Baseband impedance and linearization of FET circuits

Baseband impedance has been identified as having a positive or negative effect on the intermodulation distortion of microwave circuits. The effect can be assessed or utilized with the aid of previously proposed figures-of-merit. Under certain situations, intermodulation cancellation can be achieved simply by adding resistance to the bias network. The impact of baseband impedance on the performance of derivative superposition amplifiers is analyzed. A bias region was studied that exhibits a good second- and third-order intermodulation null with minimal intermodulation dependence on baseband impedance. This allows the effective use of the derivative superposition technique in baseband amplifiers, as well as giving wide-band linearization performance in RF amplifiers.