Found in a 1967 Electronics World, this preamplifier uses an integrated circuit from that time, difficult to obtain today. The maximum frequency is 15 kHz.
With this circuit it is possible to use a common hair dryer as a hand dryer. The circuit is timed...
This circuit was obtained from an American documentation from the 90's. Inductors are critical...
This configuration from the 1970s can be applied to modern equivalent operational amplifiers. The...