Slide 1 V. Paidi Department of Electrical and Computer Engineering, University of California, Santa...

V. PaidiDepartment of Electrical and Computer Engineering,

University of California, Santa Barbara

High Frequency Power Amplifiers

Outline• Research to date

• Class B Power amplifiers in GaN HEMT technology for applications in X-band.

• Design of G-band (140-220 GHz) Power Amplifiers in InP mesa DHBT technology.

• Proposed Future Research

• Fabrication and measurement of G-band ( 140-220 GHz) Power amplifiers in InP DHBT technology

• Process improvements for better yield and performance.

Class B Power amplifiers in GaN HEMT technology

• Push-Pull Vs Single-ended topology.

• Common Source Class B.

• Common Drain Class B.

Why Class B? and Why GaN HEMTs?• Why Class B ?

– Class A: Ideal PAE 50%, feasible PAE 20-30%. However , good linearity.

– Switch mode Amplifiers: Ideal PAE 100%, feasible PAE 60-70 %. Poor Linearity.

– Class B: Ideal PAE 78.6%; feasible PAE 40-50% (typical GaN HEMT at X-band). Potential Low distortion Operation.

• Why GaN HEMTs ?

– Excellent Power density, as high as 12 W/mm in X-band.

– ft ~ 50 GHz and fmax ~ 80 GHz for Lg ~ 0.25m due to high saturation velocity.

– ‘Near Linear’ Id-Vgs Characteristics about threshold leading to a potential low distortion Class B operation.

• Half sinusoidal drain current on each device, but full sinusoidal drain voltage. • Even harmonics are suppressed by symmetry => wide bandwidth (limited by the power combiner). • To obtain high efficiency (78%), a half-sinusoidal current is needed at each drain. This requires an even-harmonic short. This can be achieved at HF/VHF frequencies with transformers or bandpass filters. However,

1. Most wideband microwave baluns can not provide effective broadband short for even-mode. Efficiency is then poor.

2. They occupy a lot of expensive die area on MMIC.

UCSBPush-pull Class BV. Paidi, S. Xie

RL

VG

Vin

Cbias

Cbias

VD

1:1

1:1

Vin-

Vin+

ID+

ID-

Vout

VDS+

VDS-

Push-pull Class B

Single-ended Class B with an output filter

Even harmonics suppressed by symmetry

Even harmonics suppressed by filter

UCSBSingle-ended Class B = push-pull

Bandwidth restriction < 2:1

V. Paidi, S. Xie

Id1Id1

Vin

Id2

Vin Vin

Id

Actual Tranfer Function Even-order components Odd-order components

Id

Vin

Id

Vin Vin

Id

.....33

221 ininincd VIVIVII .....3

32

21 ininincd VIVIVII ..22 331 inin VIVI

.....33

221 ininincd VIVIVII .....2

2 incd VII .....331 inin VIVI

Only harmonic distortion

harmonic + IMD distortion

UCSBLinearity Analysis-Id vs Vgs V. Paidi, S. Xie

.........*** 33

2210 gsgsgs VIVIVIII

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

-5 -4 -3 -2 -1 0

Experimental (A/mm)Modeled (A/mm)

Dra

in C

urr

en

t (A

/mm

)

Gate Bias (V)

Near linear characteristics of GaN HEMTs on SiC

The third order term is small about the threshold Voltage

Odd-part creates distortion

UCSBLinearity Analysis-Id vs Vgs Contd.V. Paidi, S. Xie

Ideal Class B Bias too low:Class C

Bias too high:Class AB

Id2

Id

Id

Vin

Vin

Vin

Id Id

Id2Id2

IdId

Vin Vin

Vin Vin

VinVin

Class B bias has the minimum distortion

RF Performance at Vds=15V, Vgs=-3.5V of 0.25X150m2 device

Process and Device Performance

• Lg ~ 0.25um,Idss ~ 1A/mm

• ft ~ 55 GHz (~ 50 GHz for dual gate)

• Vbr ~ 40V (~ 55V for dual gate)

Pulsed IV Curve(80sec) 600m Single gate GaN HEMT

~1.2 A

0

5

10

15

20

25

30

35

40

1 10 100

Sh

ort

Circ

uit

Cu

rre

nt G

ain

(h21

), d

B

frequency, GHz (log scale)

fT = 50GHz

Good Passivation,600mA at Vgs=0V fT~50 GHz

SiC substrate ~400 um

1.4 um GaN buffer

25 nm Al0.3Ga0.7N barrier

60nm AlN Nucleation layer

1nm AlN layer

400 nm Silicon Nitride

Plated Airbridge

Silicon Nitride Passivation Layer

Ti/ Al/ Ni/ Au ohmic Contact

Ni/Au Schottky Contact

UCSBV. Paidi, S. Xie

UCSB

RLTLIN

R1 L1

L2

C1

RF IN

Vg

Vd

BIASTEE Input

matchingnetwork

Outputmatchingnetwork

Cds BIASTEE

(short at 2fo, 3fo...)

Gate 2

Gate 1

Single-ended Class B Power AmplifierS. Xie, V. Paidi

Lossy input matching - section lowpass filter

Class B bias @Vgs = - 5.1V

Single tone performance @ f0 = 8GHz:

Two tone performance @ f1=8GHz, f2=8.001GHz :

15

20

25

30

35

40

0

0.1

0.2

0.3

0.4

0.5

0 5 10 15 20 25 30

Ou

tpu

t po

wer,

db

m

PA

E

Input power, dbm

-50

-40

-30

-20

-10

0

10

20

30

0

0.05

0.1

0.15

0.2

0.25

-15 -10 -5 0 5 10 15 20

Out

put

pow

er,

dBm

PA

E

Input power, dBm

f1,f2

2f1-f2, 2f2-f1

Gain ~ 13 dB,PAE (maximum) ~ 34%

Saturated output power 36 dBm

Good IM3 performance: • 40dBc at Pin = 15 dBm, and• > 35 dBc for Pin < 17.5 dBm

V. Paidi, S. XieUCSB

Summary of IM3 suppression

10

20

30

40

50

60

0 5 10 15 20 25 30 35

IM3 c

om

pre

ssio

n,

dB

c

Pout, dBm

Class BClass A

Class C

Class ABPsat

• Low output power levels (Pout < 24 dBm), Class A and Class B both exhibit good linearity (Class B > 36 dBc, Class A > 45 dBc).

