Re: Circuit Analysis
Maverickmax,
The square wave consists of a funamental (50Hz), plus odd harmonics in the relative ratios of (2/Pi)*1, (2/Pi)*(1/3), (2/PI)*(1/5), etc. The purpose of the filter is to attenuate the harmonics without excessive attenuation of the fundamental. A single pole filter has a slope of 6dB/octave. An n pole filter has a slope of 6n dB/octave. So the more poles you have, the greater will be the harmonic attenuation compared to the fundamental attenuation. I don't have time to provide a complete analysis, but here is how you may procede to calculate the voltage at the junction of the two 33K Ohm resistors. Number the components R1, R2, R3, C1, C2 (left to right).Let
Z1 = R3||XC2.
Z2 = Z1 + R2
Z3 = Z2||XC1
Where
XC2 = capacitive reactance of C2 = 1/(2PI*f*22E-9), etc.
|| means "parallel combination of"
Then,
The voltage divider ratio from input to the junction of R1, R2 is given by
A = Z3/(Z3+R1)
You can now calculate the component of each harmonic of the input.
This is a lot of work. It would be a lot easier to use a circuit simulator such as SPICE.
Regards,
Kral