Next: Bode Plots
Up: Low Frequency Brute Force
Previous: Low Frequency Brute Force
To understand the effects of the capacitors, it is often
useful to re-arrange equation (4.5)
in the following form:
| |
(71) |
The first term in the parentheses of
equation (4.6)
represents the midband gain, the second term represents the high
pass filter at the input, and the third term comes from the high
pass filter at the output.
In electronics, it is useful to write polynomial expressions like those in
equation (4.6) in the notation of
what is commonly known as poles and zeros.
If we define
zeros as z1=0 and z2=0, and poles as
and
, then equation (4.7) can
again be expressed as:
| |
(72) |
As can be seen from equation (4.7), the zeros are the constants
in each factor of the form (s-z) found in the numerator of the
equation. The poles, on the other hand, are the
constants
in each factor of the form (s-p) found in the denominator.
The overall equation for
is called the transfer function.
The poles and zeros are important because they indicate the
angular frequencies where changes in the transfer function
occur.
In the notation of poles and zeros, we describe equation (4.7)
as a second order transfer function
with zeros z1=0, z2=0, and poles
,
.
Next: Bode Plots
Up: Low Frequency Brute Force
Previous: Low Frequency Brute Force
Neil Goldsman
10/23/1998