low noise amplifier and design
LNA Design
Iulian Rosu, YO3DAC / VA3IUL http://www.qsl.net/va3iul/ An LNA combines a low noise figure, reasonable gain, and stability without oscillation over entire useful frequency range.
The Low Noise Amplifier (LNA) always operates in Class A, typically at 15-20% of its maximum useful current. Class A is characterized by a bias point more or less at the center of maximum current and voltage capability of the device used, and by RF current and voltages that are sufficiently small relative to the bias point that the bias point does not shift.
The smallest signal that can be received by a receiver defines the receiver sensitivity.
The largest signal can be received by a receiver establishes the upper power level limit of what can be handled by the system while preserving voice or data quality. The dynamic range of the receiver, the difference between the largest possible received signal and the smallest possible received signal, defines the quality of the receiver chain. The LNA function, play an important role in the receiver designs. Its main function is to amplify extremely low signals without adding noise, thus preserving the required Signal-to-Noise Ratio (SNR) of the system at extremely low power levels. Additionally, for large signal levels, the LNA amplifies the received signal without introducing any distortions, which eliminates channel interference.
• An LNA design presents a considerable challenge because of its simultaneous requirement for high gain, low noise figure, good input and output matching and unconditional stability at the lowest possible current draw from the amplifier.
• Although Gain, Noise Figure, Stability, Linearity and input and output match are all equally important, they are interdependent and do not always work in each other’s favor. • Carefully selecting a transistor and understanding parameter trade-offs can meet most of these conditions.
• Low noise figure and good input match is really simultaneously
Iulian Rosu, YO3DAC / VA3IUL http://www.qsl.net/va3iul/ An LNA combines a low noise figure, reasonable gain, and stability without oscillation over entire useful frequency range.
The Low Noise Amplifier (LNA) always operates in Class A, typically at 15-20% of its maximum useful current. Class A is characterized by a bias point more or less at the center of maximum current and voltage capability of the device used, and by RF current and voltages that are sufficiently small relative to the bias point that the bias point does not shift.
The smallest signal that can be received by a receiver defines the receiver sensitivity.
The largest signal can be received by a receiver establishes the upper power level limit of what can be handled by the system while preserving voice or data quality. The dynamic range of the receiver, the difference between the largest possible received signal and the smallest possible received signal, defines the quality of the receiver chain. The LNA function, play an important role in the receiver designs. Its main function is to amplify extremely low signals without adding noise, thus preserving the required Signal-to-Noise Ratio (SNR) of the system at extremely low power levels. Additionally, for large signal levels, the LNA amplifies the received signal without introducing any distortions, which eliminates channel interference.
• An LNA design presents a considerable challenge because of its simultaneous requirement for high gain, low noise figure, good input and output matching and unconditional stability at the lowest possible current draw from the amplifier.
• Although Gain, Noise Figure, Stability, Linearity and input and output match are all equally important, they are interdependent and do not always work in each other’s favor. • Carefully selecting a transistor and understanding parameter trade-offs can meet most of these conditions.
• Low noise figure and good input match is really simultaneously
References: 1. RF Design Magazine (1994-2002) 2. Applied Microwave & Wireless Magazine (1998-2002) 3. Microwaves & RF Magazine (1998-2002) 4. U.L. Rohde, D.P. Newkirk - RF/Microwave Circuit Design – John Wiley & Sons, Inc-2000 5. G. Gonzales – Microwave Transistor Amplifiers – Pretince-Hall – 1984 6. Design of Analog CMOS Integrated Circuits – B. Razavi 7. GaAs FET Pre Amp Cookbook – K. Britain WA5VJB 8. Agilent Technologies – IP3 Measurements Data Sheets 9. Avago Technologies – Application Datasheets 10. LNA Design Trade-Offs in the Working World - Freescale