Gallium Nitride (GaN) HEMTs (High Electron Mobility Transistors) are the next generation
of RF power transistor technology that offers the unique combination of higher power, higher efficiency and wider bandwidth than competing GaAs and Si based technologies. With Nitronex’s commercial offering of GaN-on-Si products, this performance advantage is combined with the reliability, low cost and ease of use advantages of industry-standard silicon wafers.
GaN Essentials™ is a collection of application notes targeted toward designers who want to take advantage of GaN devices while avoiding many common implementation pitfalls of this new technology. Be sure to check back for updates to GaN Essentials™ and other design support material.
GaN for LDMOS Users
GaN HEMTs offer efficiency, bandwidth, and power advantages compared to Si LDMOS FETs. Making the switch to GaN involves assessing how the devices behave compared to Si LDMOS to understand what aspects of a design need to be rethought. This application note compares device behavior between the two technologies and highlights issues that are important to traditional LDMOS designers.
Substrates for GaN RF Devices
GaN is primarily offered on silicon (Si), silicon carbide (SiC), and sapphire substrates and it is sometimes difficult to understand the pros and cons of the various substrates. This application note gives an overview of GaN substrates and the advantages and disadvantages of each.
Bias Sequencing and Temperature Compensation of GaN HEMTs
HERE for the related spreadsheet
GaN HEMTs are depletion mode devices, meaning a negative gate voltage and gate-drain bias sequencing is required for proper operation. The circuits to implement these functions are well understood by GaAs FET users and can be reused by GaN users. This application note discusses proper biasing requirements and bias circuit recommendations, highlighting the mistakes most commonly made when using depletion mode devices.
Broadband Performance of GaN HEMTs
Broadband applications are the heart of today’s market for GaN RF power devices. The higher operating voltage and power density of GaN results in significant performance advantages for GaN in broadband applications. This application note shows theoretical and practical broadband matching techniques and limitations, and a methodology for modeling devices and synthesizing an output matching network. Broadband capability of GaAs FETs, Si LDMOS, and GaN HEMTs is compared and a design example with measured results using a Nitronex device is presented.
Thermal Considerations for GaN Technology
GaN HEMTs offer much higher power density than competing technologies, providing significant performance advantages in many applications. However, this also leads to a thermal challenge of removing the heat from a relatively small FET area. This application note illustrates thermal design challenges and offers measured and simulated results for various circuit board and flange mounting configurations. Recommendations are made for junction temperature limits and choosing the proper device for a given application.