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I simulated the 555 as Astable Multivibrator example applying a VCC of 4V and I still got vout at 5 V... Similar results whatever vcc...

Furthermore: I swept VCC, but pressing "simulate" I got simulated only the circuit with vcc having the first value of the sweep... How can I see the results for the other values of vcc?

Thanks in advance, CU, Elia

Can you share your circuit?

As with all digital elements in CircuitLab, the digital output pin of the 555 timer currently has a 5V output for high regardless of what's connected to the VCC pin. This is a simplification that allows the simulator to handle mixed-mode circuits.

We may provide other digital modes in the future, but the fact is that digital simulation (integrated within an analog simulator) is hard, and choosing sensible defaults makes mixed-mode simulation reasonable to work with.

Not sure about the sweep issue -- as rkuris says, share your circuit so we can take a look! :)

I just drew one up and found the same problem! Apparently there is a bug in the 555 timer.

Hi mrobbins & rkuris, thanks a lot fo you answers! I made public the small circuit "555_Astable_Multivibrator_sweepVCC"... as you can see, nothing really special: but with it you can try to sweep vdd5 and give me a feedback if you get my same results (only the first value taken for only one simulation...).

To mrobbins: special thanks to your prompt answer: I understand your explanation perfectly, but maybe my post will trigger a further development... maybe you simply need to introduce a a2real converter at the VCC input instead of a2d beeing therefore capable to recognize different vcc arranging accordingly the high level of the outputs...

Ciao!