Capacitor Types Explained
Not all capacitors are interchangeable. Picking the wrong family can mean a circuit that drifts out of spec — or, with electrolytics, a part that fails outright if you get the polarity wrong.
What a Capacitor Does
A capacitor stores and releases electrical energy, smoothing out voltage ripples, filtering noise, and timing circuits. The material used to build it determines its capacitance range, voltage tolerance, size, and lifespan.
Ceramic Capacitors
Small, cheap, and non-polarized — you can insert them either way round. Great for decoupling and filtering in the pF to low-µF range. They're the default choice for most digital circuits.
Electrolytic Capacitors
Polarized — the longer lead (or the side without the stripe) is positive. They cover much larger capacitance values (µF to mF), making them the go-to for power supply smoothing. Reversing polarity can cause the capacitor to fail, sometimes venting or bulging, so always check orientation before powering on.
Tantalum Capacitors
Also polarized, but more stable and compact than electrolytics for a given capacitance — common in space-constrained boards. They're less tolerant of voltage spikes than electrolytics, so derate the voltage rating (use a part rated well above your circuit's actual voltage).
How to Choose
- Filtering high-frequency noise near an IC → ceramic
- Smoothing a power supply rail → electrolytic
- Compact, stable filtering on a tight board → tantalum
- Always check the voltage rating is comfortably above your circuit's working voltage