Method and apparatus for providing a low voltage level shift

A wideband level shift circuit (200) used with low voltage ECL or CML topologies. includes a sub-Vbe voltage reference (201) whose output voltage is offset some fraction of a diode voltage drop below a supply voltage, where the fraction is held at a constant value as the diode voltage varies with temperature. A comparator circuit (203) is attached to the reference voltage circuit (201) as well as to a current sourcing transistor and differential buffer circuit (205). The comparator circuit (203) maintains the DC potential at the output of a current sourcing transistor so that the common-mode DC level of the output signal from a differential buffer is shifted down by a fraction of a diode drop from the common-mode DC level of a wideband AC input signal. The shift circuit (200) offers the advantages of a fraction of a diode DC voltage drop with little loss of AC signal bandwidth for circuits operating from low supply voltages.