The paper introduces a linearization technique based on a modified complex gain predistorter. The look-up table (LUT) digital adaptive predistortion (PD) approaches are effective for power amplifier (PA) linearization for reducing the PA power back-off and increasing the efficiency. Unlike other LUT predistorter based on uniform spacing of the LUT entries, the paper proposes a robust and behavioral method. The density of the table entries is directly proportional to the amplifier nonlinearity so the optimum table spacing could be realized. Besides, the proposed algorithm is able to optimize the LUT spacing without prior knowledge of the PA characteristics or input signal statistics and the LUT index calculation is made by a simple and fast algorithm.