Schmitt Trigger design
You are doing something wrong. Are you doing a DC sweep?

When the opamp is in negative saturation, the opamp will switch states when

$$V_\mathrm{in-} \frac{10}{14} &gt; V_\mathrm{ref}.$$

When the opamp is in positive saturation, the opamp will switch states when

$$V_\mathrm{in+} + (V_\mathrm{cc} - V_\mathrm{in+}) \frac{4}{14} &lt; V_\mathrm{ref}.$$

Substituting yields \$V_\mathrm{in-} &gt; 3.5\$ and \$V_\mathrm{in+} &lt; 1.5\$.

Here is the circuit and the time domain simulation results.







simulate this circuit &ndash; Schematic created using CircuitLab