[en] The design criteria of the first fully integrated charge preamplifier completely based on HEMTs, together with few preliminary tests of the circuit, has been already presented by the authors [G. Bertuccio et al., Nucl. Instr. and Meth. A 338 (1994) 582]. In the previous work the circuit was tested directly on wafer using coplanar probes. In this Letter we present a more accurate characterisation of the amplifier, including its noise and linearity. The results here presented have been obtained with the amplifier diced and bonded in a suitable package for low noise applications. (orig.)