Discrete Components Vs. Analog Integrated Circuits

One integrated circuit can replace thousands of discrete analog parts.

Before integrated circuits (ICs) were developed, all electronic circuits were made with discrete components. Operational amplifiers (op-amps) were one of the first general-purpose analog circuits to be produced as analog ICs, and their popularity continues today. Other designs, such as oscillators, tuners and filters were implemented as integrated circuits in the 1970s and 80s, though their popularity has faded with more interest going to digital circuits. While few would debate the lower costs and greater efficiency of integrated circuits, some designers favor discrete components for specialized applications.

History

Some discrete components, such as resistors and capacitors, date back to the 18th century from the earliest experiments with electricity. Transistors and diodes were developed in the 1940s and replaced vacuum tubes in most applications by the 1970s. Electronics companies sold the first ICs in the 1960s. By the 1980s, analog IC design had become more economical and engineers introduced many new circuits. The falling cost and increased capability of digital designs displaced many analog ICs in the 1990s. In 2010, many analog ICs have been discontinued.

Precision

On an analog IC, all components reside on the same small piece of silicon. Since transistors and diodes are heat-sensitive components and everything on an IC has the same temperature, this gives ICs an advantage. ICs can, however, fall prey to production compromises, making one batch better than others. When building precision circuits, discrete transistors can be measured and matched by hand. Only high-end manufacturers perform this laborious task, but it yields a better result.

Cost

Electronics made with integrated circuits are less expensive than those made exclusively with discrete components. A 50 cent IC can replace a hundred dollars' worth of transistors and other parts. In addition to the lower cost of the parts themselves, circuits need fewer parts, making production costs lower.

Size

The main reason our electronics have become steadily smaller and more capable is due to integrated circuits. An IC a few millimeters square can do the work of a truckload of discrete components. Discrete transistors perform one function per package, and they need their own small case and wiring. An analog IC has hundreds or thousands of transistors in its package and eliminates the extra wiring that discrete components would need.

Repair

Integrated circuits cannot be repaired, but they can be replaced. If you replace it, you may need to re-adjust the rest of a circuit to make up for small variations between ICs. The same is true for discrete components. Many analog ICs have gone out of production, forcing technicians to scour second-tier sources and pay more for parts if they can find them. With the exception of the very oldest transistors, many are still in production. Isolating and replacing a discrete component can be relatively simple.

References

• IC Knowledge: 1960s
• Parts Connexion: Burson Opamps

Resources

• Part Hunters: Obsolete and Hard-to-Find Parts