• Higher output power levels, Class A behaves almost the same as Class B.

• Class AB and C exhibit more distortion compared to Class A and B.


Why Common Drain Class B ?

RL

vi vout

bandpass filter @fo

InputMatchingnetwork

Vdd

Vin Vout


)( gsmLoadin

out VgRV

VGain

)(1

)(

gsmLoad

gsmLoad

in

out

VgR

VgR

V

VGain

Gain of the Common Drain Class B

Gain of the Common Source Class B

In Common drain design the nonlinearity in gm is suppressed by the feedback term in the denominator.If , then voltage Gain is independent of gm

1)( gs

Vm

gLoad

R

Circuit Schematic

Disadvantage : Maximum stable gain is less for common drain configuration resulting in reduction in efficiency With higher fmax MSG could be better.

Comparison between Common Drain and Common source designs

.15~)36log(10)1log(10

56

30~*

2*

*

dBRgfactorLinearity

V

VV

I

VV

V

IRgfactorFeedback

Loadm

p

kbr

dss

kbr

P

dssLoadm


0

10

20

30

40

50

60

70

5 10 15 20 25 30 35

IM3

Sup

pre

ssio

n, d

Bc

pout, dBm

12 dB

Common Drain

Common Source

•Common drain and common source designs are @ 10GHz

• Both have 36 dBm of saturated output power.1.2 mm GaN HEMTs are used.

•Common drain design has ~12 dB superior IM3 suppression over the equivalent Common Source design.

• At 1W total output power Common drain exhibits 46 dBc IMD3 Common source exhibits 36 dBc IMD3.

Common Drain Class B Power Amplifier

10

15

20

25

30

35

40

0

0.1

0.2

0.3

0.4

0.5

5 10 15 20 25 30 35

Ou

tpu

t P

ower

, dB

m

PA

E

input power, dbm

0

10

20

30

40

50

60

10 15 20 25 30 35

IM3

Su

ppre

ssio

n,

dBc

Total output power, dBm


Specifications

• 37 dBm saturated output power at 5 GHz• 8 dB Class B gain, 4-6 GHz bandwidth.• 38% maximum PAE• 44 dBc at 1W total output power under Class B bias.•Being fabricated by Shouxuan Xie

Layout ~6 mm X 2.5mm

Psat ~ 37 dbm

PAE ~ 38 %

IMD3 > 42 dBc for Pout <2 W

Power Amplifiers in InP mesa DHBT technology

• Motivation.

• Layer Structure and process ( Mattias, Zach ).

• Performance of InP mesa DHBT technology ( Mattias, Zach).

• G-band ( 140-220 GHz) Power amplifier design and layout.

Motivation for 140- 220 GHz power amplifiers and Previous results

• Applications for electronics in 140-220 GHz frequency band

Wideband communication systems Atmospheric sensing Automotive radar

• Small signal amplifier results

6.3 dB @ 175 GHz single stage amplifier in InP TSHBT technology, Miguel et.al.,12 dB @ 170 GHz three stage CE amplifier in InP TSHBT technology, Miguel et.

al., 3-stage amplifier with 12-15 dB gain from 160-190 GHz, InP HEMT, Lai et. al. 6-stage amplifier with 20 6 dB from 150-215 GHz, InP HEMT, Weinreb et. al.

• Power amplifier results 12.5 dBm @90 GHz with 8.6 dB gain in TS InP DHBT technology, Yun et. al., 14-16 dBm @140-170 GHz with 10 dB gain in InP HEMT technology, Lorene et. al., 14-16 dBm @65-145 GHz with > 10 dB gain in InP HEMT technology, Lorene et. al.,

Why mesa -InP HBTs for 140- 220 GHz power amplifiers ?

• fmax > 400 GHz for 2100A Collector, 300A base HBT( Technologies like SiGe have fmax ~ 210 GHz Jae- Sung Rieh et al., IBM ( IPRM 2003) )

• High bandwidth as ft > 250 GHz for 2100A Collector, 300A base HBT

• Current density > 3 mA/ m2 at Vbe = 0.7 V and Vcb = 0 V for Tc = 2100A.

• Vbr,ce0 > 6V

• Low thermal resistance.

Layer Structure UCSBMattias, Zach

InP Emitter n+ doped

P+ InGaAs Base: doping grading

2100 Å n- InP Collector

Material Doping (cm-3) Thickness ()

n-InGaAs 3∙1019 300

n-InP 3∙1019 1000

n-InP 8∙1017 100

n-InP 5∙1017 500

p+-InGaAs 5-8∙1019 (C) 350

n-InGaAs 1.5∙1016 200

Base Collector Grade

1.5∙1016 240

n-InP 3∙1018 30

n-InP 1.5∙1016 1630

n+-InP 1.5∙1019 100

n+-InGaAs 2∙1019 100

n+-InP 2∙1019 3000

InP SI N/A

Mesa IC Process: Key Features

Slide 1

polymide NiCr metal 1 SiN Air bridge


Slide 2



Slide 3



Slide 4



Slide 5


SI InP

CollectorBaseE

sub-collector


Slide 6


SI InP

CollectorBaseE

sub-collector


Slide 7


SI InP

CollectorBaseE

sub-collector

• Both junctions defined by selective wet-etch chemistry

• Narrow base mesa allows for lowAC to AE ratio

• Low base contact resistance—Pd based ohmics with C < 10-7 ∙cm2

• Collector contact metal and metal ‘1’ used as interconnect metal

• NiCr thin film resistors = 40 /

• MIM capacitor, with SiN dielectric… -- used only for bypass capacitors

Mesa IC Process: overview

SI InP

CollectorBaseE

sub-collector

• CPW wiring environment….

