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A low-cost linearity test methodology for high-resolution analog-to-digital converters (ADCs) is presented in this paper. Linearity testing of ADCs requires high-precision digital-to-analog conversion (DAC) capability, commonly 3-bit higher resolution than the ADC under test. Further, a large number of ADC output data samples must be collected making conventional histogram testing impractical for high-resolution ADCs with 18-24 bit precision. In the proposed test methodology, two low-precision and low-cost DACs are used to generate a high-resolution ADC test stimulus. Significant reductions in test cost and test time are achieved by using low-cost instrumentation and by making fewer measurements than required for conventional histogram test. A least-squares-based polynomial fitting approach is used to determine the transfer function of the ADC under test. The generated transfer function is used to compute the non-linearity of the ADC accurately. No assumption is made regarding the linearity of the lower precision signal generators (DACs) used in the testing procedure. Software simulations and hardware experiments are performed to validate the proposed test methodology.