We found this circuit in an English publication from the 1980s. The circuit uses current components and can be tuned for frequencies between 300 and 1500 Hz.
This simple preamplifier was published in Radio Electronics magazine in February 1958. The battery...
The sensors in this circuit are NTCs and PTCs that work in a differential way by directly...
This interesting op-amp signal generator circuit was found in a 1977 documentation. The circuit has...