A capacitor is a capacitor — until you notice that two capacitors with the same capacitance value can behave very differently in a circuit. The type determines not only how much charge a capacitor stores, but also how fast, how stable and under what conditions it does so.
The three most commonly used types
Electrolytic capacitors
An electrolytic capacitor is polarized. If it is connected the wrong way round, it can be damaged or fail. Electrolytic capacitors are useful for high capacitance values at relatively low cost. They are often used in power supplies as buffer capacitors and in audio circuits.
Limitations: limited lifetime at high temperatures, relatively high ESR and usually not intended for AC voltage. Always check the datasheet and the application.
Ceramic capacitors (MLCC)
Small, inexpensive and non-polarized. Because of their low ESR, ceramic capacitors are often used for decoupling close to ICs. Pay attention to X7R/X5R specifications: capacitance can decrease at higher voltage because of the DC bias effect.
Film capacitors
Non-polarized, low leakage current and often stable across temperature and frequency. The PME271 from Kemet is an X2 capacitor. For applications around mains voltage, the safety class, datasheet and manufacturer instructions are leading.
When do you choose which type?
| Application | Often used type |
|---|---|
| Power supply buffering, large capacitance | Electrolytic |
| Decoupling near ICs | Ceramic, for example close to the IC according to the design or datasheet |
| Filtering applications, audio | Film when stability and low distortion are important |
| EMI suppression around mains voltage | Only capacitors with the appropriate safety class, such as X2 where specified |
| High frequency, RF | Ceramic, for example NP0/C0G when stability is needed |
Which capacitor do I need?
You do not choose a capacitor by capacitance alone. Also check the voltage rating, type, polarity, physical size and application. When replacing a part, the schematic, datasheet or markings on the old component are leading.
Checklist for choosing or replacing
- Capacitance: check the unit, such as pF, nF or µF.
- Voltage rating: do not simply choose a lower voltage rating than the original.
- Type: ceramic, electrolytic, film, tantalum and polymer capacitors behave differently.
- Polarity: check plus and minus on polarized capacitors.
- Size and mounting: check diameter, height, lead spacing, SMD or through-hole.
- Application: in power supplies, ESR, ripple current, temperature and lifetime can be important.
Unsure about a replacement? Check the datasheet or search by manufacturer part number, part number or marking. If you cannot find the part directly in the shop, use the request block on the search page.
The PME271 in practice
The PME271 is an X2 capacitor that can occur in mains filtering applications. In these applications, use only components that are suitable according to the datasheet, safety class and manufacturer instructions.
Practical points to watch
- Check the voltage rating. Do not choose a lower voltage rating than the original. The right margin depends on the application, environment and datasheet.
- ESR matters in power supplies. In switching power supplies, low-ESR properties can be important; check the original type and datasheet.
- Check the temperature class. Electrolytic capacitors are available, for example, in 85°C and 105°C variants. Choose based on the application, environment and original specification.
- Check polarity. Many electrolytic capacitors mark the negative terminal. Film and ceramic capacitors are usually non-polarized.
Looking for a capacitor? Search by capacitance, voltage, type or manufacturer part number. No result? Use the request block on the search page and we will look with you.
Search for your capacitor