Capacitor is a basic passive component in electronic circuits, whose core function is to store charge. It is composed of two conductors (called plates) that are close to each other and a dielectric material that is insulated in the middle. When a voltage is applied to the two plates of a capacitor, positive charges accumulate on one plate and negative charges accumulate on the other plate, forming an electric field between the two plates and storing electrical energy.
1、 Core parameters of capacitors
Capacity value
Unit: Farad (F), commonly used units include microfarads (μ F), nanofarads (nF), and picofarads (pF).
Formula: C=VQ, where Q is the amount of stored charge and V is the voltage between the plates.
Example: A 1 μ F capacitor represents the ability to store 1 μ C of charge at a voltage of 1V.
Voltage Rating
The maximum DC voltage or pulse voltage that a capacitor can operate safely for a long time.
Importance: Exceeding the rated voltage may cause dielectric breakdown and damage to capacitors.
Equivalent series resistance (ESR)
The equivalent resistance of capacitor pins and dielectric materials affects high-frequency performance and power consumption.
Low ESR advantage: reduces energy loss and is suitable for high-frequency filtering.
Loss tangent (DF/tan δ)
Reflecting the energy loss of capacitors in AC circuits, the smaller the value, the better.
Temperature coefficient (TC)
The percentage change of capacitance value with temperature affects the stability of the circuit.
2、 The role of capacitors in circuits
Energy storage
Application: Provide backup power for real-time clock (RTC), flash memory, etc.
filtering
Application: Smooth power output (such as LDO, DC-DC converter output terminals) to reduce ripple.
coupling
Application: Transmitting AC signals (such as inter stage coupling of audio amplifiers), isolating DC components.
bypass
Application: Provide a low impedance path for high-frequency noise (such as bypass capacitors for chip power pins).
harmonious
Application: Adjust oscillation frequency in conjunction with inductors (such as radios, wireless communication modules).