This circuit was found in a Radio Electronics from April 1990. The circuit has 5 equalization bands given by the capacitors used.
Found in a 1966 documentation, this “coin finder” uses components from the era operating at 2.1...
This circuit is from a documentation on the MC1539 from Motorola and may, however, be implemented...
The 747 is an old operational amplifier, but the configuration applies to modern operatives. In...