M–2M current digital-to-analog converter (DAC) is one of the best architectures for the implantable stimulation systems where the available area near the tissue is restricted. However, due to the nonlinear behavior of the employed transistors, the conventional M-2M DAC does not resemble an accurate resistive R-2R ladder. This is due to the fact that the operating point and therefore the drain-source resistance of each transistor depend not only on its location in the ladder, but also on the selected digital input code. Therefore, in this paper, a highly-linear M-2M current DAC is proposed that alleviates the effect of the selected digital input code by replacing the employed fixed resistive dump load with an array of resistors controlled by the input code. Moreover, a correction circuit is utilized to improve the non-linearity effect caused by the location of each transistor in the ladder. The proposed circuit is designed and simulated in a 0.13-μm CMOS technology. Post-layout simulation results show that the proposed M-2M DAC achieves a spurious-free dynamic range (SFDR) of 56.2 dB and signal-to-noise-and-distortion ratio (SNDR) of 46.7 dB at the cost of 25 μW power consumption for the reference current of 20 μA.

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