Download Low power analog or RF amplifier

Low Power RF/Analog
Amplifier Design
Tong Zhang
Auburn University
Motivation and Design Objective
•
Motivation
Design a low power CMOS LNA (Low-Noise
Amplifier)
Design Objective
f0
2.4 GHz
NF
< 2.5 dB
Vdd
2V
S12
< -25 dB
Gain
> 15 dB
My Work
•
This Work
1. Design a 2.4 GHz cascode CMOS LNA.
2. Design a low power CMOS LNA with
comparable performance.
3. Comparison between the two LNAs.
Tools and Techniques
• Tools
Virtuoso Schematic Composer and Spectre
Simulator from Cadence Design Systems,
Inc.
• Techniques
0.13 µm CMOS process
Circuit Diagram Comparison
VDD=2V
VDD=2V
Rout
Lout
P1
out
M2
Vg2
Cout
Cout
Vg2
M2
Vg1
RFin
C1
Ld
Rout
C2
Lg
Vg1
M1
RFin
Lg
M1
Ls
Ls
Traditional CMOS LNA
out
Low Power CMOS LNA
Lout
Schematic of Traditional CMOS
LNA
Schematic of Low Power CMOS
LNA
Circuit Description
•
Traditional CMOS LNA
1. A inductance network (Lg, Ls ) is used for are
used for input matching.
2. A RLC filter network (Lout, Cout, Rout ) is used
for selecting the output frequency.
3. Vg1 is biased at 0.53V; Vg2 is biased at
1.7V;Vdd is biased at 2 V.
Circuit Description (cont’)
•
Low Power CMOS LNA
1. M2 and P1 operates as inverter-type amplifier
stages to make LNA high linearity due to its
symmetric structure.
2. C1 couples the ac signal amplified by M1 to
M2, while the source of M2 is bypassed by
C2.
3. 3.Vg1 is biased at 0.5V; Vg2 is biased at 1.3V;
Vdd is biased at 2 V.
Simulation Result
• Input reflection coefficient (S11)
• output reflection coefficient (S22)
Traditional CMOS LNA
Low Power CMOS LNA
Simulation Result (cont’)
• Power gain(S21)
• noise figure (NF)
Traditional CMOS LNA
Low Power CMOS LNA
Simulation Result (cont’)
• Reverse isolation(S12)
S12=-40dB <-20
S12=-49.3dB<-20
Traditional CMOS LNA
Low Power CMOS LNA
Simulation Result Summary
Traditional LNA Low Power LNA
Gain (S21)
20 dB
22 dB
NF
1.7 dB
2.8 dB
S12
-40 dB
-49 dB
Power
7.23 mW
4.3 mW
Power Consumption
Traditional CMOS LNA
P = Idd x Vdd = 3.668mA x 2V = 7.23 mW
Low Power CMOS LNA
P = Idd x Vdd = 2.147mA x 2V = 4.3 mW
Power Reduction = 41.5%
Conclusion
Highlights
• A current reuse technique is used to
decrease power dissipation with increasing
amplifier transconductance for the LNA.
In my project, for nearly the same power gain, by
decreasing gates bias we get 41.5% power reduction
• An inverter-type amplifier which has a
symmetric structure is used to achieve high
linearity for the LNA (not discussed)
Conclusion (cont’)
What need to improve?
• Input impedance was not well matched, which
means the ac signal of the input will not be able
to be fully delivered to the output.
• Noise figure shows that the noise of output is a
little bit large.
A different input matching as well as output
matching topology may improve the
efficiency and minimize noise of the LNA
Reference
• Ickjin Kwon and Hyungcheol Shin , “Design of a New
Low-Power 2.4 GHz CMOS LNA” , Journal of the
Korean Physical Society, Vol.40, No. 1, Jan. 2002, pp. 47.
• John D. Cressler and Guofu Niu, “Silicon-Germanium
Heterojunction Bipolar transistors”, Artech House, inc.
Boston, 2002.
• Thomas H. Lee, The Design of CMOS Radio-Frequency
Integrated Circuits, Cambridge University Press, 1998.
THANKS!