In addition to common mode interference immunity, the differential approach also has an inherent cancellation of even-order harmonics. Shown here is a review of the single-ended approach. A non-linear device, in this case a single-ended amplifier, is described by a power-series expansion transfer function and is supplied by a sinusoid at its input. The expansion of the power series (the equation at the bottom) reveals that a constant is tied to each frequency multiple, even and odd.