On-Chip Charge-Trap-Transistor-Based Mismatch Calibration of an 8-Bit Thermometer Current-Source DAC

This letter presents an on-chip mismatch calibration technique for current-source digital-to-analog converters (DACs) using charge-trap transistors (CTTs) in 22nm FDSOI technology. The proposed method exploits programmable threshold voltage (VTH) shifts in CTTs to locally tune the current of near-minimum-sized devices without external trimming. A compact 8-bit thermometer DAC is implemented to demonstrate the concept. The on-chip calibration loop iteratively measures and programs each CTT using short high-voltage pulses until the CTT current matches a reference, achieving device-level current uniformity. Measurement results show an 8x reduction in current-source mismatch and linearity improvements to 0.1/0.5 LSB DNL/INL. The proposed approach provides a scalable, low-cost, and nonvolatile solution for analog calibration in deeply scaled CMOS technologies.