VDS protection for high voltage swing applications

摘要

The invention provides apparatus, methods and systems for providing voltage protection at the drain-to-source path of an output transistor. The invention discloses circuit apparatus and system giving excess voltage protection in a circuit having a voltage swing up to approximately twice the voltage capacity of a circuit output transistor. Methods of the invention disclose maintaining the source-to-drain voltage of a protection transistor coupled to the circuit output transistor below its maximum value, while also maintaining the protection transistor gate-to-source voltage below its maximum value. The drain-to-source voltage of the circuit output transistor is guarded from exceeding its maximum acceptable drain-to-source voltage value by the protection transistor. Also disclosed are methods of selecting a protection transistor and related components such that the bias of the protection transistor is adjusted in response to the circuit output.