Thousands of different types of integrated circuits (ICs) are available for electronic devices. Most of these were designed for very specific applications. However, many integrated circuits have been designed for general-purpose use and so are used in a wide variety of circuits.
All of these ICs have been around for decades, but their multipurpose design, wide availability, and low cost have given them enduring popularity.
555 timers
The 555 timer chip was invented in 1971 but remains today one of the most popular integrated circuits in use. By some estimates, more than a billion of them are made and sold every year.
As its name implies, the 555 is a timer circuit. The timing interval is controlled by an external resistor/capacitor (RC) network. In other words, by carefully choosing the values for the resistors and capacitors, you can vary the timing duration.
The 555 can be configured in several different ways. In one configuration (called monostable), it works like an egg timer: You set it, and then it goes off after a certain period of time has elapsed. In a different configuration (called astable), it works like a metronome, triggering pulses at regular intervals.
Besides the basic 555 chip, which comes in an 8-pin DIP package, you can also get a 556 dual timer, which contains two independent 555 timers in a single 14-pin DIP package. Because many common circuits call for two 555 timers working together, the 556 package is very popular.
741 and LM324 op-amps
An op-amp is a special type of amplifier circuit that has many applications throughout electronics. Although there are many different types of op-amp circuits, the 741 and LM324 are the most common.
The 741 is a single op-amp circuit in an eight-pin DIP package. It was first introduced in 1968 and is still one of the most widely used integrated circuits ever made. The 741 is one of those ICs that require both positive and negative voltage.
The LM324 was introduced in 1972. It consists of four separate op-amp circuits in a single 14-pin DIP package. Unlike the 741, the LM324 doesn't require separate negative and positive voltage supplies.
78xx voltage regulators
The 78xx is a family of simple voltage regulator integrated circuits. A voltage regulator is a circuit that accepts an input voltage that can vary within a certain range and produces an output voltage that is a constant value, regardless of fluctuations in the input voltage.
The xx in 78xx represents the actual voltage regulated by the chip. For example, a 7805 produces a 5 V output. The input voltage must be at least a couple of volts over the output voltage, and can be as high as 35 V.
74xx logic family
One of the primary uses for integrated circuits is for digital electronics, and the 74xx is one of the oldest and still most widely used families of digital integrated circuits. The 74xx family includes a wide variety of chips that provide basic building blocks for digital circuits. You won’t find complete microprocessors in the 74xx family. But you will find circuits such as logic gates, flip-flops, counters, buffers, and others.