The absolute value of Ao(ω) becomes linear after ω > 3.3 ω c. To determine the absolute value, we need to write the square-root of the sum of the real part squared and the imaginary part squared.Īs ω increases, the ratio ω/ω c becomes quickly large, so 1 can be neglected. A particular op amp, characterized by a gainbandwidth product of 20 MHz, is operated with a closed-loop gain of +100 V/V.
The graph shows the absolute value of Ao(ω). Let’s multiply the function with the conjugate of 1+jω/ω c. Equation 1 is a complex number, so we need to apply some complex numbers transformation to find its absolute value. We can prove that the gain bandwidth product is constant by first finding the absolute value of the gain and then multiply it by ω. I used the parameter stepping function in TINA, varying the dominate pole to. For final simulations, you should use the macro-model for the op amp you select. With these results you might decide that a GBW less than 100MHz could be satisfactory. The amplitude decreases as the frequency increases showing a constant gain-bandwidth product. I simulated the design using the three gain-bandwidths shown in figure 2, 5MHz, 10MHz and 100MHz. This means that the amplitude of a signal that goes through this op amp decreases 10 times for each frequency decade. This is a one pole system, therefore it drops constantly at 20 dB/decade after the cutoff frequency, as the graph shows.
Where ω is the variable, or the function argument, which is 2 π times frequency, ω c is the op amp cutoff frequency, or 2 π times f c, Aol is the open-loop gain at DC, and j is the imaginary unit. FYI the gain is the 'noise gain' which is the non. 'Gain bandwidth product' refers to what Georacer mentioned, that voltage feedback opamps follow a basic rule: Bandwidth of closed loop op amp GBP / Gain of closed loop op amp. Also, in that article, the mathematical expression of the graph is shown as My understanding is that they are the same number but have a very subtle difference in definition.
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