Front-end multi-channel PMT-associated readout chip for hodoscope application

For developing a prompt gamma imaging system, we have designed a 16-channel readout chip in a BiCMOS process to be associated with multi-anode photomultipliers (MaPMTs). Each channel has one current input and two separated outputs. The input has very low impedance to minimize electrical crosstalk and effects of capacitances. The two outputs serve to respectively detect signal event and quantify signal charge. The channel architecture is a current-mode one, employing a current conveyor to drive both a buffered current comparator and a charge-sensitive amplifier (CSA). The current conveyor is built with super-common-base (SCB) transistor structures to obtain input impedance in the order of a few ohms. Circuit design with the use of bipolar transistor components also improves frequency and noise performances. The chip has been tested and the evaluated characteristics meet the system requirements.