Electronic analogue

Bipolar transistor, a highly used component in analog systems.

Analog electronics is a branch of electronics that studies systems whose variables (voltage, current, etc.) vary continuously over time and can take (at least theoretically) values infinite. In contrast, in digital electronics the variables can only take discrete values and always have a perfectly defined state.

For example: considering a specific real measurement, such as the total length of a car:

• In a digital system, this measure could be 4 meters or 4 meters and 23 centimeters.

It is possible to give it the desired precision, but it will always be integer amounts.

• In an analog system, the measure in decimals would be 4,233648596... In theory until we reach the minimum amount of existing matter (as long as the measurement system is accurate enough).

History

Electronics is considered to have started with the vacuum diode invented by John Ambrose Fleming in 1904. The operation of this device is based on the Edison effect. Thomas Alva Edison was the first to observe thermionic emission in 1883, by placing a sheet inside a light bulb to prevent the blackening that the carbon filament produced in the glass bulb. When the metal foil was positively biased with respect to the filament, a small current was produced between the filament and the foil. This fact occurred because the electrons of the atoms of the filament, upon receiving a large amount of energy in the form of heat, escaped from the attraction of the nucleus (thermionic emission) and, crossing the empty space inside the bulb, were attracted by the positive polarity of the sheet.

The other big step was taken by Lee De Forest when he invented the triode in 1906. This device is basically like the vacuum diode, but a control grid was added between the cathode and the plate, in order to modify the electron cloud from the cathode, thus varying the plate current. This was very important for the first sound amplifiers, radio receivers, televisions, etc., to be manufactured.

As time passed, vacuum tubes were refined and improved, and other types emerged, such as tetrodes (four-electrode tubes), pentodes (five-electrode tubes), other tubes for high-power applications, and so on. Within the improvements of the valves was their miniaturization.

But it was definitely with the transistor, introduced by John Bardeen and Walter Brattain, from Bell Telephone in 1948, when further miniaturization of devices such as radios became possible. The junction transistor appeared somewhat later, in 1949; It is the device currently used for most analog electronics applications. Its advantages with respect to valves are, among others: smaller size and fragility, greater energy efficiency and lower supply voltages. The transistor does not work in a vacuum like tubes, but in a solid state semiconductor (silicon), which is why they do not need hundreds of volts of voltage to work.

Valves in Audiophile Circles

Despite the spread of semiconductors, tubes are still used in small audiophile circles, as they seem to offer sonic qualities that transistors do not.

Transistor Terminals

The transistor has three terminals: the emitter, the base, and the collector. It resembles a triode. The base would be the control grid, the emitter the cathode, and the collector the plate. By properly biasing these three terminals it is possible to control a large collector current from a small base current.

The semiconductor diode

The vacuum diode was superseded more quickly than tube amplifiers by the semiconductor diode, which came into use in the 1920s, although it was known earlier for use in the galena radio receiver, a diode that was made up of by galena crystal.