Broadband GaN MMICs:
Multi-Octave Bandwidth PAs
to Multi-Watt Linear LNAs
Kevin W. Kobayashi and Karthik Krishnamurthy
2012 PA Symposium, La Jolla Cove California
Good Morning!
Page  2
La Jolla Cove California
Page  2
OUTLINE
• Need: BW, Power, Linearity, PAE, Sensitivity, Survivability
• Broadband Application
• GaN Flavors (fT, Lg, BVdg, LN, Power Density)
• Broadband Amplifier Topology – Trades
• Cascode FB
• Darlington FB
• Lossy Match
• DA and NDPA
• Recent Results
• Summary & Future Directions
Page  3
GaN Enables Broadband Front-End Performance
 wide band-gap
Linearity
Power/Efficiency
Spectral Efficiency
Multi-band
 electron velocity
Bandwidth
Sensitivity
(Low NF)  2-D Gas Channel
Network Reach
Page  4
> Decade BW
bigger pipe-line
Power Frequency (PF2) Limit
Pmax 
Eg4 v 2
s
F
2
Maximum Power (Watts)
100,000.0
10,000.0
Property
Si
GaAs
GaN
Eg (eV)
1.1
1.4
3.4
vs (10 7 cm/s)
0.7
0.8
2.5
X-Band Military Radar
Commercial Satcom Transmitters
(VSAT - 1MBPS)
1,000.0
Commercial Broadband Satcom
(VSAT - 16MBPS)
100.0
10.0
Point to Point
millimeter wave radios
Commercial
Communications
Base Stations
sensing and imaging
1.0
0.1
1
10
100
Frequency (GHz)
Page  5
IMS 2010 WE4E-5
OUTLINE
• Need: BW, Power, Linearity, PAE, Sensitivity, Survivability
• Broadband Application
• GaN Flavors (fT, Lg, BVdg, LN, Power Density)
• Broadband Amplifier Topology – Trades
• Cascode FB
• Darlington FB
• Lossy Match
• DA and NDPA
• Recent Results
• Summary & Future Directions
Page  6
Example: SDR need for broadband / efficiency
• Emerging Software Defined Radio Architectures
Joint Tactical Radio Systems (JTRS)
Public Mobile Radio
30 MHz
1
10
100
Frequency (MHz)
2000 MHz
1000
10000
• Requirements
- Multi-decade bandwidth (30MHz - 2 GHz)
- Medium power (10W and higher)
- Multi-band / multi-standard operation
- Reconfigurable hardware
Page  7
2009 SDR Forum
Example: GaN Device CATV Need for Decade BW Linearity
GaN Power Doubler Amplifier
Typical NTSC CATV Spectrum
Block Diagram
Courtesy Rainer Hillermeier - RFMD
CATV requires > 67 dBc C/I beyond 1 GHz
to support analog, HDTV, VOD, & high speed internet
Page  8
BCTM 2009, Shealy et.al.
