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Gain
 
 
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In electronics
Electronics

Electronics refers to the flow of charge through nonmetal electrical conductor , whereas electrical refers to the flow of charge through metal electrical conductor....
, gain is a measure of the ability of a circuit
Electrical network

An electrical network is an interconnection of electrical elements such as resistors, inductors, capacitors, transmission lines, voltage sources, current sources, and switches....
 (often an amplifier
Amplifier

Generally, an amplifier or simply amp, is any machine that changes, usually increases, the amplitude of a Signal . The "signal" is usually voltage or current....
) to increase the power
Power (physics)

In physics, power is the rate at which mechanical work is performed or energy is transmitted, or the amount of energy required or expended for a given unit of time....
 or amplitude
Amplitude

Amplitude is the magnitude of change in the oscillating variable, with each oscillation, within an oscillating system. For instance, sound waves are oscillations in atmospheric pressure and their amplitudes are proportional to the change in pressure during one oscillation....
 of a signal
Signal (electrical engineering)

In the fields of telecommunications, signal processing, and in electrical engineering more generally, a signal is any time-varying or spatial-varying quantity....
. It is usually defined as the mean ratio
Ratio

A ratio is an expression which compares quantities relative to each other. The most common examples involve two quantities, but in theory any number of quantities can be compared....
 of the signal output of a system to the signal input of the same system. It may also be defined as the decimal logarithm
Logarithm

In mathematics, the logarithm of a number to a given base is the Power or exponent to which the base must be raised in order to produce the number....
 of the same ratio.

Thus, the term gain on its own is ambiguous
Ambiguity

Ambiguity is the property of being ambiguous, where a word, term, notation, sign, symbol, phrase, Sentence , or any other form used for communication, is called ambiguous if it can be interpreted in more than one way....
. For example, "a gain of five" may imply that either the voltage
Voltage

Electrical tension is the potential difference between two points of an electrical or electronic circuit, expressed in volts. It is the measurement of the potential for an electric field to cause an electric current in an electrical conductor....
, current
Current

Current may refer to:* Current affairs* Electric current* Current ** Ocean current* Current , geometrical current in differential topology...
 or the power
Electric power

Electric power is defined as the rate at which electrical energy is transferred by an electric circuit. The SI unit of power is the watt .When electric current flows in a circuit, it can transfer energy to do mechanical work or work ....
 is increased by a factor of five.






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Encyclopedia


In electronics
Electronics

Electronics refers to the flow of charge through nonmetal electrical conductor , whereas electrical refers to the flow of charge through metal electrical conductor....
, gain is a measure of the ability of a circuit
Electrical network

An electrical network is an interconnection of electrical elements such as resistors, inductors, capacitors, transmission lines, voltage sources, current sources, and switches....
 (often an amplifier
Amplifier

Generally, an amplifier or simply amp, is any machine that changes, usually increases, the amplitude of a Signal . The "signal" is usually voltage or current....
) to increase the power
Power (physics)

In physics, power is the rate at which mechanical work is performed or energy is transmitted, or the amount of energy required or expended for a given unit of time....
 or amplitude
Amplitude

Amplitude is the magnitude of change in the oscillating variable, with each oscillation, within an oscillating system. For instance, sound waves are oscillations in atmospheric pressure and their amplitudes are proportional to the change in pressure during one oscillation....
 of a signal
Signal (electrical engineering)

In the fields of telecommunications, signal processing, and in electrical engineering more generally, a signal is any time-varying or spatial-varying quantity....
. It is usually defined as the mean ratio
Ratio

A ratio is an expression which compares quantities relative to each other. The most common examples involve two quantities, but in theory any number of quantities can be compared....
 of the signal output of a system to the signal input of the same system. It may also be defined as the decimal logarithm
Logarithm

In mathematics, the logarithm of a number to a given base is the Power or exponent to which the base must be raised in order to produce the number....
 of the same ratio.

Thus, the term gain on its own is ambiguous
Ambiguity

Ambiguity is the property of being ambiguous, where a word, term, notation, sign, symbol, phrase, Sentence , or any other form used for communication, is called ambiguous if it can be interpreted in more than one way....
. For example, "a gain of five" may imply that either the voltage
Voltage

Electrical tension is the potential difference between two points of an electrical or electronic circuit, expressed in volts. It is the measurement of the potential for an electric field to cause an electric current in an electrical conductor....
, current
Current

Current may refer to:* Current affairs* Electric current* Current ** Ocean current* Current , geometrical current in differential topology...
 or the power
Electric power

Electric power is defined as the rate at which electrical energy is transferred by an electric circuit. The SI unit of power is the watt .When electric current flows in a circuit, it can transfer energy to do mechanical work or work ....
 is increased by a factor of five. Furthermore, the term gain is also applied in systems such as sensor
Sensor

A sensor is a device that measures a physical quantity and converts it into a signal which can be read by an observer or by an instrument. For example, a mercury thermometer converts the measured temperature into expansion and contraction of a liquid which can be read on a calibrated glass tube....
s where the input and output have different units; in such cases the gain units must be specified, as in "5 microvolts per photon" for a photosensor.

In laser physics
Laser Physics

Laser Physics is an international scientific journalpublished by Nauka/Interperiodica Publishing. It is distributed through the Springer Science+Business Media publishing company....
, gain may refer to the increment of power along the beam propagation in a gain medium, and its dimension is m-1 (inverse meter) or 1/meter.

Logarithmic units and decibels


Power gain

Power gain
Power gain

The power gain of an electrical network is the ratio of an output Power to an input power. Unlike other signal gains, such as voltage and Electric current gain, "power gain" may be ambiguous as the meaning of terms "input power" and "output power" is not always clear....
, in decibel
Decibel

The decibel is a logarithmic units of measurement that expresses the magnitude of a physical quantity relative to a specified or implied reference level....
s (dB), is defined as follows: where Pin and Pout are the input and output powers respectively.