• has predictable characteristic impedance

• CPWs are modeled using ADS momentum

• Air bridges are used to strap the ground planes


DC and RF measurements

• Common emitter characteristics• Device geometry: emitter metal = 0.6 8.0 m2, real device = 0.54 ∙ 7.7 m2

• Collector to emitter area ratio, AC / AE = 5

• f = 282 GHz, fmax = 400 GHz

• Measurement condition:VCE = 1.7 Volts, Jc = 3.6 mA/m2

• IB = 50 A per step

• DC beta = 20• Vbr = 7 V

UCSBMattias, Zach

0

1

2

3

4

5

0 0.5 1 1.5 2 2.5 3

I C (m

A)

VCE

(V)

emitter junction area: 0.44 m x 7.4 mIB step = 50 uA

0

0.5

1

1.5

2

2.5

3

0 1 2 3 4 5 6 7 8

0

5

10

15

20

25

30

1010 1011 1012

Ga

ins

(dB

)

Frequency (Hz)

ft=282 GHz

fmax

=400 GHz

U

H21

Thermal considerations

• Device geometry: emitter metal = 0.8 12.0 m2

• Vbr = 7 V, Imax = 3 mA/ m2.• θth = 1.25 K/ mW. ( Dr. Ian Harrison’s simulations)• Bias conditions, VCE = 3.5 V, IC = 13 mA (1.5 mA/ m2).

125*/5.126

/1.1/25.145

* 22

mmmAmV

KmVmWKmW

exR

cI

TV

Tbe

V

dP

TdP

TK

• The device is thermally stable even without external ballast resistance

• However, improvements in Rex could be dangerous.

• Few backup designs with ballast resistance are included.

Single stage Common Base G band ( 140- 220 GHz) power amplifier in InP DHBT technology

0

5

10

15

20

0

0.05

0.1

0.15

0.2

0 5 10 15 20

Out

put P

ow

er,

dB

m

PA

E

Input Power, dBm

Objectives: G band, Psat~ 20 dBm

Approach: InP mesa-DHBTs, microwave amplifier design

Simulations: S-parameter and harmonic and momentum simulation in ADS

Accomplishments:f0=180 GHz, BW3dB ~ 45 GHz,

GT=5.3 dB, Psat ~ 20 dBm.

common base PA

2 x2x0.8m x 12 m, AE=38 m2

-10-8-6-4-20246

100 125 150 175 200 225 250

S21S11S22

S2

1, S

11

, S

22 d

B

frequency, GHz

Two stage Common Base G band ( 140-220 GHz) power amplifier in InP DHBT technology

0

5

10

15

20

0 2 4 6 8 10 12 14

Out

put P

ow

er,

dB

m

Input Power, dBm

Objectives: G band, Psat~ 19.5 dBm




GT=8.7 dB, Psat ~ 19.5 dBm.

common base PA

6 x 0.8m x 12 m, AE=58 m2

-10

-5

0

5

10

15

150 160 170 180 190 200 210 220

S21S11S22

S2

1, S

11,

S22

dB

frequency, GHz

Cascode G band ( 140-220 GHz) power amplifier in InP DHBT technology

-5

0

5

10

15

20

0

0.08

0.16

0.24

0.32

0.4

-10 -5 0 5 10 15

Out

put P

ow

er,

dB

m

PA

E

Input Power, dBm





GT=8.5 dB, Psat ~ 16.5 dBm.

Cascode PA

4 x 0.8m x 12 m, AE=38 mm2

-10

-5

0

5

10

60 80 100 120 140 160 180 200 220

S21S11S22

S2

1

Frequency, GHz

Two stage Common Base G band ( 140- 220 GHz) power amplifier With Emitter ballasting Resistance

0

5

10

15

20

0 2 4 6 8 10 12 14

Out

put P

ow

er,

dB

m

Input Power, dBm

-10

-5

0

5

10

15

120 130 140 150 160 170 180 190 200

S21S11S22

S2

1, S

11

, S

22 d

B

Frequency, GHz


Approach: InP mesa-DHBTs, microwave amplifier

design, 1Ώ per each finger, ~ 20 Ώ / m2



GT=8 dB, Psat ~ 16.5 dBm.

common base PA

4 x 0.8m x 12 m, AE=38 m2

Single stage Common Base W band ( 75-110 GHz) Power Amplifier

0

5

10

15

20

25

0

0.05

0.1

0.15

0.2

0.25

0 3 6 9 12 15

Out

put P

ow

er,

dB

m

PA

E

Input Power, dBm

-10

-5

0

5

10

50 60 70 80 90 100 110 120

S21S11S22

S2

1, S

11, S

22 d

B

Frequency, GHz

Objectives: W band, Psat~ 20 dBm

Approach: InP mesa-DHBTs, microwave amplifier

design,



GT=8 dB, Psat ~ 20 dBm.

common base PA

4 x 0.8m x 12 m, AE=38 m2

Summary of All DesignsThe mask has

• 0 - 50 GHz : One Single Stage 100 mW design

• 50 – 70 GHz : One Single Stage 100 mW design

•70 - 110 GHz : Three Single Stage 100 mW designs

•110 – 140 GHz : Two Single Stage 100 mW designs, One Cascode 50 mW design

•140 – 220 GHz : Eight Single Stage 50 mW designs, Four Single Stage 100 mW designs, Six Two Stage 50 mW designs, Two Two Stage 100 mW designs, Four Cascode 50 mW designs

• RF Calibration Structures

• Thermal Calibration Structures

• Successful fabrication of X-band Class B Power amplifier in

GaN HEMT technology for good linearity and efficiency.

