Calculadora de divisor de tensão

Two resistors in series split input voltage proportionally. Output at the junction: Vout = Vin × R2 ÷ (R1 + R2). Load current drawn from the tap lowers Vout — this formula assumes negligible load current.

Dividers set reference voltages, scale sensors, and bias transistors. For stable output under load, use a buffer op-amp or size resistors small enough that load current is negligible (watch power dissipation).

Example: 5 V input, R1 = 10 kΩ, R2 = 10 kΩ → Vout = 2.5 V. Current through divider = 5 V ÷ 20 kΩ = 0.25 mA.

Equal resistors give half the supply at the midpoint — the classic 2.5 V reference from 5 V logic. Unequal values scale anywhere from near 0 V to near Vin depending on the R1:R2 ratio.

Power dissipation in each resistor is I²R. High-value resistors minimize current but become noise-sensitive; low values stabilize voltage under light load but waste power — pick a compromise for battery-powered sensors.

Worked example with defaults: Vin = 5 V, R1 = R2 = 10 kΩ → Vout = 2.5 V, divider current 0.25 mA. If a load draws significant current from Vout, measured voltage will sit below 2.5 V unless buffered.

ADC scaling maps a 0–5 V sensor output into a 3.3 V microcontroller range using unequal dividers. If Vin = 5 V and you need Vout ≈ 3.3 V, ratio R2/(R1+R2) = 0.66 — solve for R1 and R2 from standard E24 values, then verify divider current stays low. Unequal dividers scale 0–5 V sensors into 3.3 V ADC range — pick E24 pairs near R2/(R1+R2) ≈ 0.66 before layout.

Thevenin equivalent at the tap is R1∥R2 in parallel. A 10 kΩ load on a 10 kΩ∥10 kΩ divider (5 kΩ Thevenin) pulls Vout below 2.5 V significantly — either buffer with an op-amp or size R1/R2 an order of magnitude below expected load. 10 kΩ load on a 5 kΩ Thevenin tap sags Vout — buffer with an op-amp when load current rivals divider current.

Changing R1 from 10 kΩ to 20 kΩ while R2 stays 10 kΩ drops Vout from 2.5 V to 5 × 10/(20+10) ≈ 1.67 V. Small resistor tolerance (±1%) shifts the tap by tens of millivolts — critical when feeding a 10-bit ADC spanning 3.3 V on the default 5 V supply.