Editing Gain (electronics) (section)

===Example===
Q. An amplifier has an input impedance of 50 ohms and drives a load of 50 ohms. When its input (<math>V_\text{in}</math>) is 1 volt, its output (<math>V_\text{out}</math>) is 10 volts. What is its voltage and power gain?

A. Voltage gain is simply:

:<math>\text{gain} = \frac{V_\text{out}}{V_\text{in}} = \frac{10}{1} = 10~\text{V/V}.</math>

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'' = ''V''<sup>2</sup>/''R'', the power gain is:

:<math>\text{gain} = \frac{V_\text{out}^2/50}{V_\text{in}^2/50} = \frac{V_\text{out}^2}{V_\text{in}^2} = \frac{10^2}{1^2} = 100~\text{W/W}.</math>

Again, the units W/W are optional. Power gain is more usually expressed in decibels, thus:

:<math>\text{gain-db} = G_\text{dB} = 10 \log G_\text{W/W} = 10 \log 100 = 10 \times 2 = 20~\text{dB}.</math>