Electro-optic modulators (EOMs) are indispensable elements for integrated photonic circuits. However, optical insertion losses limit the utilization of EOMs for scalable integration. Here, we propose a novel, to the best of our knowledge, EOM scheme on a heterogeneous platform of silicon- and erbium-doped lithium niobate (Si/Er:LN). In this design, electro-optic modulation and optical amplification are simultaneously employed in phase shifters of the EOM. The excellent electro-optic property of lithium niobate is maintained to achieve ultra-wideband modulation. Meanwhile, optical amplification is performed by adopting the stimulated transitions of erbium ions in the Er:LN, leading to effective optical loss compensation. Theoretical analysis shows that a bandwidth exceeding 170 GHz with a half-wave voltage of 3 V is successfully realized. Moreover, efficient propagation compensation of ∼4 dB is predicted at a wavelength of 1531 nm.