The parameters of the integrated circuit generally have little effect on the analysis of the working principle of the circuit, but they have a non-negligible effect on the fault analysis and maintenance of the circuit. In the maintenance practice, most of the IC parameters provided by the manufacturer are not available, but understanding the relevant knowledge of integrated circuits is still helpful to the maintenance work.

1. Electrical parameters

Different functions of integrated circuits, the electrical parameters of the items are also different, but most integrated circuits have a few basic parameters (usually measured at a typical DC operating voltage).

(1) Static working current. It refers to the DC current in the power supply pin circuit when the input signal of the integrated circuit is not added to the input signal. This parameter is of great significance to confirm the fault of the integrated circuit.

Generally, the static working current of integrated circuit is given typical value, small value and large value. If the DC operating voltage of the integrated circuit is normal, and the grounding pin of the integrated circuit is reliably grounded, when the static current of the integrated circuit is greater than or less than a small value, it indicates that the integrated circuit is faulty.

(2) Gain. It refers to the amplification capacity of the amplifier inside the integrated circuit, usually marked open-loop gain and closed-loop gain, and also gives three indicators of typical value, small value and large value respectively.

The gain of integrated circuits cannot be measured by conventional maintenance means (only a multimeter is a detection instrument), and can only be measured by special instruments.

(3) Large output power. Refers to the power amplifier integrated circuit output pin output electrical signal when the distortion of the output signal is rated (usually 10[[%]]]). 2. Limit parameters

The limit parameters of integrated circuits mainly have the following items.

(1) Large power supply voltage. It refers to the limit value of DC operating voltage that can be added between the power supply pin and the ground pin of the integrated circuit. It is not allowed to exceed this value in use, otherwise the integrated circuit will be damaged.

(2) Allowable power consumption. Refers to the integrated circuit can withstand the large dissipation power, mainly used in all kinds of high-power integrated circuits.

(3) Working environment temperature. It refers to the low and high ambient temperature at which integrated circuits can maintain normal operation.

(4) Storage temperature. Refers to the low and high temperature of the integrated circuit in the storage state.

3. Fault performance

There are mainly the following types of integrated circuit faults, of which (1) and (2) are more common in maintenance.

(1) The integrated circuit is burned out. Usually caused by overvoltage or overcurrent. After the integrated circuit is burned out, it is generally not visible from the outside. In severe cases, the integrated circuit may burn a small hole or have a crack and other marks. After the integrated circuit is burned out, the DC operating voltage of some pins will also change significantly, and the fault location can be found by conventional inspection. The burn out of integrated circuits is a hard fault, and the repair of this fault is very simple: it can only be replaced.

(2) Pin break and virtual welding. Pin break failure of integrated circuit is not common, the cause of pin break of integrated circuit is often caused by improper insertion and removal of integrated circuit. If the pin of the integrated circuit is too thin, it is easy to tear during maintenance. In addition, due to falling, water or artificial pulling caused by broken feet, virtual welding is also a common phenomenon.

(3) The gain is seriously decreased. When the gain of the integrated circuit is seriously decreased, the integrated circuit has basically lost the amplification ability and needs to be replaced. For the integrated circuit with a slight decrease in gain, it is mostly a soft fault of the integrated circuit, which is difficult to be found by the general detection instrument, and can be remedied by reducing the amount of negative feedback, which is not only effective but also simple to operate.

When the integrated circuit has a serious gain deficiency fault, the DC voltage of some pins will also change significantly, so it can be found by conventional inspection methods.

(4) Loud noise. When there is a big noise fault in the integrated circuit, the signal can be amplified, but the noise is also very large, which results in the decrease of the signal-to-noise ratio and affects the normal amplification and processing of the signal. If the noise is not obvious, it is mostly a soft fault of the integrated circuit, and it is very difficult to check with conventional instruments. Because the DC voltage of some pins will also change when there is a big noise fault in the integrated circuit, the fault location can be found by conventional inspection methods.

(5) Performance deteriorates. This is a soft fault, a variety of fault phenomena, and the change of the integrated circuit pin DC voltage is generally small, so the use of conventional inspection means often can not be found, only the use of alternative inspection method.

(6) Internal partial circuit damage. When the local circuit in the integrated circuit is damaged, the DC voltage of the related pin will change greatly, and it is easy to find the fault part in the maintenance. Such faults should usually be replaced. However, for some specific cases, discrete components can be used to replace the internal damage of the local circuit, but such operations are often quite complex. If you do not have a deep knowledge of the basics of electronics, it is impossible to complete.