Purpose: Signals above a specific frequency are short-circuited to the main circuit

Example: It is known that the resistance is R, and the AC signal with a frequency higher than F is approximately a short circuit. Find the value of the bypass capacitor in the picture.

Solution: The purpose of the bypass capacitor C is to short-circuit the current at frequencies above F, so the capacitive reactance is much smaller than the impedance. R>>1/(2πfc) gives c>>1/(2πf*R)

F=1KHz, R=1K, when C is much larger than 0.16uf, 47uf is enough

Use capacitors to transmit signals

Example: It is known that Rs represents the output resistance of the previous stage, and R represents the input resistance of the subsequent stage. If the frequency of the signal transmitted between stages is above F, find the value of C?

Solution: The signal is required to be transmitted to R as much as possible, then the capacitive reactance of C is much smaller than R, R>>1/(2πfc) gets c>>1/(2πf*R)

When F=1KHZ, R=5K, C=0.032uf, just go to 3.2uf

Note: The above formula restrains the size of C from being affected by Rs. So what does Rs affect? When Rs is larger, the R side is smaller, and the voltage value transmitted from the front-stage signal to the subsequent stage is smaller. That is to say, if Rs is too large or R is too small, increasing the value of the capacitor (increasing the degree of inter-stage coupling) cannot be restored. Overall, the voltage signal will still drop a lot.

Store electrical energy and release it when necessary

Generally, electrolytic capacitors have the function of storing energy. For capacitors with special energy storage function, the mechanism of capacitor energy storage is double-layer capacitor and Faraday capacitor. Its main form is supercapacitor energy storage. Supercapacitor is a capacitor that utilizes the double-layer principle. When the external voltage is added to the supercapacitor, When the two plates of a capacitor are on, like an ordinary capacitor, the positive electrode of the plate stores positive charges, and the negative plate stores negative charges. Under the action of the electric field generated by the charges on the two plates of the supercapacitor, the electrolyte and the electrode are Opposite charges are formed on the interface to balance the internal electric field of the electrolyte. This positive charge and negative charge are arranged in opposite positions with a very short gap between the positive and negative charges on the contact surface between two different phases. This charge distribution layer is called an electric double layer, so the capacitance is very large.

Turns conductor switching elements on or off at predetermined times

System tuning of frequency-dependent circuits, such as mobile phones, radios, televisions, induction cookers

Capacitors and resistors work together to determine the time constant of a circuit

Time constant: Taking the common RC series connection forming an integrating circuit as an example, when the input voltage is applied to the input terminal, the voltage on the capacitor rises, and the charging current decreases as the voltage rises.

Aiming at the impact of insufficient adaptability of other components to temperature, compensation is performed to improve circuit stability;

A polyester capacitor with a positive temperature coefficient and a polypropylene capacitor with a negative temperature coefficient are connected in parallel.

It is very important for the circuit. The capacitors behind the CPU basically have this function.

Serves as a link between two circuits, allowing AC signals to pass through and be transmitted to the next circuit

example:

Provides a low impedance path for certain parallel components in AC circuits