Low-Noise Analog ASIC for Silicon and CdTe Sensors

We report on the recent development of a 32-channel low-noise analog front-end ASIC "KW03" for hard X-ray and gamma-ray detectors. The ASIC aims for the readout of strip or pixel (pad) detectors utilizing silicon and cadmium telluride (CdTe) as detector materials. Each readout channel includes a charge-sensitive amplifier, bandpass filters and a sample-and-hold circuit. It also includes a leakage current compensation and pole-zero cancellation circuits to meet the various detector requirements. The equivalent noise level of a typical channel reaches 89 e^- @ 0 pF (rms) and shows an input-capacitance characteristic of 7.5 e^-/pF between 0 pF and 10 pF with a power consumption of 3 mW per channel. We mounted the ASIC on a low-temperature co-fired ceramic (LTCC) package and evaluated the spectral performance by combining with a CdTe diode detector. As a result, the gamma-ray spectrum of radioactive source 241 Am was obtained with a good energy resolution of 2.23 keV (FWHM) for gamma rays of 59.5 keV at -20°C.