Flipflop stationary state

Two MOSFET inverters are coupled to a flipflop, see Figure 1. The equations describe the stationary state. Because of the two identical inverters this problem has a natural symmetry, and we may expect bifurcation. In fact there is a bifurcation for $\lambda_0\approx 1.192$, see Figure 2.

For the stationary states we have $y_1\approx y_2$ and $y_3\approx y_4$. For $\lambda=5$ there are three stationary states with y1=5, y3=0.16087 (stable) y1=y3=1.88577 (unstable) y1=0.16087, y3=5 (stable).

The dynamical behavior for $\lambda=5$ is indicated in the phase diagram of Figure 3. Some trajectories are shown that approach the stable states.

The model is based on material kindly delivered by Siemens, München.

Figure 1
Two identical inverters coupled to a flipflop

Figure 2
Bifurcation diagram y1 versus $\lambda$.

Figure 3
(y1,y3) phase diagram for $\lambda=5$.

Figure 4
(y1,y3) phase diagram for $\lambda=1$.

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