1. Common Base Amplifier with 7- dB gain at 176 GHz in InP mesa DHBT Technology
V. Paidi,
Z. Griffith, Y. Wei, M. Dahlstrom,
N. Parthasarathy, M. Seo, M. Urteaga,
M. J. W. Rodwell ,
Department of Electrical and Computer Engineering,
University of California, Santa Barbara, CA 93106
L. Samoska, A. Fung,
Jet Propulsion Labs, Pasadena, CA 91109

2. Outline Motivation. Why Common-base?
Effect of layout parasitics on circuit stability and MSG.
InP mesa DHBT process.
Circuit simulations.
Device Results
G-band Power amplifier results.
W-band Power amplifier results.
First, I will explain briefly how class B power amplifier work and why single-ended Class B. Then I will talk about the design and simulation of the single ended class B power amplifier. Finally I will show you the measurement result and the conclusions.

3. Motivation and Previous Results
Applications for electronics in GHz frequency band
Wideband communication systems
Atmospheric sensing
Automotive radar
Small signal amplifier results
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.,
6-stage amplifier with 20  6 dB from GHz, InP HEMT, Weinreb et. al.
Power amplifier results
14-16 GHz with 10 dB gain in InP HEMT technology, Lorene et. al.,
12.5 GHz with 8.6 dB gain in TS InP DHBT technology, Yun et. al.,
14-16 GHz with > 10 dB gain in InP HEMT technology, Lorene et. al.,

4. Why mesa -InP HBTs for 140- 220 GHz power amplifiers ?
fmax > 400 GHz, ft > 250 GHz
High current density > 3 mA/ m2.
Vbr,ce0 > 6V
Low thermal resistance.
High power density, high gain in GHz frequency range

5. Why Common Base ? Common base has the highest MSG/MAG.
Common Base Circuit Schematic
Common base has the highest MSG/MAG.

6. Base inductance Ground 0.8 m base contact width
emitter
Ground
Emitter access
Interconnect metal
Polyimide
base
0.8m each
0.8 m base contact width
Leads to base access inductance.
Lb ~ 3 pH for 0.8 mX12 m HBT.
Longer finger length results in larger base access inductance

7. Collector emitter overlap Capacitance reduction
Double-sided collector Contact
Single-sided collector Contact
Single-sided Collector contact reduces Collector to emitter overlap capacitance

8. Cce, Lb degrade MSG/MAG
Lb reduces MSG in GHz frequency range.

9. Single-sided collector Contact improves MSG
2-3-dB improvement in MSG.

10. Mesa IC Process: overview
Both junctions defined by selective wet-etch chemistry
Low contact resistances
NiCr thin film resistors s = 40  / 
MIM capacitor, SiN dielectric.
ADS momentum modeled CPW transmission lines
Air bridges strap ground planes

11. Single-stage Common Base power amplifier
Objectives: 180 GHz amplifier, Psat~ 20 dBm
Approach: InP mesa-DHBTs
Simulations: ADS S-parameter, harmonic balance and momentum simulations
Circuit Schematic

12. Output Large-signal Load-line match
(Simulations)
Device Model
Load-line match
Circuit optimized for output power not gain

13. Single-stage Common Base power amplifier
(Simulations)
Frequency of operation =180 GHz
3-dB bandwidth = 45 GHz,
Gain = 5.3 dB at 180 GHz,
Pout,sat = 20 dBm.
2 x 2 x 0.8 m x 12 m, AE=38 mm2
5.3 dB at 180 GHz, 3-dB Bandwidth = 45 GHz, Saturated Pout, = 20 dBm

14. Two-stage Common Base amplifier
Objectives: 180 GHz amplifier, Psat~ 20 dBm
Approach: InP mesa-DHBTs
Simulations: S-parameter and harmonic and momentum simulation in ADS
Circuit Schematic

15. Two-stage Common Base amplifier
(Simulations)
Frequency of operation =180 GHz
3-dB bandwidth = 45 GHz,
Gain = 8.7 dB,
Pout,sat = 19.5 dBm.
6 x 0.8m x 12 m, AE=58 mm2
Power simulations at 180 GHz

16. Device Performance Vbr = 7 V. ft = 240 GHz, fmax = 290 GHz.
DC characteristics of a 2 X 0.8 m X 12 m
Common-base InP HBT
RF characteristics of a 1 X 0.8 m X 8 m
HBT biased at Jc= 3 mA/m2, Vce =1.7 V
Vbr = 7 V.
ft = 240 GHz, fmax = 290 GHz.
Relatively lower fmax –
larger base mesas
relatively poorer base ohmics.

17. Power measurement setup 170-180 GHz
Frequency
doubler
Power
meter
DUT
W-band PA

18. Power measurement setup 150 GHz
DUT
Gunn Oscillator
Calorimeter
Var Attn

19. 176 GHz single-stage Power amplifier
7- dB gain at 176 GHz.
3-dB bandwidth = 23 GHz.
Pout = 8.7 dBm with 5 dB associated power gain at 172 GHz.
2 x 0.8m x 12 m, AE=20 mm2
Bias conditions Ic = 30 mA, Vcb= 1 V
Power measurements at 172 GHz
Bias conditions Ic = 40 mA, Vcb= 2 V

20. 176 GHz single-stage Power amplifier
At 172 GHz 7.53 mW output power with 5 dB associated gain.
Maximum power measured = 8.37 mW at 176 GHz

21. 176 GHz two-stage Power amplifier
7- dB gain at 176 GHz.
Pout = 8.1 dBm with 6.3 dB associated power gain at 176 GHz.
Saturated Pout = 9.1 dBm
4 x 0.8m x 12 m, AE=38 mm2
Power measurements at 176 GHz
Ist stage Ic = 40 mA, Vcb= 2 V
IInd stage Ic = 51 mA, Vcb= 1.8 V
Ist stage Ic = 25 mA, Vcb= 1 V
IInd stage Ic = 30 mA, Vcb= 1 V

22. 176 GHz two-stage Power amplifier
At GHz 10.3 dBm Pout with 3.4 dB associated gain.

23. 84 GHz single-stage Power amplifier
6.5- dB gain at 84 GHz.
Pout = 32.4 mW with 4 dB associated power gain at 84 GHz.
4 x 0.8m x 12 m, AE=38 mm2
Power measurements at 84 GHz
Bias conditions Ic = 56 mA, Vcb= 2.2 V
Bias conditions Ic = 37 mA, Vcb= 1 V

24. Accomplishments Design and fabrication of W-band (75-110-GHz) G – band
( GHz) power amplifiers in InP mesa DHBT technology
7-dB at 176 GHz with a single-stage common-base amplifier.
Obtained 8.77dBm output power with 5-dB associated power gain at 172 GHz.
Obtained 32 mW at 84 GHz.
This work was supported by the ONR , JPL , DARPA (USA).