  In this article it is presented an FPGA based $M$ulti-$V$oltage $T$hreshold
(MVT) system which allows of sampling fast signals ($1-2$ ns rising and falling
edge) in both voltage and time domain. It is possible to achieve a precision of
time measurement of $20$ ps RMS and reconstruct charge of signals, using a
simple approach, with deviation from real value smaller than 10$\%$.
Utilization of the differential inputs of an FPGA chip as comparators together
with an implementation of a TDC inside an FPGA allowed us to achieve a compact
multi-channel system characterized by low power consumption and low production
costs. This paper describes realization and functioning of the system
comprising 192-channel TDC board and a four mezzanine cards which split
incoming signals and discriminate them. The boards have been used to validate a
newly developed Time-of-Flight Positron Emission Tomography system based on
plastic scintillators. The achieved full system time resolution of
$\sigma$(TOF) $\approx 68$ ps is by factor of two better with respect to the
current TOF-PET systems.
