The Gain Bandwidth Product (GBWP) of an amplifier is the product of the amplifier open-loop gain times the frequency at any point in the frequency range where the amplifier's response is attenuating at a rate of -20dB per decade of frequency. And GBWP keeps constant where the slope is -20dB/decade. GBWP is used to estimate the bandwidth when the gain is known. The picture below demonstrates the -20dB/decade decay as well as the -3dB point.
- The Gain Bandwidth Product (GBWP) applies to voltage feedback op-amps only. For the current feedback amplifiers, the GBWP is not constant and is less than 20dB/decade.
- The bandwidth at the maximum output swing is called the Full Power Bandwidth (fFPBW). It is limited by the
Slew Rate (SR) for the amplifiers.