Patent ID: 7276966
Filing Date: 2007-10-02
Classification: H03F,H03G

Abstract:
1. Envelope tracking apparatus for use in an RF transmitter and/or receiver circuit, comprising: an input node; a first transistor device having a control terminal in electrical communication with said input node; a resistor disposed electrically between said input node and said control terminal of said first transistor; a second transistor device in electrical communication with said first device, the first and second transistor devices each having a conduction terminal coupled to a conduction terminal of the other of the first and second transistor devices; a third transistor device in electrical communication with said first device; a fourth transistor device having a control terminal in electrical communication with said first transistor device and said third transistor device, a conduction terminal of said fourth device being in electrical communication with a control terminal of said second device and an output node; wherein when a first voltage applied to the input node is lower than a second voltage at said output node, said third and fourth transistor devices cooperate to lower said second voltage, said lowered second voltage substantially tracking said first voltage.