A triode is an electronic amplification Generally, an amplifier or simply amp, is any device that changes, usually increases, the amplitude of a signal. The relationship of the input to the output of an amplifier—usually expressed as a function of the input frequency—is called the transfer function of the amplifier, and the magnitude of the transfer function is termed the gain device having three active electrodes. The term most commonly applies to a vacuum tube In electronics, a vacuum tube, electron tube , or thermionic valve (elsewhere, especially in Britain) is a device used to amplify, switch, otherwise modify, or create an electrical signal by controlling the movement of electrons in a low-pressure space. Some special function vacuum tubes are filled with low-pressure gas: these are so-called soft (or valve in British English) with three elements: the filament The incandescent light bulb, incandescent lamp or incandescent light globe is a source of electric light that works by incandescence . An electric current passes through a thin filament, heating it until it produces light. The enclosing glass bulb prevents the oxygen in air from reaching the hot filament, which otherwise would be destroyed rapidly or cathode A cathode is an electrode through which electric current flows out of a polarized electrical device. Mnemonic: CCD, the grid The control grid is an electrode used in thermionic valves used to modulate the flow of electrons in the cathode to anode or plate circuit, and the plate See anode. A plate is a type of electrode that formed part of a vacuum tube. The plate is impressed with a positive charge so that it may capture and flow electrons within a circuit or anode An anode is an electrode through which electric current flows into a polarized electrical device. Mnemonic: ACID. The triode vacuum tube is the first electronic amplification An electronic amplifier is a device for increasing the power of a signal. It does this by taking energy from a power supply and controlling the output to match the input signal shape but with a larger amplitude. In this sense, an amplifier may be considered as modulating the output of the power supply device.
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Invention
Lee De Forest "Triode" Audion tube from 1908The original three-element device was patented in 1908 by Lee De Forest Lee De Forest was an American inventor with over 180 patents to his credit. De Forest invented the Audion, a vacuum tube that takes relatively weak electrical signals and amplifies them. De Forest is one of the fathers of the "electronic age", as the Audion helped to usher in the widespread use of electronics. He is also credited with who developed it from his original two-element 1906 Audion The Audion is an electronic amplifying vacuum tube invented by Lee De Forest in 1906. It was the forerunner of the triode, in which the current from the filament to the plate was controlled by a third element, the grid. A small amount of power applied to the grid could control a larger current from the filament to the plate, allowing the Audion to. The Audion did provide amplification. However it was not until around 1912 that other researchers, while attempting to improve the service life of the audion, stumbled on the principle of the true vacuum tube. The name triode appeared later, when it became necessary to distinguish it from other generic kinds of vacuum tubes with more or fewer elements (eg diodes In electronics, a diode is a two-terminal electronic component that conducts electric current in only one direction. The term usually refers to a semiconductor diode, the most common type today. This is a crystalline piece of semiconductor material connected to two electrical terminals. A vacuum tube diode is a vacuum tube with two electrodes; a, tetrodes A tetrode is an electronic device having four active electrodes. The term most commonly applies to a two-grid vacuum tube. It has the three electrodes of a triode and an additional screen grid which significantly changes its behaviour, pentodes A pentode is an electronic device having five active electrodes. The term most commonly applies to a three-grid vacuum tube , which was invented by the Dutchman Bernhard D.H. Tellegen in 1926. Pentodes (termed "triple-grid amplifiers" in some early literature) are closely related to Beam tetrodes and Kinkless tetrodes, and an improvement etc.). The Audion tubes deliberately contained some gas at low pressure. The name triode is only applied to vacuum tubes which have been evacuated of as much gas as possible.
There was a parallel invention of the triode in charge of Austrian Robert von Lieben.
Operation
Schematic symbol for an indirectly heated triode.The principle of its operation is that, as with a thermionic diode In electronics, a diode is a two-terminal electronic component that conducts electric current in only one direction. The term usually refers to a semiconductor diode, the most common type today. This is a crystalline piece of semiconductor material connected to two electrical terminals. A vacuum tube diode is a vacuum tube with two electrodes; a, the heated cathode(either directly or indirectly by means of a filament) causes a space charge of electrons The electron is a subatomic particle carrying a negative electric charge. It has no known components or substructure, and therefore is believed to be an elementary particle. An electron has a mass that is approximately 1/1836 that of the proton. The intrinsic angular momentum of the electron is a half integer value in units of ħ, which means that that may be attracted to the positively charged plate (anode in UK parlance) and create a current. Applying a negative charge to the control grid will tend to repel some of the (also negatively charged) electrons back towards the cathode: the larger the charge on the grid, the smaller the current to the plate. If an AC signal is superimposed on the DC bias of the grid, an amplified version of the AC signal appears (inverted) in the plate circuit.
The triode is very similar in operation to the n-channel JFET The junction gate field-effect transistor is the simplest type of field effect transistor. It can be used as an electronically-controlled switch or as a voltage-controlled resistance. Electric charge flows through a semiconducting channel between "source" and "drain" terminals. By applying a bias voltage to a "gate"; it is normally on, and progressively switched off as the grid/gate is pulled increasingly negative of the source/cathode.
