The temperature dispersion of the quarter-wave voltage has been studied for four crystals of KD_2xH_2(1-x)PO₄ with x=0.500, 0.885, 0.935 and 0.985 respectively, in the -120 to 120 degrees C range, at lambda =0.63 mu m and 1.06 mu m. The linear dependence of the static longitudinal quarter-wave voltage, previously reported at low temperatures, was observed up to the high temperature phase transition, and a fairly parallel shift of the V_lambda4/=f(T) curves, dependent on the degree of deuteration, was confirmed. To avoid this temperature dispersion (and the deuteration dependence) of the quarter-wave voltage being an obstacle to the use of this material in applications where operation in a wide temperature range is required, the authors designed a simple compensation circuit with adjustable slope dV/dT and adjustable voltage limits.