BUG REPORT: high level voltage at OUTPUT pin of CL 555 timer model does not track +ve supply.

The high level voltage at the OUTPUT pin of the CL 555 timer model does not track the vcc supply.

This is incorrect and can be misleading.

by signality
December 12, 2012

In addition, the output voltage drop vs. current sourced or sinked does not match the 555 spec sheet well, even for Vcc = +5V.

by magicsmoke51
January 21, 2013

Indeed, there is a big problem with the "internal source" in the 555. In the circuit https://www.circuitlab.com/circuit/8ymg74/555-monostable/ I provide a 12 V source and the output only goes to 5V, not close to 12 V as it should according to specs and my experiments with an LM555.

by carlos1w
January 29, 2013

Update: it looks like CL have fixed the thresholds problem in that the upper and lower thresholds in their 555 model now track 2*VCC/3 and VCC/3 respectively.

However V(output) still does not track VCC!

The CL 555 model in my example circuit above also still does not run at VCC = 10V.


by signality
June 12, 2013

Hello everyone,

It is July 2016 and I am still experiencing the same problems:

  • V(output) = 5V even for Vcc = 9V.
  • resetbar seems to be switching on immediately on any non-zero voltage no matter how small

The things that are working correctly now:

  • The 1/3 and 2/3 threshold voltages seem to be correct now. At least my 9V circuit is functioning properly.

Is it something that is intended to be fixed? Thanks!

by Akh
July 13, 2016

Still nothing... =/

by GabrielPauka
August 17, 2016

Having the same issue here.

by Pyroteknikid
August 20, 2016

Still having this issue 9 years after it was originally reported.

by awushensky
July 27, 2021

Post a Reply

Please sign in or create an account to comment.

Go Ad-Free. Activate your CircuitLab membership. No more ads. Save unlimited circuits. Run unlimited simulations.

About CircuitLab

CircuitLab is an in-browser schematic capture and circuit simulation software tool to help you rapidly design and analyze analog and digital electronics systems.