The Series R-C Network

Author: N.H. Crowhurst

Dividing networks are circuits capable of discriminating (to some extent) between frequencies that are higher or lower than a certain value. Although this may sound quite an "intelligent" action on the part of a mere circuit, there is nothing basically difficult about it.

Action of the series RC divider

At a low frequency, the charge on the series capacitor follows the fluctuations, and the voltage across it very closely follows the input voltage, only a small current flows, and very little fluctuation appears across the resistor. At a high frequency, the charge on the capacitor does not have time to follow each fluctuation, and the whole of the applied voltage appears across the resistor.

At a medium frequency, some of the voltage appears across the capacitor and some across the resistor due to the current required for charging the capacitor. When a combined program is applied across the resistor-capacitor combination, the low frequencies get concentrated across the capacitor, and the high ones across the resistor.