We found this circuit in an American documentation from the 80s. In it we have the way to control the amplifier gain by an input voltage.
This circuit emits a sound when a magnetic field, of a magnet, for example, approaches the sensor....
This circuit is from the 1993 Motorola Linear Interface Circuits. The source does not have to be...
This circuit is from a 1964 Electronic Design. The transistors are from that time. They can be...