# User Contributed Dictionary

### Noun

gains- Plural of gain

### Verb

gains- third-person singular of gain

# 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

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.

### Example

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.

- \frac=\frac=\frac=100\ \mathrm.

- 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

- Transmitter power output
- Absolute gain (physics)
- Loop gain
- Insertion gain
- Power gain
- Directive gain
- Net gain
- Process gain
- Signal processing gain
- Automatic gain control
- Attenuation (loss), Aperture-to-medium coupling loss, Effective radiated power
- gain medium

gains in Arabic: أرباح

gains in Catalan: Guany

gains in German: Verstärkung (Physik)

gains in Spanish: Ganancia (electrónica)

gains in French: Gain (électronique)

gains in Italian: Guadagno (elettronica)

gains in Japanese: 利得 (電気工学)

gains in Polish: Współczynnik wzmocnienia

gains in Portuguese: Ganho

gains in Sundanese: Gain

gains in Chinese: 增益

# Synonyms, Antonyms and Related Words

avails,
box office, capital gains, cleanup, clear profit, commissions, credit, credits, disposable income,
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gross receipts, hoard,
income, increase, intake, interest, killing, lucre, make, makings, neat profit, net, net income, net profit, net
receipts, output, paper
profits, pelf, percentage, perk, perks, perquisite, pickings, proceeds, produce, profit, profits, rake-off, receipt, receipts, receivables, return, returns, revenue, royalties, store, take, take-in, takings, unearned income,
wealth, winnings, yield