A tetrode is an electronic device having four active electrodes. The term most commonly applies to a two-grid vacuum tube. It has four electrodes instead of three, as in the case of a triode. A tetrode is a group of wire bundles used in electrophysiological studies in the neurosciences to record extracellular field potentials from nervous tissue, e. ... An electrode is an electrical conductor used to make contact with a metallic part of a circuit (e. ... Structure of a vacuum tube diode Structure of a vacuum tube triode In electronics, a vacuum tube, electron tube, or (outside North America) thermionic valve or just valve, is a device used to amplify, switch or modify a signal by controlling the movement of electrons in an evacuated space. ... Simplified diagram of a triode. ...

Grids

The first grid of a tetrode, i.e. the grid nearest the cathode, is the "control grid", because the voltage applied to it causes the plate current to vary. In normal operation, with a resistive load, this varying current will result in varying (AC) voltage measured at the plate. With proper biasing, this voltage will be an amplified (but inverted) version of the AC voltage applied to the control grid, thus the tetrode can provide voltage gain. The control grid is an electrode used in thermionic valves (vacuum tubes) used to modulate the flow of electrons in the cathode to anode or plate circuit. ... International safety symbol Caution, risk of electric shock (ISO 3864), colloquially known as high voltage symbol. ... In electricity, current refers to electric current, which is the flow of electric charge. ... holly i think im weird Biasing in electronics is the method of establishing predetermined voltages and/or currents at various points of a circuit to set the appropriate quiescent point. ... In electronics, gain is usually taken as the mean ratio of the signal output of a system to the signal input of the system. ...

The second grid, usually called a "screen grid" or "shield grid", provides a screening effect, isolating the control grid from the plate. This helps (1) to suppress oscillation and (2) to reduce an undesirable effect in triodes called the "Miller effect", where the gain of the tube causes a feedback effect which increases the apparent capacitance of the tube's grid, thus limiting the tube's high-frequency performance. The screen grid is connected to a positive voltage, and bypassed to the cathode with a capacitor. This shields the grid from the plate, thus reducing Miller capacitance to a very low level and improving the tube's performance at high frequencies. Thus as a result tetrodes are commonly used in radio equipment, because the need for neutralization is less (see Radio transmitter design and Valve amplifier for more details) A grid introduced into a thermionic valve or tube to greatly reduce the capacitance between two other parts of the electrode structure. ... In electronics, the Miller effect describes the fact that a capacitance between input and output of an amplifier is multiplied by (with is the voltage gain) in a electrical circuit. ... It has been suggested that this article or section be merged with Feedback loop. ... Capacitance is a measure of the amount of electric charge stored (or separated) for a given electric potential. ... Radio transmitter design is a complex topic which can be broken down into a series of smaller topics. ... A valve amplifier (UK and Aus. ...

Under certain operating conditions, the tetrode exhibits negative resistance due to secondary emission of electrons from the anode. The shape of the characteristic curve of a tetrode operated in this region led to the term "tetrode kink". The negative resistance is exploited in the dynatron oscillator. However, in many applications the tetrode kink is undesirable and therefore a further, third, grid called the suppressor grid was added; the resulting vacuum tube is called a pentode. A VI curve with a negative differential resistance region Negative resistance or negative differential resistance (NDR) is a property of electrical circuit elements composed of certain materials in which, over certain voltage ranges, current is a decreasing function of voltage. ... Secondary emission is a phenomenon that occurs in electron tubes where electrons impact an electrode with sufficient energy to knock additional electrons from the surface of that electrode. ... In theory, if a perfect charged capacitor is connected in parallel with a perfect inductor, the circuit will oscillate forever as the energy is transferred back and forth between the capacitor and the inductor. ... A grid used in a thermionic valve (also called vacuum tube) to suppress secondary emission. ... This article does not cite any references or sources. ...

Operation

The triode vacuum tube also develops a "space charge" between the cathode and control grid, which reduces its gain, especially at low plate voltages. The screen grid neutralizes the space charge and increases the tube's gain. Space charge is the electrical current that results when a metal object is heated to incandescence in a vacuum. ...

Invention

The tetrode tube was developed by Dr. Walter H. Schottky of Siemens & Halske GMBH in Germany during World War I. Thousands of variations of the tetrode design, as well as its later development the pentode, have been manufactured since then. Walter H. Schottky (July 23, 1886, Zürich, Switzerland - March 4, 1976, Pretzfeld, West Germany) was a German physicist who invented the screen-grid vacuum tube in 1915 and the tetrode in 1919 while working at Siemens. ... Siemens AG (ISIN: DE0007236101, FWB: SIE, NYSE: SI) is one of the worlds largest companies and Europes largest engineering firm. ... This article does not cite any references or sources. ...

Tetrode transistors also exist, in the form of dual-gate MOSFETs. They are used mainly in radio receiver equipment like mobile phones. A tetrode transistor is any transistor having four active terminals. ... The metal-oxide-semiconductor field-effect transistor (MOSFET, MOS-FET, or MOS FET) is by far the most common field-effect transistor in both digital and analog circuits. ...

See also

• Beam tetrode