A circuit with a few components quickly leads to a complicated expression for the transfer function. It is often sufficient, and of course, easier to work with approximations to the transfer function.

Let be the ratio of two polynomials

where

If one term dominates in each polynomial

Thus

We define and plot

which is a straight line on a log-log plot with integer slope.

As an example, consider our *RCL* circuit:

where and .

At low frequencies and

On a log-log plot

which has a slope of +1.

At high frequencies and

On a log-log plot

which has a slope of -1.

Tue Jul 13 16:55:15 EDT 1999