tantalum capacitors polarity
Tantalum capacitors are electrolytic type. They have big capacitance for relatively small size, the best Farad-per-volume-unit ratio and this is the best type of electrolytic caps, but most expensive one. They are kind of low frequency devices. When you use electrolytic caps you need to keep in mind that they are polarized and therefore must be connected according to their polarity. MLCC or Multi-Layer Ceramic Capacitors are high quality caps. They are able to work on high frequencies (depends on dielectric type). They may be very small and use in high frequency electronics, RF and microwave circuits. The major parameters are capacitance, ESR (Equivalent Series Resistance), ESL (Equivalent Series Inductance), SRF (self-resonant frequency), and Q-factor. Capacitance is ability to store an electrical field energy and this is what we need; next two parameters are parasitic. They reduce upper usable frequency of capacitor as well as Q-factor. The latter shows how much energy will lost into cap, but usually Q is not the problem for capacitors. What is important to know it is what the actual capacitance is. For majority of practical applications this parameter can be calculated as Ceff=C/(1-f/SRF)^2. Here f is frequency of interest and SRF is self-resonant frequency from the data sheet. This formula assumes that cap is used well below the SRF. It is easy to see that very often we have much higher capacitance than shown on the cap itself. Even when when we use cap on frequency about half of SRF the effective capacitance Ceff will be 4 times higher than expected.
Best regards,
RF-OM