Dynamic Compression of the Signal in a Charge Sensitive Amplifier: Experimental Results

This work is concerned with the experimental characterization of a Charge Sensitive Amplifier featuring dynamic signal compression, fast recovery time, low noise and reduced area occupancy. The device takes advantage of the non-linear characteristic of a feedback transistor which behaves like a voltage controlled capacitance. This property has been exploited to fit a wide input dynamic range into the available output swing. The charge amplifier can be operated in synchronous mode at high frame rates, of the order of few MHz, thanks to a wide bandwidth, an improved output stage and a fast reset network. Thanks to the small area occupancy the amplifier is suitable for integration in a 100×100 μm2 pixel area. All these features make the device a good candidate for applications where a fast frontend with a non-linear response is required, such as in imaging instrumentation for Free Electron Laser experiments. The aim of the paper is to present and discuss the experimental results coming from the characterization of the first prototype of the circuit which has been designed in a 65 nm CMOS technology. The work has been carried out in the frame of the PixFEL Project funded by the INFN, Italy.