Schimitt-Trigger NE555

There is a simple rule "no positive feedback, no schmitt trigger". Cuz there is no hysteresis. Instead you can see this way of using a 555 as simple comparator.

@hurz Are you saying there IS or IS NOT hysteresis in this circuit?

I ask this because i believe there IS positive feedback AND zero hysteresis in the interaction between the gates. Of course i could be wrong. :-)

Just see my 555 timer circuit

@UncleRick, there is no feedback from output to input. So there is also no hysteresis. Were do you see an impact from out to in? All analoge signal pathes are forward.

With the exception of one gate back to the input of the other gate. This makes for a very fast transition at the output. That same feature has the same switch-over point (going up or down), so no hysteresis in the output as well. As always, i could be wrong. But that is what i see. :-)

Hoo boy... I hate to eat my own words, but here goes. Firstly I am not at all sure I am getting the operation of the New Scope Trace. It appears to me that two different signals can be displayed, with a common sweep of a third signal. If that is true... Open this circuit, activate the trace of the second gate's output. (Orange) Then go to the sine input and change it's trace to horizontal. I believe what is now displayed is a very small hysteresis in the two gate outputs. That is IF I understand the operation of this new scope trace. // Also, it appears that the two op-amps play no part in the oscillation, except to provide the necessary biasing to trigger (or enable) the oscillator. Is that correct? Mind you there is an amount of guessing in my thinking going on here. ;-)

With the parametric scope you get just a hysteresis because of limited number of points sampled for a graph. Go closer, less voltage in peak and place additional 3kHz ac source to slow down simulation. The "hysteresis" will disapear

Another effect, the RC input network is a "phaseshifter" together with the comparator it looks like a schmitt trigger hysteresis but it is not! It will change over frequency and input peak voltage.

@hurz Hi!! Is there a location where a person can find some instructional documentation for this new scope tracing? As I mentioned, it is all a guessing game for me at this point. I have used (for instance) Techtronix scopes since 1969, but this trace is new to me. Without proper instructions, I might be causing myself to see things that are untrue.

I don't know about any manuel for EC, just the example tab. However, you for sure know what a xy plotter does, right? Just put two voltages on your scope (or currents, or current and voltage) but just two. Now select one of them you would like to have on X axis. The second one is automatically Y. Voila! Now you have a plot f(x)=y

Thanks hurz! That confirms what I was suspecting. My example above put two signals on the Y axis and one on the X axis, acting like a scope sweep. After all , isn't that just what a scope is? Vertical = Y axis. Horizontal sweep = X axis. In my example it served to directly compare the two signals from the output of each gate, and swept by the sine signal from the input. Thanks much! You really cleared it up by showing me the X-Y plotter as similar. ;-)

Things came to me a lot easier 35 years ago.