OUTLINE
• Need: BW, Power, Linearity, PAE, Sensitivity, Survivability
• Broadband Application
• GaN Flavors (fT, Lg, BVdg, LN, Power Density)
• Broadband Amplifier Topology – Trades
• Cascode FB
• Darlington FB
• Lossy Match
• DA and NDPA
• Recent Results
• Summary & Future Directions
Page  9
Flavors of Microwave GaN HEMT MMIC Technology
Passives
HEMT Device
GaN Short Lg MMIC Technologies – Recent Literature
(0.1um-0.25um)
Page  10
Parameter
Units
TQNT [1,2]
TQNT [ 3]
Northrop
Grumman [ 4]
Fraunhofer
Institute [ 5]
HRL [ 6]
Intended
Frequency
GHz
Ku-band
Ka-band
Ka-band
Ka-band
W-band
Gate Length
um
0.25
0.15
0.25
0.1
0.14
T-gate
T-gate
T-gate
Gate Structure
Field Plate
Imax
mA/mm
900
1150
1050
1300
1200
Gm
mS/mm
300
380
300
550
381
Vbd
V
70
> 50
75
Practical
Operating Vds
V
30
20
20-28
15
10-14
fT/fmax
GHz
29
56
>80/200
97/230
Power Density
W/mm
5-8 @ 10GHz
~4
2-4
Backside Vias
-
Yes
Yes
Yes
Yes
MIC Caps
-
3
1
1
TFR Resistors
-
TaN
Interconnect
-
3
2
2
Wafer thickness
um
100
100
75
Commercial
Qual
-
YES
100
YES
~1.8
Yes
50
OUTLINE
• Need: BW, Power, Linearity, PAE, Sensitivity, Survivability
• Broadband Application
• GaN Flavors (fT, Lg, BVdg, LN, Power Density)
• Broadband Amplifier Topology – Trades
• Cascode FB
• Darlington FB
• Lossy Match
• DA and NDPA
• Recent Results
• Summary & Future Directions
Page  11
Multi-Octave BW MMIC GaN Amplifier
Topology Consideration Highlights
Cascode
FB
BW
Linearity
2nd Order
Linearity
CSO-BW
Proven
NF
Good NFBW
Efficiency
Page  12
LossyMatch
1.5*fT
capability
Great
IP3/IP2BW
Thermal
Mitigation
Darlington
FB
fT-doubler
Great
Great
Po-BW
Great
IP3-BW
Actively
limited
DA &
NDPA
Passively
limited
Passively
limited
> 40%
PAE
Up to 40%
PAE
flexible
flexible
More Voltage
More Current
Cascode
• Cascode
• Reduces Miller Capacitance – better BW
• Increased output impedance – better linearity BW
• Stacked devices – higher Vdd
• Spread devices – lower Tj
• Breaks thermal electric feedback in BJTs
• noisier, unstable, and less linear power efficient (I-V knee)
Page  13
Cascode – Higher Voltage & Power Operation
Performance
Practical Vdd
Commonsource
Cascode/*Dual
gate
20V (T-gate)
40V
Pout , IP3
Page  14
4-6 dB improvement
Idd
250mA/mm
same
Tj @ 85C
base
~200C
~*200C
NF
higher (id1_n,id2_n)
BW
much wider
Gain
much higher, flatter
Stability
poorer
IMS 2012 WS: WFE
Cascode Electrical Characteristics
I-V characteristics
Maximum Available Gain
A/mm
Wg = 500um HEMT
50
1.2
COMMON-SOURCE
CASCODE
Max Gain (dB)
IDS (A/mm)
1.0
0.8
0.6
0.4
0.2
40
CASCODE
30
20
10
COMMON-SOURCE
0
0.0
0
10
20
30
40
50
60
70
80
0
VDS
Cascode has higher Ro, good IP3
But higher Vknee, poorer PAE
*Tj~200C @ 20V-250mA/mm
Page  15
IMS 2012 WS: WFE
10 20 30 40 50 60 70 80 90 100
Frequency (GHz)
Cascode has higher MAG
but less stable
