CMOSLNA - Design of CMOS Low-Noise Amplifiers Masoud...

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Design of CMOS Low-Noise Amplifiers Masoud Zargari Atheros Communications Irvine, California
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2 Outline Outline ± Introduction ± Narrowband vs. Broadband Amplifiers ± Stability ± Practical LNA Implementations ± Layout Considerations ± Special Topics ± Noise Cancellation Techniques ± ESD protection ± Conclusions
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3 LNA Design Constraints LNA Design Constraints ± Noise Figure ± Sufficient gain ± Degradation in Signal-to-Noise ratios as the signal passes through the receive chain ± Matching ± Ability to accommodate large blockers ± High linearity and dynamic range ± Large common-mode rejection ± Gain Control ± LNA is part of the receiver ARC algorithm ± Stability ± Power Dissipation
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4 Low-Noise Amplifier Design Constraints Low-Noise Amplifier Design Constraints ± As the entry point to the receiver chain, LNA inputs are quite susceptible to interference ± Interference can be ± In-band/image signals from other radios ± Clock harmonics ± Supply noise ± Some external filtering is necessary in any practical application ± Loss!
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5 Low-Noise Amplifier Design Constraints Low-Noise Amplifier Design Constraints The use of external LNA may be required in order to ± Overcome any external loss due to filtering, etc. ± Increase the signal level relative to spurs
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6 Link Budget Link Budget
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7 Dynamic Range Dynamic Range P I 3 1 P (2 ω 1 - ω 2) P ω 1 P in (dBm) P out (dBm) Noise Floor SNR min P 1dB IIP3 DR
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8 Matching Matching Matching is needed at the LNA input because ± To transfer max power from the source to the receiver (power matching ) ± To optimize noise figure (noise matching) ± Antenna, external filters, etc. all require 50 Ω termination ± Improper termination results in ± Large bandpass ripple ± Poor transition band Filter Loss Frequency Matched Unmatched
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9 Narrowband vs. Broadband Design Narrowband vs. Broadband Design L V in V out C R V in V out C R f f 0 A v Gain . BW = (gm.R) . ( ) = R.C 1 C g m f f 0 A v Gain . BW = (gm.R) . ( ) = R.C 1 C g m BW BW Using inductors at the output will bias the drain at Vdd and improve the amplifier headroom ±
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This note was uploaded on 08/03/2010 for the course EE 314 taught by Professor Abad during the Spring '10 term at American International.

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CMOSLNA - Design of CMOS Low-Noise Amplifiers Masoud...

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