Patent ID: 7332969

Claim:
A power amplifier circuit having a protection circuit comprising: a first power transistor provided in a first amplifier ( 2 A); a second power transistor provided in a second amplifier ( 2 B); a bias block ( 4 ) operable to provide a bias signal to said first and second amplifiers; a protection switch ( 7 A) provided in a path for sending the bias signal; a protection switch block ( 71 ) operable to provide a control signal to the protection switch ( 7 A); and an output offset protection circuit ( 8 ) operable to provide a cutoff signal (Sc) which causes the generation of said control signal, said output offset protection circuit ( 8 ) comprising: a first temperature sense transistor (Q 1 ) located near said first power transistor to generate a first temperature sense signal when said first power transistor is heated above a predetermined temperature; a second temperature sense transistor (Q 2 ) located near said second power transistor to generate a second temperature sense signal when said second power transistor is heated above predetermined temperature; and a cutoff block ( 83 ) for generating a cutoff signal (Sc) when at least one of said first and second temperature sense transistors generates at least one of said first and second temperature sense signals.