Fleming valveThe Fleming valve, also called the Fleming oscillation valve, is a thermionic valve or vacuum tube invented in 1904 by English physicist John Ambrose Fleming as a detector for early radio receivers used in electromagneticwireless telegraphy. It was the first practical vacuum tube and the first thermionic diode, a vacuum tube whose purpose is to conduct current in one direction and block current flowing in the opposite direction.
Vacuum tubeDevice that controls current between electrodesLater thermionic vacuum tubes, mostly miniature style, some with top cap connections for higher voltagesA vacuum tube, vac tube, electron tube, thermionicvalve (British usage), or tube (North America) is a device that controls electric current flow in a high vacuum between electrodes to which an electric potential difference has been applied.
Plate electrodeA plate, usually called anode in Britain, is a type of electrode that forms part of a vacuum tube. It is usually made of sheet metal, connected to a wire which passes through the glass envelope of the tube to a terminal in the base of the tube (or to a metal cap on the top of the tube), where it is connected to the external circuit. The plate is given a positive potential, and its function is to attract and capture the electrons emitted by the cathode.
AudionThe Audion is an electronic detecting or amplifying vacuum tube invented by American electrical engineer Lee de Forest as a diode in 1906. Improved, it was patented as the first triode in 1908, consisting of an evacuated glass tube containing three electrodes: a heated filament (the cathode, made out of tantalum), a grid, and a plate (the anode). It is important in the history of technology because it was the first widely used electronic device that could amplify.
TetrodeA tetrode is a vacuum tube (called valve in British English) having four active electrodes. The four electrodes in order from the centre are: a thermionic cathode, first and second grids, and a plate (called anode in British English). There are several varieties of tetrodes, the most common being the screen-grid tube and the beam tetrode. In screen-grid tubes and beam tetrodes, the first grid is the control grid and the second grid is the screen grid.
PentodeA pentode is an electronic device having five electrodes. The term most commonly applies to a three-grid amplifying vacuum tube or thermionic valve that was invented by Gilles Holst and Bernhard D.H. Tellegen in 1926. The pentode (called a triple-grid amplifier in some literature) was developed from the screen-grid tube or shield-grid tube (a type of tetrode tube) by the addition of a grid between the screen grid and the plate.
TriodeA triode is an electronic amplifying vacuum tube (or thermionic valve in British English) consisting of three electrodes inside an evacuated glass envelope: a heated filament or cathode, a grid, and a plate (anode).
CathodeA cathode is the electrode from which a conventional current leaves a polarized electrical device such as a lead–acid battery. This definition can be recalled by using the mnemonicCCD for cathode current departs. Conventional current describes the direction in which positive charges move.
AmplifierAn amplifier, electronic amplifier or (informally) amp is an electronic device that can increase the magnitude of a signal (a time-varying voltage or current). It is a two-port electronic circuit that uses electric power from a power supply to increase the amplitude (magnitude of the voltage or current) of a signal applied to its input terminals, producing a proportionally greater amplitude signal at its output.
ElectrodeAn electrode is an electrical conductor used to make contact with a nonmetallic part of a circuit (e.g. a semiconductor, an electrolyte, a vacuum or a gas). In electrochemical cells, electrodes are essential parts that can consist of a variety of materials (chemicals) depending on the type of cell. An electrode may be called either a cathode or anode according to the direction of the electric current, unrelated to the potential difference between electrodes.
DiodeA diode is a two-terminalelectronic component that conducts electric current primarily in one direction (asymmetric conductance). It has low (ideally zero) resistance in one direction and high (ideally infinite) resistance in the other. A semiconductor diode, the most commonly used type today, is a crystalline piece of semiconductor material with a p–n junction connected to two electrical terminals. It has an exponentialcurrent–voltage characteristic.
Lee de ForestLee de Forest (August 26, 1873 – June 30, 1961) was an American inventor, electrical engineer, and early pioneer in electronics of fundamental importance. He invented the first practical electronic amplifier, the three-element "Audion" triodevacuum tube in 1908. This helped start the Electronic Age, and enabled the development of the electronic oscillator.*As an Amazon Associate I earn from qualifying purchases.