"1 GHz, 200 ºC, SiC MESFET Clapp Oscillator"
- Zachary D. Schwartz and George E. Ponchak

A SiC Clapp oscillator fabricated on an alumina substrate with chip capacitors and spiral inductors is designed for high temperature operation at 1 GHz. The oscillator operated from 30 to 200 ºC with an output power of 21.8 dBm at 1 GHz and 200 ºC. The efficiency at 200 ºC is 15 %. The frequency variation over the temperature range is less than 0.5 %.

"Application of GaN Class E Amplifers in EER/ET Amplifier Systems"
- D. Kimball, J. Jeong, C. Hsia, P. Draxler, P. Asbeck, D. Choi, W. Pribble and R. Pengelly

Class E amplifiers offer significant advantages for high efficiency operation, although they have been largely limited to relatively low microwave frequencies and/or low output powers. GaN HFETs are well suited to Class E at high powers and high frequencies, inasmuch as their output capacitance is particularly low for a device with a given output power, and has little voltage dependence.

"Applied Wave Research (AWR), Macquarie University and Cree, Inc. Success Story" (AWR Link)
- Michael Boers

Michael Boers, Ph.D. Student, Wins IEEE MTT-S Power Amplifier Competition, 85% PAE Achieved with Microwave Office and Cree, Inc. GaN HEMT.

"Architectural benefits of wide bandgap RF power transistors for frequency agile basestation systems"
- George Fischer

This paper focuses on how specific characteristics of wide band gap RF power transistors at device level map to benefits at architectural level with those frequency agile systems.

Class-E Silicon Carbide VHF Power Amplifier
- Marc Franco and Allen Katz

This paper investigates the use of silicon carbide (SiC) metal-semiconductor field effects transistors (MESFETs) in high-efficiency, class-E, RF power amplifiers in the VHF range. A maximum drain DC to RF efficiency of 87% was predicted and 86.8% achieved.

"A Comparison between Class E Power Amplifiers Employing LDMOS FETs and SiC MESFETs"
- Raymond S. Pengelly

This paper demonstrates the use of optimized analytical procedures to design lossy Class E amplifiers at 1 and 2 GHz using Si LDMOS FETs and SiC MESFETs respectively. The designs use new large-signal models for the LDMOS FETs and SiC MESFETs which provide accurate simulations in both deep sub-threshold (Class C) and fully RF driven "on" states.

"Design of a High Power Doherty Amplifier Using a New Large Signal LDMOS FET Model"
- Simon M. Wood and Raymond S. Pengelly

This paper describes the use of a new large signal LDMOS FET model in the design of a high power, UMTS band 60W Doherty amplifier. This new model will be shown to be capable of providing accurate predictions of power, gain, efficiency and most importantly, linearity of the complete amplifier.

"Energy Efficient Wide Bandgap Devices"
- John W. Palmour

As wide bandgap devices begin to become commercially available, it is becoming clear that electrical efficiency improvement is one of the key drivers for their adoption.

"A GaN HEMT Class F Amplifier at 2 GHz With >80% PAE"
- David Schmelzer and Stephen I. Long

A Class F amplifier has been designed, fabricated, and tested using a GaN HEMT transistor and hybrid printed circuit board (PCB) packaging.

"A GaN HEMT Class F Amplifier at 2 GHz with > 80 % PAE"
- David Schmelzer and Stephen I. Long

A Class F amplifier has been designed, fabricated, and tested using a GaN HEMT transistor and a hybrid PCB.

"A GaN HEMT Power Amplifier with Variable Gate Bias from Envelope and Phase Signals"
- Ellie Cijvat, Kevin Tom, Mike Faulkner, and Henrik Sjöland

This paper describes the design, simulation and measurement of a GaN power amplifier suitable for envelope and phase signal combination.

"A High Efficiency Class-E Amplifier Utilizing GaN HEMT Technology"
- William L. Pribble, Jim M Milligan, and Raymond S. Pengelly

• Abstract from the 2006 IEEE Topical Workshop on PAs for Wireless Communications (RWS)
• Presentation from the 2006 IEEE Radio and Wireless Symposium in San Diego

A class-E power amplifier based on a GaN HEMT cell has been designed and tested.

