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Either I'm making some foolish newbie error, or 555 output appears to be clamped to 5V for any Vcc in the range 3.3V .. 24V. This confuses me greatly.

Exactly which which 555 part is modeled by the simulator's 555 timer, and with what characteristics?

There are a few 555 ICs that limit output to 5V, but most should deliver Vcc - ~1.7V which for my 12V circuit should be 10.3V or so. But I'm getting 5V.

Example circuit:

https://www.circuitlab.com/editor/#?id=2g9m6c42c954

If I double the supply voltage to 24V I still get 5V out. If I halve the supply voltage to 6V I still get 5V out.

Even more astonishing if I drop the supply voltage to 3.3V I still get 5V out, and over a long enough interval that I doubt it's just a cap discharging.

I'm trying to use a 555 to drive an IRF540 as a more convenient way to actively drive the gate high and low so I don't have to deal with this mess:

https://www.circuitlab.com/circuit/2g9m6c42c954/mosfet-led-strip-switching-with-3_3v-control-active_active/

Oops wrong example link. That should've been https://www.circuitlab.com/circuit/z888gr27326n/mosfet-led-strip-switching-with-3_3v-control-using-555-timer/

Also posted on stackexchange

Anybody? Is the 555 in CircuitLab b0rked? Or am I doing something stupid?