Teach you how to understand the circuit diagram of integrated circuits

The integrated circuit application circuit diagram function integrated circuit application circuit diagram has the following functions:

1 It expresses the circuit structure and component parameters of each pin of the integrated circuit, thus indicating the complete working condition of an integrated circuit.

2 In some integrated circuit application circuits, the internal circuit block diagram of the integrated circuit is drawn. At this time, it is quite convenient to analyze the integrated circuit application circuit, but this representation is not much.

3 integrated circuit application circuit has two typical application circuits and practical circuits, the former can be found in the integrated circuit manual, the latter appears in the practical circuit, the two application circuits are not much different, according to this feature, there is no actual A typical application circuit diagram can be used as a reference when applying a circuit diagram, which is often used in repairs.

4 General The integrated circuit application circuit expresses a complete unit circuit, or a circuit system, but in some cases a complete circuit system uses two or more integrated circuits.

Integrated Circuit Application Circuit Features The integrated circuit application circuit diagram has the following features:

1 Most of the application circuits do not draw the internal circuit block diagram, which is unfavorable for the identification of the picture, especially for beginners to perform circuit work analysis.

2 For beginners, it is more difficult to analyze the application circuit of an integrated circuit than to analyze the circuit of a discrete component. This is the original reason for not knowing the internal circuit of the integrated circuit. In fact, it is good to know the picture and repair it. More convenient than discrete component circuits.

3 For integrated circuit application circuits, it is convenient to know the internal circuit of the integrated circuit and understand the function of each pin in detail. This is because the same type of integrated circuits have regularity. After mastering their commonalities, many integrated circuit application circuits of the same function and different types can be conveniently analyzed.

Integrated circuit application circuit identification method and precautions The methods and precautions for analyzing integrated circuits mainly include the following:

(1) Understand the role of each pin is the key to understanding the picture. The role of each pin can be found in the relevant IC application manual. After knowing the role of each pin, it is convenient to analyze the working principle of each pin and the function of the components. For example, if the pin 1 is an input pin, then the capacitor connected in series with the pin 1 is the input coupling circuit, and the circuit connected to the pin 1 is the input circuit.

(2) Understanding the three methods of the function of each pin of the integrated circuit There are three methods for understanding the function of each pin of the integrated circuit: one is to consult the relevant data; the other is to analyze the block diagram of the internal circuit according to the integrated circuit; the third is the application circuit according to the integrated circuit. The characteristics of the external circuit of each pin are analyzed. The third method requires a better basis for circuit analysis.

(3) Circuit Analysis Steps The integrated circuit application circuit analysis steps are as follows:

1 DC circuit analysis. This step is mainly to analyze the external circuit of the power supply and ground pins.

Note: When there are multiple power supply pins, it is necessary to distinguish the relationship between these power supplies, such as whether it is the power supply pin of the pre-stage and post-stage circuits, or the power supply pins of the left and right channels; The pins should also be distinguished as such. Separating multiple power and ground pins is useful for repairs.

2 signal transmission analysis. This step mainly analyzes the signal input pin and the output pin external circuit. When an integrated circuit has multiple input and output pins, it is necessary to find out whether it is the output pin of the pre-stage or post-stage circuit; for the two-channel circuit, the input and output pins of the left and right channels are also distinguished.

3 other external circuit analysis of the pin. For example, to find the negative feedback pin, the anti-vibration pin, etc., the analysis of this step is the most difficult, for beginners to use the pin action data or internal circuit block diagram.

4 After having a certain ability to recognize pictures, it is necessary to learn to summarize the rules of the external circuit of the various functional integrated circuits, and to master this law, which is useful for improving the speed of drawing. For example, the law of the external circuit of the input pin is: connected to the output end of the pre-stage circuit through a coupling capacitor or a coupling circuit; the law of the external circuit of the output pin is: connected to the input end of the post-stage circuit through a coupling circuit.

5 When analyzing the internal circuit of an integrated circuit for signal amplification and processing, it is preferable to consult the internal circuit block diagram of the integrated circuit. When analyzing the internal circuit block diagram, it can be indicated by the arrow in the signal transmission line to know which circuits have been amplified or processed by the signal, and finally which pin is output from the signal.

6 Knowing some key test points of the integrated circuit and the DC voltage law of the pin are very useful for the maintenance circuit. The DC voltage at the output of the OTL circuit is equal to half of the DC operating voltage of the integrated circuit; the DC voltage at the output of the OCL circuit is equal to 0V; the DC voltage at the two outputs of the BTL circuit is equal, and is equal to half of the DC operating voltage when the single power supply is supplied. The time is equal to 0V. When a resistor is connected between two pins of an integrated circuit, the resistor will affect the DC voltage on the two pins; when a coil is connected between the two pins, the DC voltages of the two pins are equal. When the unequal times, the coil must be open; when there is a capacitor or RC series circuit between the two pins, the DC voltages of the two pins are definitely not equal. If they are equal, the capacitor has broken down.

7 Under normal circumstances, do not analyze the internal circuit working principle of the integrated circuit, which is quite complicated.