  We present the design and characterization of a cryogenic phonon-sensitive 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.