Cascode vs. CS Output Characteristics
Common-Source
Cascode
m4
freq=11.01
S(1,1)=0.8
impedance
m5
freq=11.01GHz
S(3,3)=0.827 / -123.994
impedance = Z0 * (0.121 - j0.526)
m5
freq=11.01
S(3,3)=0.8
impedance
S(4,4)
S(3,3)
S(2,2)
S(1,1)
Cout ~ 0.8 pF/mm
S22
S11
m7
m6
m5
m4
Cin ~ 1.5 pF/mm
freq (10.00MHz to 20.00GHz)
S(4,4)
S(3,3)
S(2,2)
S(1,1)
m4
freq=11.01GHz
S(1,1)=0.829 / -119.769
impedance = Z0 * (0.125 - j0.573)
Cout ~ 0.16 pF/mm
m6
freq=11.01GHz
S(2,2)=0.408 / -65.397
impedance = Z0 * (1.008 - j0.898)
S22
m7
freq=11.01GHz
S(4,4)=0.394 / -62.568
impedance = Z0 * (1.066 - j0.884)
m4
m5
S11 Cin ~ 1.1 pF/mm
freq (10.00MHz to 20.00GHz)
Cascode has ~ 1/5th the output capacitance than a CS
Page  16
m6
m7
m6
freq=11.01
S(2,2)=0.9
impedance
m7
freq=11.01
S(4,4)=0.9
impedance
Cascode -Thermal Mitigation
+
Vds2
-
+
Vds1
-
Tj ~ 200C
Vds = 20V
Ids = 250mA/mm
Courtesy of Don Willis, Rob Dry RFMD
Cascode allows distributed thermal layout vs. dual-gate
Page  17
CSIC 2011
Cascode BD-Vds Robustness: Vds1/Vds2 partition
• Zsource & AV1 vs. Cshunt
• Vds1 & Vds2 vs. Cshunt
80
+
Vds2
-
30
70
Cshunt
Vds1_pp & Vds2_pp (V)
Zsource (Ohms) & Av1(dB)
40
Zsource
+
Vds1
-
Av (dB)
20
10
60
50
Vds1_pp (V)
40
Vds2_pp (V)
30
20
10
0
0.1
1
10
100
0
0.1
Cshunt (pF)
1
10
Cshunt (pF)
Cshunt controls Vds_p-p voltage swing partition between devices
Page  18
Stacked calculations described by
UCSD papers
100
Multi-Watt GaN LNA Motivation
• Low NF of GaAs PHEMTs, but with greater linearity
• Enables Future Linear RF Applications
• Software Defined Radios
• Higher Spectral Efficient P2P
• RF on Fiber
• Extended CATV
Page  19
8-Watt Cascode LNA MMIC
60
54.3
OIP3 (dBm)
50
750 mA
53.3
52.7
51.9 51.8 51.4 50.8 52.0
500 mA
40
30
20
0
40V-750mA
S21
10
0
S11
-10
S22
-20
-30
-40
0
1
2
3
3.0
5
4
2.5
3
2.0
2
1.5
Noise Figure (dB)
20
1
0
CSIC 2011, RFIC2012
4
2.57 2.534.6
750 mA
2.20 2.19 3.8
2.08
3.73.6
3.2 3.0
3.0
2.9 2.7 2.7 3.0
2.9
1.48 2.4
2.5
2.5
1.42
2.3
500 mA 1.42
1.23
1.22
1.09
1.10
0.89
0.88
1.32
1.32
2 2.0 2.5 3 3.0
Freuency (GHz)
(GHz)
Frequency
3.5
1.24
1.01
0.5
0
3
2.28
1.0
Frequency (GHz)
Page  20
2
Frequency (GHz)
40V-500mA- High Linearity Bias
10V-200mA - Low NF Bias
2.8325V-300mA - High Dynamic Range Bias
6
Noise Figure (dB)
Gain & Return-Loss (dB)
30
1
0.0
0.5
1
1.0
1.5
1.08
4
IP3-NF Technology Comparison
Multi-Watt
LNA is required
to achieve
55
> 45 dBm IP3
Summary of S-band LNA & Gain Block
Performance
[2012 RFIC]
50
OIP3 (d Bm)
GaN
[14]
[14]
[6]
45
[7]
40
HBT-NB
HBT-WB
HFET
[3]
D PHEMT
[12-13]
E PHEMT
[10]
E-PHEMT
[1]
35
GaAs HBT
HFET/MESFE
T
GaN HEMT
[5]
30
D-PHEMT
25
0
1
2
NB= Narrow band tuned
WB= Wide band tuned
3
4
5
Noise Figure (dB)
IMS 2012 WS: WFE
6
7
8
Example: GaN Device EPI linearization for CATV
[2009 BCTM Conference, Jeff Shealy, et.al.]
