TTL-Compatible CMOS inputs are high impedance and are typically modeled as a resistor from the input to ground in parallel with the input capacitance given in the GUID-404108F1-8DE3-4781-900D-294BAE4314A4.html#GUID-404108F1-8DE3-4781-900D-294BAE4314A4. The worst case resistance is calculated with the maximum input voltage, given in the GUID-DD23330B-12CB-4826-8541-805FA5913F68.html#GUID-DD23330B-12CB-4826-8541-805FA5913F68, and the maximum input leakage current, given in the GUID-404108F1-8DE3-4781-900D-294BAE4314A4.html#GUID-404108F1-8DE3-4781-900D-294BAE4314A4, using ohm's law (R = V ÷ I).

Signals applied to the inputs need to have fast edge rates, as defined by Δt/Δv in the GUID-5A4D84AD-AFF3-4EF2-AFBB-CA44234D5D5C.html#GUID-5A4D84AD-AFF3-4EF2-AFBB-CA44234D5D5C 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 TTL-compatible CMOS input.

TTL-Compatible CMOS inputs have a lower threshold voltage than standard CMOS inputs to allow for compatibility with older bipolar logic devices. See the GUID-5A4D84AD-AFF3-4EF2-AFBB-CA44234D5D5C.html#GUID-5A4D84AD-AFF3-4EF2-AFBB-CA44234D5D5C for the valid input voltages for the CD74HCT10.