This interesting sensor for RF signals was found in an article in the June 1989 Radio Electronics magazine. It is a field strength meter with an LED bargraph indicator.
The circuit shown in the figure can be used to connect a loudspeaker to an amplifier only after...
The circuits shown below consist of diode protections against accidental polarity reversal in the supply...
This circuit was obtained from an 80's EDN. The components used are still common. The circuit can be...