Band‐Pass Filter and Relaxation Oscillator using Electric Double‐Layer Capacitor.

Supercapacitors are electrochemical devices that can store and restore electrical energy and are mostly used for powering dc or close‐to‐dc applications. As such they have not been explored enough for non‐dc circuits. In this study, we implement a band‐pass for frequency selectivity purposes and a relaxation oscillator for timing applications using a solid‐state carbon electric double‐layer capacitor. The expected behavior was observed for both circuits in the sub‐Hertz and tens of Hertz frequency ranges. This confirms the possibility of using the frequency‐dependent capacitive behavior of such devices in non‐conventional low frequency applications not related to dc energy storage but requiring large time constants. A band‐pass filter for frequency selectivity purposes and a relaxation oscillator for timing applications using a solid‐state carbon electric double‐layer capacitor (EDLC) is implemented. Specifically, in the band‐pass circuit, the device's capacitive behavior is clear with a resonance frequency centered at 130 Hz. Whereas from the relaxation oscillator circuit, the device performs well at frequencies below the Hertz up to 22 Hz. This highlights the possibility of using the frequency‐dependent capacitive behavior of EDLC for low frequency applications. [ABSTRACT FROM AUTHOR]