Abstract
In paper the concept of interaction of cholesteric liquid crystals (CLC) with creatinine and urea to designing the active medium material for optical sensor of biological substances are presented. It is shown that there is a general tendency to reduce the pitch of supramolecular helical structure versus of increasing of concentrations of aqueous solutions for all investigated substances. A decision to designing the scheme of signal converter of optical sensors with frequency selection is proposed. In basis of the proposed decision is impedance converter provided the inductive nature of the impedance circle of load photodiode and therefore suppressing of direct component of the photocurrent.