Patent ID: 6991367

Claim:
An amplifier circuit having a transistor for amplifying a radio frequency signal fed thereto, such amplified signal being coupled to a load, such amplifier comprising: (A) a circuit for determining temperature of the transistor, comprising: (a) a semiconductor substrate having thereon the transistor; (b) a bridge circuit comprising: (i) a first thermal sensitive device disposed in thermal contact with an electrode of the transistor, such first thermal sensitive device having a pair of terminals, a first one of the pair of terminals being connected to a first node and a second one of the pair of terminals being connected to a second node; (ii) a second thermal sensitive device disposed in thermal contact with the electrode of the transistor, such second thermal sensitive device having a pair of terminals, a first one of the pair of terminals being connected to a third node and a second one of the pair of terminals being connected to a fourth node; (iii) a third thermal sensitive device disposed in thermal contact with the substrate, such third thermal sensitive device having a pair of terminals, a first one of the pair of terminals being connected to the second node and a second one of the pair of terminals being connected to the fourth node; (iv) a fourth thermal sensitive device disposed in thermal contact with the substrate, such fourth thermal sensitive device having a pair of terminals, a first one of the pair of terminals being connected to the first node and a second one of the pair of terminals being connected to the third node; (v) a voltage source providing a voltage potential between the first node and the fourth node; (vi) an output provided by the second node and the third node; (B) a tuning circuit coupled between an output electrode of the transistor and the load, such tuning circuit having a tunable element controlled by a control signal fed to such tunable element; (C) an electrical device coupled between the voltage source and the transistor for providing a measure of power fed to the transistor; and (D) a processor coupled to the electrical device and to output provided by the second node and the third node for producing the control signal.