Frequently Asked Questions

eGaN® Devices in Circuits

EPC’s eGaN® FETs and ICs will displace their silicon counterparts over the next few years due to superior performance and affordable costs. EPC has published several application notes and white papers on using these high-performance power devices which can be found on the Design Support page. EPC has also authored multiple textbooks that can be purchased at Amazon.com or through EPC’s web site.

Titles include:

GaN Transistors for Efficient Power Conversion
Wireless Power Handbook

We also have a series of video presentations showing how to use and applications for eGaN FETs.

Generally, the eGaN FET should be treated as any other MOSFET, keeping in mind that it does have the capability of higher performance operation because of its relatively low total gate charge (Qg) and small CRSS. Some general guidelines:

  • Drive the gate with 5 V, keep max gate voltage below 5.5 V. There are several ICs available to make this task easy.
  • Minimize gate source circuit impedance. It is advisable keep the gate source loop as small as possible, even at the cost of longer paths in drain circuit.
  • Use a low impedance driver
  • There are driver IC’s developed to optimize the performance of eGaN FETs in circuit. For a list of current available eGaN FET optimized IC’s please see the eGaN Drivers and Controllers page.

The “Using Enhancement Mode GaN-on-Silicon Power FETs application note, has further information. In addition, land pad layouts that minimize inductance can be found on all EPC data sheets on the Product Selector Guide for eGaN FETs and ICs page. Chapter 3 of the book titled, “GaN Transistors for Efficient Power Conversion” covers this topic in detail. Layout techniques to minimize switching time and voltage overshoot can be found in the white paper Impact of Parasitics on Performance and the white paper Optimizing PCB Layout. There is also a video that you can review at How to GaN 06: Design Basics – Layout.

eGaN devices have a very low temperature coefficient for their threshold voltage. This gives the user added safety margin despite the lower threshold voltages at room temperature. The Miller Capacitance, CGD of EPC eGaN devices is also very low, hence the switching speed is quite high; it can be turned off in a few nano seconds. In order to avoid dv/dt turn-on, it is critical to have very low impedance in the gate-source circuit as well as a low impedance pull down for the gate circuit. There are available gate drivers designed specifically for eGaN devices that will take care of many of these requirements. A list of GaN compatible drivers and controllers can be found on the eGaN Drivers and Controllers page. For more tips on driving eGaN FETs, see eGaN FET Drivers and Layout Considerations.

It should also be noted that eGaN devices have a very low temperature coefficient for their threshold voltage. This gives the user added safety margin despite the lower threshold voltages at room temperature. The ratios of CGD to CGS are quite good in holding the device off under a dV/dt condition. This is a capacitive divider, so care must be taken in the gate drive to have a low resistance turn off and good layout such that inductance is minimized in the turn off loop to keep the effective impedance low. The magnitude will depend on dV/dt and voltage. Gate drivers designed specifically for eGaN FETs are listed on the eGaN Drivers and Controllers page

eGaN Devices are positive temperature coefficient devices and are good candidates for parallel operation. However, since these devices can switch up to 10x faster than standard silicon FETs, special care must be taken in the layout and driving aspects of this configuration. EPC has written aan application note identifying the best paralleling configuration. Please refer to the Effectively Paralleling Gallium Nitride Transistors for High Current and High Frequency Applications application note.

EPC has conducted electro-thermal experiments using our standard development boards, EPC9002C and EPC9006C, to evaluate the impact of providing top side die cooling. A small heatsink was mounted on top of the EPC devices using a thermal interface material, that also provided electrical isolation, and tests were conducted to determine the impact on the temperature of the devices when operated under increased power loss conditions. Details of the experimental setup and results can be found in the white papereGaN FETs for Envelope Tracking and in the videoHow to GaN 03: Design Example – Hard-Switching Applications.

EPC’s eGaN FETs and ICs are superb for wireless charging and wireless power applications! Wireless power is ready to be incorporated into our daily lives. Transmitters can be placed in furniture, walls, floors, to efficiently and economically power or charge our electronic and electrical devices. There are a couple of popular wireless power architectures available in the market. The capability of eGaN FETs and ICs to operate efficiently in the multi-MHz range offers a unique opportunity; enabling large surface area transmission, spatial freedom for placement of receiving devices, and the ability to power multiple devices simultaneously. We have many resources discussing how to apply eGaN power devices for wireless power. Please visit the Wireless Power page for more information.