• Design of Common Drain Class B for further linearity enhancement. ( Currently being fabricated by Shouxuan Xie)

• Design of G – band ( 140-220 GHz) power amplifiers in InP mesa DHBT technology.

Accomplishments

• Fabrication of the power amplifiers in UCSB InP mesa DHBT process.

• Testing and measurement in collaboration with Jet Propulsion Labs.

• Improve the InP mesa process for better yield and performance.

• More iterations to improve the amplifier performance.

Proposed Work

This work was supported by the ONR , JPL , DARPA.

Acknowledgements

• Till 110 GHz we have measurement set up

• Several 160- 200 GHz Schottky diode amps Psat ~ 50 mW ( Lorene)

• 140, 180 doublers and triplers and power heads. ( Lorene )

• JPL has sources and power heads from 40-120 GHz ( Lorene)

What does JPL have?

15

20

25

30

35

40

0

10

20

30

40

50

60

70

0 5 10 15 20 25 30

Out

put p

ower

, dBm PAE (%

)

Input power, dBm

Simulation of class B amplifier @10GHz

Saturated PAE ~48%

Class B bias: Saturated output power ~ 37 dBm,Saturated PAE ~ 48%

UCSBSimulations of Class BS. Xie, V. Paidi

10

15

20

25

30

35

40

45

50

0 50 100 150 200

Dra

in V

olt

ag

e, V

time, psec.

0

200

400

600

800

1000

0 50 100 150 200

Dra

in C

urr

en

t, m

A

time, psec.

Waveforms of drain voltage and current

Saturated output power ~37 dBm

Best IM3 suppression is achieved at Class B and Class A

UCSBSimulations of Class B Contd.S. Xie, V. Paidi

36

38

40

42

44

46

48

50

20

25

30

35

40

45

50

-5.5 -5 -4.5 -4 -3.5 -3 -2.5 -2 -1.5

Sat

urat

ed P

AE

(%

)

IMD

3 @6dB

back_off (dB

c)

Gate Bias, V

Class B bias: C/IMD3~44dBcPAE ~ 48% Class A bias

C/IMD3~42dBcPAE ~ 35%

Class AB bias

Class C bias

Measurement setup

Signalgenerator_1

Signalgenerator_2

Poweramplifier_1

Poweramplifier_2

Powercombiner Coupler

Powermeter

Bias T DUT

Coupler

Bias T

- 20 dB - 20 dB

Coupler 50 OhmLoad

Spectrum Analyzer

CH_A

CH_B

- 20 dB- 20 dB - 20 dB

UCSB

• Single tone from 4 GHz to 12 GHz;

• Two-tone measurement at f1 = 8 GHz, f2 = 8.001 GHz;

• Bias sweep: Class A (Vgs = -3.1V), Class B (Vgs = -5.1V, Class C (Vgs = - 5.5 V) and AB (Vgs = -4.5 V).

Measurements:

V. Paidi, S. Xie

Class B vs. Class A

10

20

30

40

50

0

0.05

0.1

0.15

0.2

0.25

0.3

-5 0 5 10 15 20 25 30 35

IM3

supp

resi

on,

dBc P

AE

, twoto

ne

Output power, dBm

Class B

Class A

IM3 suppression and PAE of two-tone

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

10 15 20 25 30 35 40

PA

E,

sing

le

Output power, dBm

PAE of single tone

Class BClass A

Maintaining good IM3 suppression Class B can get 10% PAE improvement over Class A during low distortion operation.


Class A bias @Vgs = - 3.1V

-10

0

10

20

30

40

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

-20 -10 0 10 20 30

Out

put

pow

er,

dBm

PA

E

Input power, dBm

-30

-20

-10

0

10

20

30

40

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

-20 -15 -10 -5 0 5 10 15 20

Outp

ut

pow

er,

dB

m

PA

E

Input power, dBm

f1,f2

2f1-f2, 2f2-f1

Single tone performance @ f0 = 8GHz:

Two tone performance @ f1=8GHz, and f2=8.001GHz :

Saturated output power 36 dBm

Good IM3 performance at low power level but becomes bad rapidly at high power levels

Saturated output power each tone ~ 33dBm


PAE (maximum) ~ 34%

100

200

300

400

500

600

700

-8 -7 -6 -5 -4 -3 -2 -1 0

Experimental (fF/mm)

modeled (fF/mm)

Cg

s (fF

/mm

)

Gate Bias (V)

