I tried to build a 555 timer using the Multisim live online (free version).
I refer to the Ben Eater's video which I believe referred to the 555 timer datasheet.
Here is my circuit and the simulation result.
All the settings are default except the output threshold of the amplifier is set as 0-5V.
The simulation is as I expected but I don't understand why the absolute output voltage of the two NOR is so much different.
- Why is the lower output voltage of the NOR gate U3 not 0?
- The higher output voltage of NOR gate U4 is 1V which is below the high threshold (2V) of the logic gate input. How can that work?
You can open my circuit in this link.