The electro-optic (EO) coefficients r22 of a congruent LiTaO3 bulk crystal, with dimensions of 6 × 5 × 20 mm3, have been measured over a wide frequency range (from dc up to 150 MHz) using the novel and elaborate step-voltage time-response method (TRM). At low frequencies, these results are compared with those obtained with the frequency-doubling EO-modulation (FDEOM) method. From these measurements, the clamped and unclamped EO coefficients, r22S and r22T, respectively, have been derived and the acoustic contribution r22a to the EO effect has been deduced and compared with theoretically calculated values. Also, using the values of acoustic contribution, ra, the true value of the EO coefficient r22 has been extracted. Lastly, the above results are compared with those obtained for a pure congruent LiNbO3 crystal in the framework of a typical intensity–modulation (IM) EO system.