CATV linearity is related to device Cdg (Vds) linearity.
Lower Al composition results in improved GaN CATV linearity.
Page  22
Page  22
IMS 2012 WS: WFE
Darlington & fT-Doubler
• Sidney Darlington (1953 Patent)
• Increase DC current gain of a BJT
• Two poles – hard to stabilize in FB
• Tektronix fT-doubler , 2*fT (1980 Patent)
• Two poles separated – RF feedback now feasible
• Today- Millions of GaAs based RF Darlingtons are sold each year
• High linearity for repeaters, driver line ups in BTS, CATV, instrumentation, Fiber
• GaN has elevated performance to multi-octave, multi-watt power
• Linear driver amps in a wideband amplifier line up
• Linearity-BW can enable future wideband radio architectures
Page  23
Sidney Darlington 1906-1997 [1]
C
B
Q1
Q2
b  b2
E
Bell Labs (1953)
Pat. No. 2,663,806
Darlington-pair key analog building block for several decades
Page  24
APMC 2010
Tektronix Darlington Amplifier [2] Pat. No. 4,236,119 (1980)
“fT Doubler”
Enhancement
b2  2b
B
Q1
2b
Q2
fT  2 fT
12dB/Oct  6 dB/Oct
E
Less excess Phase  stable
FB feasible
fT-doubler enables RF feedback
Page  25
APMC 2010
C
Darlington Cascode Amplifier – Enhanced BW
RF Darlington FB Amp
Darlington Cascode FB Amp
Rdc
Rdc
OUT
Cfb
OUT
Cfb
MC
MC
Rfb
Rfb
Rfb
Rfb
IN
MC
IN
M1
MC
M1
M2
Rg
Rg3
M3
M2
Rg
Rs
R1
Cbyp
Rs
Vg2
Vg1
Cbyp
Vg1
Cbyp
linearization
[2006 CSIC]
large signal
[Krishnamurthy-UCSB]
Darlington FB provides high Linearity-BW
Page  26
R2
RFIC 2007 RTU4A-5
Cbyp
Darlington Cascode Device Characteristics
GaNGB1_DC_Vgs_vs_Ids..IDS.i
(V)
Ids
IDS.i
Darlington vs. DCAS I-V
Darlington vs. DCAS Gain
Conventional-Darlington
Darlington-Cascode
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
Higher Knee
Higher Ro
0
5
10
15
20
25
30
VDS
Vds
(V)
GaNGB1_DC_Vgs_vs_Ids..VDS
Higher Knee, lower Go
Page  27
RFIC 2007 RTU4A-5
Higher Gain
GaN HEMT MMIC Darlington-Cascode – P1dB > Watt
0.2um GaN HEMT MMIC
fT~60GHz, BVgd ~ 60V
Darlington
Cascode
D (IP3-P1dB) ~ 11-12 dB (3-Octaves!)
