Current-mode logic

The bipolar equivalent emitter-coupled logic (ECL) operates in a contrasting fashion, still differential but with the output being taken from the emitters of the BJT transistors (rather than the collectors, which would be analogous to the drains of the FETs).

As a differential PCB-level interconnect, it is intended to transmit data at speeds between 312.5 Mbit/s and 3.125 Gbit/s across standard printed circuit boards.

[1] The transmission is point-to-point, unidirectional, and is usually terminated at the destination with 50 Ω resistors to Vcc on both differential lines.

CML is the physical layer used in DVI, HDMI and FPD-Link III video links, the interfaces between a display controller and a monitor.

Studies show that while the leakage current in conventional static CMOS circuits is becoming a major challenge in lowering the energy dissipation, good control of CML current consumption makes them a very good candidate for extremely low power use.