when the closed loop gain crosses 0 dB or 1 V/V).

Where, BW(f_unity) represents 'Closed Loop Bandwidth' at unity gain cross over frequency (i.e. Note: the gain-bandwidth product is only valid if the Op Amp's 'Open Loop Gain' has a single dominant pole.Īnother relevant concept is the Unity Gain Bandwidth, UGBW, can be defined as: BW_CL represents 'Closed Loop Bandwidth'.Īnother way to look at this is that the 'Closed Loop Bandwith' of your Op Amp will be the GBWP divided by your 'Closed Loop Gain', that is:.A_CL represents the 'Closed Loop Voltage Gain'.I think his point is that this is not a correct expression, which is what is explored in the Wikipedia article, again, the GBWP is defined by the Closed Loop Gain no the 'Open Loop Gain'.ĭuring the ret of his calculations Ghar expands on the frequency dependency of the 'Closed Loop Gain' and its relationship with the 'Open Loop Gain' and 'Loop Gain'īelow a graphical summary of of said relationship: GBP = A_0 w_o doesn't equal unity frequency unless A0^2 > 1 'However, reading Ghar's post makes me confused.' 'The wikipedia proves gain-bandwidth product constant for open-loop opamp while Ghar proved for closed loop opamp.' The dotted lines show you that for different 'Closed Loop Gains' and the GBPW product will be the same, as long as there is a single dominant pole AND a constant -20 dB/decade slope. What the Wikipedia article is trying to convey can be seen graphically in the following figure, the 'Open Loop Gain' plot of a system with a single dominant pole: The so called 'proof' itself is wrong simply because they are using the Open Loop Gain to calculate it, and that is not the definition of GBWP, in addition to several unexplained simplifications (see appendix for details). On x-axis we have frequency and on y-axis we have ratio of output power to input power. Could you please tell me that if the wikipedia proof is wrong? I don't see any thing wrong with it. Answer: Say you have a low pass active filter it will have an output response similar to the one given below.

Gain bandwidth product