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PUBLIC
JEFFREY HORF APPLICATIONS ENGINEERRF POWER GROUP, NXP SEMICONDUCTORSSEPTEMBER, 20, 2016ELECTRONIC DESIGN INNOVATION CONFERENCE (EDI CON)
TECHNIQUES AND CHALLENGES IN DESIGNING WIDEBAND POWER AMPLIFIERS USING GAN AND LDMOS
PUBLIC 11
AgendaGaN and LDMOS Parametric Comparison
• Device Technology Benefits• System Level Tradeoffs
GaN Advantages• Bandwidth, Efficiency, Power Density
Wideband PA Design and Challenges• Wideband Techniques• Thermal, Linearity, Ruggedness
GaN and LDMOS Wideband PA Applications• Nonlinear Model Simulation • CW and Pulsed Performance
NXP Power Product PortfolioConclusion
PUBLIC 2
GaN and LDMOS Technology
• GaN-on-SiC 50V technology provides higher efficiency, power density and more gain in a small package.
• GaN devices are capable of best in-class solutions for broadband applications.
• GaN’s high output impedance and low Cdscapacitance enables broadband design. Bandwidth limitation on the input match.
• For identical power level, GaN transistors have smaller parasitic capacitance, which makes the wideband matching easier than LDMOS transistors.
GaN LDMOS
• LDMOS is still demonstrating high power and efficiency in cellular and broadcast narrow-band applications.
• 50V LDMOS are primarily used for frequencies < 1.5 GHz. 28V LDMOS can provide compelling performance up to 4 GHz.
• LDMOS transistor’s large peripheries imply large Cgs/Cds capacitances which limit the bandwidth.
PUBLIC 3
GaN and LDMOS: Parametric Comparisons
Typical ParametersLDMOS (28V)
LDMOS(50V)
GaN(50V)
GaNAdvantage
Fmax (GHz) 22 15 30 High frequency operation 2.5GHz and above
Power Density (W/mm) 0.8 2 5-10 Higher Power density smaller device footprint
Efficiency @ P1dB (%) 60 < 55 70 Higher efficiency 2.5 GHz and above
Bandwidth (MHz) 100-400 100-500 500-2500 One device covers multi-bands
Cds (pf/W) Output Capacitance
0.23 ½ smaller ¼ smallerSmaller device capacitance
broadband operationCgs (pf/W) Input Capacitance
0.94 ½ smaller ½ smaller
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Leveraging the Benefits of GaN and LDMOS
• Differentiating performance exceeding LDMOS above 2.5 GHz
• Enables 5G at higher frequencies• Broadband design• High efficiency at high frequencies• Comparable thermal package as LDMOS• Compact PA design (more power in smaller
package, smaller matching circuitry)• Wideband CW and Pulse PA applications:
− 200-2600 MHz at 100 W− S-band 2.7-3.5 GHz at 700 W
GaN Benefits LDMOS Benefits
• Competitive performance to 2.7 GHz• Cost effective PA solutions• Mature process technology• High ruggedness up to 65:1 VSWR• Consistent thermal behavior• Broadband VHF/UHF below 1 GHz• Highest power up to 1.5 GHz• Narrow-band PA applications:
− Cellular bands up to 2.7 GHz− Avionics and L-band 1.2-1.4 GHz up to 1.5 kW− S-band 2.7-3.1 GHz at 300 W
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Material Characteristics Drive System Level TradeoffsMaterial Properties Device Operates Improved Device FOM System Advantage
Increased BWSmaller # of Die
Per System
