A high efficiency Class-E amplifier utilizing GaN HEMT technology - presentation

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A high efficiency Class-E amplifier utilizing GaN HEMT technology - presentation Powered By Docstoc
					             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™
  Does Efficiency Matter?
                                    1.6
    Dissipated Power/Output Power




                                                                                        Class A
                                    1.4

                                    1.2
                                                                                        Class B
                                     1
                                                                                        Switchmode
                                    0.8
                                                                                        Class D,E
                                    0.6                                                 Class C,F?
                                    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                                          DCVS


        assumed to have high off-
                                                                       ID=V1
                                                                       V=1 V



        resistance
        Switch on-resistance                                           IND
                                                                       ID=L2             IND        CAP


        assumed to be constant
                                                                       L=L1 nH           ID=L1      ID=C1
                                                                                         L=L2 nH    C=C2 pF



        and must be minimized to
                                                                                 2
                                                                                  D
                                                                        1        T


        achieve high PAE
                                                                        G
                                                                                                       RES
                                                                                     S                 ID=R1
                                                                                 3                     R=RL Ohm
                                                     ACVS


        Output capacitance
                                                     ID=V2
                                                     Mag=1 V
                                                     Ang=0 Deg


        assumed to be
        independent of switch
        voltage                                                  κo         j⋅ θ         Optimum Class-E fundamental
                                               Zload :=               ⋅e                 load for ideal operation – Mader
        Q factor of output circuit                         ω⋅ C1                         1995

        assumed large enough to
        suppress harmonics –
        “flywheel” effect insures
        sinusoidal output
Creating Technologies That Create Solutions™                                                                                4
  Class E Power Calculations
                                     Relates peak output power for ideal class-
                      pout ⋅ rl
           vcc :=                    E wavefroms to supply voltage – This
                       0.577         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                          Fundamental frequency limit for ideal class-e
                      fmax :=                                                      operation related to output capacitance
                                                     − 12
                                          56.5⋅ 10          ⋅ cs ⋅ vcc
                                cs=C1

                                  2                                                                           GaAs PHEMT
  Class-E Peak Current (A/mm)




                                1.8
                                1.6
                                1.4                                                           0.05
                                1.2                                                                           High-Voltage GaAs
                                                                                              0.1
                                  1
                                                                                              0.15
                                0.8
                                0.6                                                           0.2
                                                                                                              Cree GaN – qualified
                                0.4                                                                           process available 1st
                                0.2                                                                           quarter 2006
                                  0
                                      0    10          20        30           40       50                     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
                                                                                        Current (I)         Voltage (across Q1)

                                                             80                                                                                                    2.0


                                                             60                                                                                                    1.5




                                                                                                                                                                         Current (A)
                                               Voltage (V)
                       C1 absorbed       RL
                 (I)                                         40                                                                                                    1.0
                       in device

                                                             20                                                                                                    0.5


                                                                   0                                                                                               0.0
                                                                              0.0                0.2              0.4             0.6         0.8         1.0
     Freq = 2.0 GHz
                                                                                                                   time, nsec
     Q1 = Cree 15 watt GaN HEMT                                                   50                                                                          100


     RON = 1.7Ω
                                                             Output Power (dBm)
                                                                                  40                                                                          80

     VD=V=35V                                                                     30                                                                          60




                                                                                                                                                                   PAE (%)
     RL=26 , C1=0.64pF, L1 = 50uH                                                 20                                                                          40

     L2=13nH,C2=0.612pF                                                           10                                                                          20
     POUT=10 Watts, =82%
                                                                                   0                                                                          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
                                             Measured Performance @ 30 V
                            43                                                   90
                            42                                                   80
                            41                                                   70
      Output Power (dBm )




                            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
                      50                                                         90                                50                                              80
                      48                                                         80                                48                                              78
                      46                                                         70                                46                                              76




                                                                                              Output Power (dBm)
 Output Power (dBm)




                      44                                                                                           44                                              74
                                                                                 60
                      42                                                                                           42                                              72
                                                                                 50   power                                                                              power
                      40                                                                                           40                                              70
                                                                                 40   pae                                                                                pae
                      38                                                                                           38                                              68
                                                                                 30
                      36                                                                                           36                                              66
                      34                                                         20                                34                                              64
                      32                                                         10                                32                                              62
                      30                                                         0                                 30                                               60
                           2.5   2.6     2.7         2.8         2.9   3   3.1                                       3.25   3.3   3.35     3.4     3.45   3.5   3.55
                                               Frequency (GHz)                                                                       Frequency (GHz)



                                       ~10 Watts RF Out                                                                           ~10 Watts RF Out
                                       12 dB Power Gain                                                                           11 dB Power Gain
                                       76-82% PAE                                                                                 72-78% PAE
                                       2.7 – 2.9 GHz                                                                              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
                                                                                              amp 1
                                                                                      Output Power, dBm
                                                                       50
                                                                     49.5




                                               output power (dBm )
                                                                       49
                                                                     48.5
                                                                       48                                               amp 1
                                                                     47.5
                                                                       47
                                                                     46.5
                                                                       46
                                                                         1.85    1.9      1.95        2    2.05   2.1
                                                                                         frequency (ghz)



                                                                                        amp 1
                                                                                Power Added Efficiency, %
                                                                     80
                                                                     75
                                                                     70

                                               pae
                                                                     65                                                 amp 1
      63 Watts Peak RF Output Power                                  60

      18 dB Power Gain                                               55
                                                                     50
      75% PAE                                                          1.85     1.9      1.95        2     2.05   2.1
                                                                                         frequency (ghz)
      2 GHz Operation

Creating Technologies That Create Solutions™                                                                                    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

				
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posted:10/21/2011
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