A CMOS Charge Sensitive Amplifier with sub-electron equivalent noise charge

We present a CMOS Charge Sensitive Amplifier (CSA) specifically designed for low capacitance pixel or silicon drift detectors for high resolution X-ray spectrometry. The intrinsic noise of the CSA has been measured at different operating temperatures with a triangular shaping with peaking time from 0.8 μs to 102 μs. At room temperature, the intrinsic Equivalent Noise Charge (ENC) shows a minimum of 1.18 e-. m.s. and at -30°C a minimum ENC of 0.89 e- r.m.s. has been measured, corresponding to a line width of 7.8 eV FWHM for a Silicon detector.