Electronics Handbook/Circuits/Voltage Divider

Voltage Divider

If two circuit elements are in series, there is a voltage drop across each element, but the current through both must be the same. The voltage at any point in the chain divides according to the resistances. A simple circuit with two (or more) resistors in series with a source is called a voltage divider.

Figure A: Voltage Divider circuit.

Transfer Function of Voltage Divider

Consider the circuit in Figure A. According to KVL the voltage $V_{in}$ is dropped across resistors $R_{1}$ and $R_{2}$. If a current i flows through the two series resistors then by Ohm's Law.

$i={\frac {V_{in}}{R_{1}+R_{2}}}$.

So

$V_{out}=iR_{2}\,\!$

Therefore

$V_{out}=V_{in}{\frac {R_{2}}{R_{1}+R_{2}}}$

$V_{out}=V_{in}{\frac {R_{2}}{R_{1}+R_{2}}}$