Introduction In the design of RF power amplifiers, wide-band transformers play an important role in the quality of the amplifier as they are fundamental in determining the input and output impedances, gain flatness, linearity, power efficiency and other performance characteristics. The three forms of transformers that are encountered, unbalanced-to-unbalanced (unun), balanced-to-balanced (balbal), and balanced-to-unbalanced (balun), are used in various combinations to accomplish the desired goals.