Contents

**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 **I _{total} **is given by

**I _{total} = Vin/(R1+R2) = V1/R1**

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

**I _{total} = 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 kÎ©**and**R2 = 8.8 kÎ©****R1 =2.2 MÎ©**and**R2 = 8.8 M****Î©**

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:

**Related Posts and Calculators**

- Voltage Divider Calculator with 2 resistors
- Voltage Divider Calculator with 3 resistors
- Voltage Divider Calculator with 4 resistors
- Voltage Divider Calculator with 5 resistors
- Current through voltage divider