The voltage divider is the most fundamental resistor network. It produces a fraction of the input voltage determined by the resistor ratio. However, any load connected to the output draws current and changes the effective division ratio. For precision applications, use a high-impedance buffer or ensure RL >> R2.
⚠A loaded divider always has lower Vout than ideal. The error depends on RL/R2 ratio. For <1% error: RL > 100×R2. For precision: use a voltage regulator instead of a divider.
Understanding the Voltage Divider
A voltage divider uses two series resistors to produce a lower voltage from a higher one. The output voltage depends on the ratio of R2 to total resistance. The divider itself consumes current (I = Vin/(R1+R2)), which must be considered in low-power designs. The load effect is critical when the divider feeds into another circuit.
Ideal Divider
Vout = Vin × R2/(R1+R2). No load connected. Used as voltage reference if no current is drawn from the output node.
Loaded Divider
RL in parallel with R2 reduces effective R2. Vout drops. Rule: RL > 100×R2 for <1% error. Op-amp buffer eliminates loading.
Design Trade-offs
Low R values = stiff divider (less load effect) but high power consumption. High R = low power but more load sensitivity. Balance based on application.
Vout = Vin × R2/(R1+R2). The output voltage is R2's fraction of total resistance times input voltage. Simple ratio.
How does load affect Vout?▼
Any load in parallel with R2 reduces effective R2, lowering Vout. Keep RL > 100×R2 for <1% error. Use buffer if precise Vout needed.
Can a divider replace a regulator?▼
Only for reference (no current draw). For power, a regulator is needed. Dividers are not regulated: Vout changes with Vin. Use regulators for stable supply voltages.
How to choose R1 and R2 values?▼
Target ratio R2/(R1+R2) = Vout/Vin. R1+R2 should limit current: for mW power, R1+R2 > Vin²/0.001. Use standard values. Consider load impedance.
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