UCSBLinearity Analysis-Cgs vs Vgs V. Paidi, S. Xie

Anti-symmetric Cgs vs Vgs characteristics of GaN HEMTs on SiC

C2 is small due to the anti-symmetric Cgs vs Vgs

2210

2321 32)( VcVccVqVqq

V

QVC

33

2210 VqVqVqqQ

Even-part creates distortion

UCSBLinearity Analysis-Cgs vs Vgs Contd. V. Paidi, S. Xie

Ideal Class BBias too low:Class C

Bias too high:Class AB

Vin

Vin

Vin VinVin

Vin Vin

Cgs

Cgs

Cgs

Cgs

Cgs

Cgs

Cgs

Vin Vin

Class A

Vin

Cgs

Cgs

Cgs

Vin

Vin

2C0 2C0 2C0 2C0

Cgs

Cgs

C0 C0C0

C0

C0C0C0C0

Class B bias has low distortion

Measured Gain

Gain vs. frequency

-5

0

5

10

15

20

2 4 6 8 10 12 14 16

Gain

, dB

Frequency, GHz

Class AB

Class B

3 dB bandwidth: 7GHz - 10GHz

S. Xie, V. PaidiUCSB

Summary of All Designs UCSBpaidi

Design Topology f0, GHz Area(m2) Psat, dBm Gain BW3dB

Common Base, Single Stage 40 4 x 0.8 x 12 20 dBm 10 dB 30 GHz




Common Base, Single Stage 120 4 x 0.8 x 12 20 dBm 7.5 dB 55 GHz

Common Base, Single Stage 140 2 x 0.8 x 12 16.5 dBm 8.3 dB 40 GHz





Common Base, Single Stage 140 2 x 2 x 0.8 x 12 20 dBm 7.6 dB 60 GHz



Common Base Single Stage 160 2 x 2 x 0.8 x 12 20 dBm 7.1 dB 45 GHz



Common Base Single Stage (no cap) 100 4 x 0.8 x 12 20 dBm 9 dB 30 GHz



Common Base Single Stage (no cap) 180 2 x 0.8 x 12 17 dBm 5.3 dB 40 GHz


Common Base Two Stage 140 4 x 0.8 x 12 17 dBm 16 dB 35 GHz


Common Base Two Stage 180 4 x 0.8 x 12 17 dBm 9.3 dB 60 GHz



Common Base Two Stage 180 6 x 0.8 x 12 19.5 dBm 8.6 dB 45 GHz


Common Base Two Stage ( no cap) 180 4 x 0.8 x 12 17 dBm 10.5 dB 45 GHz

Common Base Two Stage ( no cap)Ballast resistance 20 ohm m2

180 4 x 0.8 x 12 17 dBm 8.6 dB 50 GHz

Common Base Two Stage ( no cap)Ballast resistance 40 ohm m2

180 4 x 0.8 x 12 17 dBm 7.2 dB 50 GHz

Cascode 120 4 x 0.8 x 12 17 dBm 13 dB 35 GHz

Cascode 140 4 x 0.8 x 12 17 dBm 8 dB 110GHz

Cascode 160 4 x 0.8 x 12 17 dBm 8 dB 40 GHz

Cascode 180 4 x 0.8 x 12 17 dBm 8.5 dB 50 GHz

Cascode 200 4 x 0.8 x 12 17 dBm 4.5 dB 190 GHz

• For less than octave bandwidth, push-pull and single-ended Class B amplifiers have equivalent PAE and linearity.

• A single-ended Class B MMIC power amplifier in GaN HEMT technology is designed and 36dBm of saturated power and 35dBc of IM3 suppression are obtained.

• Class B is better than Class A because it can get good IM3 performance comparable to that of Class A, while providing more than 10% improvement in PAE under low distortion operation.

UCSBConclusions S. Xie, V. Paidi

Chip photograph of Class B power amplifier

(Approximately 6mmX1.5mm)

Air bridges

Source

Drain

Gate 1Gate 2

UCSBV. Paidi, S. Xie

Comparison between Common Drain and Common source designs Contd. V. Paidi, S. Xie

UCSB

0

10

20

30

40

50

60

-8 -7 -6 -5 -4 -3 -2

IM3

supp

ress

ion

, dB

c

bias point, V

Class ABClass C

Class B Class A

IM3 suppression at 1W total output power as a function of bias point

Common source

Common Drain

Common Drain Class B Power AmplifierV. Paidi, S. Xie

UCSB

Layout ~6 mm X 2.5mm

Specifications

• 37 dBm saturated output power at 5 GHz• 8 dB Class B gain, 4-6 GHz bandwidth.• 38% maximum PAE• 44 dBc at 1W total output power under Class B bias.

• Two identical devices working in 50% duty cycle with 180° phase shift. • Half sinusoidal drain current on each device, but full sinusoidal drain voltage. • Even harmonics are suppressed by symmetry => wide bandwidth (limited

by the power combiner). • Class B: Ideal PAE 78.6%; feasible PAE 40-50% (typical GaN HEMT at X-

band); Class A: Ideal PAE 50%, feasible PAE 20-30%.

VinVout = VDS1 – VDS2

0

180

0

180

+Vin

-Vin VDS2

VDS1

UCSBHow does push-pull Class B PA work?V. Paidi, S. Xie

Common Base Power Amplifier @40GHz

30 50 7010 80

-7.5-5.0-2.50.02.55.07.5

10.012.515.017.5

-10.0

20.0

freq, GHz

dB

(S(2

,1))

dB

(S(1

,1))

dB

(S(2

,2))

Technology:• InP mesa HBT•Ft~200 GHz, fmax ~400 GHz•Vbr ~ 7V•Current density ~ 3mA/um2•Area ~4 fingersX0.8X12 um2

Pout ~ 21 dBm

Approximate Layout (1.1 mm X0.3 mm) Performance gain > 10 dB

2 4 6 8 10 120 14

12

14

16

18

20

10

22

0.1

0.2

0.3

0.0

0.4

p

pout P

AE


20 40 60 80 1000 110

-7.5-5.0-2.50.02.55.07.5

10.012.515.017.5

-10.0

20.0

freq, GHz

dB

(S(2

,1))

dB

(S(1

,1))

dB

(S(2

,2))

2 4 6 8 10 120 14

12

14

16

18

20

10

22

0.1

0.2

0.3

0.0

0.4

p

pout P

AE


Pout > 21 dBm



70 90 110 13050 150

-7.5-5.0-2.50.02.55.07.5

10.012.515.017.5

-10.0

20.0

freq, GHz

dB

(S(2

,1))

dB

(S(1

,1))

dB

(S(2

,2))


Pout > 21 dBm


2 4 6 8 10 120 14

12

14

16

18

20

10

22

0.05

0.10

0.15

0.20

0.25

0.30

0.00

0.35

p

pout P

AE


Pout > 20 dBm


2 4 6 8 10 120 14

10

12

14

16

18

20

8

22

0.05

0.10

0.15

0.20

0.00

0.25

p

pout P

AE

100 120 14080 150

-7.5-5.0-2.50.02.55.07.5

10.012.515.017.5

-10.0

20.0

freq, GHz

dB

(S(2

,1))

dB

(S(1

,1))

dB

(S(2

,2))



