Patent ID: 7123096

Claim:
An amplifier, comprising: a pair of amplifier sections coupled between a common input node and a common output node; (A) a first one of the amplifier sections having: (i) a first transistor having a first electrode, an output electrode coupled to the common output node, and a control electrode for controlling a flow of current between the first electrode and output electrode; (ii) a first bias source; (iii) a switch for coupling the control electrode of the first transistor to the first bias source to bias such first transistor to a conducting state during a relatively high power operating mode or for removing such control electrode from the first bias source to place the first transistor in a non-conducting condition during a relatively low power operating mode selectively in accordance with a control signal; and (B) a second one of the amplifier sections having: (i) a second transistor having a first electrode, an output electrode, and a control electrode for controlling a flow of current between the first electrode and the output electrode of the second transistor; (ii) a second bias source coupled to the control electrode of the second transistor to bias such second transistor to a conducting state during both the relatively high power operating mode and the relatively low power operating mode; (iii) first circuitry, coupled between the output of the second transistor device and the common output node; (iv) second circuitry coupled between the common input node and the control electrode of the second transistor device; (C) wherein one of the first circuitry and the second circuitry provides a phase lead and the other one of the first circuitry and second circuitry provides a phase lag; (D) wherein the first circuitry includes a phase shifting network providing a phase shift between the output of the second transistor and the common output node different from the phase shift between the output of the first transistor and the common output node; and (E) a DC voltage source coupled to the common output node.