Design of new front-end electronics for animal PET

Highly pixilated detector modules for animal PET such as LSO-APD module require power-efficient, highly integrated and reliable front-end electronics. A new waveform sampling front-end chip for animal PET has been developed. The front-end electronics consist of a preamplifier, a variable gain amplifier (VGA) and a fast ADC per channel. The preamplifier picks up detector signals while the ADC samples the output signals of the preamplifier and converts them into digital waveforms. The VGA adjusts the signal amplitude to the maximum input range of the ADC. Digitizing the whole waveform on-chip would provide large flexibility for signal processing, e.g. the energy and time information can be extracted by either a simple linear interpolator or a more complex statistics estimator. The preamplifier, VGA and 6 bit 100 MSPS folding ADC have been designed using Rohm 0.35 μm CMOS ASIC technology. Full custom ASIC technique allows us to integrate analog and digital circuits into one chip. The preamplifier occupies 180×100 μm² and has a rise time of 22 ns while the VGA occupies 180×90 μm² and have a variable gain from 3.6 to 25. The ADC occupies 0.24 mm² (excluding digital circuit), dissipates 1 W for 8 channels with a 3.3 V power supply and has a DNL of 0.7 LSB and INL of 1.4 LSB.