltage (V); Vref—Internal reference voltage (V); R1—Resistor from output to feedback (Ω); R2—Resistor from feedback to ground (Ω).

What does Vout mean in the Regulator Feedback Divider formula?

Vout is Regulated output voltage (V).

Regulator Feedback Divider

Q: How do you calculate Regulator Feedback Divider?

Use the formula Vout = Vref × (1 + R1/R2). Almost every adjustable regulator—LDO or switcher—sets its output by comparing a divided-down sample of the output against an internal reference. Enter the values you know in the calculator above and it solves for the remaining variable.

Vout = Vref · (1 + R1/R2)

Calculator

Output Voltage

Reference Voltage

Top Resistor

Bottom Resistor

Result

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Formula

Vout = Vref × (1 + R1/R2)

Description

Almost every adjustable regulator—LDO or switcher—sets its output by comparing a divided-down sample of the output against an internal reference. The feedback divider R1 (top, output to FB) and R2 (FB to ground) program the output voltage. This formula gives the output for a chosen divider, or the resistor needed for a target output.

Variables

Vout — Regulated output voltage (V)
Vref — Internal reference voltage (V)
R1 — Resistor from output to feedback (Ω)
R2 — Resistor from feedback to ground (Ω)

Practical Notes

Keep divider current well above the FB pin bias current (e.g. R2 ≤ 10–100 kΩ) for accuracy, but not so low it wastes power. Add feedforward capacitance across R1 for better transient response.

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