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Output Impedance
In electrical engineering, the output impedance of an electrical network is the measure of the opposition to current flow ( impedance), both static ( resistance) and dynamic ( reactance), into the load network being connected that is ''internal'' to the electrical source. The output impedance is a measure of the source's propensity to drop in voltage when the load draws current, the source network being the portion of the network that transmits and the load network being the portion of the network that consumes. Because of this the output impedance is sometimes referred to as the source impedance or internal impedance. Description All devices and connections have non-zero resistance and reactance, and therefore no device can be a perfect source. The output impedance is often used to model the source's response to current flow. Some portion of the device's measured output impedance may not physically exist within the device; some are artifacts that are due to the chemical, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electrical Engineering
Electrical engineering is an engineering discipline concerned with the study, design, and application of equipment, devices, and systems that use electricity, electronics, and electromagnetism. It emerged as an identifiable occupation in the latter half of the 19th century after the commercialization of the electric telegraph, the telephone, and electrical power generation, distribution, and use. Electrical engineering is divided into a wide range of different fields, including computer engineering, systems engineering, power engineering, telecommunications, radio-frequency engineering, signal processing, instrumentation, photovoltaic cells, electronics, and optics and photonics. Many of these disciplines overlap with other engineering branches, spanning a huge number of specializations including hardware engineering, power electronics, Electromagnetism, electromagnetics and waves, microwave engineering, nanotechnology, electrochemistry, renewable energies, mechatronics/control ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bias Point
In electronics, biasing is the setting of DC (direct current) operating conditions (current and voltage) of an electronic component that processes time-varying signals. Many electronic devices, such as diodes, transistors and vacuum tubes, whose function is processing time-varying ( AC) signals, also require a steady (DC) current or voltage at their terminals to operate correctly. This current or voltage is called ''bias''. The AC signal applied to them is superposed on this DC bias current or voltage. The operating point of a device, also known as bias point, quiescent point, or Q-point, is the DC voltage or current at a specified terminal of an active device (a transistor or vacuum tube) with no input signal applied. A bias circuit is a portion of the device's circuit that supplies this steady current or voltage. Overview In electronics, 'biasing' usually refers to a fixed DC voltage or current applied to a terminal of an electronic component such as a diode, transistor ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nominal Impedance
Nominal impedance in electrical engineering and audio engineering refers to the approximate designed impedance of an electrical circuit or device. The term is applied in a number of different fields, most often being encountered in respect of: * The nominal value of the characteristic impedance of a cable or other form of transmission line. * The nominal value of the input, output or image impedance of a port of a network, especially a network intended for use with a transmission line, such as filters, equalisers and amplifiers. * The nominal value of the input impedance of a radio frequency antenna The actual impedance may vary quite considerably from the nominal figure with changes in frequency. In the case of cables and other transmission lines, there is also variation along the length of the cable, if it is not properly terminated. It is usual practice to speak of nominal impedance as if it were a constant resistance, that is, it is invariant with frequency and has a zer ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Input Impedance
In electrical engineering, the input impedance of an electrical network is the measure of the opposition to current ( impedance), both static ( resistance) and dynamic ( reactance), into a load network or circuit that is ''external'' to the electrical source network. The input admittance (the reciprocal of impedance) is a measure of the load network's propensity to draw current. The source network is the portion of the network that transmits power, and the load network is the portion of the network that consumes power. For an electrical property measurement instrument like an oscilloscope, the instrument is a load circuit to an electrical circuit (source circuit) to be measured, so the input impedance is the impedance of the instrument seen by the circuit to be measured. Input impedance If the load network were replaced by a device with an output impedance equal to the input impedance of the load network (equivalent circuit), the characteristics of the source-load network w ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electromotive Force
In electromagnetism and electronics, electromotive force (also electromotance, abbreviated emf, denoted \mathcal) is an energy transfer to an electric circuit per unit of electric charge, measured in volts. Devices called electrical ''transducers'' provide an emf by Energy transformation, converting other forms of energy into electrical energy. Other types of electrical equipment also produce an emf, such as Battery (electricity), batteries, which convert chemical energy, and Electric generator, generators, which convert mechanical energy. This energy conversion is achieved by Force, physical forces applying Work (physics), physical work on electric charges. However, electromotive force itself is not a physical force, and ISO/International Electrotechnical Commission, IEC standards have deprecated the term in favor of source voltage or source tension instead (denoted U_s). An Hydraulic analogy, electronic–hydraulic analogy may view emf as the mechanical work done to water by a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Battery (electricity)
