implemented using a lumped-element series LC circuit. We use a simpler lithography process where the entire device — impedance transformer and JPA — are patterned in a single electron beam lithography step, followed by a double-angle Dolan bridge technique for Al-AlOx-Al deposition. We observe nearly quantum-limited amplification with 18 dB gain over a wide 400 MHz bandwidth centered around 5.3 GHz, and a saturation power of -114 dBm. To accurately explain our experimental results, we extend existing theories for impedance-engineered JPAs to incorporate the full sine nonlinearity of both the JPA and the transformer. Our work shows a path to simpler realization of broadband JPAs and provides a theoretical foundation for a novel regime of JPA operation.