What's the result of this circuit

Question

schematic

^{simulate this circuit – Schematic created using CircuitLab}

Int the above schematic I tried to calculate the what the end product would be.
So I considered Input as A and Output as B.

. is and, + is or and ' is not
(A.B)'= B
=> A' + B' = B

Here if B is 1, A has to be 0
but if B is 0 then B' becomes 1 making the equation nonsensical
(Is there a reason why the simulation is showing 0?)

Is this a digital simulation or an analog simulation aware of the actual construction of the gates? — nanofarad, Sep 02 '21 at 14:47
It's a digital simulation. I just want to see how to breakdown this logic — Saphereye, Sep 02 '21 at 14:49
A digital simulation cannot accommodate this behavior because it is not well-described using digital principles alone. Depending on the exact analog behavior of both gates, you've built either an inverting amplifier in feedback with enable, or a ring oscillator with enable, or some other pathological behavior. — nanofarad, Sep 02 '21 at 14:53
you are right, but what you are not taking into account is the timely behavior of the model. in your design, think of A as an enable signal, since if A is 0, output is always high but if it's 1, lets say output initially is 0, after the time it takes for the signal to go thorough AND and inverter, output then becomes 1, and then 0, and 1 again, and so on — NeuroEng, Sep 02 '21 at 14:59
Good question. The same question, a different tone, was here on Engineering — jay, Sep 02 '21 at 15:48

hacktastical · Answer 1 · 2021-09-02T15:33:53.717

What you have is a gated oscillator: the output will feed back the input, which changes the output state (after a time), and it does this over and over until the other AND input is brought low. This is a useful circuit for some purposes (like PLLs or clock generators) but as a logic element it doesn’t make sense.

Digital simulators will show this behavior if they model gate delays, with the frequency being determined by the gate unit delays. An analog sim will show this oscillation (try it in Falstad for example.)

This oscillation comes up with a circuit commonly referred to as a ‘JK flip flop’ that is actually a JK latch: when both J and K inputs are high, it oscillates when the ‘clock’ (actually enable) is high. More about this here: JK latch, possible Ben Eater error?

What's the result of this circuit

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