Methods and apparatuses are disclosed for a high speed, low power, isolated multiplexer having architecture and operation that control current flow to minimize coupling and power consumption. Multiplexer architecture may include one or more of BiCMOS components, an input disabling circuit operated to additionally disable an input circuit when it is also disabled by a selection circuit, a multiplexer disabling circuit operated to disable a multiplexer when input circuits are disabled by the selection circuit, a buffer having a buffer input disabling circuit operated to additionally disable a buffer input circuit when it is also disabled by a buffer selection circuit and a buffer disabling circuit operated to disable a buffer when the buffer input circuit is disabled by the buffer selection circuit. Any one or more of these features may be implemented to improve isolation performance. The architecture may be operated by a one-hot coding scheme.