Lower TotalEnergy Usage
Higher SystemFrequency
Smaller PackageCheaper Package
Relaxed SystemCooling
Power DensityPower GainEfficiency
Output Impedance
High ftHigh fmax
Smaller Die SizeMore Power/Die
HighBreakdownField
High ElectronVelocity
High ThermalConductivity
High VoltageHigh Current
High Temperature
High Frequency
PUBLIC 6
Gain Compression Comparison – P1dB, P3dB
LDMOS: Hard Gain Compression 1.2dB delta between P-1dB and P-3dB
LDMOS 32V @ 1.96 GHz
GaN: Soft Gain Compression1.8dB delta between P-1dB and P3-dB
GaN 50V @ 2.50 GHz
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20 22 24 26 28 30 32 34 36 38
Pout
(dB
m)
Pin (dBm)
MMRF5014HR5 - Max Pout Load - 2.5 GHz - 50 V
Actual
Ideal
P-1dB = 50.2 dBm = 105 W
P-3dB = 52 dBm = 160.9 W
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GaN Advantage: Wider Bandwidth in S-BandMMRF5300N - 50V GaN60 W Pulsed PowerWideband over 2.7 – 3.5 GHz Flat Gain 14.6-14.9 dBEfficiency > 50%
MRF7S35120H - 32V LDMOS120 W Pulsed PowerBroadband over 3.1 – 3.5 GHzGain 12-13 dBEfficiency > 40%
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-10
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IRL
(dB
)
D
rain
Eff
icie
ncy
(%)
Pow
er G
ain
(dB
)
Frequency (MHz)
PMRF5300N Performance at 60W PulsedVdd=50V, Idq=60mA, Vgs=-3V, 300us Pulse Width, 20% Duty Cycle
Power Gain
Drain Efficency
IRL
PUBLIC 8
GaN Advantage: Higher Efficiency
GaN provides high efficiency at peak power, and 6dB power back-off efficiency across wide bandwidth
Power drive-up gain response is less sensitive to bias current variation. Flat gain response can achieve over a wide power dynamic range
GaN is well suited for high efficiency amplifiers, such as classes D/E modes and switch-mode PA’s, where transistor operates like a switch
GaN on SiC technology is continuously improving linearized efficiency for Doherty PA operation at 7-8 dB peak power back-off
PUBLIC 9
GaN Advantage: High Efficiency and Output Power
PAE and Output Power vs. Frequency for NXP GaN and LDMOS devices
High Efficiency Beyond 2.5 GHz High Power Beyond 3.5 GHz
PUBLIC 10
Wideband PA Design Techniques1. Multi-sections LC matching networks2. Multi-sections quarter-wave line transformers
Consider Factors: 1. Power level2. Package3. PCB size4. Phase shift5. Broadband matching
Lower Q Matching
PUBLIC 11
Wideband PA Design Techniques
• Broadband impedance transformer < 1 GHz− Coaxial 4:1 transformer with ferrite beads can extend frequency range from 50 to 1000 MHz
Zcoax= Z1 * Z2 = 12.5 * 50 = 25 ohm
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Wideband PA Design Techniques
• Multi-sections transmission lines – broadband matching over 400-3000 MHz
PUBLIC 13
Wideband PA Design Techniques
1 2 3
Reactive Matching makes gain adjustment
across wideband by mismatching at the input, but results in higher input
VSWR.
L-R Lossy Matching absorbs gain to achieve
flat gain across wide band. Reduce low frequency
gain.
R-C Feedback improves the input and output match to achieve
broadband matching. Improve circuit stability by
reducing gain at low frequency.
