A transistor is a semiconducting device that switches and amplifies electronic signals. It has a minimum of three terminals that connect it to an electronic circuit. The transistor was invented during the early 1950s, and it quickly replaced vacuum tubes in electronic devices. These devices are now an essential component of almost all electronic devices, such as the central processing unit (CPU) of a computer. A CPU transistor is typically part of an integrated circuit although it can also be purchased individually as well.
The terminals in a CPU transistor have specific names depending on the type of transistor. The terminals of a simple bipolar transistor are called the collector, emitter and base. The current or voltage that’s applied to the base affects the current flow from the collector to the emitter.
The voltage at the base of the transistor can be used to turn on and off the current flow from the collector to the emitter. This type of transistor is a switch and is a common type of CPU transistor called a logic gate. A switch generally does not allow current to flow through it unless the voltage at the base is above a minimum threshold. The voltage at the base is controlled by other components in the circuit.
A CPU transistor can also be an amplifier. This type of transistor uses the voltage at the base to control the amount of the current that flows through the amplifier. This means that a small change in the voltage at the base can produce a large difference in the voltage between the collector and emitter.
Transistors provide significant advantages over vacuum tubes in computers. A CPU transistor is much smaller than its vacuum tube equivalent, allowing for the miniaturization of computers. The manufacture of transistors can be automated to a greater extent than that of vacuum tubes, which means that transistors are cheaper than vacuum tubes.
The first patent for a transistor was filed by Julius Edgar Lilienfeld in 1925 although he did not actually construct such a device. Herbert Matare discovered semiconductor effects while working on a Doppler radar system in 1942. Then technology progressed, and in 1947 while working at AT&T's Bell Labs, Walter Brattain and John Bardeen discovered that a germanium crystal could amplify an electrical current. Gordon Teal built the first silicon transistor for Texas Instruments in 1954, and the CPU transistor, which is a metal oxide semiconductor (MOS) transistor, was first built at Bell Labs in 1960.