arXiv subjects

Vassil N. Gourev

Publications and source records attributed to Vassil N. Gourev.

6 recordsLinked to original sources

arXiv2021

Probability distribution function of crossover frequency of operational amplifiers

For the first time the cumulative distribution function of the crossover frequency of a contemporary operational amplifier ADA4898-2 is experimentally studied. Using a USB Lock-In amplifier, which allows automatic frequency sweep of the current response of a non-inverting amplifier with significant static amplification, we measure the crossover frequency of 200 samples of ADA4898-2 operational amplifiers. This new method gives a significant advantage in accuracy and speed of study of every operational amplifier. The theory we use is based on the universal relation between time dependent output and input voltages. This common relation for all operational amplifiers is applicable for frequencies much smaller than the crossover frequency and the frequencies of non-dominant poles. In other words, this approximation is adequate, when an operational amplifier is included in a circuit with significant amplification.

eess.SP↗

arXiv2019

The Day of the Inductance. Problem of the 7-th Experimental Physics Olympiad, Skopje, 7 December 2019

This is the problem of the 7-th international Experimental Physics Olympiad "The Day of the Inductance". A large inductance made by a general impedance converter is measured by the Maxwell-Wien bridge. The youngest students (S category) have the problem to measure the parameters of the elements in the experimental set-up. The students at middle age (category M) should balance a Wheatstone bridge with resistors only. The inductance measurement is supposed to be accomplished by the students from the upper age (L category) only. From the university students (XL category) we expect error estimation and professionally made measurement protocol. As a homework problem (Sommerfeld price) the general formula for the impedance of the general impedance converter, where the general equation for operational amplifiers is included, has to be derived. Problems for further work are also given in the text. The described set-up can be considered as a prototype for companies producing laboratory equipment.

physics.ed-ph↗

arXiv2019

Measurement of the electron charge $q_e$ using Schottky noise. Problem of the 6-th Experimental Physics Olympiad. Sofia 8 December 2018

Several consecutive experiments are described with a printed circuit board PCB set-up, especially designed for these experiments. Doing the consecutive experimental tasks opens up possibility to determine the value of electron charge $q_e.$ The fluctuations of the voltage $U(t)$ should be measured for different illuminations of a photodiode. The voltage is amplified 1 million times $Y=10^6$. The amplified voltage $YU(t)$ is applied to the device, which gives the result of the value of the time averaged square of the voltage $U_\mathrm{S}=\left<(Y U(t))^2\right>/U_0$. This voltage $U_\mathrm{S}$ is measured with a multimeter. The series of measurements gives the possibility to determine the $q_e$ using the well known Schottky formula for the spectral density of the current noise $(I^2)_f=2q_e\left .$ For the junior high school students, the basic problem is to analyze the analog squaring. Students' work is separated and graded in four categories S, M, L, XL divided by age of students. For the last XL categories, the tasks contain problems oriented to physics university education program and include theoretical research of the PCB set-up as an engineering device. This is the problem of EPO6, December 2018 ``Day of the Charge'' considered. EPO6 is organized by Sofia branch of Union of physicists in Bulgaria in cooperation with Faculty of physics of Sofia University and Society of Physicists of Republic of Macedonia.

physics.ed-ph↗

arXiv2018

Planck's constant measurement by Landauer quantization for students laboratories

A simple experimental setup for measuring the Planck's constant, using Landauer quantization of the conductance between touching gold wires, is described. It consists of two gold wires with thickness of 0.5 mm and 1.5 cm length, and an operational amplifier. The setup costs less than $30 and can be realized in every teaching laboratory in two weeks. The usage of oscilloscope is required.

physics.ed-ph↗

arXiv2016

Measuring the speed of light with electric and magnetic pendulum

This problem was given at the Fourth Open and International Experimental Physics Olympiad (EPO4) Day of Light on 23 April 2016 in Sofia organized by the Sofia Branch of the Union of Physicists in Bulgaria and the Society of Physicists of the Republic of Macedonia, Strumica.

physics.ed-ph↗

arXiv2016

Measuring Plank constant with colour LEDs and compact disk

This problem was given on the Open Experimental Physics Olympiad (OEPO) "The day of the photon" on 25 April 2015. The Olympiad was a part of the celebration of the International Year of Light (IYL) http://www.light2015.org/Home/Event-Programme/2015/Competition/Bulgaria-Second-Experimental-Physics-Olympiad--25-April-2015-in-Sofia.-The-Day-of-the-Photon-in-the-International-Year-of-the-Light.html and was organized by the Sofia Branch of the Union of Physicist in Bulgaria and the Regional Society of Physicists of Strumica, Macedonia.

physics.ed-ph↗