LFOM= IP3/Pdc > 2.5:1
Page  28
RFIC 2007 RTU4A-5
GaN HEMT MMIC Darlington-Cascode – P1dB > Watt
OIP3
Pout @ 3.5 GHz
IP3 Comparison @ 15V, 400 mA
Darlington-Cascode: 15V, 400 mA
46
35
OIP3 (dBm)
45
Pout & Gain (dB), PAE (%)
Conventional-Darlington
Darlington-Cascode
44
43
42
41
OIP3 > 41 dBm over a 4 GHz Bandwidth
40
Fo = 3.5 GHz
P1dB = 30.3 dBm
Psat = 31.7 dBm
PAE = 21.4%
30
25
20
15
10
5
Pout(dB)
Gain(dB)
PAE%
0
-5
-10
0
1
2
3
4
Frequency (GHz)
Improvement in IP3
Page  29
5
-30
-20
-10
0
10
Pin (dBm)
Pout~1.5W, PAE~20%
RFIC 2007 RTU4A-5
20
30
Summary of GaN Darlington/fT-doubler FB Amps
Comparison of Broadband GaN PAs (fT-Doubler, Darlington, Darlington Cascode)
Technology
Design
fT
doubler/dualgate
0.75-um AlGaN/GaNGaAs-GaN
Saphire
Cascode
delay-matched
TWA
fT
doubler/singlegate
0.7-um GaN/AlGaNSaphire
fT
doubler/dualgate
GaN-SiC
fT-doubler
Cascode FB
Amp
0.2um T-gate GaN-SiC
HEMT
0.8um GaN
Page  30
Darlington
Feedback
DarlingtonCascode
Feedback
fT-doubler
Construction
Bandwidth
Gain (dB)
(GHz)
2-8
Flip-chip on
ALN
w/passives
Flip-chip on
ALN
w/passives
hybrid:
GaN+GaAs
Passive (IPC)
Fully
Monolithic
(MMIC)
Fully
Monolithic
(MMIC)
Fully
Monolithic
(MMIC)
10
Vsupply
Pout (W)
(V)
28
5.12
fout
(GHz)
PAE (%)
6
21
REF
[1]
1-9
11
19
1.35
8
14
0.2-7.5
11
19
>1
1-7
10
[2]
0.2-8
10
24
1.5
6
0.2-4
9-10
28
>1
1-3
15
[3]
0.2-4
10-11
28
>1
1
0.05-18.7
11
15
>1
1-4
> 20
[4]
0.05-12.3
14.5
15
>1
1-4
> 20
1.0-6.0
12.2
20
>2
1-6
24-37
*Modified from RFIC 2007
*[5]
Lossy-Matched Power Amplifier Approach
• Lossy match trades off Q for BW
• Applied to input which is BW limited (Cgs ~ 2x Cds)
• Power-BW limited by parasitic capacitance, Cds
• Lumped element is thermally challenging
PA Power Bandwidth Limit
Gain (dB) Return Loss (dB)
Wideband HPA’s covering multiple communication bands
Fhigh  Flow
Fo


 QL ln()
Bode-Fano Limit
frequency
Lumped element reactive match with lower Q  more BW
Page  32
Page  32
IMS 2010 WE4E-5
Schematic of Lossy Matched PA
Vg
Vd
Bias
Networks
Ld
RF
IN
Cdiv
Zg
Impedance
Lossy match
transformation
Cd
RF
OUT
Output
match
Apply lossy match to input which is BW-limited by Cgs
Page  33
CSIC 2008
Output Match : Small signal vs. large signal match
vc
vc
Constant out contour
Pout ReZ L 

if Z L  Z o
Popt
Zo
Pout
 ReYL Z o if Z L  Z o
Popt
Constant Pout contour
RL,opt=Zo
Page  34
So, minimize Im(Z L ), Im(YL )
Karthik Dissertation UCSB 2000
Comparison of broadband output networks
50
~1.5pF
40
Drain efficiency (%)
Zo ~ 50 Ohms
30
20
10
0
no compensation
0
0.5
1
F F
1.5
2
f
fo
L-section
“best” small-signal Pi-section
best large-signal pi-section compensation
Page  35
Karthik Dissertation UCSB 2000
0.5 – 2.5 GHz, 10W Lossy Matched P3dB,
GaN
MMIC PA
Drain Efficiency
43
80
P3dB (dBm)
• Gain :15 – 16 dB
• Pout : 9 – 13.6 W
• Efficiency :45% – 64%
Drain Efficiency
70
41
60
40
50
39
40
Vdq = 48V, Idq = 44mA
38
20
20
16
10
12
0
8
-10
4
-20
0
-30
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
1.0
1.5
Frequency (GHz)
(Die size : 2mm x 1mm)
Frequency (GHz)
Page  36
2.0
S11 (dB) , S22 (dB)
S21 (dB)
0.5
CSIC 2009 Session D2
30
2.5
Drain Efficiency (%)
P3dB
42
Distributed Power Amps
• Extends Power-BW over lossy matched approach
• Absorbs output device capacitance Cds, Ropt load
• Device thermal mitigation
• > 4x Pd of GaAs PHEMTs
• NDPA enable widest power-BW and Efficiency
• Optimizes Ropt for each device section
• Cascode may enable higher power-BW
• Practical Limitations
Page  37
Distributed Amplifier Topologies & Techniques
• Convention DA [1-proceedings IRE 1936]
• DC to microwave BW
• Low power efficiency
• Capacitive Coupled DA [2,3 - Ayasli, et.al.]
