I know that most of you know this, but here it is anyway:
It might be enlightening to show why voltage and current use the formula
20LOG(V1/V2), or 20LOG(I1/I2), while power uses the formula 10LOG(P1/P2).
Remember that power is (E^2)/R. And that LOG(E^2) = 2LOG(E). So,
10LOG((E^2)/R) becomes 20LOG(E/R). Decibels always tell us the ratio of powers
(given a constant impedance).
So when we say the gain is 3 dB it means that the power has increased by a
factor of 2 and that the voltage has increased by a factor of sq. rt. 2
(1.414). We don't have to say if the voltage or the current or the power has
increased by 3 dB- they all have.
Dave Cuthbert
Micron Technology
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