Electronics Handbook/Devices/Filter/Low Pass Filter

RC

Configuration

Characteristics

${\frac {V_{o}}{V_{i}}}={\frac {\frac {1}{j\omega C}}{R+{\frac {1}{j\omega C}}}}={\frac {1}{1+j\omega T}}$

$T=RC$

$\omega _{o}={\frac {1}{T}}={\frac {1}{RC}}$

LR

Characteristics

${\frac {V_{o}}{V_{i}}}={\frac {R}{R+j\omega L}}={\frac {1}{1+j\omega T}}$

$T=RC$

$\omega _{o}={\frac {j\omega L}{R+j\omega L}}={\frac {1}{1+j\omega T}}$

Summary

The two configurations above can be used for Low Pass Filter which has stable voltage which does not change with frequency over low range of frequencies