Apparatuses and methods for diffusion sensing are disclosed. In one embodiment, an apparatus includes a complimentary metal oxide semiconductor (CMOS) switch and a switch sense block. The switch includes a gate, a drain, a source, and a well. The source and drain are formed in the well. The gate is formed adjacent the well between the source and drain, and the source is configured to receive a bias voltage from a power amplifier. The switch sense block is configured to measure a signal indicative of the voltage of at least one of the source or drain voltage of the switch and to generate an output signal based on the measurement.