The linear response of the silicon photomultiplier (SiPM) device depends on the number of APD cells, their effective dead time and is related to a width of the detected light pulses or a decay time of a scintillation crystal. The aim of this work was determination of the effective dead time of APD cells on the basis of the measured linear response of the SiPM for light pulses of different width. A closer analysis of the SiPM response to the light pulses shorter than the effective dead time of pixels, made possible evaluation of a number of fired pixels (or number of photoelectrons) in cases when a single photoelectron peak was not well defined. This analysis also allows determination of the position of the single photoelectron peak, necessary in case of measurements of the number of photoelectrons for light pulses with various widths. Measurements were done with SiPMs manufactured by three companies: Hamamatsu, Zecotek and SensL.