On-chip MOS circuitry couples a communication path between an output stage amplifier and an output port and disables a circuit path between an input amplifier and the output port by creating a high impedance circuit during transmit operations. Alternatively, the circuitry opens the transmit circuit path with an isolated MOSFET and enables the second circuit path by creating an impedance matched circuit. The switch is formed within an isolated region to allow it to float with a signal to avoid breakdown. This floating MOS switch can be used for a variety of other applications in addition to its use as a transmit/receive switch even though formed on the same die as the communication circuitry.