Quantcast INTEGRATED CIRCUIT (IC) TESTING

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2-28 INTEGRATED CIRCUIT (IC) TESTING Integrated circuits (ICs) constitute an area of microelectronics in which many conventional electronic components are combined into high-density modules. Integrated circuits are made up of active and passive components, such as transistors, diodes, resistors, and capacitors. Because of their reduced size, use of integrated circuits can simplify otherwise complex systems by reducing the number of separate components and interconnections. Their use can also reduce power consumption, reduce the overall size of the equipment, and significantly lower the overall cost of the equipment concerned. Many types of integrated circuits are ESDS devices and should be handled accordingly. Q-18. Name two advantages in using ICs. Your IC testing approach needs to be somewhat different from that used in testing vacuum tubes and transistors. The physical construction of ICs is the prime reason for this different approach. The most frequently used ICs are manufactured with either 14 or 16 pins, all of which may be soldered directly into the circuit. It can be quite a job for you to unsolder all of these pins, even with the special tools designed for this purpose. After unsoldering all of the pins, you then have the tedious job of cleaning and straightening all of them. Although there are a few IC testers on the market, their applications are limited. Just as transistors must be removed from the circuit to be tested, some ICs must also be removed to permit testing. When ICs are used in conjunction with external components, the external components should first be checked for proper operation. This is particularly important in linear applications where a change in the feedback of a circuit can adversely affect operating characteristics of the component. Any linear (analog) IC is sensitive to its supply voltage. This is especially the case among ICs that use bias and control voltages in addition to a supply voltage. If you suspect a linear IC of being defective, all voltages coming to the IC must be checked against the manufacturer’s circuit diagram of the equipment for any special notes on voltages. The manufacturer’s handbook will also give you recommended voltages for any particular IC. When troubleshooting ICs (either digital or linear), you cannot be concerned with what is going on inside the IC. You cannot take measurements or conduct repairs inside the IC. You should, therefore, consider the IC as a black box that performs a certain function. You can check the IC, however, to see that it can perform its design functions. After you check static voltages and external components associated with the IC, you can check it for dynamic operation. If it is intended to function as an amplifier, then you can measure and evaluate its input and output. If it is to function as a logic gate or combination of gates, it is relatively easy for you to determine what inputs are required to achieve a desired high or low output. Examples of different types of ICs are provided in figure 2-23. Figure 2-23.—Types of ICs.


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