ICs and timers

Moore’s law, actually more an observation than an edict, states that the number of transistors that can sit on a single semiconductor chip may be expected to double every two years. (Another version sets the time frame as 18 months.) The assertion is flawed because it suggests that before long the device population on a single chip would be greater than the number of elementary particles in the universe.

Thus eventually Moore’s law will cease to apply. Nevertheless, the idea is relevant to our time. At present, ICs contain billions of devices. Because such an architecture is impossible for any single individual to comprehend or visualize, automated design has entered the picture. Complementary metal-oxide semiconductor (CMOS) technology permits ever higher numbers of devices to populate a single substrate because CMOS switches only dissipate power when switching from one state to the other.

There are possible “brick walls” that may eventually nullify Moore’s law. Circuits the size of single molecules are now feasible using nanomaterials. Beyond that, the quantum world may provide a way to make use of elementary particles, eventually perhaps those with only virtual reality, to achieve unlimited material contraction.

For now, possibilities abound. Chips may be digital, analog or mixed design. Digital IC’s include random access memory (RAM), read only memory (ROM), flash computer memory, field programmable gate arrays (FPGAs) and numerous application specific integrated circuits (ASICs).

A long-standing IC and perennial favorite of electronic engineering students world-wide has been the 555 timer. Despite its name, this versatile device has additional uses beyond just timing. It can provide delays of various durations and intervals constituting a duty cycle, serve as an oscillator, flip-flop device, or comprise a bounce-free push-button switch. Telephones, printers and any devices with blinking lights usually contain 555’s.

The 555 was introduced in 1971 by Signetics, later acquired by Philips. It is now made by various manufacturers. The versions differ internally and have somewhat different operating characteristics and part numbers, but the pinouts are universal.

The 555 contains only 25 transistors, 15 resisters and two diodes. This modest device has eight pins and a dual in-line package, making it easy to work with, especially in conjunction with an IC socket.

Another ubiquitous circuit element found in ICs is the operational amplifier. It is a subcategory of the differential amplifier, but it is characterized by having only one rather than two outputs. The op amp is noted for its great stability, in contrast to previous, more primitive amplifiers that lacked negative feedback. It is worth a closer look, which, along with more 555 details, will appear in subsequent articles.