TF and Bode plot for Bandpass filter

[jonnybgood]

Hi,
I am trying to derive the transfer function for this bandpass filter by breaking it up into two parts, the lowpass and high pass.

I am I doing something wrong in the pdf? I simulated the ciruit to get the bod plot. However with the transfer function I derived, the maximum gain matches but there seems to be a shift of about 1 decade from one plot to another.

is it a good idea to use the logarithms are as derived in the pdf, to plot the bode plots by hand? thanks

 

[godfreyl]

The frequency response shown above looks right for the given circuit, and also agrees with the following part of your calculation, (allowing for an extra zero at lower frequency due to the fact that the gain can't drop below unity):



Sorry, but the rest of the math just gives me a headache.

is it a good idea to use the logarithms are as derived in the pdf, to plot the bode plots by hand?

If it will earn you extra marks for a university assignment, or someone's actually paying you to do it, then yes. Otherwise I wouldn't bother.

....the maximum gain matches but there seems to be a shift of about 1 decade from one plot to another.

The horizontal scale of your second Bode plot (from the calculated transfer function) is radians per second, not Hertz. I suspect if you convert the units it will agree with the first plot (from the simulation).