Gain - juxtapix/IMA_E4I GitHub Wiki

Gain is the measure of an amplifier's ability to increase the magnitude of an input signal. It is defined as a ratio of the signal amplitude or power at the output to the signal amplitude or power at the input. A defining characteristic of an amplifier circuit is having a gain greater than 1.0. Gain can be thought of as the effectiveness of the amplifier.

There are amplifier circuits (DC or AC) that are designed to amplify Voltage, Current or Power. Therefore, gain can refer to voltage gain, current gain, or power gain.

Since the gain ratio is of equal units (power out / power in, voltage out / voltage in, or current out / current in), gain does not have a measured unit. It is represented in formulas by the capital letter A.

Multiple Amplifiers

In a multi-amplifier set up, the resulting overall gain is equal to the product (multiplication) of the individual amplifier gains.

I.E. - An amplifier of gain 3 followed by an amplifier of gain 5 equals an overall gain of 15.

Decibel (dB)

Although gain is a unit-less measurement, it is often expressed in decibels (dB). The decibel is a unit of measurement that expresses the ratio of two field quantities (voltage) or energy quantities (power). It can be thought of as the ratio of the voltage at the output to the voltage at the input, expressed in a logarithmic unit.

Gain in Audio Circuits

For audio electronics, gain measures the ability of the audio amplifier to increase the amplitude of a signal from input to output. The gain controls the shape of the signals coming out of the amplifier circuit and therefor effects the quality of the sound, not to be confused with the volume. Like non-audio amps, it also is defined as a ratio of the signal output and signal input of a system.

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References: https://www.allaboutcircuits.com/textbook/semiconductors/chpt-1/amplifier-gain/ http://www.sengpielaudio.com/calculator-FactorRatioLevelDecibel.htm