First, direct substitution
Direct substitution refers to the IC without any changes other directly replace the original IC, substitution does not affect the machine after the main performance and targets.
The substitution principle is: IC substitution function, performance, package, pin-use, pin number and spacing of other aspects were the same. Which not only means the same IC features the same functionality; should also note that the same logic polarity, input level that the output polarity, voltage, current range must be the same. For example: the image put ICTA7607 and TA7611, the former high-level radioactive reverse AGC, the latter being high up AGC, it can not be directly substituted. In addition there is the output of different polarity, AFT voltage, output synchronization pulses of different polarity such as IC can not directly change even in the same company or manufacturer's products, should be a distinction. IC performance is the main electrical parameters (or the main characteristic curve), maximum power dissipation, maximum operating voltage, frequency and the signal input and output impedance of IC similar to the original. Alternative power small pieces to increase the heat sink. Among
1. The same type of substitution IC
The substitution of the same type IC is generally reliable, install integrated circuits, we should pay attention to the direction of no mistake, otherwise, power is likely to be destroyed when the integrated circuit. Some single in-line amplifier IC, although the type, function, feature the same, but the direction of pins in the order is different. For example, two-channel amplifier IC LA4507, pin a "positive" and "anti" parts, the initial foot mark (colored spots or pits) in a different direction: no suffix and the suffix "R", the IC, etc. For example M5115P and M5115RP.
2. Different types of IC's substitution
. The same type prefix letters, numbers, the substitution of different IC. This substitution between the pin function as long as the same, its internal circuitry, and slightly different electrical parameters can also be substituted with each other directly. Such as: audio in put IC LA1363 and LA1365, the latter than the former first ⑤ feet in the IC within the addition of a Zener diode, the other exactly the same.
. Model different prefix letters, numbers, the substitution of the same IC. In general, the prefix letter is that the manufacturer and the type of circuit, the same number prefix letters followed, most can be directly substituted. But a few, though the same number, but the functionality is completely different. For example, HA1364 is audio IC, which uPC1364 is color decoding IC; 4558,8 feet is the operational amplifier NJM4558, 14 feet is the CD4558 digital circuits; so the two can not substitution.
. Model prefix letters and numbers are different IC substitution. Some manufacturers introduced the IC chip is not packaged, and then processed into products by factory name. There are certain parameters as indicators to improve the improve the product. These products are used for different models or model name suffix to be distinguished. For example, AN380 and uPC1380 direct substitution; AN5620, TEA5620, DG5620, etc. can be directly substituted.

Second, non-direct substitution
Indirect substitution is not a direct substitution of IC slightly modified the external circuit, to change the original arrangement of pins or other changes in individual components, making the method can be substitution of the IC.
Substitution principle: IC can be used in substitution of the original IC pin with different functions, different shape, but the function to the same characteristics to similar: after substitution should not affect the performance of the original machine.
1. Different package
IC substitution
The same type of IC chips, but the package shape or substitution of a new device when the pin as long as the original device pin shape and arrangement of the shaping. For example, AFT circuit CA3064 and CA3064E, the former round package, radial pin: the latter is dual in-line plastic package, the internal characteristics of the two exactly the same, according to the connection pin can function. Two-column IC AN7114, AN7115 and LA4100, LA4102 is basically the same package, pin and fin just have a difference of 180 degrees. AN5620 with mentioned earlier, heat sinks 16-pin DIP package, TEA5620 DIP 18-pin package, 9,10 feet in the right IC, equivalent to AN5620 heat sink, the same arrangement of the two other legs will 9,10 feet can be used to link ground.
2. Circuit functions the same but different functions of individual pins of substitution lC
Substitution when the IC according to the specific parameters of each model and instructions. Such as the TV in the AGC, video signal output are positive and negative nature of the difference, as long as the increase in output can be connected inverter after the substitution.
3. Class of plastic pin functions the same but the substitution of different Ic
This substitution need to change the external circuit and pin arrangement, which requires a certain theoretical knowledge, complete information and a wealth of practical experience and skills.
4, some empty ground pin should not be arbitrarily
Application of the internal equivalent circuit and leads to foot some of the circuit does not indicate encountered empty leads to foot should not arbitrarily ground, these lead to the replacement or alternate legs for the foot, sometimes as an internal connection.
5. Combined substitution
Portfolio substitution is to the same type of multi-block within the IC circuit part is not damaged, re-assembled into a complete IC, IC to replace the dysfunctional ways. Buy Original IC on the case is very applicable. But requires the use of the internal IC circuit must have a good interface, lead to foot.
Indirect substitution key is to check each other IC substitution of two basic electrical parameters, the internal equivalent circuit, the functions of each pin, IC connection relations between Ministry of component information. The attention of the actual operation
~ IC pin number in order not to take wrong.
~ In order to meet the characteristics of IC after the substitution, and its external circuit components connected to a corresponding change to
~ After the power supply to work with the substitution in line C, if the original circuit in the power supply voltage, high blood pressure should try; voltage is low, depending on whether the work of IC substitution.
~ Substitution after work to measure the IC's quiescent current, such as the current is much larger than normal, it indicates the possible self-excitation circuit, this time to carry out decoupling adjustment. If the gain is somewhat different from the original, adjustable feedback resistor.
~ After the IC's input substitution, output impedance to match the original circuit; check their driving ability.
~ In the changes to take full advantage of the original circuit board feet hole and lead, external leads required neat, avoiding cross before and after to check and prevent the circuit from shock, particularly to prevent high-frequency self-excited.
~ In the power circuit before the power supply Vcc in series with a DC ammeter again the best, step-down resistor from big to small changes in observed total current integrated circuits are normal.
6. Substitution Sichuan sub-Guang not IC components
Sometimes work can be discrete components C substitution in the damaged part of its recovery. Substitution should be aware of the work prior to the internal C function theory, each lead to foot the normal voltage, waveform, and the composition of the circuit components and external works. Should also consider:
(1) signal can remove C from the work connected to the external inputs of the circuit:
(2) processed by the external circuit signals, whether connected to the integrated circuit to the next level within the re-processing (connection to match the signal should not affect the main parameters and performance). Such as the IC put damage from the typical application circuit and internal circuits of view, the audio in place, frequency, and Jin-frequency amplification stage into, into the law can be used to identify intelligence Wang No. damaged part, if the audio amplification part of the damage, you can use discrete components place.