This circuit is from an ancient American documentation. The integrated circuit is 741 and the power supply must be symmetrical. The passing band is centered at 1 kHz.
Found in documentation from the 1980s, this amplifier uses an integrated circuit from the time....
The purpose of this circuit is to monitor the operation of an alternator in cars with a 12 V...
High selectivity filters can be obtained by combining same frequency crystals in series as shown...