A tristate buffer circuit for mixed voltage applications. The circuit is built from field effect transistors and is used as an output buffer in applications where a low voltage component needs to drive both components which are powered by the same low voltage and components which are powered by a higher voltage. The circuit uses a floating n-well technique in combination with a pass-gate network, a one-shot circuit, and a process-dependent bias voltage reference. It is particularly useful on CMOS semiconductor chips which have bus interfaces, such as local area network (LAN) protocol chips.