A multichannel ASIC for interfacing with an array of photodetectors in a PET imaging system includes a front-end circuit configured to be coupled to the array of photodetectors and to receive analog signals therefrom. The ASIC includes a time discriminating circuit including a low input impedance amplifier configured to be coupled to the array of photodetectors and to receive a signal summing the analog signals from the array of photodetectors and to generate a hit signal for timing pickoff based on the signal. The ASIC includes an energy circuit operably coupled to the front-end circuit and configured to generate a summed energy output signal based on each of the analog signals and summed positional output signal based on each of the analog signals.
