High Efficiency Class-E Amplifier Utilizing GaN HEMT

High Efficiency Class-E Amplifier Utilizing GaN HEMT
High Efficiency Class-E
Amplifier Utilizing GaN HEMT
Technology
William L. Pribble, Jim M Milligan, and
Raymond S. Pengelly
Cree Inc
4600 Silicon Drive,
Durham, NC 27703
Creating Technologies That Create Solutions™
Dissipated Power/Output Power
Does Efficiency Matter?
1.6
Class A
1.4
1.2
Class B
1
Switchmode
Class D,E
Class C,F?
0.8
0.6
0.4
0.2
0
0.4
0.5
0.6
0.7
0.8
0.9
1
Effciency
Increasing efficiency from 50% to 80% reduces dissipated power by
80% for a fixed output power
Switchmode amplifier configurations can operate above 80% efficiency
Problem: Extend switchmode operating frequency beyond VHF
Creating Technologies That Create Solutions™
2
Why Switch Mode Amplifiers?
With a suitable high frequency transistor
technology they offer very high efficiencies
compared with Class A/B amplifiers
GaN HEMT technology is ideal
–
–
–
–
High fT
Low input capacitance
Manageable output capacitance
Low RDSON
GaN HEMT is the first technology to offer the
ability of realizing switch mode amplifiers to
well over 3.5 GHz!
Creating Technologies That Create Solutions™
3
Class E Amplifier Basics
FET used as switch is
assumed to have high offresistance
Switch on-resistance
assumed to be constant
and must be minimized to
achieve high PAE
Output capacitance
assumed to be
independent of switch
voltage
Q factor of output circuit
assumed large enough to
suppress harmonics –
“flywheel” effect insures
sinusoidal output
Creating Technologies That Create Solutions™
DCVS
ID=V1
V=1 V
IND
ID=L2
L=L1 nH
IND
ID=L1
L=L2 nH
CAP
ID=C1
C=C2 pF
2
D
1
G
T
S
3
ACVS
ID=V2
Mag=1 V
Ang=0 Deg
Zload :=
κo
ω⋅ C1
⋅e
j⋅ θ
RES
ID=R1
R=RL Ohm
Optimum Class-E fundamental
load for ideal operation – Mader
1995
4
Class E Power Calculations
vcc :=
pout ⋅ rl
0.577
Relates peak output power for ideal classE wavefroms to supply voltage – This
value is ~78% of peak Class-B output
power
To achieve peak Class-E output power as shown,
peak voltage is calculated to be 3.56Vcc, peak drain
current 2.86Idc (Solid State Radio Engineering – Krauss, Bostian, Raab)
Typical class-B voltage waveforms peak at ~2X the
supply voltage
Ideal class-E operation produces lower power for
higher peak voltage – but with 100% efficiency
The optimum class-E device must exhibit both low Ron
and high breakdown voltage to function as a switch
Creating Technologies That Create Solutions™
5
Basic Class E Equations/Limitations
Imax
fmax :=
− 12
56.5⋅ 10
Fundamental frequency limit for ideal class-e
operation related to output capacitance
⋅ cs ⋅ vcc
Class-E Peak Current (A/mm)
cs=C1
2
1.8
1.6
1.4
1.2
1
0.8
0.6
0.4
0.2
0
GaAs PHEMT
0.05
0.1
High-Voltage GaAs
0.15
0.2
0
10
20
30
40
50
Cree GaN – qualified
process available 1st
quarter 2006
Cree GaN Process Goal
Operating Drain Voltage (V)
Plot shows required peak current vs supply
voltage for operation at 4GHz for given output
capacitance
Creating Technologies That Create Solutions™
6
Summary of Class-E Device Requirements
High switching speed (related to input capacitance)
