Patent ID: 6967533
Filing Date: 2005-11-22
Classification: H03G

Abstract:
1. An arrangement for saving energy in a radio device transmitter, radio frequency amplifiers of which being at least a VGA and a power amplifier, which VGA comprises at least one main differential pair, total current of which being arranged to be dependent on input signal of the VGA and a collector current of one transistor of the main differential pair being output signal of the VGA, the VGA further comprising a control circuit to change mutual steering of transistors in the main differential pair so that VGA's current gain changes corresponding to changes in a gain control signal, the arrangement comprising in the VGA a bias current source controllable by said gain control signal, output of which bias current source being connected to said power amplifier to make a steady current of the power amplifier dependent on the current gain and thus transmitting power, wherein; said bias current source comprises a bias differential pair, the bases of the transistors of which are connected parallel to the bases of the transistors of the main differential pair for steering these pairs by one and the same control signal, and a current of said output of the bias current source is arranged to track in proportion collector current of the transistor of the bias current source, the base of which is parallel with the base of said one transistor of the main differential pair.