Electronics

What is electronics?

Electricity powers things; electronics controls them. This branch of the map covers the components and circuits that switch, shape and process electric currents, from a single resistor to a chip holding a whole computer.

The US Bureau of Labor Statistics draws the line like this. Electronics engineers design and develop the components and circuitry of electronic products, such as audio-visual equipment or radar and sonar systems. Electrical engineers design electrical systems and equipment such as electric motors, navigation and communications systems, and power generation equipment.^[1]

The building blocks

Every electronic device is built from a small set of components:

• Resistors are common components used to reduce current or provide a drop in voltage.^[2]
• Diodes let current flow in only one direction, like a one-way valve.^[4]
• Transistors let a small current control a much larger one.^[4]

Components are joined into circuits, loops through which current can flow. How they are arranged decides what the circuit does.

Semiconductors: the key material

Diodes and transistors are made from semiconductors. NIST, the US standards laboratory, describes them as materials such as silicon with tunable electrical conductivity, the base for most electronics.^[13] A semiconductor has a filled band of electron energies, an empty one above it, and a relatively small energy gap between the two.^[3] Adding impurity atoms of another element, called doping, changes how it conducts, creating “n-type” and “p-type” material.^[3] Diodes and junction transistors are built by joining these two types together.^[4]

From crystals to chips: a short history

• 1874: Ferdinand Braun found that current flowed freely in only one direction through a galena crystal probed with a thin wire. The effect found its first use decades later, as the detector in early “crystal radio” sets.^[5]
• 1947: John Bardeen and Walter Brattain got the first transistor working at Bell Labs on 16 December, using a slab of germanium with two gold contacts, and showed it to lab officials a week later.^[6] It was designed to replace unreliable vacuum tubes and electromechanical switches.^[6]
• 1958: Jack Kilby of Texas Instruments etched transistor, capacitor and resistor elements from slices of germanium and wired them into a working circuit: an early microcircuit made entirely of semiconductor material.^[7]
• 1959–1960: Atalla and Kahng at Bell Labs made the first successful MOS (metal-oxide-semiconductor) transistor. Today over 99 percent of microchips use MOS transistors.^[8]
• 1965: Gordon Moore predicted that the number of components on a chip would double every year. In 1975 he revised it to every two years.^[9]
• 1971: Intel’s 4004, with 2,300 transistors, put the central processing functions of a computer on a single chip.^{[10, 14]}
• 1974: Texas Instruments announced the TMS 1000, a general-purpose microcontroller with processor and memory on one chip.^[11]

Working in electronics

Becoming an electrical or electronics engineer usually takes at least a bachelor’s degree in engineering, with courses in electrical circuit theory, digital systems design and calculus.^[1] You can start experimenting much earlier. Arduino boards, for example, were created as an easy prototyping tool for students with no background in electronics or programming.^[12]

Where to go next

• Electric Circuits: how current flows, series and parallel, and staying safe.
• Semiconductors and Transistors: how silicon became the brain of every device.
• Microcontrollers and Arduino: small computers you can program yourself.