Amplitude Graphic The first characteristic of AC power is its "amplitude". Amplitude is the maximum value of current or voltage. It is represented by either of the two peaks of the since wave. This voltage level is also referred to as the peak voltage, and can be either positive or negative. Positive and negative refer only to the direction of current flow. A negative number does not mean that the voltage or current flow are less than zero, only that the current flows in the opposite direction.