This high input impedance circuit is suggested by Motorola's 1993 Linear Interface ICs. The power supply must be symmetrical. The circuit has a differential input.
This circuit, to control air conditioning systems, was found in July 1984 Radio Electronics...
Using bipolar, FETs and unijunction this long-lasting timer can reach 10 hours with good quality...
We found this circuit in an old American documentation (80's). The circuit generates sine signals...