CDIAN003: CDI GaN Bias Board User’s Guide

Gallium Nitride (GaN) transistors depletion mode devices that require special gate and drain bias sequencing to prevent catastrophic damage. This application note provides an overview of GaN device bias requirements and how to address them. Click here to download the complete application note.

CDIAN002: Choosing the Right GaN Device for Reliability and Robustness

Choosing the Right GaN Device for Reliability and RobustnessWhile Sumitomo Electric Device Innovations, Inc., SEDI, (formerly Eudyna) was the first to the marketplace with a reliable high volume GaN Power HEMT, there are many manufacturers who are offering GaN microwave power devices today. This application note will look at a few of the major factors in determining the reliability and robustness of different GaN product offerings, and will also give some perspective on the cost impact of those factors. For purposes of this paper, reliability is defined as long-term device performance and survival. Robustness is defined as the ability of the device to withstand short-term conditions that, if not properly managed, could destroy or degrade the GaN device.

When deciding which device is appropriate for a high power application, there are several key factors that need to be evaluated. These include the following:

• The nature of the driving waveform (pulsed, CW, high Peak/Average)
• VSWR conditions that result in excessive drain current (thermal issues)
• VSWR conditions that result in excessive drain voltages (breakdown issues)
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Paul E. White – Component Distributors, Inc.

CDIAN001: Stability Considerations When Designing Microwave Power Amplifiers

Today’s device landscape appears to be a gold mine for newly minted microwave engineers. In many ways, GaN has become the great equalizer, allowing even inexperienced engineers to build amplifiers with a level of performance that would have been unachievable 10 years ago.

The high gain, high power density, and reasonably high terminal impedances that are available with “high band gap” devices such as SiC and GaN HEMTs have provided some powerful tools to the PA designer’s “bag of tricks”, but there are still a few landmines that need to be considered early in the design process to insure a robust solution when designing a high power broadband amplifier. One that designers often step on is device stability (or more appropriately, instability). This application note will discuss the fundamental cause of this instability, and practical methods to mitigate the problem in a real world environment.
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Paul E. White – Component Distributors, Inc.

Sumitomo – A GaN 45W amplifier using the EGN045MK covering 1.3-1.8 GHz

Many solid state amplifier designers have shown strong interest in the higher power and wider bandwidth possible with the new GaN HEMT devices. An example of a moderate bandwidth amplifier using SEDI’s EGN045MK GaN 45W device is shown.

Amplifier Features
Instantaneous Bandwidth:

  • 1.3-1.8 GHz
  • Pout: 50 W
  • Linear Gain: 13 dB
  • Gain Flatness: < 1.0 dB
  • Class of Operation: AB
  • Power-Added Efficiency:
    >40% at Pout> 50 W Average signal
 
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Sumitomo – Power Device Mounting Considerations

A 10-W, GaN HEMT SEDI device is found to be useful for designs from low frequencies up to 5 GHz. A design example over a subband of this performs over more than one octave at lower frequencies. The device is biased class AB. A linear single-ended amplifier for broadband UHF applications using the EGN010MK was designed. The approach uses a series RC on the input to improve gain flatness. Data from the resulting design is reported. > Read More

 
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Paul E. White – Component Distributors, Inc.

Sumitomo – High Power GaAs FET Amplifiers: Push-Pull versus Balanced Configurations

Abstract:
Various methods of combining high power “push-pull” devices are often possible. Two methods, push-pull and balanced configurations, are theoretically discussed. A practical example with a push-pull and a balanced amplifier using the same 150 W, S-band GaAs device(1) is reported and amplifier data are compared and analyzed. Various methods of combining high power “push-pull” devices are often possible. Two methods, push-pull and balanced configurations, are theoretically discussed. A practical example with a push-pull and a balanced amplifier using the same 150 W, S-band GaAs device(1) is reported and amplifier data are compared and analyzed.
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Sumitomo – High-Power GaAs FET Device Bias Considerations

The purpose of this application note is to give some general basic guidelines to bias high-power GaAs FET devices safely. However these guidelines are not a complete insurance against oscillations since each device is a unique case and its stability has to be analyzed by using standard methods if needed.

While considerable effort is spent by the semiconductor companies on characterizing high-power GaAs FET devices in RF and how to match them, little effort is spent for the bias techniques. Experience shows that a lot of amplifier designers spend significant time trying to solve stability problems. These problems are due to the fact that high-power devices have very large gate periphery and consequently large transconductance. Several issues specific to high-power devices have to be addressed for the design of the bias circuits and for the turn-on and –off sequences of these devices.

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