Application of signal circuit

As an important passive component, capacitance is widely used. This paper will introduce the application of capacitance to signal circuit, and complete the functions of coupling, oscillation / synchronization and time constant.
Capacitors are used in signal circuits, which mainly perform coupling, oscillation / synchronization and time constant functions.
1) coupling
For example, the transistor amplifier has a self supplied bias resistor. It also causes the signal to generate pressure drop back to the input end to form the input and output signal coupling. This resistor is a coupling element. If a capacitor is connected at both ends of the resistor, a capacitor with appropriate capacity is used for communication. The impedance of the signal is smaller, which reduces the coupling effect produced by the resistance, so it is called the decoupling capacitor.
2) oscillation / synchronization
Including RC, LC oscillator and load capacitance of crystal belong to this category.
3) time constant
This is the common integral circuit composed of R and C. When the input signal voltage is added to the input terminal, the voltage on the capacitor (C) rises gradually. The charging current decreases with the increase of voltage. The characteristics of the current through resistance (R) and capacitance (C) are described by the following formula:
I = (V/R) e- (t/CR)