5V to 4V Voltage Divider Calculator

Introduction

In many circuit applications there is a requirement to drop 5 Volt down to 4 Volt.

For example, a circuit may not be able to tolerate input voltages greater than 4V. However, the output device can only provide 5V.

In this case it becomes necessary to divide +5V down to +4V.

One way to do this is with a voltage divider network that consists of two resistors in series as shown in the picture below. At the point between R1 and R2, there’s a +4 VDC relative to ground.

Calculator

This tool calculates the resistor values for a maximum +4V drop across resistor R2.

Enter either R1 or R2 in milliOhm/Ohm/kiloOhm/megaOhm. The tool will calculate the other resistor value.

Formula

Ohm’s law is used to calculate the voltage drop across each resistor. The current through each series resistor is the same as the total current through the circuit.

Therefore the total current Itotal is given by

Itotal = Vin/(R1+R2) = V1/R1

V1=Vin*R1/(R1+R2)

Itotal = Vin/(R1+R2) = V2/R2

V2=Vin*R2/(R1+R2)

In this case, V2 = +4V and Vin = +5V.

How to Pick Resistor Values

In general, there are many combinations of resistor values that will give the same result. For instance,

  • R1 = 2.2 kΩ and R2 = 8.8 kΩ
  • R1 =2.2 MΩ and R2 = 8.8 MΩ

Both combinations provide +4 Volt at the output.

In some cases there might be a power or an input impedance constraint. Use the following calculators to see if your chosen impedance values meet the requirements:

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