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Low-noise Amplifier
A low-noise amplifier (LNA) is an electronic amplifier that amplifies a very low-power signal without significantly degrading its signal-to-noise ratio. An amplifier will increase the power of both the signal and the noise present at its input, but the amplifier will also introduce some additional noise. LNAs are designed to minimize that additional noise. Designers can minimize additional noise by choosing low-noise components, operating points, and circuit topologies. Minimizing additional noise must balance with other design goals such as power gain and impedance matching. LNAs are found in radio communications systems, medical instruments and electronic test equipment. A typical LNA may supply a power gain of 100 (20 decibels (dB)) while decreasing the signal-to-noise ratio by less than a factor of two (a 3 dB noise figure (NF)). Although LNAs are primarily concerned with weak signals that are just above the noise floor, they must also consider the presence of larg ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electronic Amplifier
An amplifier, electronic amplifier or (informally) amp is an electronic device that can increase the magnitude of a Signal (information theory), signal (a time-varying voltage or Electric current, current). It may increase the power (physics), power significantly, or its main effect may be to boost the voltage or current (power amplifier, power, voltage or current amplifier). It is a two-port network, two-port electronic circuit that uses electric power from a power supply to increase the amplitude of a signal applied to its input terminals, producing a greater amplitude signal at its output. The ratio of output to input voltage, current, or power is termed gain (electronics), gain (voltage, current, or power gain). An amplifier, by definition has gain greater than unity (if the gain is less than unity, the device is an attenuator (electronics), attenuator). An amplifier can either be a separate piece of equipment or an electrical circuit contained within another device. Amp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Friis Formulas For Noise
Friis formula or Friis's formula (sometimes Friis' formula), named after Danish-American electrical engineer Harald T. Friis, is either of two formulas used in telecommunications engineering to calculate the signal-to-noise ratio of a multistage amplifier. One relates to noise factor while the other relates to noise temperature. The Friis formula for noise factor Friis's formula is used to calculate the total noise factor of a cascade of stages, each with its own noise factor and power gain (assuming that the impedances are matched at each stage). The total noise factor can then be used to calculate the total noise figure. The total noise factor is given as where F_i and G_i are the noise factor and available power gain, respectively, of the ''i''-th stage, and ''n'' is the number of stages. Both magnitudes are expressed as ratios, not in decibels. Consequences An important consequence of this formula is that the overall noise figure of a radio receiver is primarily establ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Common Base
In electronics, a common-base (also known as grounded-base) amplifier is one of three basic single-stage bipolar junction transistor (BJT) amplifier topologies, typically used as a current buffer or voltage amplifier. In this circuit the emitter terminal of the transistor serves as the input, the collector as the output, and the base is connected to ground, or "common", hence its name. The analogous field-effect transistor circuit is the common-gate amplifier. Applications This arrangement is not very common in low-frequency discrete circuits, where it is usually employed for amplifiers that require an unusually low input impedance, for example to act as a preamplifier for moving-coil microphones. However, it is popular in integrated circuits and in high-frequency amplifiers, for example for VHF and UHF, because its input capacitance does not suffer from the Miller effect, which degrades the bandwidth of the common-emitter configuration, and because of the relatively high is ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