2 4 6 8 10 12 14 160 18

10

15

20

5

25

0.05

0.10

0.15

0.20

0.25

0.00

0.30

p

pout P

AE

80 100 12060 140

-7.5-5.0-2.50.02.55.07.5

10.012.515.017.5

-10.0

20.0

freq, GHz

dB

(S(2

,1))

dB

(S(1

,1))

dB

(S(2

,2))


Pout > 20 dBm



Pout > 16 dBm



140 19090 240

-5

0

5

10

-10

15

freq, GHz

dB

(S(2

,1))

dB

(S(1

,1))

dB

(S(2

,2))

2 3 4 5 6 7 8 91 10

10

12

14

16

8

18

0.10

0.15

0.20

0.25

0.05

0.30

p

pout P

AE


Pout > 16 dBm



160 210110 260

-8-6-4-202468

101214

-10

15

freq, GHz

dB(S

(2,1

))dB

(S(1

,1))

dB(S

(2,2

))

2 3 4 5 6 7 8 91 10

8

10

12

14

16

6

18

0.05

0.10

0.15

0.20

0.00

0.25

p

pout P

AE


Pout > 16 dBm

Approximate Layout (0.4 mm X0.3 mm) Performance gain ~ 5 dB


140 19090 240

-5

0

5

10

-10

15

freq, GHz

dB

(S(2

,1))

dB

(S(1

,1))

dB

(S(2

,2))

2 4 6 8 100 12

6

8

10

12

14

16

4

18

0.05

0.10

0.15

0.00

0.20

p

pout P

AE


Pout ~ 16 dBm



140 19090 240

-5

0

5

10

-10

15

freq, GHz

dB(S

(2,1

))dB

(S(1

,1))

dB(S

(2,2

))

2 4 6 8 10 120 14

6

8

10

12

14

16

4

18

0.02

0.04

0.06

0.08

0.10

0.12

0.00

0.14

p

pout P

AE


Pout ~ 15 dBm



170 190 210 230 250 270150 290

-5

0

5

10

-10

15

freq, GHz

dB

(S(2

,1))

dB

(S(1

,1))

dB

(S(2

,2))

2 4 6 8 100 12

6

8

10

12

14

4

16

0.02

0.04

0.06

0.08

0.10

0.00

0.12

p

pout P

AE


Pout ~ 20 dBm

Approximate Layout (0.7 mm X0.6 mm) Performance gain ~ 7.5 dB


110 160 21060 260

-5

0

5

10

-10

15

freq, GHz

dB

(S(2

,1))

dB

(S(1

,1))

dB

(S(2

,2))

2 4 6 8 10 120 14

10

12

14

16

18

20

8

22

0.05

0.10

0.15

0.20

0.25

0.00

0.30

p

pout P

AE


Pout ~ 20 dBm



140 19090 240

-5

0

5

10

-10

15

freq, GHz

dB

(S(2

,1))

dB

(S(1

,1))

dB

(S(2

,2))

2 4 6 8 10 12 140 16

8

10

12

14

16

18

6

20

0.05

0.10

0.15

0.00

0.20

p

pout P

AE


Pout ~ 20 dBm



140 19090 240

-5

0

5

10

-10

15

freq, GHz

dB(S

(2,1

))dB

(S(1

,1))

dB(S

(2,2

))

2 4 6 8 10 12 14 160 18

10

15

5

20

0.05

0.10

0.15

0.00

0.20

p

pout P

AE


Pout ~ 19 dBm



140 19090 240

-5

0

5

10

-10

15

freq, GHz

dB(S

(2,1

))dB

(S(1

,1))

dB(S

(2,2

))

2 4 6 8 10 12 14 160 18

10

15

5

20

0.05

0.10

0.00

0.15

p

pout P

AE


Pout ~ 16 dBm

Approximate Layout (1 mm X0.7 mm) Performance gain ~ 15dB

Two-stage Common Base Power Amplifier @140GHz

-12 -10 -8 -6 -4 -2 0-14 2

5

10

15

0

20

p

pout

140 19090 240

-5

0

5

10

15

-10

18

freq, GHz

dB(S

(2,1

))dB

(S(1

,1))

dB(S

(2,2

))


Pout ~ 20 dBm

Approximate Layout (1.3 mm X0.7 mm) Performance gain ~ 15dB


110 130 15090 170

-5

0

5

10

15

-10

18

freq, GHz

dB

(S(2

,1))

dB

(S(1

,1))

dB

(S(2

,2))

-12 -10 -8 -6 -4 -2 0 2 4 6-14 8

5

10

15

20

0

25

p

pout


Pout ~ 16.5 dBm

Approximate Layout (1.3 mm X0.7 mm)Performance gain ~ 10dB


140 160 180 200 220120 230

-5

0

5

10

15

-10

18

freq, GHz

dB(S

(2,1

))dB

(S(1

,1))

dB(S

(2,2

))

1 2 3 4 5 6 70 8

12

14

16

10

18

p

pout


Pout ~ 20 dBm

Approximate Layout (1.3 mm X0.7 mm) Performance gain ~ 8.5dB


140 160 180 200 220120 230

-5

0

5

10

15

-10

18

freq, GHz

dB

(S(2

,1))

dB

(S(1

,1))

dB

(S(2

,2))

1 2 3 4 5 6 7 8 9 10 110 12

10

12

14

16

18

8

20

p

pout


Pout ~ 16.5 dBm



180 200 220 240160 260

-5

0

5

10

15

-10

18

freq, GHz

dB

(S(2

,1))

dB

(S(1

,1))

dB

(S(2

,2))

1 2 3 4 5 6 70 8

12

14

16

10

18

p

pout


Pout > 17 dBm


Cascode Power Amplifier @140GHz

-8 -6 -4 -2 0 2 4 6 8-10 10

0

5

10

15

-5

20

0.1

0.2

0.3

0.0

0.4

p

pout P

AE

90 14040 180

-5

0

5

10

-10

15

freq, GHz

dB

(S(2

,1))

dB

(S(1

,1))

dB

(S(2

,2))

