ANALYSIS OF THE INSTRUMENTAL ERROR COMPONENT OF BIT ΣΔ-MODULATORS
Background. The analysis of the instrumental error component of the ∑∆-modulator represents a complex challenge connected with impossibility of using the principle of decomposition for converters of information of non-canonical form, i.e. structure decomposition of the ∑∆-modulator on separate poorly connected elements. Therefore the only way to provide reliable assessment of an error consists in carrying out natural and model experiments. The latter are preferable as the allow to easily operate the conditions and parameters of experiments (at the minimum expenses of time and resources). The purpose of this work is to identify the influence on instrumental errors of parameters of the most critical units of the real scheme (the integrator, the comparator, DAC). Materials and methods. Based on the principle of divisions of functions the authors carried out the analysis of the instrumental error component of the bit ΣΔ-modulator transformation. The researchers created ∑∆-ADC computer models with single-bit modulators of the first, second and third orders in the NI Multisim 12.0 program environment. The results of the model experiment considering the influence of parameters of active and passive elements of direct and basic channels of transformation were given. Results. Influence of parameters of analog units of ∑∆-modulators (the integrator, the comparator, DAC) on the instrumental error was revealed. Results of model experiment were given. Importance of the basic channel of transformation was shown. Dependence of the instrumental error on parameters of the analog key as a part of DAC of the basic channel was proved. Conclusions. The instrumental error of the bit ∑∆-modulators generally is defined by parameters of elements of the basic channel. In cases when values of resistance of feedback are correlated with the key resistance in the closed state, the instrumental error is defined by the key. In cases when values of resistance of feedback considerably exceed the key resistance in the closed state, the error considerably decreases.