Abstract: A circuit and method for protecting a radio frequency power amplifier against peak drain voltage. A detector circuit has an input connected to a drain of a power transistor of an amplification stage of the power amplifier to detect a peak drain voltage therefrom. The detector circuit outputs a protection signal when the detected peak drain voltage exceeds a predetermined reference level. A shutdown circuit is coupled to the detector circuit and inputs the protection signal therefrom. The protection signal is used to remove a gate bias of at least one amplification stage of the power amplifier. High frequency components are used in the detector and protection circuits to immediately reduce the drain voltage from one or more of the amplification stages.

Abstract: A relay-less load driver circuit includes an FET that couples a battery to a load. A bias circuit that selectively turns the FET on during normal operation also turns the FET on in reverse-battery conditions to avoid high power dissipation by an intrinsic diode associated with the FET.