chapter  4
Decibels
Pages 2

A negative result denotes attenuation rather than

amplification. A negative gain is thus equivalent

to an attenuation (or loss). If desired, the formulae

may be adapted to produce a positive result for

attenuation simply by inverting the ratios, as

shown below:

where Ap, Av, or Ai is the power, voltage or

current gain (or loss) expressed in decibels, Pin

and Pout are the input and output powers, Vin and

Vout are the input and output voltages, and Iin and

Iout are the input and output currents. Again note

that the powers, voltages or currents should be

expressed in the same units/multiples (e.g. Pin and

Pout should both be expressed in W, mW, µW or

nW).