  We present the design and characterization of a cryogenic phonon-sensitive
1-gram Si detector exploiting the Neganov-Trofimov-Luke effect to detect
single-charge excitations. This device achieved 2.65(2)~eV phonon energy
resolution when operated without a voltage bias across the crystal and a
corresponding charge resolution of 0.03 electron-hole pairs at 100~V bias. With
a continuous-readout data acquisition system and an offline optimum-filter
trigger, we obtain a 9.2~eV threshold with a trigger rate of the order of
20~Hz. The detector's energy scale is calibrated up to 120~keV using an energy
estimator based on the pulse area. The high performance of this device allows
its application to different fields where excellent energy resolution, low
threshold, and large dynamic range are required, including dark matter
searches, precision measurements of coherent neutrino-nucleus scattering, and
ionization yield measurements.
