This simple circuit can work with either 4.5 V or 6 or 9 V if a 1k resistor is added in series with the set of LEDs. The circuit is from an old French publication.
In this circuit of the 80's components of the time are used. The circuit controls a direct current...
This is the basic operational amplifier configuration for gain 10. R2 can be changed to other...
The CMOS 4046 integrated circuit is not very common today, consisting of a very efficient PLL for...