Description

The ubiquity of wireless communications is driving the need for general-purpose RF amplifiers that are applicable to many categories, from 5G systems to radio and antenna applications.

When designing an RF amplifier, the first step is to define some important parameters such as target frequency and gain factor. By selecting the optimal passive components, the transmission characteristics of the amplifier may be enhanced and improved. A well-designed layout that can transmit RF signals and the DC current to power the amplifier stage on a single line without interference or cross-talk further improves RF performance.

A key component for this interference-free operation of the transmission of mixed signals (RF and DC) is the inductor for decoupling the RF and DC supplies. In addition to the usual approach of using a standard inductor, another suitable alternative is to use a multilayer ferrite. To compare and evaluate the ferrite and inductor in this application, an evaluation board of an RF amplifier was realized and measured. This application note also includes circuit design considerations and various recommendations for achieving optimal parameters using two RF amplifier examples.

 Contents:

• Component selection with REDEXPERT
• RF gain block amplifier types in comparison
• Inductors for blocking the RF signal
• DC blocking capacitor selection
• PCB layout considerations
• Measurement setup and results