Over the past years an always growing interest has arisen about the measurement technique of time-correlated single
photon counting (TCSPC), since it allows the analysis of extremely fast and weak light waveforms with a picoseconds
resolution. Consequently, many applications exploiting TCSPC have been developing in several fields such as medicine
and chemistry. Moreover, the use of multianode PMT and of single photon avalanche diode arrays led to the
development of multichannel acquisition systems, employed in even more applications. Since TCSPC basically consists
of the measurement of the arrival time of a photon, a high resolution and high linearity time measurement block is of the
utmost importance, and in order to realize multidimensional systems, it has to be integrated to reduce both cost and area.
We have designed and fabricated a 4 channel fully integrated time-to-amplitude converter (TAC), built in 0.35 μm Si-Ge
technology, characterized by a very good time resolution (less than 50 ps), low differential nonlinearity (better than 2%
peak-peak and less than 0.1% rms), high counting rate (16 MHz), low and constant power dissipation (50 mW), and low
area occupation (2.58x1.28 mm2). Moreover our measurements show a very little crosstalk between the converters
integrated on the same chip; this feature together with low power and low area make the fabricated converter suitable for
parallelization, so it can be the starting point for future large scale multi-channel acquisition chains.