voltage divider
A type of simple electronic circuit which reduces any input voltage by a fixed factor using sources of impedance (such as resistors) connected in series.
voltage divider: resistor network that scales down input voltage
A voltage divider is a circuit made from two or more impedances in series across a voltage source. The output is taken from the junction between these components, producing a voltage that is a predictable fraction of the input. The most common form uses two resistors, but capacitors, inductors, or their combinations work equally well depending on the frequency and application.
The math is straightforward. In a resistor divider with values R1 and R2 in series, if the input voltage is Vin and you measure the output across R2 to ground, then Vout equals Vin multiplied by R2 divided by (R1 plus R2). A 10 V input with equal resistors gives 5 V output. The ratio is fixed; it does not depend on the input voltage, only on the component values. This makes voltage dividers reliable for generating reference voltages, attenuating signals, or creating bias points for transistor circuits.
The critical limitation is load impedance. The formula assumes almost no current flows out of the output tap. If you connect a low-impedance load, it draws current through R2, changing the effective voltage. Engineers design around this by making the divider resistors small compared to the load, or by buffering the output with a high-impedance amplifier stage. Capacitive dividers suffer similar effects and also introduce frequency dependence; the capacitive reactance must be known at the operating frequency.
Practical use and failure modes
Voltage dividers appear in sensor conditioning circuits, measurement scaling, and analog-to-digital converter input protection. They are used to match signal levels between incompatible stages and to generate bias voltages for amplifiers. In measurement chains, they attenuate signals that would otherwise exceed input ranges; a 100:1 divider lets you measure voltages ten times larger than the instrument can directly accept.
Common problems arise from thermal drift, as resistor values change with temperature and cause output voltage to creep. Precision applications use temperature-compensated resistors or thermistor-based dividers to hold the ratio constant. In high-impedance dividers, leakage currents through the resistors themselves or across the circuit board surface become significant, especially in humid environments or at high voltages. For AC signals, capacitance in the divider creates phase shift and frequency-dependent attenuation, requiring careful design of component placement and shielding.