“…Basic assumptions adopted in the proposed mathematical model of the system 'IR photodiode -direct injection readout circuit' were first formulated in (Kunakbaeva, Lee & Cherepov, 1993) and further developed in (Kunakbaeva & Lee, 1996;Lee et al, 2010;Gumenjuk-Sichevska, Karnaushenko, Lee & Polovinkin, 2011). In calculating the transfer characteristics of the system, for the input FET we employ the model of longchannel transistor in weak inversion (Overstraeten, 1975).…”