An In-Pixel Current-Mode Amplifier for Computed Tomography

A high-dynamic-range current-mode detector for a computed-tomography application is shown. A regulated current-mirror structure that provides a 17-bit dynamic range and a noise floor below 3 <formula formulatype="inline"><tex>$\hbox{pA}_{\rm rms}$</tex></formula> has been implemented at pixel level. Nonlinearity is kept below 2%, and the signal bandwidth is higher than 10 kHz. A test structure with a 4 <formula formulatype="inline"><tex>$\times$</tex></formula> 4 pixel array is presented in this paper. Both the photodiode and the current-mode amplifier have been integrated into the same CMOS standard process.