A similar calculation can be done using a natural logarithm
Natural logarithm

The natural logarithm, formerly known as the hyperbolic logarithm, is the logarithm to the base e , where e is an irrational number constant approximately equal to 2.718281828....
 instead of a decimal logarithm. The result is then in neper
Neper

A neper is a logarithmic unit of ratio. It is not an SI unit but is accepted for use alongside the SI. It is used to express ratios, such as gain and loss, and relative values....
s instead of decibels.

Voltage gain


When power gain is calculated using voltage instead of power, making the substitution (P=V 2/R)
Joule's law

Joule's laws are a pair of laws concerning the heat produced by a current and the energy dependence of an ideal gas to that of pressure, volume, and temperature, respectively....
, the formula is:

In many cases, the input and output impedances are equal, so the above equation can be simplified to:

and then:

This simplified formula is used to calculate a voltage gain in decibels, and is equivalent to a power gain only if the impedance
Electrical impedance

Electrical impedance, or simply impedance, describes a measure of opposition to a sinusoidal alternating current . Electrical impedance extends the concept of Electrical resistance to AC circuits, describing not only the relative amplitudes of the voltage and Electric current, but also the relative Phase ....
s at input and output are equal.

Current gain

In the same way, when power gain is calculated using current instead of power, making the substitution (P=I 2R)
Joule's law

Joule's laws are a pair of laws concerning the heat produced by a current and the energy dependence of an ideal gas to that of pressure, volume, and temperature, respectively....
, the formula is:

In many cases, the input and output impedances are equal, so the above equation can be simplified to:

and then:

This simplified formula is used to calculate a current gain in decibels, and is equivalent to the power gain only if the impedance
Electrical impedance

Electrical impedance, or simply impedance, describes a measure of opposition to a sinusoidal alternating current . Electrical impedance extends the concept of Electrical resistance to AC circuits, describing not only the relative amplitudes of the voltage and Electric current, but also the relative Phase ....
s at input and output are equal.

Example

Q. An amplifier has an input impedance of 50 ohms and drives a load of 50 ohms. When its input is 1 volt, its output is 10 volts. What are its voltage gain and power gain?

A. Voltage gain is simply: The units V/V are optional, but make it clear that this figure is a voltage gain and not a power gain. Using the expression for power, P = V2/R, the power gain is: Again, the units W/W are optional. Power gain is more usually expressed in decibels, thus:

A gain of factor 1 (equivalent to 0 dB) where both input and output are at the same voltage level and impedance is also known as unity
1 (number)

1 is a number, number names, and the name of the glyph representing that number.It represents a single entity, the unit of counting or measurement....
 gain.

See also

  • Antenna gain
    Antenna gain

    Antenna Gain is defined as the ratio of the radiation intensity of an antenna in a given direction to the intensity that would be produced by a hypothetical ideal antenna that radiates equally in all directions and has no losses....
  • Transmitter power output
    Transmitter power output

    In radio transmission, transmitter power output is the actual amount of power of radio frequency energy that a transmitter produces at its output....
  • Absolute gain (physics)
    Absolute gain (Physics)

    The absolute gain of an antenna , for a given direction and polarization, is the ratio of the power that would be required at the input of an ideal isotropic radiator to the power actually supplied to the given antenna, to produce the same radiant intensity in the far-field region....
  • Loop gain
    Loop gain

    In negative feedback amplifiers, loop gain refers to the product of the gain in the feedback loop and the feedback factor in that loop. In Figure 1, the loop gain is the product ?AOL....
  • Insertion gain
    Insertion gain

    In telecommunication, insertion gain is the gain resulting from the insertion of a device in a transmission line, expressed as the ratio of the Signalling Power delivered to that part of the line following the device to the signal power delivered to that same part before insertion....
  • Power gain
    Power gain

    The power gain of an electrical network is the ratio of an output Power to an input power. Unlike other signal gains, such as voltage and Electric current gain, "power gain" may be ambiguous as the meaning of terms "input power" and "output power" is not always clear....
  • Directive gain
    Directive gain

    In telecommunications, the term directive gain has the following meanings:1. Of an antenna , the ratio of 4pi times the radiant intensity in a given direction , to the total power....
  • Net gain
    Net gain

    In telecommunications, net gain is the overall gain of a transmission Telecommunication circuit.Note 1: Net gain is measured by applying a test Signalling at an appropriate dollor amountMedia:...
  • Process gain
    Process gain

    In a spread spectrum system, the process gain is the ratio of the spread bandwidth to the unspread bandwidth. It is usually expressed in decibels ....
  • Signal processing gain
  • Automatic gain control
    Automatic gain control

    Automatic gain control is an adaptive system found in many electronic devices. The average output signal level is feedback to adjust the gain to an appropriate level for a range of input signal levels....
  • Attenuation
    Attenuation

    In physics, attenuation is the gradual loss in intensity of any kind of flux through a medium. For instance, sunlight is attenuated by dark glasses, and X-rays are attenuated by lead....
     (loss), Aperture-to-medium coupling loss
    Aperture-to-medium coupling loss

    In telecommunication, aperture-to-medium coupling loss is the difference between the theoretical gain of a very large antenna , such as the antennas in beyond-the-horizon microwave links, and the gain that can be realized in practice....
    , Effective radiated power
    Effective radiated power

    In radio telecommunications, effective radiated power or equivalent radiated power is a standardized theoretical measurement of Radio frequency energy using the non-International System of Units unit Decibel, and is determined by subtracting system losses and adding system gains....
  • gain medium