High-frequency injection (HFI) is an alternative method to estimate permanent magnet synchronous motor (PMSM) rotor position using magnetic saliency. Once the maximum fundamental electrical frequency and the power converter switching frequency are set, the HFI voltage amplitude tuning is generally based on trial and error. This paper proposes a methodology to select the appropriate high-frequency signal injection voltage amplitude for rotor position estimation. The technique is based on an analytical model taking into account the noise in the voltage supply to derive the resulting currents containing the information on the rotor position. This model allows setting the injection voltage amplitude that leads to the maximum acceptable position error for a given signal-to-noise ratio and a speed range. The approach is validated with the analytical and the global drive models through extensive simulations. Experimental results on a 1-kW PMSM drive confirm the interest of the proposed solution.