5.3 Gain Bandwidth Product (GBWP)

The GBWP is an estimation of the maximum amount of gain possible at a given circuit bandwidth. At DC, the starting value is Open Loop Gain. For low frequencies, the gain will remain relatively stable–but not necessarily equal to Open Loop Gain–until a critical frequency, at which point the gain will start to fall by -20 dB per decade. The GBWP is the point at which the gain of the operational amplifier reaches 0 dB (unity gain). Figure 5-2 shows the open loop gain plotted by frequency for the operational amplifier on an AVR^® DB microcontroller, with a GBWP of 5 MHz.

The GBWP can be used to estimate the maximum gain of an operational amplifier at a given bandwidth. If an operational amplifier has a GBWP of 5 MHz, then at a gain of five, the maximum bandwidth is 1 MHz.