This circuit was obtained from the February 1992 Radio Electronics magazine. In it, a bar of 4 LEDs flashes continuously at a speed given by C1 and the setting of R3.
Using a voltage comparator, we find this AND gate on a Popular Electronics from the 90s. The...
This crystal oscillator circuit is indicated for use as a frequency reference in the calibration...
Any operational amplifier can be used in this circuit. The 741 is the most common. Power supply must...