![Sample our Engineering & Technology journals, sign in here to start your access, latest two full volumes FREE to you for 14 days]({"type":"image" , "src" : "/sda/5933/TOC-Subject-Sample-2021-Engineering-Tech.jpg"})
Abstract
Choppers are often required for obtaining low drift performance of low level d.c. amplifiers. The chopper amplifier basically consists of a modulator, an a.c. amplifier, a synchronous demodulator and a low pass filter. The drift-free performance results from the use of the ‘drift-less’ a.c. amplifier for amplification.
The a.c. amplifier used may be an untuned amplifier or an amplifier tuned to the chopper frequency. Though the chopper amplifier is discussed well in literature, no information seems to be available regarding the choice of the a.c. amplifier as a tuned or untuned one. In the case of sub-microvolt level d.c. inputs, the noise introduced by the amplifier itself will set a limit to the utility of this arrangement. In such a case, in the first instance, it would appear that the use of an amplifier tuned to the chopper excitation frequency will have advantages, as regards signal to noise ratio, over an untuned amplifier. This aspect has been investigated by a time analysis of modulator and demodulator circuit arrangements encountered normally. The theoretical results obtained with a digital computer are compared with results obtained in a simulated set up.
