A scaling apparatus and method for compensating nonlinearity due to the finite output impedance of current sources in current-steering digital-to-analog converters (DACs) are disclosed herein. In an example, a DAC may receive a digital input signal. The DAC may determine an output current weight for each of a plurality of unit cells, based on an output impedance of the unit cell. Further, the DAC may generate an analog output signal by applying the plurality of output current weights to the digital input signal. Then, the DAC may output the analog output signal. The analog output signal may be a high frequency analog output signal, which may be an optical high frequency analog output signal. In an example, a transfer curve of the analog output signal may be linear in terms of analog output signal voltage versus digital input code. The output current weights may include one or more polynomial terms.