Question

What makes a active high pass filter different from an active low pass filter? How are they set up different in a circuit?

Answer 1

An active highpass filter blocks all the frequencies that are below the cut-off frequency and allows all the higher frequencies to pass .

To the basic RC highpass filter circuit, an operational amplifier is added to enhance the amplification and the control of gain factor as shown in figure 1.

Similarly,

An active lowpass filter blocks all the frequencies that are above the cut-off frequency and allows all the lower frequencies to pass . The difference from basic RC lowpass circuit is again the addition of the operational amplifier at the end of the circuit as shown in figure 2.