Application Note: SRF And PRF And Their Relation To RF Capacitor Applications

Capacitors exhibit both series and parallel resonant frequencies. There is a frequency for a capacitor with a given physical size/construction and a given capacitance value at which the component looks like an inductive impedance. Indeed, above this frequency one can have essentially a "DC blocking inductor." This frequency is called the Series Resonant Frequency (SRF). The magnitude of the transmission impedance the capacitor presents will be extremely low from the bottom frequency end determined by the capacitance value, right through the SRF until one approaches the first Parallel Resonant Frequency (PRF).