The role of electrolytic capacitors

1. Classification and function of capacitors

Capacitors (electric capacity) are composed of two metal poles with an insulating material (dielectric) in between. Due to the different insulating materials, the types of capacitors formed are also different.

According to the structure, it can be divided into: fixed capacitors, variable capacitors, and fine-tuning capacitors.

According to the dielectric material, it can be divided into: gas dielectric capacitors, liquid dielectric capacitors, inorganic solid dielectric capacitors, organic solid dielectric capacitors and electrolytic capacitors.

According to polarity, they are divided into polar capacitors and non-polar capacitors. The most common ones we see are electrolytic capacitors.

Capacitors have the function of blocking direct current and passing alternating current in circuits, so they are often used for inter-stage coupling, filtering, decoupling, bypassing and signal tuning.

2. Unit of Capacitance

The basic unit of resistance is: F (farad), in addition there are μF (microfarad), pF (picofarad), and another less used unit is: nF (nanofarad). Since the capacity of capacitor F is very large, we usually see units of μF, nF, and pF instead of F.

The specific conversion between them is as follows:

1F=1000000μF

1μF=1000nF=1000000pF

3. Capacitor withstand voltage unit: V (volt)

Each capacitor has its withstand voltage value, which is one of the important parameters of the capacitor. The nominal withstand voltage values ​​of ordinary non-polar capacitors are: 63V, 100V, 160V, 250V, 400V, 600V, 1000V, etc. The withstand voltage value of polar capacitors is relatively lower than that of non-polar capacitors. The general nominal withstand voltage values ​​are: 4V, 6.3V, 10V, 16V, 25V, 35V, 50V, 63V, 80V, 100V, 220V, 400V, etc.

4. Types of capacitors

There are many types of capacitors, which can be divided into: non-polar variable capacitors, non-polar fixed capacitors, polar capacitors, etc. based on principles; and can be divided into: CBB capacitors (polyethylene), polyester capacitors, ceramic chip capacitors, mica capacitors, monolithic capacitors, electrolytic capacitors, tantalum capacitors, etc. based on materials.

5. Features

The non-inductive CBB capacitor is made of 2 layers of polypropylene plastic and 2 layers of metal foil alternately sandwiched and then bundled. It is non-inductive, has good high-frequency characteristics, is small in size and is not suitable for large capacity, has a relatively high price, and has poor heat resistance.

Electrolytic capacitors are made of two aluminum strips and two layers of insulating film stacked on top of each other, bundled and immersed in an electrolyte (a synthetic solution containing acid). They have large capacity but poor high-frequency characteristics.

The role of electrolytic capacitors is:

DC isolation: its function is to prevent DC from passing and allow AC to pass.

Bypass (decoupling): Provide a low impedance path for certain parallel components in an AC circuit.

Coupling: Acts as a connection between two circuits, allowing AC signals to pass through and be transmitted to the next level circuit.

Filtering: Convert the rectified sawtooth wave into a smooth pulsating wave, close to direct current.

Energy storage: Storing electrical energy for release when necessary.

1uF/100V, 0.1uF/100V, 0.01uF/100V, 0.0033uF/100V. The above are non-inductive CCB capacitors. The functions are as follows:

DC isolation: its function is to prevent DC from passing and allow AC to pass.

Bypass (decoupling): Provide a low impedance path for certain parallel components in an AC circuit.

Coupling: Acts as a connection between two circuits, allowing AC signals to pass through and be transmitted to the next level circuit.

Filtering: Convert the rectified sawtooth wave into a smooth pulsating wave, close to direct current.