Several common methods of analyzing circuits

1: DC equivalent circuit analysis

When analyzing the circuit principle, it is necessary to understand the DC path and the AC path in the circuit. The DC path refers to the static bias of each semiconductor transistor and integrated circuit when there is no input signal, that is, their static operating point. The AC circuit refers to the way of AC signal transmission, that is, the ins and outs of the AC signal.

In an actual circuit, an AC circuit and a DC circuit coexist in the same circuit, and they are connected to each other and different from each other.

The DC equivalent analysis method is a method for separately analyzing the DC system of the circuit being analyzed. When performing the DC equivalent analysis, the processing function of the input AC signal is not considered at all, and only the direct current voltage of the power supply is considered. The resulting quiescent DC current, voltage, and the relationship between them.

For DC equivalent analysis, the DC equivalent circuit diagram should be drawn first. The following principles should be followed when drawing the DC equivalent circuit diagram: the capacitors are always treated as open circuits, and the inductors that can ignore the DC resistance should be regarded as short circuits. The inductors that cannot ignore the resistance components can be equivalent to resistors. Take the voltage after the buck decoupling as the supply voltage of the equivalent circuit; consider the semiconductor diode in the reverse bias state as an open circuit.

2: AC equivalent circuit analysis method

The AC equivalent circuit analysis method is a method of separating the AC system in the circuit from the circuit and performing separate analysis.

When AC equivalent analysis, the AC equivalent circuit diagram should be drawn first. To draw the AC equivalent circuit diagram, the following principles should be followed: the power supply is regarded as a short circuit, and the capacitors of the AC bypass are always short-circuited and the direct-coupled coupler is always regarded as a short circuit.

3: Time constant analysis

The time constant analysis method is mainly used to analyze the properties of the circuit composed of R, L, C and semiconductor diodes. The time constant is a parameter reflecting the speed of energy accumulation on the energy storage element. If the time constant is different, although the form and connection of the circuit are similar, But the role played in the circuit is different. Commonly there are coupling circuits, differential circuits, integration circuits, clamp circuits and peak detection circuits.

4: Frequency characteristic analysis

The frequency characteristic analysis method is mainly used to analyze whether the frequency of the circuit itself is compatible with the frequency of the signal it processes. In the analysis, it should be simple to calculate its center frequency, upper and lower limit frequency and bandwidth. Through this analysis, the properties of the circuit, such as filtering, notching, resonance, frequency selection circuits, etc., can be known.