XICOR X9258T, 9250T

One of the most important aspects of PA design is the biasing network. It is important for the bias network to reject RF power. Using high impedance sources where possible accomplishes this. Where low impedance sources are used, it is imperative to maintain a good decoupling regime, to maximize the transistor’s performance.At the FET drain (GaAs or LDMOS), it is necessary to use a low impedance bias supply. For transistors not biased class A, the current versus output power characteristic is dynamic, and any residual power supply impedance will cause amplitude modulation of the drain voltage.