We present a low-noise Charge-Sensitive Amplifier (CSA) manufactured in a standard 0.35 μm CMOS process. The CSA is part of an integrated sensor named Topmetal-S, an array of which forms a charge readout plane in a high-pressure gaseous TPC for 0νββ search. A single-ended folded cascode amplifier with a 73 dB open-loop gain and 340 MHz gain-bandwidth product forms the main amplification stage in this CSA. Measurements show that the conversion gain of the CSA with a 3 fF feedback capacitor is 163 mV/fC. With a 5 pF detector capacitance, the CSA achieved an equivalent noise charge of 28.7 e- using a digital trapezoidal pulse shaper.