Found in a documentation from the 90's, this circuit uses only one integrated circuit. The resistors in series with the LEDs depend on the power that can be between 5 and 12 V.
Using a pair of 741 op amps, this 90 s Radio Electronics circuit works with the previous one. The...
This circuit was found in a 1962 publication. At the time there were high voltage batteries like the...
This circuit was obtained in a 1991 Electronics Handbook. The publication no longer exists, but...