I know how to find the static voltage transfer characteristics (output low voltage, input low voltage etc) for one input gates like an inverter from the graph of Vout v Vin. My question is how do I apply this to gates with two inputs? These graphs have two curves by keeping one input constant and the fluctuating the other, and then vice versa. Would the worst-case low noise margin become the smaller input low voltage minus the larger out low voltage and the worst-case large noise margin become the smaller output high margin minus the smaller input high margin? Or would I find the noise margins as I would for one curve, and taking the smaller of the two?