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=Transistors=

What is the difference between vacuum tubes and transistors? A vacuum tube is a current amplifier where the transistor amplifies voltage http://wiki.answers.com/Q/Difference_between_vaccum_tubes_and_transistors

=Vacuum Tubes=

In [|electronics], a **vacuum tube**, **electron tube** (in North America), **thermionic valve**, or **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.

Vacuum tubes were critical to the development of electronic technology, which drove the expansion and commercialization of [|radio] broadcasting, [|television],[|radar], [|sound reproduction], large [|telephone] networks, analog and digital [|computers], and industrial [|process control]. Some of these applications pre-dated electronics, but it was the vacuum tube that made them widespread and practical. ( http://en.wikipedia.org/wiki/Vacuum_tube)

On 17 November 1947 [|John Bardeen] and [|Walter Brattain], at AT&T [|Bell Labs], observed that when electrical contacts were applied to a crystal of germanium, the output power was larger than the input.

=Transistors =

In [|electronics], a **transistor** is a [|semiconductor device] commonly used to [|amplify] or switch [|electronic] signals. A transistor is made of a solid piece of a [|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. Because the controlled (output) [|power] can be much larger than the controlling (input) power, the transistor provides [|amplification] of a signal. The transistor is the fundamental building block of modern [|electronic devices], and is used in [|radio], [|telephone], [|computer] and other systems. Some transistors are packaged individually but most are found in[|integrated circuits].

A [|logic gate]consists of about twenty transistors whereas an advanced microprocessor, as of 2006, can use as many as 1.7 billion transistors ([|MOSFETs]).[|[7]] "About 60 million transistors were built this year [2002] ... for [each] man, woman, and child on Earth."[|[8]]

Comparison with **tubes**
Prior to the development of transistors, [|vacuum (electron) tubes] (or in the UK "thermionic valves" or just "valves") were the main active components in electronic equipment. 

** [[|edit]] Advantages **
The key advantages that have allowed transistors to replace their vacuum tube predecessors in most applications are: 
 * Small size and minimal weight, allowing the development of miniaturized electronic devices.
 * Highly automated manufacturing processes, resulting in low per-unit cost.
 * Lower possible operating voltages, making transistors suitable for small, battery-powered applications.
 * No warm-up period for cathode heaters required after power application.
 * Lower power dissipation and generally greater energy efficiency.
 * Higher reliability and greater physical ruggedness.
 * Extremely long life. Some transistorized devices produced more than 30 years ago are still in service.
 * Complementary devices available, facilitating the design of [|complementary-symmetry] circuits, something not possible with vacuum tubes.
 * Insensitivity to mechanical shock and vibration, thus avoiding the problem of [|microphonics] in audio applications.

** [[|edit]] Limitations **

 * Silicon transistors do not operate at voltages higher than about 1,000 [|volts] ([|SiC] devices can be operated as high as 3,000 volts). In contrast, electron tubes have been developed that can be operated at tens of thousands of volts.
 * High power, high frequency operation, such as used in over-the-air [|television broadcasting], is better achieved in electron tubes due to improved [|electron mobility] in a vacuum.
 * On average, a higher degree of [|amplification] [|linearity] can be achieved in electron tubes as compared to equivalent solid state devices, a characteristic that may be important in [|high fidelity] [|audio reproduction].
 * Silicon transistors are much more sensitive than electron tubes to an [|electromagnetic pulse], such as generated by a [|nuclear explosion].

=Types of Transistors (Just for fun to see how complex of a topic we are talking.)=


 * [|Point-contact transistor], first type of transistor ever constructed
 * [|Bipolar junction transistor] (BJT)
 * [|Heterojunction bipolar transistor] - up to 100s GHz, common in modern ultrafast and RF circuits
 * [|Grown-junction transistor], first type of BJT
 * [|Alloy-junction transistor], improvement of grown-junction transistor
 * [|Micro-alloy transistor] (MAT), faster than alloy-junction transistor
 * [|Micro-alloy diffused transistor] (MADT), faster than MAT, type of a [|diffused-base transistor]
 * [|Post-alloy diffused transistor] (PADT), faster than MAT, type of a [|diffused-base transistor]
 * [|Schottky transistor]
 * [|Surface barrier transistor]
 * [|Drift-field transistor]
 * [|Avalanche transistor]
 * [|Darlington transistors] are two BJTs connected together to provide a high current gain equal to the product of the current gains of the two transistors.
 * [|Insulated gate bipolar transistors] ([|IGBTs]) use a medium power IGFET, similarly connected to a power BJT, to give a high input impedance. Power diodes are often connected between certain terminals depending on specific use. IGBTs are particularly suitable for heavy-duty industrial applications. The [|Asea Brown Boveri] (ABB) [|**5SNA2400E170100**]illustrates just how far power semiconductor technology has advanced. Intended for three-phase power supplies, this device houses three NPN IGBTs in a case measuring 38 by 140 by 190 mm and weighing 1.5 kg. Each IGBT is rated at 1,700 volts and can handle 2,400 amperes.
 * [|Photo transistor] React to light
 * [|Field-effect transistor]
 * [|JFET], where the gate is insulated by a reverse-biased PN junction
 * [|MESFET], similar to JFET with a Schottky junction instead of PN one
 * [|High Electron Mobility Transistor] (HEMT, HFET, MODFET)
 * [|MOSFET], where the gate is insulated by a thin layer of insulator
 * [|Inverted-T field effect transistor] (ITFET)
 * [|FinFET] The source/drain region forms fins on the silicon surface.
 * [|FREDFET] Fast-Reverse Epitaxial Diode Field-Effect Transistor
 * [|Thin film transistor] Used in LCD display.
 * [|OFET] Organic Field-Effect Transistor, in which the semiconductor is an organic compound
 * [|Ballistic transistor]
 * [|Floating-gate transistor] Used for non-volatile storage.
 * FETs used to sense environment
 * [|Ion sensitive field effect transistor] To measure ion concentrations in solution.
 * [|EOSFET] Electrolyte-Oxide-Semiconductor Field Effect Transistor ([|Neurochip])
 * [|DNAFET] Deoxyribonucleic acid field-effect transistor
 * [|Spacistor]
 * [|Diffusion transistor], formed by diffusing dopants into semiconductor substrate; can be both BJT and FET
 * [|Unijunction transistors] can be used as simple pulse generators. They comprise a main body of either P-type or N-type semiconductor with ohmic contacts at each end (terminals //Base1//and //Base2//). A junction with the opposite semiconductor type is formed at a point along the length of the body for the third terminal (//Emitter//).
 * [|Single-electron transistors] (SET) consist of a gate island between two tunnelling junctions. The tunnelling current is controlled by a voltage applied to the gate through a capacitor.[|[1]][|[2]]
 * [|Spin transistor] Magnetically-sensitive
 * [|Nanofluidic transistor] Control the movement of ions through sub-microscopic, water-filled channels. [|Nanofluidic transistor, the basis of future chemical processors]
 * Multigate devices
 * [|Tetrode transistor]
 * [|Pentode transistor]
 * [|Multigate device]
 * [|Trigate transistors] (Prototype by Intel)
 * **Dual gate FETs** have a single channel with two gates in [|cascode]; a configuration that is optimized for **high frequency amplifiers**, **mixers**, and [|oscillators]. (http://en.wikipedia.org/wiki/Transistor)