MEASUREMENT OF THERMAL NOISE
(JOHNSON NOISE)
September 2, 2014
The basic documentation for this experiment can be found in the manual:
• Thermal Noise (located on the course webpage under “manuals”)
and references therein.
1
Objectives of the experiment
• Measurement of the thermal noise and determination of the Boltzmann constant.
2
Physics pre-requisites
• Basics of electrical circuits.
3
Data analysis pre-requisites
• Basic plotting tools.
• Tools for fitting.
• Software for numerical integration.
In general, python is recommended. A basic introduction to python can be found on the
course web page: “Intro do Python (1)” and “Intro to Python (2)”.
4
Goal of the experiment
At the end of this project the student should be able to:
• understand the Nyquists theorem;
• characterize an electrical circuit:
– linearity of response;
– gain function (circuit order, linearity of attenuator).
1
5
Timeline
• 1st week: Familiarize with the experimental setup and define the configuration
providing linear response.
• 2ns week: Measure the gain and determine the Boltzman constant
• 3rd week: Review the assumptions made if any
• 4th week: Start writing the report/presentation
• 5th week: Wrap up the results and write the final report/presentation.
6
Challenges
The acquisition of data seems deceivingly simple, however to reduce the uncertainty on
the extracted physical properties requires some experimental planning and appropriate
error propagation. Crucial is the analysis and plot of the data immediately after its
acquisition. Special care must be taken in measuring the gain function. It is important
to address all points raised in the manual.
2