Bandwidth Enhancement Techniques:
PUBLIC 14
Wideband PA Design Challenges
• At high power density, GaN is in the high end of its operating junction temperature
• GaN on SiC can reduce thermal resistance in air cavity ceramic and plastic-molded packages
• GaN die design to spread heat sources evenly and use highly conductive copper flange packages
GaN Thermal Challenges GaN Linearity Challenges
• GaN drain lags result in poor linearity, which results in a slow drain current response to fast change in drain amplitude swing
• GaN is being optimized for better DPD correction for switching signals in TDD based systems
PUBLIC 15
Wideband PA Design Challenges
• 50V LDMOS is designed for high breakdown voltage and can survive 65:1 VSWR and >3 dB input overdrive
• 50V GaN is designed for high ruggedness 20:1 VSWR
Device Ruggedness Device Reliability
• Use Mean-Time-To-Failure (MTTF) product calculators to determine device electromigration failure rate for a given set of operating conditions, junction-case temperature (Tj-c) and thermal resistance
• MTTF vs. Tj-c is calculated for CW conditions and pulse applications
PUBLIC 16
GAN AND LDMOSWIDEBAND PA APPLICATIONS
SINGLE-ENDED VS. PUSH-PULL AMPLIFIERS
PUBLIC 17
MMRF5014H GaN Wideband PA Application
• 50 V GaN on SiC Wideband Transistor• 100 W CW, 12 dB min Gain, 40% min
Efficiency covers 450-2500 MHz• Single-ended Compact
Wideband Amplifier• Full CW & Pulse Operation• Housed in NI-360 air-cavity
ceramic package • Thermal Resistance = 0.86 °C/W *
* Refer to App Note AN1955
PUBLIC 18
MMRF5014H GaN 450-2500 MHz Wideband Design• Broadband design using multi-section
transmission lines methodology with MMRF5014H non-linear device model
• Load and source impedances generated from load pull techniques to develop broadband matching networks
• ADS harmonic balance simulation to optimize power gain and efficiency
• Design Goals:−100 W across 450-2500 MHz−CW Gain >12 dB −Efficiency >40 %
MMRF5014H Source and Load Impedance
Freq (MHz) Zsource(ohm) Zload (ohm)
500 1.3+j3.9 5.9+j3.5
1000 1.0+j0.3 5.5+j2.9
1500 0.8-j0.5 3.4+j2.0
2000 1.2-j2.0 4.7+j0.3
2500 2.7-j3.8 3.7+j1.4
PUBLIC 19
MMRF5014H GaN Wideband Circuit Simulation – 450-2500 MHz
Input Matching Circuit
Output Matching Circuit
NXP can provide ADS device model to enable nonlinear circuit simulation
PUBLIC 20
MMRF5014H GaN Wideband Circuit Simulation Results
800 MHz 800 MHz 800 MHz
PUBLIC 21
MMRF5014H GaN 450 – 2500 MHz CW Measurement
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20 30 40 50 60 70 80 90 100 110
Effic
ienc
y (%
)
Gai
n (d
B)
Output Power (W)
MMRF5014H CW Power Drive-up
500 MHz Gain 1000 MHz Gain 1500 MHz Gain 2000 MHz Gain 2500 MHz Gain500 MHz Eff 1000 MHz Eff 1500 MHz Eff 2000 MHz Eff 2500 MHz Eff
VDD = 50 VIDQ = 300 mA
Device shows no gain expansion at selected bias current
PUBLIC 22
MMRF5014H GaN 450 – 2500 MHz CW Measurement
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400 600 800 1000 1200 1400 1600 1800 2000 2200 2400 2600
Effic
ienc
y (%
)
Gai
n (d
B)
Frequency (MHz)
MMRF5014H 450-2500 MHz CW at 100 W
100 W Gain 10 W Gain 100 W Eff
VDD = 50 VIDQ = 300 mA
PUBLIC 23
MMRF5014H GaN 450 – 2500 MHz Pulse Measurement
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Puls
e Ef
ficie
ncy
(%)
Gai
n (d
B)
Frequency (MHz)
MMRF5014H 500-2500MHz Pulse at 100 W200usec pulse width, 20% duty cycle
100 W Gain 100 W Pulse Eff
VDD = 50 VIDQ = 300 mA
Higher gain due to non-thermal heating effects in pulse operation
PUBLIC 24
MMRF1305HR5 LDMOS Broadband PA
