Standard CMOS inputs are high impedance and are typically modeled as a resistor in parallel with the input capacitance given in the . The worst case resistance is calculated with the maximum input voltage, given in the , and the maximum input leakage current, given in the , using ohm's law (R = V ÷ I).

Signals applied to the inputs need to have fast edge rates, as defined by Δt/Δv in to avoid excessive current consumption and oscillations. If a slow or noisy input signal is required, a device with a Schmitt-trigger input should be used to condition the input signal prior to the standard CMOS input.