A simple high pass filter can consist of a capacitor in series with a resistor or a resistor in series with an inductor. Why would I use one over the other? I also wonder the same thing about low pass filters. Do capacitive high pass filters have less energy usage or increased speed, or clearer filtering capabilities compared to inductive high pass filters?
Thank you!
Best Answer
You appear to be talking about these two variants: -
Both are equally good but you will find that for low frequencies of cut-off (such as audio) the parallel output inductor becomes too physically big compared against a series capacitor. Just try calculating a 100 Hz filter with a 1 kohm resistor.
The capacitor should have a reactance of 1000 ohms at 100 Hz hence, it has a value of 1.6 uF. The inductor also has a reactance of 1000 ohms and therefore has a value of 1.6 henries and will be bulky in comparison, have an annoying self resonant frequency in the kHz region and will cost possible 100 times more than the capacitor.
If you are thinking about a much lower impedance then things change; if R is now 10 ohms, L would be 16 mH and C would be 160 uF i.e. a less clear-cut differentiation.
Go do some math and look up inductors at distributors websites.
Exactly the same argument applies to low pass filters because the same components are used but the output for low-pass is taken across the "other" component: -