An ECL circuit with an active pull-down device, operated from a CMOS supply voltage, is described as a high-speed digital circuit for a 0.25-µm BiCMOS technology. A pair of ECL/CMOS level converters with build-in logic capability is presented for effective intermixing of ECL with CMOS circuits. Using a 2.5-V supply and a reduced-swing BiNMOS buffer, the ECL circuit has reduced power dissipation, while still providing good speed. A design example shows the implementation of complex logic by emitter and collector dottings and the selective use of ECL circuits to achieve high performance.