A schematic picture of the defect-engineered spin amplifier demonstrated in this work. The wave pattern symbolizes the time variation of the spin signal, namely the difference between the numbers of spin-up and spin-down electrons. The red and blue arrows represent the period with more spin-up and spin-down electrons, respectively. The amplitude of the wave reflects the strength of the spin signal, which is weak before entering the spin amplifier but becomes stronger when exiting. The defects that have enabled the spin-amplification functionality of a non-magnetic semiconductor are indicated by the yellow balls, each with a spin-polarized localized electron (indicated by the red and blue arrows). The spin direction of this localized electron rapidly follows the sign of the input spin signal, which serves to only attract and remove the incoming electrons with an undesired spin orientation. This leads to a significant enhancement in the spin polarization of the electrons passing the spin amplifier, giving rise to a strongly amplified output spin signal that has truthfully cloned the exactly same time-varying function and thus the spin-encoded information of the input spin signal.