AskDefine | Define gain

Dictionary Definition



1 a quantity that is added; "there was an addition to property taxes this year"; "they recorded the cattle's gain in weight over a period of weeks" [syn: addition, increase]
2 the advantageous quality of being beneficial [syn: profit]
3 the amount of increase in signal power or voltage or current expressed as the ratio of output to input [syn: amplification]
4 the amount by which the revenue of a business exceeds its cost of operating [ant: loss]


1 obtain; "derive pleasure from one's garden" [syn: derive]
2 win something through one's efforts; "I acquired a passing knowledge of Chinese"; "Gain an understanding of international finance" [syn: acquire, win] [ant: lose]
3 derive a benefit from; "She profited from his vast experience" [syn: profit, benefit]
4 reach a destination, either real or abstract; "We hit Detroit by noon"; "The water reached the doorstep"; "We barely made it to the finish line"; "I have to hit the MAC machine before the weekend starts" [syn: reach, make, attain, hit, arrive at]
5 obtain advantages, such as points, etc.; "The home team was gaining ground"; "After defeating the Knicks, the Blazers pulled ahead of the Lakers in the battle for the number-one playoff berth in the Western Conference" [syn: advance, win, pull ahead, make headway, get ahead, gain ground] [ant: fall back]
6 rise in rate or price; "The stock market gained 24 points today" [syn: advance]
7 increase in; "gain momentum"; "gain nerve"
8 earn on some commercial or business transaction; earn as salary or wages; "How much do you make a month in your new job?"; "She earns a lot in her new job"; "this merger brought in lots of money"; "He clears $5,000 each month" [syn: take in, clear, make, earn, realize, realise, pull in, bring in]
9 increase (one's body weight); "She gained 20 pounds when she stopped exercising" [syn: put on] [ant: reduce]

User Contributed Dictionary



  • /geɪn/, /geIn/
  • Rhymes: -eɪn


  1. The act of gaining.
  2. What one gains, as a return on investment or dividend.
    No pain, no gain.
  3. The factor by which a signal is multiplied.


act of gaining
what one gains (profit)
  • Czech: zisk
  • Dutch: winst
  • Finnish: voitto, hyöty
  • German: Gewinn
factor by which signal is multiplied
  • Finnish: vahvistus
Translations to be checked



  1. : To acquire possession of what one did not have before.






Extensive Definition

In electronics, gain is a measure of the ability of a circuit (often an amplifier) to increase the power or amplitude of a signal. It is usually defined as the mean ratio of the signal output of a system to the signal input of the same system. It may also be defined as the decimal logarithm of the same ratio.
Thus, the term gain on its own is ambiguous. For example, 'a gain of five' may imply that either the voltage, current or the power is increased by a factor of five. Furthermore, the term gain is also applied in systems such as sensors 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, 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, in decibels (dB), is defined as follows:
Gain=10 \log \left( \right)\ \mathrm
where Pin and Pout are the input and output powers respectively.
A similar calculation can be done using a natural logarithm instead of a decimal logarithm. The result is then in nepers instead of decibels.

Voltage gain

When power gain is calculated using voltage instead of power, making the substitution (P=V 2/R), the formula is:
Gain=10 \log\ \mathrm
In many cases, the input and output impedances are equal, so the above equation can be simplified to:
Gain=10 \log \left( \right)^2\ \mathrm
and then:
Gain=20 \log \left( \right)\ \mathrm
This simplified formula is used to calculate a voltage gain in decibels, and is equivalent to a power gain only if the impedances 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), the formula is:
Gain=10 \log \ \mathrm
In many cases, the input and output impedances are equal, so the above equation can be simplified to:
Gain=10 \log \left( \right)^2\ \mathrm
and then:
Gain=20 \log \left( \right)\ \mathrm
This simplified formula is used to calculate a current gain in decibels, and is equivalent to the power gain only if the impedances at input and output are equal.


Q. An amplifier has an input impedance of 50 ohms and drives a load of 50 ohms. When its input (V_) is 1 volt, its output (V_) is 10 volts. What are its voltage gain and power gain?
A. Voltage gain is simply:
\frac=\frac=10\ \mathrm.
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:
\frac=\frac=\frac=100\ \mathrm.
Again, the units W/W are optional. Power gain is more usually expressed in decibels, thus:
G_=10 \log G_=10 \log 100=10 \times 2=20\ \mathrm.
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 gain.

See also

gain in Arabic: أرباح
gain in Catalan: Guany
gain in German: Verstärkung (Physik)
gain in Spanish: Ganancia (electrónica)
gain in French: Gain (électronique)
gain in Italian: Guadagno (elettronica)
gain in Japanese: 利得 (電気工学)
gain in Polish: Współczynnik wzmocnienia
gain in Portuguese: Ganho
gain in Sundanese: Gain
gain in Chinese: 增益

Synonyms, Antonyms and Related Words

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