gain * bandwidth product = constant

[xiongshoufen]

why gain bandwidth product constant

who can tell why gain * bandwidth product= constant ,

and under what conditions, gain * bandwidth product= constant ,

why amp' feedback gain=1, it is easier to oscillate? thanks!

 

[LvW]

gain bandwith product

The gain-bandwidth-product is constant only for the special case of a gain-frequency dependence which can be approximated by a first order function (that means only one pole within the frequency range of interest with a gain>0 dB).
The reason is simple mathematics:
In a first order system the frequency term in the denominator is of first order.
Therefore a frequency increase by a factor of 2 (or 10) reduces the gain by a factor of 1/2 (or 1/10). Thus, the product of both is constant.