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UNIVERSITY OF BUCHAREST
FACULTY OF PHYSICS Guest
2024-11-21 16:24 |
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Conference: Bucharest University Faculty of Physics 2008 Meeting
Section: Electricity and Biophysics
Title:
Study of the Thermal Johnson Noise Generated by a Resistor
Authors:
Marian Mocanu and Liviu Giurgiu
Affiliation:
Faculty of Physics, University of Bucharest
E-mail
email: liviu.giurgiu@g.unibuc.ro
Keywords:
Johnson noise, metal film resistors, Boltzmann constant,
operational amplifier
Abstract:
Thermal agitation of electrons in a resistor gives rise to a random fluctuation in the voltage across its terminals, known as Johnson noise. This voltage is usually too small to be detected without amplification.
In this paper, there are presented preliminary results on the measurements of the Johnson noise of the metal film resistors. A high gain amplifier (1000 – 30000) with 10 Mohm input resistance was designed and realized for this purpose. The circuit consists of a three stages JFET operational amplifiers. The first stage is a non-inverting amplifier with a selectable gain of x1, x3, x10, x30. The second stage and third stage are the inverting amplifiers with a gain of x33. Each stage has built-in high pass filters that cut off low frequency environmental noise. The high frequency gain is limited by the operational amplifier itself . A notch filter rejects the mains hum. The small-signal bandwidth of the amplifier is about 40 kHz.
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