Found in American documentation from the 90s, this circuit is ideal for wearables and can be powered by voltages that depend on the number of LEDs.
Found in a September 1972 Radio Electronics magazine, this circuit uses RCA's CA3020, a...
This circuit was obtained in a documentation from the 90's. Several common operational amplifiers...
This 1970 General Electric circuit is an equivalent configuration to the previous one with PNP...