AC current is current sourced or sunk during the transition between low level and high level states. This current drives a capacitive load or an inductive load. A capacitive load is, for example, a cable. An inductive load, is, for example, a device interconnect.

DC current is the current that is sourced or sunk when the generation terminals are at a static voltage. The current drives a resistive load. The following illustration of a digital waveform shows when AC or DC current is sourced or sunk.

Use the following formulas to calculate AC current:

I = C · d v d t

where I is current in amps,

C is load capacitance in farads,

dV/dt is the rate of change of the voltage level in volts/s

or

I = 1 L ∫ v t d t

where I is the current in amps,

L is the inductive loading in henrys,

V(t) is the voltage in volts as a function of time.

Use the following formula to calculate DC current:

I = V R

where I is current in amps,

V is voltage level in volts,

R is resistance in ohms.