This circuit was found in a 1993 Electronics Hobbyst Handbook. The circuit operates in the FM range. The coil has 4 turns of 24 or 26 wire in a coreless form 0.5 cm diameter.
We found this circuit with 5.3V zener in a Philips publication from the 60s. The op amp could be a...
This circuit provides signals in phase with the input and with the phase inverted. The circuit was...
This sensor with two transistors triggers a relay according to the supply voltage. The power...