  Recent progress in quantum computing and the development of novel detector
technologies for astrophysics is driving the need for high-gain, broadband, and
quantum-limited amplifiers. We present a purely traveling-wave parametric
amplifier (TWPA) using an inverted NbTiN microstrip and amorphous Silicon
dielectric. Through dispersion engineering, we are able to obtain $50~\Omega$
impedance matching and suppress undesired parametric processes while phase
matching the three-wave-mixing amplification across a large range of
frequencies. The result is a broadband amplifier operating with 20 dB gain and
quantum-limited noise performance at 20 mK. At the single frequency where the
amplifier is phase sensitive, we further demonstrate 8 dB of vacuum noise
squeezing.
