Work out amplifier gain (db) instantly with clear inputs, formula shown and shareable results.
Voltage gain in decibels is 20log10 of the voltage ratio; power gain is 10log10 of the power ratio. The two are equal only when input and output impedances match, which is why RF engineers use 10log10 on power and audio engineers 20log10 on voltage.
Gain in dB
voltage gain = 20 log10(Vout/Vin); power gain = 10 log10(Pout/Pin)
Power is proportional to voltage squared, and the square becomes a factor of two in front of the logarithm.
Whenever input and output impedances are unequal. A voltage gain of 50 into a lower impedance gives a different power gain in dB.