Capacitors Decoded: Ceramic, Electrolytic, and Tantalum
A practical guide to capacitor types — when to use each, how they differ, and common pitfalls in power and signal circuits.
#Choosing the Right Capacitor
Capacitors store charge, filter noise, and stabilize power rails. But not all capacitors are interchangeable. Ceramic, electrolytic, and tantalum each have distinct characteristics — and using the wrong one can lead to oscillation, premature failure, or subtle bugs that are hard to debug.
#Ceramic Capacitors
Ceramics are small, cheap, and have low ESR. They're ideal for decoupling ICs: place 100nF (or 0.1µF) near every power pin. Beware of voltage and temperature derating: a 10µF X5R rated at 6.3V may lose half its capacitance at 5V bias. For critical applications, check the datasheet's capacitance vs. voltage curves.
MLCCs also exhibit piezoelectric effects — mechanical stress can induce voltage. Avoid them in sensitive analog front-ends or high-vibration environments.
#Electrolytic and Tantalum
Electrolytics offer high capacitance in a small package for bulk filtering. Use them on input and output of voltage regulators. They're polarized: reverse voltage can destroy them. Typical values: 10µF–1000µF for power supplies.
Tantalums have lower ESR than electrolytics and better stability. They're common in point-of-load applications. Caveat: they can fail short-circuit under surge conditions. Always use them with current limiting or soft-start if the application demands reliability.