Using the CA3140 integrated circuit, this switch was found in the June 1986 Radio Electronics magazine. Sensitivity adjustment is made at the trimpot in series with the sensor.
Although it is a common configuration today, this circuit was taken from an old publication. The...
This configuration was found in an English magazine from 1965. It is valid for any junction FET. The...
The circuit in the figure is an amplifier with gain 10 for alternating signals using the 741. The...