# Drawing Bode plots...

Discussion in 'Electronic Basics' started by David, Sep 24, 2007.

1. ### DavidGuest

I'm working through Sedra/Smith's Microelectronic Circuits and would like to
find a tutorial on drawing Bode plots both by hand and using computer
software.

I did see several sites discussing using MATLAB to accomplish this so the
by-hand methods are what I'm most interested in.

2. ### Stephen J. RushGuest

You mean the familiar amplitude / frequency plot? Just get 3- or 4-cycle
semi-logarithmic graph paper. If the nearest office-supply store doesn't
have it, a university bookstore certainly will. Generating a logarithmic X
scale by hand sounds really tedious. A ruler and the log function of a
calculator? Pull the slide out of a slide rule so you can use the C scale
for a ruler?

3. ### DavidGuest

Well even with log paper I notice the plots usually have curves to them...
Would you usually only plot the linear portions and then estimate the
curves?

4. ### EeyoreGuest

What's the problem ? It's a graph with frequency on the x-axis and gain on the
y-axis.

Typically, a logarithimic scale is used so as to display the wide range of
values conveniently.

In MATLAB etc, use the graphing tool.

Graham

5. ### JeffMGuest

That's so 20th Century.
Welcome to the Computer Age.
Simple technique:
1) Plot as many data points as it takes
to be confident you have the curve right.

2) Connect the dots.

6. ### Rich WebbGuest

As alternatives to Matlab, take a look at:
Scilab (free-as-in-beer; see their license regarding commercial use
(summary: okay but don't modify it)) at http://www.scilab.org/,
Octave (GNU) at http://www.gnu.org/software/octave/, and
OMatrix (not free but not too expensive) at http://www.omatrix.com/

IIRC, you can also do log-log and semilog plots with MS Excel and

My program of choice for this is Mathcad. I don't recommend it any
more, based on the rather restrictive licensing scheme they went to.
My old-but-working 2001i is just fine, thankyouverymuch.

7. ### neon

1,325
0
Oct 21, 2006
First choose your cycles for the paper 1.2,3 whatever is needed then scale your X MAX TO MIN and go at it x >>>>>> y  