An example apparatus includes power amplification circuitry and current-level switch circuitry. The power amplification circuitry has a first input port, a second input port, and field-effect transistor (FET) circuitry, the FET circuitry to operate in a saturation mode while drawing power provided at the first input port from a first power source. The current-level switch circuitry is to sense a change in a current-level used to maintain the FET circuitry in the saturation mode and, in response to the sensed change in the current-level, to cause the power amplification circuitry to draw power provided at the second input port from a second power source while maintaining the saturation mode of the FET circuitry.