100nF Ceramic Capacitor

The 100nF ceramic capacitor stores 0.1uF, equal to 100,000pF, and is almost always printed with the three-digit code 104 (10 followed by four zeros in picofarads). It is a two-terminal, non-polarized part built from a ceramic dielectric, so it can be inserted either way around. The version modeled here is rated to 50V, comfortably above the 3.3V and 5V rails used in most Arduino and microcontroller projects.

This value is the workhorse decoupling (bypass) capacitor. Placed right next to a chip's power pin, it acts as a tiny local charge reservoir: when the IC draws a fast burst of current, the capacitor supplies it locally before the regulator or bulk capacitor can respond, and it shunts high-frequency switching noise to ground. Its small size keeps parasitic inductance low, which is what makes it effective at the megahertz frequencies where larger electrolytics fall short.

Dielectric type matters for the details. General-purpose 100nF caps use Class 2 ceramics such as X7R or Y5V, which pack a lot of capacitance into a small body but lose effective capacitance under applied DC bias and temperature swings. For timing or filtering where precision matters, a C0G/NP0 (Class 1) 100nF is far more stable but physically larger. For plain decoupling, any 50V ceramic 104 is fine.