140 160 180 200 220120 240

-5

0

5

10

15

-10

18

freq, GHz

dB

(S(2

,1))

dB

(S(1

,1))

dB

(S(2

,2))


Pout ~ 16.5 dBm


Cascode Power Amplifier @180GHz

-4 -3 -2 -1 0 1 2 3 4 5 6 7 8 9 10 11-5 12

0

5

10

15

-5

20

p

pout


Pout ~ 19 dBm


Common Base Power Amplifier (No Cap design) @100GHz

80 100 12060 140

-7.5-5.0-2.50.02.55.07.5

10.012.515.017.5

-10.0

20.0

freq, GHz

dB

(S(2

,1))

dB

(S(1

,1))

dB

(S(2

,2))

2 4 6 8 10 120 14

10

12

14

16

18

8

20

0.05

0.10

0.15

0.20

0.25

0.30

0.00

0.35

p

pout P

AE


Pout ~ 15.5 dBm



2 4 6 8 10 120 14

10

12

14

8

16

0.06

0.08

0.10

0.12

0.14

0.04

0.16

p

pout P

AE

120 140 160 180100 190

-7.5-5.0-2.50.02.55.07.5

10.012.515.017.5

-10.0

20.0

freq, GHz

dB

(S(2

,1))

dB

(S(1

,1))

dB

(S(2

,2))


Pout ~ 16 dBm



170 190 210150 220

-7.5-5.0-2.50.02.55.07.5

10.012.515.017.5

-10.0

20.0

freq, GHz

dB

(S(2

,1))

dB

(S(1

,1))

dB

(S(2

,2))

2 4 6 8 10 120 14

6

8

10

12

14

4

16

0.04

0.06

0.08

0.10

0.12

0.14

0.02

0.16

p

pout P

AE


Pout ~ 16 dBm


2 4 6 8 10 120 14

6

8

10

12

14

4

16

0.02

0.04

0.06

0.08

0.10

0.12

0.00

0.14

p

pout P

AE


170 190 210150 220

-7.5-5.0-2.50.02.55.07.5

10.012.515.017.5

-10.0

20.0

freq, GHz

dB

(S(2

,1))

dB

(S(1

,1))

dB

(S(2

,2))


Pout > 16 dBm


Two-stage Common Base Power Amplifier (No Cap design) @180GHz

170 190 210150 220

-7.5-5.0-2.50.02.55.07.5

10.012.515.017.5

-10.0

20.0

freq, GHz

dB

(S(2

,1))

dB

(S(1

,1))

dB

(S(2

,2))

2 3 4 5 6 7 8 91 10

12

13

14

15

16

11

17

-0.5

0.0

0.5

-1.0

1.0

p

pout

nothing

PA

E <

inva

lid>

Thermal Structures--- 18 um gate length device with three partitions 0,4,8

Thermal Structures --- 2 finger device with 0,4,8 ballasting(0.8X12)

GaN HEMT Model

GaN HEMT Model Contd.-Gm block

Variables -------- gm, ft, vp, fudfactor(0.05 here)---- automatic Gds modeling. Probably

more accurate.

GaN HEMT Model Contd.-Gm blocka discussion

The Id-Vds characteristics do not show any changeOf pinch-off voltage till Vds ~ 7-10 V. Then there wouldBe a shift of 0.5-1 V per every 10V Vds increase.

This has been more accurately modeled in this new Device model.


The Id-Vds characteristics of a 1.2 mm device.

2 4 6 8 10 12 14 16 18 20 22 240 26

0.20.40.60.81.01.21.4

0.0

1.6

Vds, V

Dra

in C

urre

nt, A


The Id-Vgs characteristics of a 1.2 mm device at Vds= 15V.

-8 -7 -6 -5 -4 -3 -2 -1-9 0

0.3

0.6

0.9

1.2

0.0

1.5

Vgs, V

Dra

in C

urre

nt, A

GaN HEMT Model Contd.-Cgs


The Id-Vgs characteristics of a 1.2 mm device at Vds= 15V.

-8 -7 -6 -5 -4 -3-9 -2

0.70.80.91.0

0.6

1.1

Vgs, V

Cgs

, pF


The S-parameter match of SG device at -4V Vgs, 20V VdsModel could be fine tuned. But my point is that this model is Not way off.

Dual Gate device and linearity concerns.

The Common Source Power Amplifier Circuit:

Dual Gate device and linearity concerns.

model:

Dual Gate device and linearity concerns.One step at a time ---- Only Gm non-linearity

model:


Biased at Class B -6V here:

24 26 28 30 32 34 3622 38

15

30

45

60

75

0

90


IM3

supp

ress

ion,

dB

c


Biased at Class C -7V here:

14 16 18 20 22 24 26 28 30 32 34 3612 38

15

30

45

60

75

0

90


IM3

supp

ress

ion,

dB

c


Biased at Class AB -4.5V here:

24 26 28 30 32 34 3622 38

15

30

45

60

75

0

90


IM3

supp

ress

ion,

dB

c


Biased at Class A -3V here:

24 26 28 30 32 34 3622 38

153045607590

105

0

120


IM3

supp

ress

ion,

dB

c

Dual Gate device and linearity concerns.One step at a time ---- Gm+Cgs non-linearity

model:


Biased at Class B -6V:

22 24 26 28 30 32 34 3620 38

15

30

45

0

60


IM3

supp

ress

ion,

dB

c


Biased at Class C -7V:

15 20 25 30 3510 40

15

30

45

0

60


IM3

supp

ress

ion,

dB

c


Biased at Class AB -4.5V:

15 20 25 30 3510 40

15

30

45

0

60


IM3

supp

ress

ion,

dB

c


Biased at Class AB -3 V:

15 20 25 30 3510 40

15

30

45

60

75

0

90


IM3

supp

ress

ion,

dB

c

Dual Gate device and linearity concerns.One step at a time ---- Gm+Cgs+Vp shift non-linearity

model:

Dual Gate device and linearity concerns.One step at a time ---- Gm+Cgs+Vp shift non-linearity

Class B -6.1 V The rest does not change that much:

15 20 25 30 3510 40

15

30

45

60

75

0

90


IM3

supp

ress

ion,

dB

c

Single Gate device and linearity concerns.

