100nF Ceramic Capacitor
The near-universal decoupling capacitor value, placed right next to an IC's power pins to absorb switching noise.
How this component works
A capacitor stores charge on two conductive plates separated by an insulator (dielectric). Its capacitance, measured in farads (F), determines how much charge it can hold per volt applied.
In DC circuits, a capacitor blocks steady current once charged but allows current to flow briefly while charging or discharging — this is the basis of timing circuits and debounce filters. In AC circuits, a capacitor's impedance falls as frequency rises, which is why capacitors are used to filter out high-frequency noise or block DC while passing AC signals.
Common types differ mainly in construction: ceramic capacitors (small values, no polarity) and electrolytic capacitors (larger values, polarized — must be wired the right way round or they can fail).
Common Use Cases
- Decoupling capacitor across VCC and GND right at an IC's power pins
- High-frequency noise filtering in parallel with a larger electrolytic capacitor
- Timing capacitor in fast RC networks (e.g. debounce or short-delay circuits)
Frequently Asked Questions
Why 100nF specifically for decoupling?
It's small enough to have very low impedance at the high frequencies digital ICs switch at, while ceramic construction keeps its own parasitic inductance low — both matter more than the exact capacitance for this job.
Does it matter which way round I connect it?
No — ceramic capacitors like this one are non-polarized, so either leg can go to either node.