A Comparison between Common-source and Cascode Topologies

Matsuzawa& Okada Lab.

Matsuzawa Lab.Tokyo Institute of Technology



A Comparison between

Common-source and Cascode

Topologies for 60GHz Amplifier

Design in 65nm CMOS

Qinghong Bu, Ning Li, Kenichi Okada,

and Akira Matsuzawa

Tokyo Institute of Technology

1




Matsuzawa Lab.Tokyo Institute of Technology2012/3/23

Outline

Topologies used in this work

Common-source (CS) versus

Cascode (Cas.) topology

Gain-boost Cascode (Cas.) topology

One stage power amplifier using

CS and gain-boost topologies

Measurememt results

Conclusion

2





CS topology at mmW frequency

The features of CS Topology

comparing with Cas. Topology

Small noise figure

Reasonable power gain

×Larger power consumption

×Worse instability factor

2012/3/23

3





Cas. topology at mmW frequency

At lower frequencies, obtains a

high gain.

At mmW frequencies, a reduction

of the reverse isolation S12.

Increase maximum gain

Increase stability

×Larger parasitic capacitance in the

inter-stage node

4





Cas. structure with inductance (1)

Large parasitic capacitance decreases

the gain

Gain-boost technique is utilized to

increase gain

Cascode topology with inductance

*C. Inui, et al, APMC, Dec. 2007

5





The TEG schematics of the topologies

2012/3/23

Cas.

CS

Gain-boost Cas.

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-2-101234

0 20 40 60 80 100

Sta

bil

ity F

ac

tor

Frequency (GHz)

0

10

20

30

0 20 40 60 80 100

Ma

xG

ain

(d

B)

Frequency (GHz)

-50

-40

-30

-20

-10

0 20 40 60 80 100

S1

2 (

dB

)

Frequency (GHz)

2012/3/23

Comparison between CS and Cas. TEGs

MAG K

S12

Line color

No. of

finger

(CS & CG)

Wf

(mm)

TL

(mm)

Power

(mW)

Blue_CS 20 2 0 8.3

Red_Cas. 20 & 20 2 0 5.8

Black_Cas. 20 & 20 2 80 6.0

Vdd=1.2 V, Vg1=0.6 V

7





1-stage amp. using CS topology

TL are utilized for impedance matching

Decoupling MIM transmission line is used for AC ground

CS transistor size:20×2mm

2012/3/23

8





1-stage amp. using Cas. topology

Cas. TEG size: CS=20×2mm, CG=20×2mm, TL=80mm.

9





0

2

4

6

8

0 20 40 60 80 100

S2

1(d

B)

Frequency (GHz)

-80

-60

-40

-20

0

0 20 40 60 80 100

S1

2(d

B)

Frequency (GHz)

Measured results of CS and Cas. amps(1)

2012/3/23

Vdd=1.2 V, Vg1=0.6 V

S12 S21

0

1

2

3

4

5

6

0 20 40 60 80 100

Sta

bilit

y f

ac

tor

Frequency (GHz)

K Red: Cas.

Blue: CS

10





Measured results of CS and Cas. amps(2)

2012/3/23

Vdd=1.2 V, Vg1=0.6 V

-20

-15

-10

-5

0

0 20 40 60 80 100

S11(d

B)

Frequency (GHz)

-20

-15

-10

-5

0

0 20 40 60 80 100

S2

2(d

B)

Frequency (GHz)

Red: Cas. , Blue: CS

S11 S22

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Summary of the comparison (1)

2012/3/23

TEG MAG (dB)

(60GHz)

S12(dB)

(60GHz)

K

(60GHz)

Power

(mW)

CS 9 -13 0.5 8.3

Cas. 9 -28 2.1 5.8

Gain-boost Cas. 12 -33 2.0 6.0

Ampifier Freq.

(GHz)

S11

(dB)

S22

(dB)

S12

(dB)

S21

(dB) K

Power

(mW)

CS 66 -9 -15 -11 5.5 1.0 8.3

Gain-boost Cas. 56 -14 -11 -25 6.7 3.5 6.0

Vdd=1.2 V, Vg1=0.6 V

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MaxGain and output power versus power

2012/3/23

0

2

4

6

8

10

12

14

0

0.5

1

1.5

2

2.5

3

3 6 9 12 15 18 21

MaxG

ain

(d

B)

P1d

B,o

ut

(mW

)

Pdc (mW)

P1dB,out_CasP1dB,out_CSMaxGain_CasMaxGain_CS

The maximum gain of the Cas. topology is much larger than CS topology with less power consumption

The output power at P1dB of the CS topology is larger than the CS topology

60 GHz

Simulation results

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Chip photos

2012/3/23

280 mm

23

0 m

m

65nm CMOS process

CS: 0.064 mm2

Cas.: 0.053 mm2 185 mm

28

5 m

m

Cas. CS

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Conclusion

The comparison of CS, Cas. and gain-boost Cas. topologies are carried out in 65nm CMOS process.

Gain-boost technique is studied to increase the gain of cascode topology.

1-stage amplifiers are designed utilizing CS and gain-boost Cas. topologies

The gain-boost Cas. topology have large gain, better isolation and stability factor with less power consumption at 60GHz than the CS topology.

The 1-stage amplifier utilizing gain-boost Cas. topology achieves smaller output power than that utilizing the CS topology.

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Thank you

Q&A

Documents

A Comparison between Common-source and Cascode Topologies