Several methods for analyzing common circuits

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Several methods for analyzing common circuits [Copy link]

1. AC equivalent circuit analysis method First draw the AC equivalent circuit, and then analyze the AC state of the circuit, that is: when the circuit has a signal input, whether the voltage and current of each link in the circuit change according to the law of the input signal, whether it is amplified, oscillated, or limited, clipped, shaped, phase-detected, etc. 2. DC equivalent circuit analysis method Draw the DC equivalent circuit diagram, analyze the DC system parameters of the circuit, clarify the static operating point and bias properties of the transistor, the inter-stage coupling mode, etc. Analyze the state and role of the relevant components in the circuit. For example: the working state of the triode, such as saturation, amplification, cut-off region, the diode is in conduction or cut-off, etc. 3. The frequency characteristic analysis method mainly looks at whether the frequency of the circuit itself is compatible with the spectrum of the signal it processes. Roughly estimate its center frequency, upper and lower limit frequencies and bandwidth, such as: various filtering, notching, resonance, frequency selection and other circuits. 4. The time constant analysis method mainly analyzes the circuit and properties composed of R, L, C and diodes. 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 it plays is still different. Common ones include coupling circuits, differential circuits, integral circuits, decoupling circuits, peak detection circuits, etc. Finally, compare the actual circuit with the basic principle, and analyze it step by step according to the above method according to the role of the components in the circuit, and it will not be difficult to understand. Of course, to truly master it, you still need to study persistently. After you have a certain theory, it will be effortless to analyze the circuit diagram. Definition of circuit diagram: Circuit diagram is a diagram of the connection direction of electronic components drawn by circuit component symbols. It describes in detail the connection and direction of each component, the description of each pin, and some test data. Schematic diagram, also known as "electrical schematic diagram". This kind of diagram is generally used in designing and analyzing circuits because it directly reflects the structure and working principle of electronic circuits. When analyzing the circuit, by identifying the various circuit component symbols drawn on the drawing and the connection method between them, you can understand the actual work of the circuit. The schematic diagram is a circuit situation used to reflect the working principle of the electronic circuit. The PCB diagram is a mapping drawing of the circuit board, which describes in detail the routing of the circuit board, the location of components, etc. When looking at the circuit diagram, first look at the power supply part, understand under what power supply the circuit works, AC or DC, single power supply or multiple power supplies and voltage level. After understanding, look at the sub-circuit, first distinguish whether it is a digital circuit or an analog circuit. For analog circuits, look at signal acquisition, figure out the signal, whether it is radio frequency, audio, various sensors, instruments or other circuits, etc., analyze whether the signal is AC, DC or pulse, voltage type or current type. Analyze the function of the subsequent circuit, and find out whether it is demodulation, amplification, shaping or compensation. Finally, look at the output circuit, whether it is modulation or drive. Digital circuits mainly analyze the logical functions and functions of the circuit. To understand the circuit board, it is best to first understand its electrical schematic (i.e. circuit diagram), master the marking method of electronic components and its working principle, master the normal parameters of some commonly used components and the role they play in the normal circuit, etc., and then analyze the circuit board (called printed circuit board), you can quickly understand its working principle and some situations that need to be mastered. Molecular circuit module, then find the core component of a sub-circuit (of course, you must be familiar with this component) to find out the connection between the electrical quantities of each sub-circuit module, and finally the output and input or function of the entire circuit. The whole machine circuit has certain functions. It is composed of various unit circuits. The unit circuits form signal processing branches with certain functions, and then these branch circuits form the whole machine circuit. First, you must figure out what the function of the circuit diagram you are looking at is, what kind of circuit it belongs to, whether it is audio, video, digital, or mixed circuit, and then use the corresponding unit circuit knowledge to interpret these circuits. At the same time, you must analyze from the AC signal level and DC level. The DC part of the circuit is the basis for the normal operation of the circuit. The AC signal can only be processed accordingly after the DC circuit is normal. The circuit cannot work normally without a good DC state. It is also necessary to analyze from the frequency level and the gain level of the amplifier. When signals of different frequencies are processed by the circuit, due to the nonlinear elements in the circuit, different frequencies will have different processing results. The amplifier also has different amplification capabilities for signals of different frequencies. When the circuit is designed, the required frequency signal will be processed purposefully to meet the needs of the machine function. Another thing is to analyze the relationship between each unit circuit, as well as the relationship between the input and output of each unit circuit. What changes will the AC signal produce after passing through these circuits, etc. Only after understanding the working principle of each branch can the working principle of the whole machine be analyzed. Sometimes there are signal connections between each branch circuit. For example, the line reverse pulse of the line output circuit of the TV is used for the color decoding circuit. The line output circuit and the color decoding circuit have mutual signal connections. At this time, these branches can be understood as another unit circuit and then analyzed. I think there is a sequence problem here: for example, for high-frequency circuits, the function and input and output relationship of the circuit should be mastered first. After having a general grasp, it is like grasping the nose of the bull, because although the circuits and devices are different, their input and output relationship spectrum will not change. Then analyze the basic principles and methods of realizing such functional transformation, and analyze the specific parts. Circuit design should start with analyzing the circuit schematic diagram, but you must first understand the pins and basic functions of the required chip, which will help to better understand the working principle of the circuit, so that it can be applied to your own circuit, and it is conducive to cutting and expanding the circuit. When conducting circuit analysis, first have a general understanding of the circuit schematic diagram, and divide each functional module, such as power module, controller module, memory module, audio module, GPRS module, etc. Analyze each module one by one, and finally unify them to understand the function to be achieved by the circuit. When designing a circuit, it is best to master the principles of common or commonly used unit circuits, such as power module, voltage regulator module, memory module, etc., and commonly used chips, such as: 7805, 7812, etc. When designing a circuit, you should divide the circuit you want to design into several modules, so that they are designed in different schematics, and finally integrated. When there is a signal input in the circuit, you should have a rough estimate of the voltage and current of each basic point. For circuits with amplifiers, R, L, and C, it depends on whether it is an oscillation circuit, an amplification circuit, or a shaping circuit. Analysis of the static operating point of the transistor, analysis of the working state, etc., filtering of capacitors, inter-stage coupling, high-frequency, low-frequency circuits, etc. Generally, we use low-frequency circuits, and high-frequency is generally used more in communications. After self-analysis and self-design, you will have a better understanding and grasp of the basic principles of the circuit, and accumulate experience in design and debugging for your future designs. Of course, true proficiency still requires practice!