  The problem given to the 10 Experimental Physics Olympiad (EPO10) 7 December
2023, Skopje, 11:00-15:00. The Olympiad is organized by Society of Physicists
Macedonia and the Sofia Branch of the Union of Physicists in Bulgaria. The
experimental set-up illustrates the principle of chopper stabilized DC
amplifiers described in the patent by Edwin Goldberg and Jules Lehmann,
Stabilized direct current amplifier, U.S. Patent 2,684,999 (1949). Now this
principle is implemented in many contemporary operational amplifiers. In such a
way this student problem is related to the operation of widely used technical
device and many participants successfully solved the problem.
