Front-end counting mode electronics for CdZnTe sensor readout

The development of a front-end circuit optimized for CdZnTe detector readout, implemented in 0.25 μm CMOS technology, is reported. The ASIC comprises 17 channels of a charge sensitive amplifier with an active feedback, followed by a gain-shaper stage and a discriminator with a 5 bit fine-tune DAC. The signal from the discriminator is sensed by a 25 ns mono-stable circuit and an 18-bit static ripple-counter. The channel architecture is optimized for the detector characteristics in order to achieve the best energy resolution at a maximum counting rate of 2 million counts/second. The amplifier shows a linear sensitivity of 24 mV/fC with 50 ns peaking time and an equivalent noise charge of about 650 e^-, for a detector capacitance of 10 pF. When connected to a 3×3×7 mm³ CdZnTe detector the amplifier gain is about 8 mV/keV with a noise around 3.6 keV.