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Transistor Specification Selection Guide
Noise Figure
as an Amplifier

 PHEMTs
  ATF-36xxx space   0.2 dB   2 GHz
space   0.3 dB   4 GHz
space   0.6 dB   12 GHz
space
  ATF-35xxx space   0.3 dB
space   0.4 dB
space   1.4 dB   [10 GHz]
space
  ATF-38xxx space   0.4 dB
space   0.4 dB
space   1.4 dB   [10 GHz]
space
  ATF-34xxx space   0.4 dB
space   0.5 dB
space   1.4 dB   [10 GHz]
space
  ATF-33xxx space   0.4 dB
space   0.5 dB
space   1.3 dB   [8 GHz]
space
 MESFETs
  ATF-13xxx space   0.4 dB
space   0.5 dB
space   1.1 dB
space
  ATF-10xxx space   0.4 dB
space   0.6 dB
space   1.4 dB
space
  ATF-21xxx space   0.6 dB
space   1.1 dB
space
0 0.5 1.0 1.5 2.0 2.5  
  Gain [dB]  
                                                                                                         
 
 Low Noise Bipolar Transistors
  HBFP-0420 space   1.0 dB   900 MHz
space   1.3 dB   2.4 GHz
space
  HBFP-0450 space   0.9 dB
space   1.4 dB
space
  HBFP-0405 space   1.1 dB
space   1.4 dB
space
  AT-305xx space   0.8 dB
space   1.4 dB
space
  AT-310xx space   0.8 dB
space   1.6 dB
space
  AT-320xx space   0.8 dB
space   1.6 dB
space
  AT-414xx space   1.0 dB
space   1.7 dB
space
  AT-415xx space   1.0 dB
space   1.7 dB
space
 Moderate Noise Bipolar Transistors
  AT-420xx space   1.4 dB
space   2.2 dB
space
0 0.5 1.0 1.5 2.0 2.5  
  Noise Figure [dB]  
                                                                                                         

What:
for a receiver, the noise figure is an indication of the ability to discriminate the desired signal from background noise.

Best noise performance is only achievable with careful impedance matching, and is typically only achievable over a narrow bandwidth (10% variation in frequency or less). Very low noise figures (< 0.5 dB) are extremely difficult to achieve in practical circuits because of the losses associated with the impedance matching components.

Direction:
lower is better. However, for receivers always receiving relatively strong signals, a lower noise figure offers little real advantage, and the higher cost of a very sensitive transistor may not be appropriate.

Range:
bipolars at 1 GHz: 0.8 - 3 dB
FETs at 1 GHz: 0.2 - 1 dB
FETs at 4 GHz: 0.3 - 2 dB
FETs at 12 GHz: 0.5 -3 dB

(note: for FETs the 3rd digit of the part number typically indicates a NF sort; with lower numbers indicating lower NF)

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this page last updated: 20 October 1999