Vout = (Vin * R₂) / (R₁ + R₂)
Vin = (Vout * (R₁ + R₂)) / R₂
R₁ = (Vin * R₂ / Vout) - R₂
R₂ = (Vout * R₁) / (Vin - Vout)
Vin = In voltage (V)
Vout = Out voltage (V)
R = Resistance (Ω)
Calculate output voltage using the voltage divider rule — essential for electronics design.
"A circuit that reduces voltage by dividing it across two resistors in series."
Vout = Vin * R2 / (R1 + R2)
Where:
Vin: Input voltage (V)
Vout: Output voltage (V)
R1, R2: Resistance values (Ω)
Note: Voltage divides proportionally with resistance — higher resistance gets more voltage.
The total voltage supplied to the circuit, measured in volts (V).
Example: 5 V from a battery or power supply
The voltage dropped across resistor R2, which is the desired output.
This is commonly used to provide reference voltages for sensors, microcontrollers, or amplifiers.
The ratio of the two series resistances. This determines how the voltage is divided.
If R₁ = R₂ → Vout = Vin/2
If R₂ ≫ R₁ → Vout ≈ Vin
If R₁ ≫ R₂ → Vout ≈ 0
When resistors are connected in series:
1. They share the same current
2. Voltage divides across each resistor
3. Total voltage: Vin = V₁ + V₂
4. Current: I = Vin / (R₁ + R₂)
5. Voltage across R₂: Vout = I × R₂
1. Providing reference voltages for analog circuits
2. Scaling down sensor signals (e.g., thermistors, potentiometers)
3. Biasing transistors and operational amplifiers
4. Creating adjustable voltage sources
5. Teaching basic circuit theory in classrooms
A voltage divider is suitable for providing reference voltages to high-impedance loads (such as ADC inputs, op-amp non-inverting inputs, or sensor biasing), but it is not suitable as a power supply for low-impedance loads (such as motors, LEDs, or microcontrollers).
This is because the output voltage will drop significantly when the load draws current, as the load resistance effectively forms a parallel combination with R2, changing the divider ratio. For powering loads, use a voltage regulator (e.g., LDO or switching regulator) instead.
There are two key considerations:
① Ratio determines voltage — the output voltage depends only on the R1/R2 ratio, so any pair of resistors with the same ratio gives the same Vout;
② Absolute values affect current draw — smaller resistor values draw more current from the source (wasting power), while larger values make the output more susceptible to load interference.
A common engineering practice is to keep the divider current at least 10× the load current to minimize loading effects. For most signal-level applications, R1 and R2 in the range of 1kΩ–100kΩ work well.
Voltage dividers are widely used in:
① Level shifting — scaling down a higher voltage signal to match ADC input ranges (e.g., 12V → 3.3V for a microcontroller);
② Sensor interfacing — reading resistive sensors like thermistors, photoresistors, and strain gauges;
③ Biasing — setting DC operating points for transistors and op-amps;
④ Adjustable voltage — using a potentiometer as R2 to create a variable voltage source;
⑤ Feedback networks — setting gain in op-amp circuits.
Login