Common source Circuit Design

Single Gate device and linearity concerns.

Common drain Circuit Design

Single Gate device and linearity concerns.One Step at a time --- Only Gm nonlinearity

Model:


Class B -6V:

10 15 20 25 30 355 40

20406080

100

0

120

Total Output Power, dBm

Im3

supp

ress

ion,

dB

c


Class C -7V:

20 25 30 3515 40

15

30

45

0

60


Im3

supp

ress

ion,

dB

c


Class AB -4.5V:

20 25 30 3515 40

15

30

45

0

60


Im3

supp

ress

ion,

dB

c


Class A -3V:

20 25 30 3515 40

153045607590

0

100


Im3

supp

ress

ion,

dB

c

Single Gate device and linearity concerns.One Step at a time --- Gm+Cgs nonlinearity

model:


Class B -6V:

20 25 30 3515 40

153045607590

0

100


Im3

supp

ress

ion,

dB

c


Class C -7V:

20 25 30 3515 40

153045607590

0

100


Im3

supp

ress

ion,

dB

c


Class AB -4.5V:

20 25 30 3515 40

153045607590

0

100


Im3

supp

ress

ion,

dB

c


Class AB -3V:

20 25 30 3515 40

153045607590

0

100


Im3

supp

ress

ion,

dB

c

Single Gate device and linearity concerns.One Step at a time --- Gm+Cgs+Vpshift nonlinearitymodel:

Single Gate device and linearity concerns.One Step at a time --- Gm+Cgs+Vpshift nonlinearityClass B -6.5V:

20 25 30 3515 40

1020304050

0

60


Im3

supp

ress

ion,

dB

c

Single Gate device and linearity concerns.One Step at a time --- Gm+Cgs+Vpshift nonlinearityClass C -7.5V:

20 25 30 3515 40

1020304050

0

60


Im3

supp

ress

ion,

dB

c

Single Gate device and linearity concerns.One Step at a time --- Gm+Cgs+Vpshift nonlinearityClass AB -4.5V:

20 25 30 3515 40

1020304050

0

60


Im3

supp

ress

ion,

dB

c

Single Gate device and linearity concerns.One Step at a time --- Gm+Cgs+Vpshift nonlinearityClass A -3V:

20 25 30 3515 40

1020304050

0

60


Im3

supp

ress

ion,

dB

c

Common Drain Circuit on chip right now!

Circuit Diagram (slightly modified):


Class B -6.5V

16 18 20 22 24 26 28 30 32 34 3614 38

10

20

30

40

50

0

60

total output power, dBm

IM3

supp

ress

ion,

dB

c


Class C -7.5V

8 10 12 14 16 18 20 22 24 26 28 30 32 34 366 38

10

20

30

40

50

0

60


IM3

supp

ress

ion,

dB

c


Class AB -4.5V

18 20 22 24 26 28 30 32 34 3616 38

10

20

30

40

50

0

60


IM3

supp

ress

ion,

dB

c


Class A -3V

18 20 22 24 26 28 30 32 34 3616 38

10

20

30

40

50

0

60


IM3

supp

ress

ion,

dB

c


Class B -6.5V--- Two tone simulation

5 10 15 20 250 30

-20

-10

0

10

20

30

-30

40


Out

put P

ower

, 5G

Hz,

dB

m

Class B two-tone output spectrum

-60

-40

-20

0

20

40

7.998 7.999 8 8.001 8.002 8.003

Outp

ut

spectr

um

, dB

m

Freq, GHz

-60

-40

-20

0

20

40

7.998 7.999 8 8.001 8.002 8.003

Out

put

spec

trum

, dB

m

Freq, GHz

-60

-40

-20

0

20

40

7.998 7.999 8 8.001 8.002 8.003

Out

put

spec

trum

, dB

m

Freq, GHz

-60

-40

-20

0

20

40

7.998 7.999 8 8.001 8.002 8.003

Out

put

spec

trum

, dB

m

Freq, GHz

Pout = 4 dBm

IM3 = 43 dBc

Low input power

Medium input power 1

Medium input power 2 High input power

Pout =18 dBm

IM3 = 39 dBc

Pout = 22 dBm

IM3 = 40 dBc

Pout = 26 dBm

IM3 = 25 dBc

Class A two-tone output spectrum

-60

-40

-20

0

20

40

7.998 7.999 8 8.001 8.002 8.003

Out

put

spec

trum

, dB

m

Freq, GHz

-60

-40

-20

0

20

40

7.998 7.999 8 8.001 8.002 8.003

Out

put

spec

trum

, dB

m

Freq, GHz

-60

-40

-20

0

20

40

7.998 7.999 8 8.001 8.002 8.003

Out

put

spec

trum

, dB

m

Freq, GHz

Pout = 10 dBm

IM3 > 50 dBc

Pout = 27 dBm

IM3 = 31 dBc Pout = 31 dBm

IM3 = 15 dBc

Low input power

Medium input power 2 High input power

-60

-40

-20

0

20

40

7.998 7.999 8 8.001 8.002 8.003

Out

put

spec

trum

, dB

m

Freq, GHz

Medium input power 2

Pout = 23 dBm

IM3 = 42 dBc

Slide 1 V. Paidi Department of Electrical and Computer Engineering, University of California, Santa...

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