A method of calibrating coefficients of a calibrated decision feedback equalizer (DFE) across a process, voltage, and temperature (PVT) range, the calibrated DFE comprising a plurality of DFE taps for reducing distortions of an input signal, and a sampler for sampling the input signal, the method including applying a preset voltage to an input of the calibrated DFE, setting a DFE tap of the plurality of DFE taps to a maximum value, generating a source reference, via a source reference calibrator, to apply to the DFE tap, changing the source reference to a first level that causes an output of the sampler to transition from a first state to a second state, determining the first level as a calibrated source reference, and applying the calibrated source reference to the DFE tap during normal operation of the calibrated DFE.