The authors describe the optimal use of a printed-circuit board transformer with minimum power consumption. The proposed transformer is much smaller than a standard pulse transformer and is suitable for both signal and energy transfer. It can be operated in the megaHertz frequency range. With the use of modulation/demodulation circuits, it can be used for digital signal transmission over a wide frequency range from DC to ~300 kHz. The proposal can replace core-based transformers in many low-power applications.