Applications
Although triodes are now largely obsolete in consumer electronics Consumer electronics include electronic equipment intended for everyday use. Consumer electronics are most often used in entertainment, communications and office productivity. Some products classed as consumer electronics include personal computers, telephones, MP3 players, audio equipment, televisions, calculators, GPS automotive navigation, having been replaced by the transistor A transistor is a semiconductor device used to amplify and switch electronic signals. It is made of a solid piece of semiconductor material, with at least three terminals for connection to an external circuit. A voltage or current applied to one pair of the transistor's terminals changes the current flowing through another pair of terminals, triodes continue to be used in certain high-end High-end audio is a term used to describe a class of consumer home audio equipment marketed to audio enthusiasts on the basis of high price or quality, and esoteric or novel sound reproduction technologies. High-end audio can refer simply to the price, to the build quality of the components, or to the subjective or objective quality of sound and professional audio Professional audio equipment can be used to describe any audio equipment used or marketed for use as a sound application by or for a professional purpose. This includes, but is not limited to, loudspeakers, microphones, Mixing consoles, amplifiers, recording and playback devices such as dat or turntables, and in some cases telephony devices. Pro applications, as well as in microphone preamplifiers A preamplifier , or control amp in some parts of the world, is an electronic amplifier which precedes another amplifier to prepare an electronic signal for further amplification or processing. The preamplifier circuitry may or may not be housed as a separate component and electric guitar amplifiers A guitar amplifier is an electronic amplifier designed to make the signal of an electric or acoustic guitar louder so that it will produce sound through a loudspeaker and modify the tone by emphasizing or de-emphasizing certain frequencies and adding electronic effects.
Some guitarists routinely drive their amplifiers to the point of clipping (either grid-current limiting or valve cut-off), in order to produce a desired distortion A distortion is the alteration of the original shape of an object, image, sound, waveform or other form of information or representation. Distortion is usually unwanted, and often many methods are employed to minimize it in practice. In some fields, however, distortion is actually desirable; such is the case with electric guitar (where distortion tone. Many people prefer the sound of triodes in such an application, since the distortion of a tube amplifier, which has a "soft" saturation characteristic, can be more pleasing to the ear than that of a typical solid-state Solid-state electronics are those circuits or devices built entirely from solid materials and in which the electrons, or other charge carriers, are confined entirely within the solid material. The term is often used to contrast with the earlier technologies of vacuum and gas-discharge tube devices and it is also conventional to exclude electro- amplifier, which through negative feedback is linear up to the limits of its supply voltage and then clips Clipping is a form of waveform distortion that occurs when an amplifier is overdriven and attempts to deliver an output voltage or current beyond its maximum power capability. Driving an amplifier into clipping may cause it to put out power in excess of its published ratings abruptly.
Characteristics
ECC83 triode operating characteristic.In triode datasheets, characteristics linking the anode current(Ia) to anode voltage (Va) and grid voltage (Vg) were usually given. From here, designer would choose the operating point of the particular triode.
In the example characteristic shown on the image, with an anode voltage Va of 200 V, and a grid voltage bias Biasing in electronics is the method of establishing predetermined voltages and/or currents at various points of an electronic circuit to set an appropriate operating point. The operating point of a device, also known as bias point, quiescent point, or simply Q-point, is the point on the output characteristics that shows the direct current, of -1 volt. Using the yellow curve on the graph, a plate current of 2.25 mA at this operating point. Changing the grid voltage will change the plate current; by suitable choice of a plate load resistor, amplification is obtained.
In the class A triode amplifier, an anode resistor would be connected between the anode and the positive voltage source. For example, with Ra=10000 Ohms, voltage drop on it will be
VRa=Ia×Ra=22.5 V,
if anode current of Ia=2.25 mA is chosen.
Now, if the input voltage amplitude (at the grid) changes from -1.5 V to -0.5 V (difference of 1 V), anode current will change from 1.2 to 3.3 mA (see image). This will result in anode resistor voltage drop changes from 12 to 33 V (difference of 21 V).
Since grid voltage changes from -1.5 V to -0.5 V, and anode resistor voltage drop from 12 to 33 V, amplification of signal resulted. Amplification factor is 21 - output voltage amplitude divided by input voltage amplitude.
See also
- Vacuum tube In electronics, a vacuum tube, electron tube , or thermionic valve (elsewhere, especially in Britain) is a device used to amplify, switch, otherwise modify, or create an electrical signal by controlling the movement of electrons in a low-pressure space. Some special function vacuum tubes are filled with low-pressure gas: these are so-called soft
- List of vacuum tubes
- European triode festival Since 2000 each year the "European Triode Festival" has been held in various venues in Europe (the first three events were called "Aarhus Triode Festival" aka "ATF". The ETF focuses on do-it-yourself audio valve amplifiers using triode vacuum tubes, and brings together some 100 high end vacuum tube audiophiles from
External links
- Les lampes radio — A French page on thermionic valves. Of particular interest is the 17 minute video showing the manual production of triodes.
Categories: Vacuum tubes
Physics
Transistor inventors John Bardeen and Walter Brattain, of Bell Labs in New Jersey, described their device as a semiconductor triode . The triode was a vacuum tube with a metal "grid" interposed between a heated cathode that emitted electrons and an ...
patrickturner
Sun, 07 Feb 2010 13:10:33 GM
Also there is the SE35 with a quad of 6CA7 and all thse sound very well and probably as good as any real . triode. amp anyone likes to nominate such as the 300B, or the 845. My pages show a pair of SE55 which have two 845 per channel. ...
