Capacitance:
Capacitance is also called "capacitance", which refers to the amount of free charge stored under a given potential difference, denoted as C, and the international unit is farad (F). Generally speaking, electric charges move under force in an electric field. When there is a medium between conductors, the movement of electric charges is hindered and the electric charges accumulate on the conductors, resulting in accumulation and storage of electric charges. The amount of stored electric charges is called capacitance.
Capacitance refers to the ability to hold charge. Any electrostatic field is made up of many capacitors, electrostatic capacitance field there, capacitance electrostatic field is described. It is generally believed that an isolated conductor forms a capacitance with infinity, and the conductor grounding is equivalent to being connected to infinity and connected to the earth as a whole.
Capacitance (or capacitance) is a physical quantity that expresses the ability of a capacitor to hold charge. In terms of physics, a capacitor is a static charge storage medium, and the charge may exist forever. This is its characteristic, and it has a wide range of uses. It is an indispensable electronic component in the electronics and power fields. Mainly used in power supply filtering, signal filtering, signal coupling, resonance, filtering, compensation, charging and discharging, energy storage, DC blocking and other circuits.
Manufacturing process:
According to the different manufacturing processes, it can be divided into the following three categories:
- Film Capacitor
- Electrolytic Capacitor
- Ceramic Capacitor
Film Capacitor:
When a thin film capacitor is a metal foil electrodes, and its Polyester, polypropylene, polystyrene or polycarbonate plastic film , from both ends of the overlapped structure wound in a cylindrical shape of the capacitor . According to the type of plastic film, they are called polyethylene capacitors (also known as Mylar capacitors), polypropylene capacitors (also known as PP capacitors), polystyrene capacitors (also known as PS capacitors) and polycarbonate capacitors. Because I don't know much about this, I will give a brief introduction.
Electrolytic Capacitor:
Electrolytic capacitor is a kind of capacitor. The metal foil is the positive electrode (aluminum or tantalum), and the metal oxide film (aluminum oxide or tantalum pentoxide) close to the positive electrode is the dielectric. The cathode is made of conductive materials and electrolyte (the electrolyte can be liquid or Solid) and other materials are composed together. Because the electrolyte is the main part of the cathode, the electrolytic capacitor is named after it. At the same time, the positive and negative electrolytic capacitors cannot be connected wrongly.
And we use tantalum capacitors a lot in the circuit. The full name of a tantalum capacitor is a tantalum electrolytic capacitor , which is a kind of electrolytic capacitor. It uses metal tantalum as the medium. Unlike ordinary electrolytic capacitors, which use electrolyte, tantalum capacitors do not need to be wound with aluminum-plated capacitor paper like ordinary electrolytic capacitors. , There is almost no inductance by itself.
The full name of tantalum capacitor is tantalum electrolytic capacitor, which is also a kind of electrolytic capacitor. It uses gold tantalum as the medium. Unlike ordinary electrolytic capacitors, it does not use electrolyte. Tantalum capacitors do not need to use aluminum-plated capacitor paper like ordinary electrolytic capacitors. Firing, there is almost no inductance, but it also limits its capacity. In addition, there is no electrolyte inside the tantalum capacitor, which is very suitable for working under high temperature. Tantalum capacitors are characterized by long life, high temperature resistance, high accuracy, and excellent performance in filtering high-frequency waves. However, they are smaller in capacity, more expensive than aluminum capacitors, and have weaker voltage and current withstand capabilities. It is used in places where high-capacity filtering is used. For example, tantalum capacitors cannot be seen near the CPU socket. They are mostly used in conjunction with ceramic capacitors or electrolytic capacitors or used in places where voltage and current are not high.
Tantalum capacitors have polarity. The imperfect voltage is a defect of tantalum capacitors. Tantalum capacitors can be up to 50V, but the capacitance of tantalum capacitors can be higher, and the stability of tantalum capacitors is strong. In addition to withstand voltage, it can be competent for comparison. It can still work normally under severe conditions, and it also has the characteristics of small size and small package, so tantalum capacitors can be applied to military equipment, aerospace equipment;
When choosing a capacitor in hardware design, it is important to consider the highest voltage of the line. Usually it is used in half, that is, the capacitor withstand voltage must reach 2 times or more of the line voltage. For example, the capacitor on the 5V power supply should be 10V instead of 6.3V. The capacitor on the 20V power supply should be 50V instead of 35V. It is recommended to use more than 2 times the electrolytic capacitor to avoid hidden dangers caused by the supplier's lack of strict quality control. Tantalum capacitors must be selected strictly in accordance with 2 times or more (Huawei's standard is calculated as 3 times), because tantalum capacitors are more prone to breakdown.
Ceramic Capacitor:
Ceramic capacitors are capacitors with ceramics as dielectric . Its structure is composed of two or more alternating ceramic layers and metal layers, and the metal layers are connected to the electrodes of the capacitor.
The high frequency characteristics of ceramic capacitors are good, but the maximum capacitance value can only be 0.1uF. Ceramic capacitors are also a type of ceramic capacitors. When we use a large number of chip capacitors in circuit design, the chip capacitors are monolithic ceramic capacitors . Ceramic capacitors are non-polar, with higher voltage resistance and strong pressure-bearing capacity. The disadvantage is that the capacitance value cannot be made too high. Now the highest is 220UF. The stability cannot be compared with tantalum capacitors, but the price is relatively high. It is cheaper than tantalum capacitors;
Ceramic capacitors can be slightly smaller, and it is recommended to use about 1.6-2 times, because ceramic capacitors have better tolerance to high voltage.
Summary: The direction of the capacitor: ceramic capacitors do not distinguish between positive and negative electrodes, and electrolytic capacitors and tantalum capacitors have positive and negative differences. If it is reversed, it will break down and cause fire or explosion.