The amplitude response is the magnitude |F (jω)|. The two lines represent in mathematics the magnitude of the frequency response as a function of the circular frequency. Graphically the magnitude of the frequency response is mostly plotted on a logarithmic scale against the logarithmic value of the circular frequency ω or against the logarithm of the circular frequency ω/ω o normalised with the natural angular frequency ω o and is called the amplitude plot (Figure A 14) (DIN 19 226).
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