1. Structure
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Electrolytic Capacitors:
- Electrolytic capacitors are polarized, meaning they have a positive and a negative terminal. They consist of two metal foils (usually aluminum), with an oxide layer on one of the foils that serves as the dielectric. A porous separator soaked in an electrolyte separates the two foils. The electrolyte plays a crucial role in conducting ions and enables the capacitor to store a relatively large amount of charge. For example, in an aluminum electrolytic capacitor, the anode foil is oxidized to form a thin insulating oxide layer. The cathode is in contact with the electrolyte.
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Ceramic Capacitors:
- Ceramic capacitors are non - polarized. They are made up of a ceramic material as the dielectric, sandwiched between two metal electrodes (usually silver - palladium alloy). The ceramic dielectric is a key component that determines the capacitor's properties. Different ceramic materials result in different capacitance values and temperature and frequency characteristics. For example, the ceramic material can be classified into different types such as Class I (with excellent stability like NP0/C0G) and Class II (with higher capacitance per unit volume like X7R).
2. Capacitance Range
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Electrolytic Capacitors:
- They generally have a relatively large capacitance range. The capacitance can range from a few microfarads () up to several thousand microfarads or even farads. This makes them suitable for applications where a large amount of charge storage is needed. For example, in power - supply filtering circuits, electrolytic capacitors with capacitances of 100 - 1000 are commonly used to smooth out the DC voltage.
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Ceramic Capacitors:
- The capacitance range of ceramic capacitors is wide, but individual capacitors usually have a relatively small capacitance. They can range from a few picofarads () to a few tens of microfarads. In high - frequency circuits, such as radio - frequency (RF) circuits, ceramic capacitors with capacitances in the range of a few picofarads to a few hundred picofarads are often used for impedance matching and signal coupling.
3. Voltage Rating
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Electrolytic Capacitors:
- They typically have a lower voltage rating compared to some ceramic capacitors. The voltage rating usually ranges from a few volts to a few hundred volts. High - voltage electrolytic capacitors are available, but they are less common and more expensive. For example, in a typical consumer - electronics power - supply circuit, electrolytic capacitors might have a voltage rating of 16 - 400V.
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Ceramic Capacitors:
- Ceramic capacitors can have a very wide range of voltage ratings, including high - voltage ratings. Some ceramic capacitors can withstand voltages of several thousand volts. They are often used in high - voltage applications such as in power electronics and high - voltage pulse circuits.
4. Frequency Response
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Electrolytic Capacitors:
- Their performance degrades at high frequencies. As the frequency increases, the equivalent series resistance (ESR) and equivalent series inductance (ESL) of electrolytic capacitors become significant factors. This leads to a decrease in their ability to effectively filter or couple signals. They are generally more suitable for low - frequency applications such as power - supply filtering in DC circuits.
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Ceramic Capacitors:
- Ceramic capacitors have excellent high - frequency characteristics. They have a relatively low ESR and ESL, which allows them to function well in high - frequency circuits such as RF and microwave circuits. Class I ceramic capacitors (like NP0/C0G) have very stable capacitance values over a wide frequency range and are ideal for precision high - frequency applications.
5. Temperature Stability
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Electrolytic Capacitors:
- Their capacitance and other properties are more sensitive to temperature changes. The electrolyte can change its properties with temperature, and the oxide layer's characteristics can also be affected. In extreme temperatures, the electrolyte may dry out or the capacitor may even burst. For example, in high - temperature environments, the capacitance of an electrolytic capacitor can change significantly, and its lifespan may be shortened.
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Ceramic Capacitors:
- Different types of ceramic capacitors have different temperature stabilities. Class I ceramic capacitors have excellent temperature stability, with very little change in capacitance over a wide temperature range. Class II and III ceramic capacitors have more variable capacitance with temperature, but they often offer other advantages such as higher capacitance density.