The poles are sometimes called the cutoff frequencies of the network. The end points of these straight-line segments projected onto the frequency axis fall on the pole and zero frequencies. Idealized Bode plots are simplified plots made up of straight-line segments. The roots of the numerator are the zeros of the function while the roots of the denominator are the poles. The first step is to find the roots of the polynomials. The function to be sketched is generally a fraction or a ratio with a numerator polynomial and a denominator polynomial. In the paragraphs that follow, we will present these rules and compare sketched straight-line approximation curves with TINA’s exact curves. Nevertheless, understanding the rules for drawing Bode plots will enhance your mastery of circuits. TINA has very advanced facilities for Bode plots. Today, few engineers draw Bode plots by hand, relying instead on computers. The horizontal scale for frequency is logarithmic. The amplitude A is presented as 20log10(A). The dependence of a complex quantity upon frequency can be represented on a complex plane (Nyquist diagram) or on real planes as separate plots of the absolute value (amplitude plot) and the phase (phase plot).īode plots use a linear vertical scale for the amplitude plot, but since dB units are used, the effect is that the vertical scale is plotted according to the logarithm of the amplitude. Most of the interesting functions of AC circuits –complex impedance, voltage transfer function, and current transfer ratio– depend on frequency.
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