In an example embodiment, a circuit is provided that includes a current source with a calibrated trim circuit whose output current varies with transconductance of the current source, and tracks a current mismatch between the current source and another current source under varying bias currents and temperatures. The trim circuit may include at least one calibration digital to analog converter (CAL DAC), which may be driven by a bias circuit generating current proportional to the transconductance of the current source. In an example embodiment, the trim circuit may include at least two CAL DACs, whose output current may vary with bias current only, and with bias current and temperature. A method to calibrate the CAL DACs includes varying calibration settings of the CAL DACs under different bias currents until the output current of the trim circuit substantially accurately tracks the current mismatch under disparate bias currents and temperatures.