Click here to purchase the entire book in PDF format. Gain Bandwidth Product (GBP) Eventually, if you keep going up in frequency as you're measuring the open-loop voltage gain of the op amp, you'll reach a frequency where the gain of the system is 1. That is to say that the input is the same level as the output. If we take the gain at that frequency (1) and multiply it by the frequency (or bandwidth) we'll get the Gain Bandwidth Product. This will then tell you an important characteristic of the op amp, since the gain of the op amp rolls off at a rate of 6 dB/octave. If you take a given frequency and divide it by the GBP, you'll find the open-loop gain at that frequency.