• Improved Power-BW but lower gain, LF limited
• Cascode DA
• Thermal & Voltage Mitigation
• High IP3-BW
• Modest PAE though
• Non-Uniform DPA [1], [4-Apel], [5-Duperrier]
• Optimum Power Load for each device section
• Higher power-BW and PAE
• LF limited (no drain term)
Page  38
Distributed Amplifier Topologies
CS Distributed Amp [1]
Capacitive-coupled CS Distributed Amp [2,3]
Capacitive-coupled Cascode Distributed Amp Non-Uniform Distributed Power Amp [4,5]
TLout2
TLout
TLout9
TLout8
OUT
M8_cs
M2_cs
M1_cs
C1
...
C1
M9_cs
C1
C1
...
IN
TLin1
TLin2
TLin8
TLin9
Rin
TLin
Vg1
Cin
Cin_ext
Page  39
GaN HEMT vs GaAs PHEMT MMIC DA
An apples-to-apples comparison
Parameter
Units
Technology
Cut-off Frequency
BVdgo
Circuit Type
Bandwidth
Gain
IP3 @ 10GHz
P1dB @ 10GHz
Psat @ 10GHz
NF @10GHz
Supply Current
Supply Voltage
Power Density
Tjunction (calculated)
GHz
V
GHz
dB
dB
dBm
dBm
dB
mA
V
W/mm
C
Value
0.2um GaN HEMT
75
> 60
Cascode DA CC Cascode DA
DC-24
DC-20
16.0
12.5
40.9
42.6
30.3
32.5
34.2
33.5
3.0
5.5
300
400
30
30
1.46
0.83
161
161
30V GaN
0.15um GaAs PHEMT
85
9
Cascode DA CC Cascode DA
DC-22
DC-20
17.0
13.0
35.0
36.0
25.8
26.7
27.0
28.1
3.1
5.5
300
400
8
8
0.28
0.24
158
158
8V GaAs
Same Tj : GaN HEMT DAs achieve 6 dB improvement in IP3 & Pout
RFIC 2009 RTU1A
CW Output Power as a Function of Vdd Operation
CS NDPA
[ IMS 2010 Reese]
[ CSIC 2008 Campbell]
HV FP-gate
LV T-gate
GaN HEMT
GaAs PHEMT
GaN enables higher Pout with increasing Vdd.
GaN NDPA MMICs demonstrate > 10-Watts @ 10 GHz.
Page  41
Modified from RFIC 2009 RTU1A
Non-Uniform Distributed Power Amplifier
C1
L1
Rp Rp
i(t)
Rp
i(t)
C2
Rp/2
i(t)
L2 2 i(t)
Rp
C3
Rp/3
i(t)
L3 3 i(t)
C4
Rp/4
Rp
i(t)
LC network is tapered (Non-uniform TLINs) to present
the optimum load, Rp, to each individual device.
