THE LNA NOISE FIGURE AT DIFFERENT TEMPERATURES.
(Nov 4 2012)
This page is a sub-page to PRECISION MEASUREMENTS OF NOISE FIGURES

The images on this page are made with a dummy load which is kept at 290 K by use of a well insulated water container. A test signal is injected via a directional coupler through a cable into the LNA under test. The S/N of the injected signal is a direct measure of the NF although the zero point is a bit uncertain.

Two amplifiers were tested by comparing S/N at room temperature to S/N at an elevated temperature as well as at a low temperature. The time constants for the amplifiers are very long, about one hour is needed for an amplifier to stabilize at a new temperature.

Figures 1 and 2 show that the NF of the atf33143negimp amplifier changes by 0.001 dB for one degree centigrade. The FHX05FA/LG amplifier is about 50% more sensitive to temperature changes.

Figure 1. The ATF33143neg amplifier at room temperature and at elevated temperature. 
Time   Temperature   S/N
          (øC)      (dB)
1513      26.3
1540      26.9      -0.1618
1610      66.4      -0.2100
1635      75.5      -0.2205
1700      76.1      -0.2215
1732      25.3      -0.1625

This image shows that the NF changes by 0.06 dB for a temperature change of 50 øC. That is 0.0012 dB/degree.


Figure 2. The ATF33143neg amplifier at room temperature and at elevated temperature. 
Time   Temperature   S/N
          (øC)      (dB)
2301      23.5      
0003      23.3      -0.1407
0205      -2.7      -0.1150

This image shows that the NF changes by 0.0257 dB for a temperature change of 26 degrees. That is 0.0009 dB/degree.


Figure 3. The FHX05FA/LG amplifier at room temperature and at elevated temperature. 
Time   Temperature   S/N
          (øC)      (dB)
1745      25.1      
1813      25.1      -0.1601
1910      61.4      -0.2260
2035      23.8      -0.1405

This image shows that the NF changes by 0.076 dB for a temperature change of 37 degrees. That is 0.002 dB/degree.


Figure 4. The FHX05FA/LG amplifier at room temperature and at low temperature. 
Time   Temperature   S/N
          (øC)      (dB)
2140      23.5      -0.1421   
2220     -15.1      -0.0848
2250     -15.5      -0.0850

This image shows that the NF changes by 0.057 dB for a temperature change of 39 degrees. That is 0.0015 dB/degree.