SO i came across an exercise question in a book
Design a two-stage “bandpass” RC ﬁlter, in which the ﬁrst stage is highpass with a breakpoint of 100 Hz, and the second stage is lowpass with a breakpoint of 10 kHz. Assume the input signal source has an impedance of 100Ω. What is the worst- case output impedance of your ﬁlter, and therefore what is the minimum recommended load impedance?
- the load impedance of each circuit is 10x higher than the output impedance
- The cut-off frequency adheres to the equation 1/RC = 2pifreq.
With that the answer to worst-case output impedance of filter is the parallel addition of R1 = 1000 ohms and R2 = 100000 ohms, which is 909 ohms approximately. This means the load impedance should be at least 909 ohms. But i have an unusual approach to combine everything and resolve it. But i am not sure why this method is wrong. Can anyone advise me on this?
Calculate overall output impedance of the entire band-pass filter circuit by replacing voltage source with a short and rearranging
By taking the worst possible output impedance based on this analysis, we will use a low frequency signal and worst possible output impedance is R1+R2? Things look quite off and i am not sure where i went wrong