Page  42
Example: Simulated CS Load-Pull (Vdd=25V, Wg=300um)
Pdel_contours_p
PAE_contours_p
Calculation
m2m1
2 ∙ 𝑉𝑑𝑑
𝑅𝑜𝑝𝑡~
𝐼𝑚𝑎𝑥 ∙ 𝑊𝑔
2 ∙ 25𝑉
~
1𝐴/𝑚𝑚 ∙ 0.3𝑚𝑚
~167 Ω
57.15
31.25
indep(PAE_contours_p) (0.000 to 29.000)
indep(Pdel_contours_p) (0.000 to 48.000)
m1
indep(m1)=4
PAE_contours_p=0.772 / 8.649
level=57.052087, number=1
impedance = Z0 * (5.815 + j3.348)
m2
indep(m2)=3
Pdel_contours_p=0.610 / 8.370
level=31.237924, number=1
impedance = Z0 * (3.801 + j1.074)
LP Sim.
Pout = 31.3dBm
Page  43
Ropt (Power) ~ 205 W
Example Simulated Dynamic Load Line
No Cds
1.4
H
1.2
Higher
frequency
1.0
0.8
0.6
0.4
0.2
0.0
-0.2
0
10
20
30
Vds
(V)
ts(Vds1)
40
50
GaN_CS_FET_Gmax_Cgs_Cds_NG..VDS
60
Ids (mA/mm)
GaN_CS_FET_Gmax_Cgs_Cds_NG..IDS.i/0.38
ts(Ids1.i)/0.38
(H)
GaN_CS_FET_Gmax_Cgs_Cds_NG..IDS.i/0.38
Ids (mA/mm)
ts(Ids1.i)/0.38 (H)
Effect of device Cds
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
-0.2
0
10
20
30
40
50
Vds
(V)
ts(Vds1)
GaN_CS_FET_Gmax_Cgs_Cds_NG..VDS
Ropt_LP ~ 61.5Wmm (Vds=25V)
Theoretically NDPA absorbs Cds and Ropt for each section of the DA
Page  44
60
Example Calculation of NDPA Optimum Ropt & TLIN Width
Cascode 50V-50Ohm, 15-Watt design example
FET
NDPA Calculations
FET Rp Opt. Power (Ohmmm) from LP
123
RL _opt (Ohm)
50
Vds (V)
50
Wg_total (mm)
2.5
Est. RF Power (W), (dBm)
15
PD (W/mm)
Number, n
6
Ids (mA) (assuming Id_p/2)
600
Current Density (mA/mm)
240
PAE (%)
45
1
2
3
4
5
6
7
8
9
FET
Ropt LP
GaN TLIN
(H=100um)
Ropt_n_LP Calc. TLIN
Wg (um)
(Ohm)
Width (um)
500
250
250
250
250
250
250
250
250
246
164
123
98
82
70
62
55
49
0.0
0.9
4.7
13.1
25.8
41.8
60.1
79.7
99.9
Cumm.
Ids
120
180
240
300
360
420
480
540
600
Min M2+M1
Electromigration Min.
Width
6.0
9.0
12.0
15.0
18.0
21.0
24.0
27.0
30.0
Calculations derived from CSIC 2008 Campbell, et.al.
Min. width TLINs limited by
practical lithography & electro-migration rules
Page  45
Practical GaN TLIN Impedances - NDPA
Reduce N
Increases
Rp_opt
of the 1st
section
4um
200um
Practical impedances may be limited to 20-130 Ohms.
This imposes a power-BW limitation (~30 Watts-10GHz?)
Page  46
Summary of Recent GaN DA and NDPA Capability
Summary of Recent GaN MMIC Distributed Amplifiers
REF
Author
Circuit
Topology
Technology
Small-Signal
BW (GHz)
Gain (dB)
Pout
(Watts)
PAE (%)
IP3
(dBm)
Operating
Voltage (V)
[4]
Campbell,
et.al.
NDPA
0.25um GaN
HEMT
1.5-17
13
6-16
20-38
-
30
DC-24
15
1-2.5
-
-
30
[5]
Kobayashi,
et.al.
