Gain
In
electronics, gain is usually taken as the mean ratio of the signal output of a system to the signal input of the system. A gain of five would imply that either the
voltage or
power is increased by a factor of five. It has wide application in
amplifiers.
Encyclopedia
In
electronics,
gain is usually taken as the mean ratio of the signal output of a system to the signal input of the system. A gain of five would imply that either the
voltage or
power is increased by a factor of five. It has wide application in
amplifiers.
Logarithmic units and decibels
In electronics, it is common to use logarithmic units to measure gain. Originally, the bel was used:
- Gain = log10 bel
where P1 and P2 are the input and output
powers respectively.
Using the bel unit, however, results in small numbers, so the decibel became popular in its place. As there are ten decibels in a bel:
- Gain = 10 * log10 dB
When gain is calculated using voltage instead of power, making the substitution , the formula is:
This formula only holds true if the load impedances are identical. In many modern electronic devices,
output impedances are low enough and
input impedances high enough that load can be ignored without significantly affecting the calculation.
Example
If an amplifier produces an output of 1
volt into a 1 ohm load, then it is providing 1 watt of output power. If the amplifier is then altered to produce an output of 10 volts into the same load, it is now providing 100 watts of output power . Therefore:
voltage gain = 10 times
power gain = 100 times
— which by definition is said to be a gain of 20 dB.
A gain of factor 1 or where both input and output are at the same voltage level is also known as
unity gain.
See also
- Transmitter power output
- Absolute gain
- Loop gain
- Insertion gain
- Directive gain
- Signal processing gain
- Net gain
- Automatic gain control
- Loss
- bereavement [i] and grief [i] when a beloved friend, relative, companio ...
, Aperture-to-medium coupling loss, Effective radiated power
