Circuits for the analysis of integrated circuit application circuits

In radio equipment, the application of integrated circuits is becoming more and more widespread. Knowledge of integrated circuit application circuits is one of the key points in circuit analysis, and it is also one of the difficulties.

1

IC Application Circuit Function

The integrated circuit application circuit diagram has the following functions:

1 It expresses the external circuit structure, component parameters, etc. 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 application circuit of the integrated circuit, but there are not many such representations.

3 integrated circuit application circuit There are two kinds of typical application circuit and practical circuit, the former can be found in the manual of the integrated circuit, the latter appears in the practical circuit, the two application circuits are not the same, according to this feature, there is no actual Application circuit diagrams can be referenced using typical application circuit diagrams, which are 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.

2

IC Application Circuit Features

The integrated circuit application circuit diagram has the following characteristics:

1 Most of the application circuits do not draw the internal circuit block diagram, which is unfavorable for picture recognition, especially for beginners when analyzing the circuit work.

2 For beginners, it is more difficult to analyze the application circuit of integrated circuits than to analyze the circuits of discrete components. This is the reason for not knowing the internal circuits of integrated circuits. Actually, it is better to read or repair the integrated circuits. It is more convenient to set up a component circuit.

3 For integrated circuit application circuits, it is more convenient to understand the internal circuit of the integrated circuit and understand the role of each pin in detail. This is because the same types of integrated circuits have regularity, and after grasping their commonality, it is convenient to analyze many integrated circuit application circuits with different functionalities.

3

IC application circuit mapping methods and precautions

The methods and precautions for analyzing integrated circuits mainly include the following points:

(1) Understanding the role of each pin is the key to reading

Learn about the role of each pin can refer to the relevant integrated circuit application manual. After knowing the function of each pin, it is convenient to analyze the working principle of the external circuit of each pin and the function of the component. For example, knowing that pin 1 is an input pin, the capacitor connected in series with pin 1 is the input-side coupling circuit, and the circuit connected to pin 1 is the input circuit.

(2) Understanding the three methods of IC pins

Understand the circuit block diagram analysis within the set; the third is based on the integrated circuits of the application circuit in the pin outside the circuit characteristics of the analysis. The third method requires a better circuit analysis basis. There are three methods for each pin of the circuit: one is to look up the relevant data; the other is based on the integrated circuit

(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 and ground pins. Note: When there are multiple power pins, it is necessary to distinguish the relationship between these power supplies, for example, whether it is the front stage or the rear stage.

Distinguishing multiple power pins 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 the integrated circuit has multiple input and output pins, it is necessary to find out whether it is the output pin of the pre- 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, vibration elimination pin, etc., this step analysis is the most difficult, for beginners to use the pin action data or internal circuit block diagram.

4 After having a certain ability of mapping, it is necessary to learn to summarize the laws of the external circuit of the pins of various functional integrated circuits, and to grasp this rule, which is useful for improving the speed of picture recognition. For example, the external circuit of the input pin is connected to the output of the preceding circuit through a coupling capacitor or a coupling circuit; the external circuit of the output pin is connected to the input of the subsequent circuit through a coupling circuit.

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

6 Understanding some of the key test points of the integrated circuit, the pin DC voltage law is very useful to repair the circuit. The DC voltage at the output of the OTL circuit is equal to half the DC operating voltage of the integrated circuit; the DC voltage at the output of the OCL circuit is equal to 0V; the DC voltages at the two output terminals of the BTL circuit are equal; when the single power supply is used, it is equal to half the DC operating voltage, and the dual power supply It is equal to 0V. When a resistor is connected between two pins of an integrated circuit, this resistance will affect the DC voltage on these two pins; when a coil is connected between two pins, the DC voltage of these two pins is equal. If the capacitor is not connected to the two pins, or the RC series circuit is connected, the DC voltage of the two pins must not be equal. If they are equal, the capacitor has broken down.

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