AUTOMATIC CALIBRATION OF DAC IN CURRENT SOURCES
A digital-to-analog converter (DAC) is a device for converting a digital code into an analog signal. At present, for devices of wireline and wireless broadband communication systems, radar and satellite subsystems, high-speed and sufficiently accurate digital-to-analog converters with a small nonlinearity are required. To obtain the necessary characteristics of DACs, production calibration is performed; but calibration of the weights of multi-bit DACs in production does not solve the problem of their non-linearity, since in the further operation their accuracy deteriorates. As a result, automatic calibration has become an integral part of DACs, which is subject to increased requirements for speed and resolution. Shortcomings of production calibration do not allow, in the current conditions of CMOS technology development, to obtain a DAC with a high conversion frequency and a bit capacity of more than 16 bits. The article presents a method for automatic calibration of DAC linearity, taking into account the drawbacks of existing methods. The method under consideration is based on the use of a subchannel region of a p-channel transistor acting as a current source, as a second gate finger. The proposed solution improves the linearity of DACs by increasing the accuracy of current sources with a consistent comparison of its weights