Low overdrive voltage and low current compact comparator for a diamond dosimeter ASIC

The dosimeters for radiotherapy must comply to strict requirements in terms of sensitivity, toxicity, tissue equivalence and radiation hardness. At present time both silicon and diamond dosimeters are used as solid state devices and in recent years, monocrystalline diamond sensors have been grown with CVD techniques. Due to the low current signals, the sensor readout is made by electrometers connected to the device with multi wire shielded cables. This measurement setup may be a serious limitation for practical application of these sensors, and makes impossible the use of matrix sensors. We present some functional block design for an ASIC that could replace the electrometer and the cabling for the measurements. The system will be realized by an hybrid assembly with the detector, or the detector matrix, very closely placed and wire bonded to the readout ASIC. The device is designed in 180 nm UMC technology with dual power supply, 3.3 V for the analog front end, in order to extend the signal dynamic, and 1.8 V for the control logic.