required for switchmode operation – Ft as much as
10X operating frequency to minimize transition-time
loss
Low on-resistance/high peak current to approximate
ideal switch and increase peak operating frequency
High breakdown voltage to accommodate class-E
peak voltage for > 50 watt output power
Gallium Nitride HEMT is the only presently available
technology which provides these attributes
Creating Technologies That Create Solutions™
7
Class
-E Switch Mode Amplifier Simulation using
Class-E
Cree GaN HEMT Large
-Signal Model
Large-Signal
Freq = 2.0 GHz
Q1 = Cree 15 watt GaN HEMT
RON = 1.7Ω
VD=V=35V
RL=26 , C1=0.64pF, L1 = 50uH
L2=13nH,C2=0.612pF
POUT=10 Watts, =82%
60
1.5
40
1.0
20
0.5
0
0.0
0.0
0.2
0.4
0.6
0.8
1.0
time, nsec
50
Current (A)
RL
2.0
100
40
80
30
60
20
40
10
20
0
PAE (%)
C1 absorbed
in device
Voltage (across Q1)
80
Output Power (dBm)
(I)
Voltage (V)
Current (I)
0
10
12
14
16
18
20
22
24
26
28
Input Power (dBm) @ 2GHz
Creating Technologies That Create Solutions™
8
World Record 2.0 GHz
High Efficiency GaN Amplifier
Output Power (dBm )
Measured Performance @ 30 V
43
90
42
80
41
70
40
60
39
50
power
38
40
pae
37
30
36
20
35
10
34
0
1.7
1.8
1.9
2
2.1
2.2
2.3
Frequency (GHz)
Fabricated High Efficiency GaN Hybrid
Class E Hybrid amplifier
Vd = 30 volts
50 input/output
10 W POUT, 88% Drain Efficiency!
– 1.9 – 2.1 GHz!
Creating Technologies That Create Solutions™
9
Approach Validated at Higher
Frequencies and Moderate Bandwidths
Measured Data
Measured Data
90
50
80
48
80
48
78
46
70
46
76
44
74
42
72
40
70
38
68
36
66
44
60
42
40
38
50
power
40
pae
30
36
Output Power (dBm)
Output Power (dBm)
50
34
20
34
64
32
10
32
62
0
30
3.25
30
2.5
2.6
2.7
2.8
2.9
3
3.1
Frequency (GHz)
~10 Watts RF Out
12 dB Power Gain
76-82% PAE
2.7 – 2.9 GHz
3.3
3.35
3.4
3.45
3.5
power
pae
60
3.55
Frequency (GHz)
~10 Watts RF Out
11 dB Power Gain
72-78% PAE
3.3 – 3.5 GHz
Cree’s GaN Technology Enables High-Power
High Frequency Class-E Operation
Creating Technologies That Create Solutions™
10
Approach Validated at Higher Power Levels
output power (dBm )
amp 1
Output Power,
dBm
50
49.5
49
48.5
48
47.5
47
46.5
46
1.85
amp 1
1.9
1.95
2
2.05
2.1
frequency (ghz)
amp 1
Power Added
Efficiency, %
80
75
63 Watts Peak RF Output Power
18 dB Power Gain
75% PAE
2 GHz Operation
Creating Technologies That Create Solutions™
pae
70
65
amp 1
60
55
50
1.85
1.9
1.95
2
2.05
2.1
frequency (ghz)
11
Summary
GaN HEMT-Class E amplifier / ET
demonstrated linear PAE of 54%
–
–
–
–
–
Much Superior to GaAs MESFET and LDMOSFET
Demonstrates “leapfrog” in efficiency when compared
to conventional Class A/B biased amplifiers deployed
today
High Power GaN HEMT-Class E modules built &
measured
Overall efficiency in ET system at 56% with 20 Watts
average power under CDMA 2000
Approach suitable for telecom. bands including 3.5GHz
WiMax
Creating Technologies That Create Solutions™
12
Was this manual useful for you? yes no
Thank you for your participation!

* Your assessment is very important for improving the work of artificial intelligence, which forms the content of this project

Download PDF

advertising