# Generalized transistor equation for Collector Current including the reverse saturtion current

currentdiodestransistors

44I am referring to Millman's Integrated electronics and there I came across and equation
$$(I_c) = -\alpha(I_E)+I_{Co}(1-\exp^{V_C/V_T}) –>eqn(5.6)$$
where $$I_{Co}(1-\exp^{V_C/V_T})$$ represents shows reverse saturation current . Can any one explain me how this equation came . Also is not reverse saturation current independent of applied voltage then why is there $$V_c$$ there in equation ?