Basic knowledge analysis of PCB schematic diagram

One, what is PCB schematic diagram

Circuit diagram, also known as circuit schematic diagram, is a kind of drawings reflecting the electrical connection of each component of electronic equipment. The circuit diagram consists of some abstract symbols, according to certain rules. By analyzing and studying the circuit diagram, we can understand the circuit structure and working principle of electronic equipment. Therefore, to understand the circuit diagram is an important content of learning electronic technology, is the premise of electronic production or maintenance.

Two, PCB board circuit consists of what elements

A complete circuit diagram is made up of several elements

These elements mainly include graphic symbols, text symbols, lines and annotated characters.

1. Graphic symbols

Graphic symbol is the main body of circuit diagram. In the wireless microphone circuit diagram, various graphic symbols represent the components of the wireless microphone. For example, a small rectangle represents a resistor, two short bars represent capacitors, and a continuous semicircle represents inductors. The graphic symbols of each component are connected by wires, which can reflect the circuit structure of the wireless microphone, that is, the circuit diagram of the wireless microphone.

2. Text symbols

The text symbol is an important part of the circuit diagram. In order to further emphasize the nature of graphic symbols, but also for analysis, understanding and elaboration.

The convenience of the circuit diagram, in each component of the graphic symbol, marked with the text symbol of the component. For example, "R" stands for resistor, "C" for capacitor, "L" for inductor, "VT" for transistor, "IC" for integrated circuit, etc.

The graphic and literal symbols of commonly used components are shown in the attached table.

3. Comment characters

In addition to the uniform graphic symbol and character number of the circuit board, the circuit diagram also follows certain drawing rules. To understand and master the general drawing rules of the circuit diagram is essential to understand the circuit diagram.

Three, circuit diagram drawing rules

In addition to the uniform graphic symbol and character number of the circuit board, the circuit diagram also follows certain drawing rules. To understand and master the general drawing rules of the circuit diagram is essential to understand the circuit diagram.

The circuit type and analysis procedure suitable for each method.

Dc equivalent circuit analysis: Draw the DC equivalent circuit diagram to analyze the DC system parameters of the circuit

Find out the transistor static operating point and bias properties of the stage coupling mode. Analyze the status and function of the relevant components. For example: the working state of the transistor such as saturation, amplification, cut-off diode in the on-off or cut-off.

Ac equivalent circuit analysis: Firstly draw the AC equivalent circuit and then analyze the AC state of the circuit, that is, when the circuit has signal input, whether the voltage and current of each link in the circuit change according to the rule of the input signal, whether it is amplification, oscillation or amplitude limiting clipping, shaping and discrimination.

3. Frequency characteristics analysis: mainly to see whether the circuit itself has the frequency and the spectrum of the signal it deals with. Roughly estimate its center frequency, lower limit frequency and frequency band width, such as: all kinds of filtering, notch, resonance, frequency selection circuit.

4. Time constant analysis: mainly analyzes the circuit and properties composed of R, L, C and diode. The time constant is a parameter that reflects the speed of energy accumulation and consumption on the energy storage element. If the time constant is different, although its form and connection method are similar, the role is still different. Common coupling circuit, differential circuit, integral circuit, decoupling circuit, peak detection circuit and so on.

Finally, the actual circuit and the basic principle of the components in the printed circuit board according to the above method step by step analysis is not difficult to understand. Of course, to really understand it, you need to keep learning.