An electric battery is a source of electric power consisting of one or more electrochemical cells with external connections for powering electrical devices. When a battery is supplying power, its positive terminal is the cathode and its negative terminal is the anode. The terminal marked negative is the source of electrons. When a battery is connected to an external electric load, those negatively charged electrons flow through the circuit and reach the positive terminal, thus causing a redox reaction by attracting positively charged ions, or cations. Thus, higher energy reactants are converted to lower energy products, and the free-energy difference is delivered to the external circuit as electrical energy. Historically the term "battery" specifically referred to a device composed of multiple cells; however, the usage has evolved to include devices composed of a single cell. Primary (single-use or "disposable") batteries are used once and discarded, as the electrode mat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Internal Resistance
In electrical engineering, a practical electric power source which is a linear circuit may, according to Thévenin's theorem, be represented as an ideal voltage source in series with an impedance. This impedance is termed the internal resistance of the source. When the power source delivers current, the measured voltage output is lower than the no- load voltage; the difference is the voltage drop (the product of current and resistance) caused by the internal resistance. The concept of internal resistance applies to all kinds of electrical sources and is useful for analyzing many types of circuits. Battery A battery may be modeled as a voltage source in series with a resistance. These types of models are known as equivalent circuit models. Another common model being physiochemical models that are physical in nature involving concentrations and reaction rates. In practice, the internal resistance of a battery is dependent on its size, state of charge, chemical properties ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Impedance Matching
In electrical engineering, impedance matching is the practice of designing or adjusting the input impedance or output impedance of an electrical device for a desired value. Often, the desired value is selected to maximize power transfer or minimize signal reflection. For example, impedance matching typically is used to improve power transfer from a radio transmitter via the interconnecting transmission line to the antenna. Signals on a transmission line will be transmitted without reflections if the transmission line is terminated with a matching impedance. Techniques of impedance matching include transformers, adjustable networks of lumped resistance, capacitance and inductance, or properly proportioned transmission lines. Practical impedance-matching devices will generally provide best results over a specified frequency band. The concept of impedance matching is widespread in electrical engineering, but is relevant in other applications in which a form of energy ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Impedance Bridging
In audio engineering and sound recording, a high impedance bridging, voltage bridging, or simply bridging connection is one in which the load impedance is much larger than the source impedance. The load measures the source's voltage while minimally drawing current or affecting it. Explanation When the output of a device (consisting of the voltage source ''V''S and output impedance ''Z''S in illustration) is connected to the input of another device (the load impedance ''Z''L in the illustration), these two impedances form a voltage divider: : V_L = \frac V_S \, . One can maximize the signal level ''V''L by using a voltage source whose output impedance ''Z''S is as small as possible and by using a receiving device whose input impedance ''Z''L is as large as possible. When Z_L \gg Z_S (typically by at least ten times), this is called a ''bridging connection'' and has a number of effects including: * Advantages: ** Reduces the 6dB attenuation incurred by impedance matc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hifi
High fidelity (hi-fi or, rarely, HiFi) is the high-quality reproduction of sound. It is popular with audiophiles and home audio enthusiasts. Ideally, high-fidelity equipment has inaudible noise and distortion, and a flat (neutral, uncolored) frequency response within the human hearing range. High fidelity contrasts with the lower-quality " lo-fi" sound produced by inexpensive audio equipment, AM radio, or the inferior quality of sound reproduction that can be heard in recordings made until the late 1940s. History Bell Laboratories began experimenting with various recording techniques in the early 1930s. Performances by Leopold Stokowski and the Philadelphia Orchestra were recorded in 1931 and 1932 using telephone lines between the Academy of Music in Philadelphia and the Bell labs in New Jersey. Some multitrack recordings were made on optical sound film, which led to new advances used primarily by MGM (as early as 1937) and Twentieth Century Fox Film Corporation (as ear ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Damping Factor
In an audio system, the damping factor is defined as the ratio of the rated impedance of the loudspeaker (usually assumed to be ) to the Output impedance, source impedance of the power amplifier. It was originally proposed in 1941. Only the magnitude of the loudspeaker impedance is used, and the power amplifier output impedance is assumed to be totally resistive. In typical solid state and tube amplifiers, the damping factor varies as a function of frequency. In solid state amplifiers, the damping factor usually has a maximum value at low frequencies, and it reduces progressively at higher frequencies. The figure to the right shows the damping factor of two amplifiers. One is a solid state amplifier (Luxman L-509u) and the other is a tube amplifier (Rogue Atlas). These results are fairly typical of these two types of amplifiers, and they serve to illustrate the fact that tube amplifiers usually have much lower damping factors than modern solid state amplifiers, which is an undes ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Power Amplifier
An audio power amplifier (or power amp) amplifies low-power electronic audio signals, such as the signal from a radio receiver or an electric guitar pickup, to a level that is high enough for driving loudspeakers or headphones. Audio power amplifiers are found in all manner of sound systems including sound reinforcement, public address, home audio systems and musical instrument amplifiers like guitar amplifiers. It is the final electronic stage in a typical audio playback chain before the signal is sent to the loudspeakers. The preceding stages in such a chain are low-power audio amplifiers which perform tasks like pre-amplification of the signal, equalization, mixing different input signals. The inputs can also be any number of audio sources like record players, CD players, digital audio players and cassette players. Most audio power amplifiers require these low-level inputs, which are line level. While the input signal to an audio power amplifier, such as the si ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
