RF Gain Block Amplifier with Integrated Multilayer Ferrite for Broadband Operation

The constantly growing demand for devices with wireless communication ports is pushing devices to operate at increased bandwidths over a wide frequency range. It is becoming increasingly important to ensure every design engineer has an all-purpose radio frequency (RF) amplifier at hand.It is possible to design a versatile RF amplifier that will fit into many categories, for example from 5G systems to radio and antenna equipment applications. The standard process when changing the operating frequency range of an existing RF amplifier usually requires a new design that includes extensive simulation and a new circuit board. However, this may not be necessary, depending whether the new frequency range is far from the original.

A key component for this smooth operation of the transmission of mixed-signals (RF and DC) lies in the RF bias inductor for decoupling the RF from the DC supply. Apart from the usual practice of using a standard inductor, another suitable alternative is the use of a multi-layer ferrite. To compare and evaluate the multi-layer ferrite and the inductor in this application, an evaluation board of an RF amplifier is created to verify the outcome with measurements. This application note describes circuit design considerations and compares alternative recommendations to achieve optimum parameters through two RF amplifier examples.