Frequency Response of an Electrical System

This page shown an electrical system that is analogous to the mass-spring-dashpot system seen elsewhere.  (Hit start button to show animation)

The transfer function of the system is given by (with C=0.625, R=0.5, L=1, vi=input to system, vo=output):


You can see by the animation that at low frequencies the input and output are equal, and in phase.  At intermediate frequencies the system is somewhat resonant, and the output actually gets larger than the input (but there is a growing phase lag).  As frequency increases further, the output decreases.   The outline of the peaks of the output plot is similar to those in magnitude plots (the phase plot is not obvious, but it obviously starts at 0° and then decreases - if you type "ctrl +" you can zoom in to see the phase shift).  In this case, the magnitude plot would start at one (output=input) at low frequencies, it would then increase, followed by a decrease.


© Copyright 2005 to 2015 Erik Cheever    This page may be freely used for educational purposes.

Erik Cheever       Department of Engineering         Swarthmore College