Abstract: A transmission line balun transformer for providing a single ended output signal from a pair of differential input signals includes two transmission line signal couplers. The couplers are individually designed to be relatively loosely coupled devices, i.e. having a coupling factor greater than 3 dB, but are coupled together with proper phase relationships so as to achieve a relatively tighter composite coupling characteristic in the order of 3 dB, thereby resulting in an increase in bandwidth.

Abstract: An apparatus and method is provided that uses a simple voltage ratio technique to supply specific voltages to a voltage variable attenuator, and the gates of a GaAs RF power amplifier in order to control the efficiency of the amplifier. The output of the power amplifier is sampled and then fed back to the variable voltage attenuator as a control signal. A ratio portion of the control signal is then used to control the gate biases of the power amplifier. When the power requirements are less than maximum, the voltage ratio will become more negative, resulting in less current. As the RF output increases, the voltage ratio will become more positive. Therefore, as the DC voltage varies, the power amplifier's output power will vary accordingly providing the desired output power with enhanced efficiency.