Input buffer with CMOS driver gate current control enabling selectable PCL, GTL, or PECL compatibility

摘要

An input/output buffer is provided which can be used to make an integrated circuit selectively compatible with one of a number of interface types, such as PCI, GTL, PECL, ECL and SSTI. The input buffer portion includes a first pair of CMOS transistors for driving the output (OUT) between the VSS and VDD rails similar to CMOS logic. Switching circuitry includes transistors which drive gates of the CMOS transistors to set the output (OUT) with a current level and a voltage level depending on a desired output drive current and voltage.