Ensure the desired supply voltage is within the range specified in the Recommended Operating Conditions. The supply voltage sets the device's electrical characteristics as described in the Electrical Characteristics section.

The positive voltage supply must be capable of sourcing current equal to the total current to be sourced by all outputs of the SN74LV138A plus the maximum static supply current, I_CC, listed in the Electrical Characteristics, and any transient current required for switching. The logic device can only source as much current that is provided by the positive supply source. Be sure to not exceed the maximum total current through V_CC listed in the Absolute Maximum Ratings.

The ground must be capable of sinking current equal to the total current to be sunk by all outputs of the SN74LV138A plus the maximum supply current, I_CC, listed in the Electrical Characteristics, and any transient current required for switching. The logic device can only sink as much current that can be sunk into its ground connection. Be sure to not exceed the maximum total current through GND listed in the Absolute Maximum Ratings.

The SN74LV138A can drive a load with a total capacitance less than or equal to 50 pF while still meeting all of the data sheet specifications. Larger capacitive loads can be applied; however, it is not recommended to exceed 50 pF.

The SN74LV138A can drive a load with total resistance described by R_L ≥ V_O / I_O, with the output voltage and current defined in the Electrical Characteristics table with V_OH and V_OL. When outputting in the HIGH state, the output voltage in the equation is defined as the difference between the measured output voltage and the supply voltage at the V_CC pin.

Total power consumption can be calculated using the information provided in CMOS Power Consumption and Cpd Calculation.

Thermal increase can be calculated using the information provided in Thermal Characteristics of Standard Linear and Logic (SLL) Packages and Devices.