Abstract

The article discusses the principles of construction of generators of the identical currents with high output resistances for use in multi-bit DACs. Approaches to the construction of generators of the identical currents for multi-bit DACs with primary current generators connected to the output stages by means of current mirrors are considered. Variants of circuits using an additional generator of bias currents and with auto bias in the output stage of generators of the identical currents are shown. The sources of errors that occur when the output voltage changes and affect the output resistance of the current generator are analyzed. Analytical relations are derived for calculating the output resistance value. Computer simulation of identical current generators for multi-bit DACs was carried out using the integrated software package for analog and digital simulation of electrical and electronic circuits MicroCap 11 and the correctness of the derived relations was confirmed. The approaches to the construction of generators of the identical currents for multi-bit DACs with primary current generators connected directly to the output stages are considered. Variants of this scheme using an additional bias current generator and with auto-bias in the output stage of current generators are also shown. The sources of errors that occur when the output voltage changes and affect the output resistance of the current generator are analyzed. Analytical relationships are derived for calculating the output impedance values ​​and computer simulation of generators of identical currents is carried out using a program for modeling electrical and electronic circuits and the correctness of the derived relationships is confirmed. Modifications of the above mentioned schemes with extremely large output impedance are considered. For these schemes analytical relationships for calculating the output impedance values ​​are also derived and computer simulation is carried out and the correctness of the derived relationships is also confirmed. The parameters of the considered generators of the identical currents for multi-digit DACs are compared, their advantages and disadvantages are evaluated, and recommendations for their use are provided.

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