• 50 V Wideband LDMOS Transistor• 100 W PEP, 14 dB min Gain, 30%
min Efficiency• Push-pull Amplifier covers 400-1000
MHz• Broadband Coaxial transformer
design• Housed in a NI-780H air-cavity
ceramic package • Low Thermal Resistance = 0.38
°C/W *
* Refer to App Note AN1955
PUBLIC 25
MMRF1305HR5 LDMOS 400-1000 MHz Broadband Design• Broadband design using two-section
impedance transformer with MMRF1305HR5 nonlinear device model
• ADS load pull and source pull techniques to obtain maximum power impedances between 400 MHz to 1 GHz
• ADS harmonic balance simulation to optimize power gain and efficiency
• Design Goals:−100 W across 400-1000 MHz−CW Gain >14 dB −Efficiency >30 %
MMRF1305H Source and Load Impedance (Simulated in balanced configuration)
Freq (MHz) Zsource (ohm) Zload (ohm)
400 4.21-j0.85 6.63+j0.27
500 3.82-j1.05 6.82+j0.18
600 3.44-j0.97 6.98+j0.01
700 3.23-j0.75 7.09-j0.25
800 3.21-j0.55 7.11-j0.55
900 3.31-j0.49 7.00-j0.88
1000 3.50-j0.60 6.80-j1.16
PUBLIC 26
MMRF1305H LDMOS Broadband Circuit Simulation400-1000 MHz
Output Matching Circuit
NXP can provide ADS or AWR MWO device models to enable nonlinear circuit simulation
Balun
Balun
Input Matching Circuit
4:1 Impedance Transformer
PUBLIC 27
MMRF1305H LDMOS Broadband Circuit Simulation Results
PUBLIC 28
MMRF1305H LDMOS 400 – 1000 MHz CW Measurement
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Effic
ienc
y (%
)
Gai
n (d
B)
Output Power (W)
MMRF1305H 400-1000 MHz CW Power Drive-up
400 MHz Gain 700 MHz Gain 1000 MHz Gain400 MHz Eff 700 MHz Eff 1000 MHz Eff
VDD = 50 VIDQ = 400 mA
Device exhibits gain expansion at low drive power and specified bias current
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Dra
in E
ff (%
)
Gai
n (d
B)
Frequency (MHz)
MMRF1305H 400-1000MHz CW at 100 W
100 W Gain 10 W Gain 100 W Eff
VDD = 50 VIDQ = 400 mA
MMRF1305H LDMOS 400 – 1000 MHz CW Measurement
PUBLIC 30
MMRF1305H LDMOS 400 – 1000 MHz Pulse Measurement
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400 450 500 550 600 650 700 750 800 850 900 950 1000
Dra
in E
ff (%
)
Gai
n (d
B)
Frequency (MHz)
MMRF1305H 400-1000MHz Pulse at 100 W200usec pulse width, 20% duty cycle
100 W Gain 100 W Eff
VDD = 50 VIDQ = 400 mA
Higher gain due to non-thermal heating effects in pulse operation
PUBLIC 31
GaN and LDMOS Wideband Application Comparison
ParametersGaN
MMRF5014HLDMOS
MMRF1305H
Circuit Topology Single-ended Push-pull
Bandwidth @ 100 W 450-2500 MHz 400-1000 MHz
Gain @ 100 W 12-14 dB 13-17.5 dB
Efficiency @ 100 W > 39 % > 32 %
P3dB 160 W 140 W
PUBLIC 32
LDMOS Power Product Portfolio
• 1
1.8 MHz 500 MHz 915 MHz 1400 MHz 2900 MHz 3500 MHz
10W
100W
1kW
1200 MHz
S-Ba
nd R
adar
270
0-31
00
Industrial
FM/VHF Broadcast
Aerospace
UHF Broadcast
Industrial
Aerospace
2450 MHz
1.5kW MRF1K50NTo 500MHz, 1500W CW
Cellular ICs28V class AB
Cel
lula
r 34
00-3
600
Cel
lula
r 180
0-20
50C
ellu
lar 2
100-
2200
L-B
and
Rad
ar
IFF
50V LDMOS
28/32V LDMOS
Cel
lula
r 230
0-27
00IS
M 2
500
AerospaceIndustrial500W
Frequency (MHz)
Pea
k P
ower
(W)
PUBLIC 33
GaN Power Product Portfolio – Compliments LDMOS to Address High Frequency, High Power Applications
Frequency (MHz)
1000
400
100
10
2
Pea
k P
ower
(W)
PUBLIC 3434
Conclusion• Benefits have been presented for GaN and
LDMOS technologies. Including device parameters with performance trade-offs, design challenges, and wideband PA applications.
• GaN devices have great potential for high-power cellular and defense aerospace markets in wideband, multi-band PA applications
• NXP provides full product support forGaN and LDMOS product solutions