Abstract
A fully differential ASIC with cooled input termination is presented as a solution for the Upgrade of the Calorimeter front end electronics. The LHCb experiment needs to increase about ten times the integrated luminosity in order to study new physics. The increase in signal has to be compensated reducing the gain of the photomultipliers which implies stringent noise requirements. The proposed solution offers an active termination at the input and avoids the noise originated by the use of a resistor. The circuit is based on a two interleaved channel with a first amplifier stage, a switched integrator, and a Track-and-Hold. Two prototypes have been implemented and tested in SiGe BiCMOS 0.35um technology.
Highlights
To be increased and, at the same time, decreasing the input noise; the total input referred noise voltage of the front should be smaller than 1 LSB
An ASIC development was proposed because the FE board has 32 channels and a transistor level approach was required for any a√ctive termination scheme
An integrated circuit for the LHCb Calorimeter electronics upgrade has been presented which is reported to be able to cope with the upgrade stringent noise requirements
Summary
The presented implementation of the ASIC includes two alternated switched signal paths where the input current is first amplified and converted to differential signaling in order to be integrated through a fully differential amplifier with capacitive feedback. The input pulse signal (from a measured PMT clipped pulse) is first integrated in subchannel 1 during the first half of the clock cycle. The output charge from the integrator is transferred in the hold capacitors of the T/H while the other subchannel integrator is in reset state. During the half clock cycle, the integrator of subchannel 1 is being reset and subchannel 2 performs the integration of the tail of the signal. Swiftly stabilized with the main signal output in subchannel 1 and in the half clock cycle the tail integrated signal has already been tracked and it is hold at the output of subchannel 2. Further studies of the packages power dissipation are envisaged, but no problem is expected
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