We found this circuit in the September 1992 issue of Radio Electronics magazine. It can be triggered by any signal above ½ Vcc, where Vcc is the supply voltage.
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...