Patent ID: 7486138

Claim:
An audio signal switch, comprising: a plurality of inputs; an output; and a plurality of transmission chains selectively connecting each input to the output, respectively, each transmission chain including: a bipolar first transistor, of a first type, connected to the respective input and having a base-emitter junction; a bipolar second transistor, of a second type, complementary to said first type, connected to the output; a bipolar intermediate transistor, of the second type, connected between said first and second transistors, wherein said first and second transistors are arranged in an emitter-follower circuit configuration, and said intermediate transistor is arranged to act as a diode to protect the first transistor from a large reverse voltage applied to its base-emitter junction; and a first current source coupled between a first voltage supply terminal and a first node at which the intermediate transistor is coupled to an emitter of the first transistor to maintain an operative bias condition, the intermediate transistor having a conduction path extending between the emitter of the first transistor and a second node at which the intermediate transistor is coupled to a base of the second transistor.