Closed Loop Gain Bandwidth

The band of frequencies over which the gain of the closed loop is called closed-loop gain bandwidth, which is almost constant, to within a certain number of decibels (usually 3 dB).

If the operational amplifier (op-amp) has been stabilized to operate at unity gain, then the unity gain bandwidth is approximately equal to the Gain Bandwidth Product (GBWP).

The relation between closed-loop gain bandwidth, GBWP, and noise gain G_N (G_N =1/β):

BW ~ GBWP / G_N

Now we can approximately calculate the closed-loop gain bandwidth based on GBWP and noise gain.