DC-20
12
1-3
-
-
30
2-18
13
11-14
24-28
-
35
0.01-10
~11
10
< 15
47
48
2-42
> 25 (2-stage)
> 0.5
5-7
-
15
0.5-6
18.7
3.6-7
28-43
-
28
0.02-6
18
30-42
33-37
-
50
0.05-20
10
1-4
~12
45.5
40
Cascode DA
[6]
[7]
[8]
[9]
[10]
Page  47
Capacitivecoupled
Cascode DA
0.2um T-gate
GaN HEMT
IMS2010
Capacitive- 0.25um GaN
Reese, et.al. coupled NDPA
HEMT
Hittite
HMC999
datasheet
Capacitivecoupled
Cascode DA?
?
Fraunhofer,
Capacitive0.1um GaN
IMS2012 coupled NDPA
HEMT
CREE
CMPA006000
DA
2D Datasheet
CREE
CapacitiveCMPA006002
coupled NDPA
5D
2012 PA
Symposium
Capacitivecoupled DA
?
0.25um GaN
HEMT
Page  47
OUTLINE
• Need: BW, Power, Linearity, PAE, Sensitivity, Survivability
• Broadband Application
• GaN Flavors (fT, Lg, BVdg, LN, Power Density)
• Broadband Amplifier Topology – Trades
• Cascode FB
• Darlington FB
• Lossy Match
• DA and NDPA
• Recent Results
• Summary & Future Directions
GaN Wideband Amplifier IP3-BW
1-4 Watt
60
Cascode FB
IP3/Pdc~5.3:1
OIP3 (dBm)
55
Cascode DA
50
IP3/Pdc~1.5:1
45
40
fT-Doubler FB
35
IP3/Pdc~4.3:1
30
0
2
4
6
8
10
12
Frequency (GHz)
Page  49
RFMD Recent Results
14
16
18
20
OUTLINE
• Need: BW, Power, Linearity, PAE, Sensitivity, Survivability
• Broadband Application
• GaN Flavors (fT, Lg, BVdg, LN, Power Density)
• Broadband Amplifier Topology – Trades
• Cascode FB
• Darlington FB
• Lossy Match
• DA and NDPA
• Recent Results
• Summary & Future Directions
APMC 2010
Multi-Octave BW MMIC GaN Amplifier
Topology Demonstrated Capability
Metric
Cascode FB
Darlington
FB
fT-doubler
Gain-BW
Up to 4 GHz
Up to18 GHz
Up to 2.7 GHz
Up to 42 GHz
8W-3GHz
2W-6GHz
5W-8GHz
13.6W-2.5GHz
30W-2.7GHz
30W-6GHz
10W-10GHz
Power-BW
Page  51
LossyMatch
DA &
NDPA
NF
< 1.5 dB
~3-4 dB
~3-4 dB
~3-4 dB
LF limited
IP3
> 51
43.5
-
45-47
LFOM =
IP3/Pdc
5.3:1
2.5:1 - 4.3:1
-
~1:1 - 1.5:1
PAE
up to 21%
21-37%
45-65%
up to 43%
Future Directions
• Device Optimization
• Linearize gate, EPI, Gm
• E-mode
• insulated gate
• THz fT
• higher thermal conductivity (diamond)
• MMIC Design Techniques
• Applying typical PA linearization to broadband topologies
• Linearize the stack (Cascode) approach
• System Techniques
• Apply ET, PDP, etc.
Page  52
Acknowledgment
• RFMD
– Tony Sellas, Curtis Kitani, Rainer Hillermeier, Robert Dry, Don Willis,
Daniel Jin, Rama Vetury, Dave Runton, Jeff Shealy, Dave Aichele, Joe
Johnson, Norm Hilgendorf
• Northrop Grumman
– Mike Wojtowicz, Willie O. Simmons, Don Sawdai, Schaffer Grimm, Ed
Rezek, Aaron Oki, and Frank Kropschot
Page  53
Thank you
for your attention!
Page  54
La Jolla Cove California