A 4-Channel Low-Noise GEM Detector Readout Front Ends

The Gas Electron Multiplier detector (GEM) is developed for the measurement of Coherent Pion Production.GEM is a robust and accurate new particle detector technique with simple structure, and it is used to detect the particle spatial-resolution by the measurement of depth charge. Compared with general front-end electronics readout, GEM detectors have to cope with high data rates but with low power consumption and low cost. The ASIC chip used in the GEM detectors is introduced in this paper.With the rise time of 80ns and the fall time of 100ns, that is the signature of the GEM signal for one pad,with the analysis of the character of different amplifiers and different shaping circuits and the noise of the CMOS circuits, charge-sensitive amplifier,pole-zero cancellation circuit and Gaussian shaper circuits are designed due to the signature of signal in GEM detectors. For the pre-amplifier, Charge-sensitive amplifier was chose to the requirements for the electronics. And the structure of the amplifier was chose for the noise level and linearity level. With appropriate time constant and values of resistances and capacitances, the design of the filtering and shaping circuits are ready for the ASIC chip. The design of chip schematics and layout are finished, and some tests for the requirement also have been done. The first tape out of the ASIC chip has been done, and when the chip back to the IHEP, it also has been tested.This chip is the first ASIC chip made by the IHEP used on the GEM detectors. And it contains the circuits of Charge-sensitive amplifier,bios circuits,Pole-zero cancellation circuit and Gaussian shaper circuits in the same chip.The result of the test show that this CMOS chips match most item of the requirement.