For OPAM, LM741 IC is used. The LM741 is a general purpose OPAM (operational amplifier) with a low input impedance (mega ohm) as compared to FET OPAM. The FET OPAM has a high input impedance in Giga ohms. The output impedance of 741 should be ideally zero but it is usually about 75 ohms. The maximum supply current of 741 IC is about 2.8 mA with a supply voltage up to +/- 18V.
This is the second order called key band pass filter. This filter only passes the frequency which is in its cut off frequency range. The band pass filter has two cut off frequencies, one is lower cut off and another one is upper cut off frequency. The center frequency and bandwidth of the filter decide the lower and upper cut off frequencies as shown in frequency curve below –