In contrast to switch-based passive pixel sensor readout circuits, pixel architectures incorporating on-pixel amplification have recently surfaced for large-area, noise-vulnerable, medical imaging applications. In this article, the noise performance of a current-mediated amorphous silicon pixel amplifier readout circuit for diagnostic medical imaging is presented. In addition, reset noise, commonly the limiting noise component in complementary metal-oxide-semiconductor pixel amplifiers, is investigated for amorphous silicon pixel circuits. Theoretical analysis and measurements of pixel noise sources are presented in which the amorphous silicon pixel amplifier appears promising for large-area, noise-sensitive, real-time digital fluoroscopy. (C) 2004 American Vacuum Society.