The L1 coil is formed by 4 turns of wire 20 in the form of 0.5 to 0.6 cm without core. The circuit is from an 80's documentation. The range reaches a few tens of meters.
With the CMOS circuit shown, rectangular signals up to a few megahertz can have their frequency divided...
This circuit, found in a publication of the year 1968, uses a MOSFET at the input to increase...
The operational amplifier of this circuit is not very common today, because we removed the circuit...