Editing Amplifier (section)

===Transistors===
{{Further|History of the transistor|MOSFET|Audio power amplifier|RF power amplifier}}

The first working [[transistor]] was a [[point-contact transistor]] invented by [[John Bardeen]] and [[Walter Brattain]] in 1947 at [[Bell Labs]], where [[William Shockley]] later invented the [[bipolar junction transistor]] (BJT) in 1948. They were followed by the invention of the [[metal–oxide–semiconductor field-effect transistor]] (MOSFET) by [[Mohamed M. Atalla]] and [[Dawon Kahng]] at Bell Labs in 1959. Due to [[MOSFET scaling]], the ability to scale down to increasingly small sizes, the MOSFET has since become the most widely used amplifier.<ref>{{Cite web|url=https://www.computerhistory.org/siliconengine/timeline/|title = Timeline &#124; the Silicon Engine &#124; Computer History Museum}}</ref>

The replacement of bulky electron tubes with transistors during the 1960s and 1970s created a revolution in electronics, making possible a large class of portable electronic devices, such as the [[transistor radio]] developed in 1954.  Today, use of vacuum tubes is limited to some high power applications, such as [[radio transmitter]]s, as well as some [[musical instrument amplifier#Tube amplifiers|musical instrument]] and high-end [[audiophile]] amplifiers.{{Cn|date=December 2024}}

Beginning in the 1970s, more and more transistors were connected on a single chip thereby creating higher scales of integration (such as small-scale, medium-scale and [[large-scale integration]]) in [[integrated circuit]]s. Many amplifiers commercially available today are based on integrated circuits.{{Cn|date=December 2024}}

For special purposes, other active elements have been used. For example, in the early days of the [[satellite communication]], [[parametric amplifier]]s were used. The core circuit was a diode whose capacitance was changed by an RF signal created locally. Under certain conditions, this RF signal provided energy that was modulated by the extremely weak satellite signal received at the earth station.{{Cn|date=December 2024}}

Advances in [[digital electronics]] since the late 20th century provided new alternatives to the conventional linear-gain amplifiers by using digital switching to vary the pulse-shape of fixed amplitude signals, resulting in devices such as the [[Class-D amplifier]].{{Cn|date=December 2024}}