On the design of a low noise readout circuit for in-vivo dosimeter

The paper presents a readout circuit associated with photodiodes dedicated to an in-vivo dosimeter. The circuit consists of a fully differential charge sensitive amplifier (CSA) stage, a differential-to-single-ended amplifier stage and a buffered double sampling stage. The CSA implements a switched integration method to minimize dark current contribution to integrated output signal. Its fully differential operation rejects charge injection effect and further cancels dark current effect. Noise analysis is performed to identify main parameters for low-noise design. The double sampling stage is operated by non correlated double sampling (NCDS) to effectively reduce 1/f noise. The circuit operation is validated by transistor-level simulations.