"High Efficiency, High Linearity GaN HEMT Amplifiers for WiMAX Applications" 2006 Edition
- S. Wood, P. Smith, W. Pribble, R. Pengelly, and J. Crescenzi

An article in High Frequency Electronics about the use of Cree's GaN HEMTs for WiMAX applications.

"High Efficiency, High Linearity GaN HEMT Amplifiers for WiMAX Applications" 2007 Edition (HFE Archive)
- U. H. Andre, R. S. Pengelly, A. R. Prejs and S. M. Wood, and E. J. Crescenzi

An article in High Frequency Electronics about the recent advances in the use of Cree's GaN HEMTs for WiMAX applications.

"A high linearity, high efficiency WiMAX power amplifier using SiC MESFETs"
- Simon M. Wood, Raymond S. Pengelly, William L. Pribble, Dustin E. Hoekstra

• Abstract from the 2006 IEEE Topical Workshop on PAs for Wireless Communications (RWS)
• Presentation from the 2006 IEEE Radio and Wireless Symposium in San Diego

This paper describes the results of a broadband, high linearity, high efficiency power amplifier for WiMAX basestation applications in the 3.3 - 3.9 GHz band.

"High Linearity, Robust, AlGaN-GaN HEMTs for LNA & Receiver ICs"
- Primit Parikh, Yifeng Wu, M. Moore, P. Chavarkar, U. Mishra, R. Neidhard, L. Kehias, T. Jenkins

AlGaN-GaN HEMTs have not only been identified as the technology of choice for next generation high-power, high frequency applications but recently have also garnered interest for low noise receiver applications.

"High-power GaN HEMTs battle for vacuum-tube territory"
- Yifeng Wu and Primit Parikh

The vacuum tubes used in today's millimeter-wave transmitters face an increasing threat from GaN HEMTs. Cree's Yifang Wu and Primit Parikh are leading the GaN charge with designs that incorporate field plates, iron-doped buffer layers and a thin AIN interlayer to deliver a record power at 30GHz.

"A High Power, High Efficiency Amplifier using GaN HEMT"
- Bumjin Kim, D. Derickson, and C. Sun

A class B and a class F power amplifier are described using a GaN HEMT device.

“High Power Hybrid and MMIC Amplifiers Using Wide-Bandgap Semiconductor Devices on Semi-insulating SiC Substrates”
- S. T. Sheppard, R. P. Smith, W. L. Pribble, Z. Ring, T. Smith, S. T. Allen, J. Milligan and J. W. Palmour

An overview of hybrid and monolithic high-power microwave amplifiers using SiC MESFET and GaN HEMT active devices is presented. High power densities of 5.2 W/mm and 63% power added efficiency (PAE) have been demonstrated for SiC MESFETs at 3.5 GHz. This performance has driven the development of wide-bandwidth MMIC amplifiers, which have yielded 37 W of pulsed power at 3.5 GHz.

"High Temperature Performance of a SiC MESFET Based Oscillator"
- Zachary D. Schwartz and George E. Ponchak

A hybrid, UHF-Band differential oscillator based on 10 W SiC RF Power Metal Semiconductor Field Effect Transistor (MESFET) has been designed, fabricated and characterized through 475 °C. The circuit is fabricated on an alumina substrate with thin film spiral inductors, chip capacitors, chip resistors, and wire bonds for all crossovers and interconnects.

"Semiconductor Hardnut"
- Dr. Mike Cooke

Silicon Carbide (SiC) has been proposed for some time as a substrate for high-speed, high-temperature devices, and products are now entering the market. Dr. Mike Cooke reviews some of SiC's device opportunities and tough process challenges.

"Two-Stage Ultrawide-Band 5-W Power Amplifier Using SiC MESFET"
- Ahmed Sayed and Georg Boeck

This paper describes a two-stage 5-W broad-band amplifier covering the frequency range from 10 MHz to 2.4 GHz. The design procedure is given in detail, and the results are being discussed and compared with simulations.

“An Ultra Wideband 5 W Power Amplifier Using SiC MESFETs”
- Ahmed Sayed, Stefan von der Mark and Georg Boeck

A 5-watt wideband power amplifier using a SiC MESFET has been designed. The frequency range covers 10 MHz to 2.4 GHz with small-signal gain of 8 dB. A broadband choke structure with a new technique was developed to obtain good isolation and low loss over the desired bandwidth. Input and output matching networks and shunt feedback topology were introduced to increase the bandwidth.