Found in an American 1980s documentation, this circuit compares signals from two TTL sources, providing an output that depends on the frequency difference. The circuit can be used as a shield.
This high-performance circuit was found in the 1982 SGS Linear Integrated Circuits Manual. The...
This circuit was found in Radio Electronics magazine from the 90's. The circuit is for small NiCad...
The circuit in the figure is a comparator for negative voltages, and a pair of polarization...