3

Input Stages

As described in chapter 1, most radiation sensors can be modeled as a current source with a capacitor in parallel. The input stage of the front-end must read the sensor current, which is in general weak, transforming it into a signal strong enough to drive the following circuitry. The first element of the processing chain takes therefore the form of a transimpedance or a current amplifier. For reasons that will become clear in the remainder of the book, the former configuration is often preferred, but the latter in also employed in particular cases. A transimpedance amplifier can be realized by connecting an appropriate network in the feedback path of a high gain voltage amplifier. After a review of basic concepts on the transimpedance ...

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