EPC’s eGaN FETs and ICs are superb for applications in RF power amplifiers – especially in envelope tracking. Today Power Amplifiers (PA) commonly use depletion mode GaN FETs since they are capable of switching at several hundreds of MHz. The typical efficiency of PA is in the 20 to 30% since the Peak to Average Ratio (PAR) is very low. With the emerging technologies like LTE for wireless, the demand for power is going up and several new techniques like Envelope Tracking (ET) – where the voltage feeding the power amplifier is modulated corresponding the modulating signal – are evolving to improve the efficiency of PAs. eGaN FETs and ICs can switch at several tens of MHz at the voltage of interest in PAs, enabling the adoption of efficient Envelope Tracking architectures in these applications for improving the efficiencies. See the Envelope Tracking page more information on eGaN FETs and ICs in Envelope Tracking applications.

In Class D audio systems, the audio performance is impacted by the FET characteristics. GaN FETs enable higher fidelity Class D Audio Amplifiers.

The low on resistance and low capacitance of the eGaN FET enables high efficiency and lowers open loop impedance for low Transient Intermodulation Distortion (T-IMD). The fast switching capability and zero reverse recovery charge enable higher output linearity and low cross over distortion for lower Total Harmonic Distortion (THD).

For more information on eGaN FETs in Class-D audio amplifier applications and a list of available reference designs visit the Class D Audio Amplifiers page.

eGaN FETs have a distinct advantage over silicon MOSFETS in hard switching applications because of the reduction of two key parameters – QGD and QRR,both of which have little impact in resonant and soft-switching converters. It has been demonstrated that eGaN FETs can also provide significant improvements in resonant and soft-switching applications when compared to Si MOSFETs by offering reduced output charge, QOSS, and gate charge, QG.

For more information, please refer to the white paper eGaN FETs in High Frequency Resonant Converters.

Using eGaN FETs and ICs in these designs reduces switching losses resulting in higher efficiency and/or higher switching frequency. Inverter size and cost are dominated by thermal management and the passive elements used for bulk energy storage and filtering. Using eGaN FETs and ICs to increase efficiency and/or increase switching frequency can reduce the overall size and cost of the power inverter. For more information visit the Power Inverter Applications page.

The use of LEDs for illumination (not just backlighting) has proliferated in recent years and there are numerous applications and topologies. The EPC9001C and EPC9078 development boards can be used to create LED backlighting solutions with very high contrast ratio, but are designed for buck / half-bridge type topologies. For anyone experienced in the art it is possible to operate this ‘backwards’ as a synchronous boost – noting that the input PWM will now be complimentary to what is required. Care should be taken in doing so as the output bus voltage can easily be boosted above the rated maximum voltage.

To get more information about EPC’s growing list of development and demo boards, or to purchase these boards, please see the Demo Boards page.

The main question here would be the choice of topology to be employed. The EPC9001C and EPC9078 development boards can be used to create LED backlighting solutions with very high contrast ratio, but are designed for buck / half-bridge type topologies. For anyone experienced in the art it is possible to operate this ‘backwards’ as a synchronous boost – noting that the input PWM will now be complimentary to what is required. Care should be taken in doing so as the output bus voltage can easily be boosted above the rated maximum voltage.

To get more information about EPC’s growing list of development and demo boards, or to purchase these boards, please see the Demo Boards page.

EPC has worked with industry leaders to test high-reliability GaN products for military and space applications. These products have shown excellent radiation performance under Total Ionizing Dose (TID) and Single Event Effects (SEE) environments.  For more information visit the Radiation Tolerant Enhancement Mode Gallium Nitride FETs page.

It is important to keep the max gate voltage below 6V for long term reliability. To make this easy for the designer, we have developed drive level shifters, and discrete gate drivers that not only manage drive voltage, but also manage deadtime. For a detailed description of our recommended discrete solution please see the article How2 Get The Most Out Of GaN Power Transistors.

In June of 2011, Texas Instruments announced the industry’s first eGaN FET driver. Subsequently additional GaN compatible driver and controller options have become available in the market. A list of known partner IC’s is maintained on the eGaN Drivers and Controllers page.

To make this easy for the designer, in June of 2011, Texas Instruments announced the industry’s first eGaN FET driver. The LM5113 is a 100V half-bridge driver addressing a wide range of power converter topologies. Subsequently additional GaN compatible driver and controller options have become available in the market.

A list of known partner IC’s is maintained on the eGaN Drivers and Controllers page.

Additionally, we have developed drive level shifters, and discrete gate drivers that not only manage drive voltage, but also manage deadtime. For a detailed description of our recommended discrete solution please see the article “How2 Get the Most Out of GaN Power Transistors”. It should also be noted that eGaN devices have a very low temperature coefficient for their threshold voltage. This gives the user added safety margin despite the lower threshold voltages at room temperature.

Ask and EPC Engineer a Question FAQ

Have a question not covered in the FAQs? Submit a question on EPCs Ask a GaN Expert page.