  We show that a cryogenic amplifier composed of a homemade GaAs
high-electron-mobility transistor (HEMT) is suitable for current-noise
measurements in a mesoscopic device at dilution-refrigerator temperatures. The
lower noise characteristics of our homemade HEMT leads to a lower noise floor
in the experimental setup and enables more efficient current-noise measurement
than is available with a commercial HEMT. We present the dc transport
properties of the HEMT and the gain and noise characteristics of the amplifier.
With the amplifier employed for current-noise measurements in a quantum point
contact, we demonstrate the high resolution of the measurement setup by
comparing it with that of the conventional one using a commercial HEMT.
