is it safe to control 8 leds using this chip, seeing the max current 74HC595 can provide is 70mA and 1 LED uses about 20mA?
This is the rating for the continuous current.If you use 6x multiplex, it's only 16.6% modulation.
At 3 volts the currents are lower than 20mA, so it can work 50% or 100%.
there are 10 to 20 factors that limit current, otherwise the IC (Arduino) would really use 3 Amps
The lowest gap, 0.5 volts, has really large increase in current. What becomes the limit then are the MOS channels, to the current distributes. They work like resistors and that's OK for them. 120 ohms, but i do not know it can change due to voltage. not a ohm resistor.
Makes no sense.