Temperature compensation of Gm-C filters using resistive bridge

A new technique for temperature compensation of G_m-C filters is presented. Using negative feedback the G_m-cells´ transconductance is locked to the reciprocal of a resistance array. Temperature dependency of the G_m/C ratio, which determines the unity-gain frequency, is minimised by arranging the temperature dependency of the resistors. Unique properties of a proposed resistive bridge allow for the synthesis of temperature coefficients beyond the range of coefficients of constituent elements. With a set of practical elements a variation of only 0.66% in G_m/C has been achieved over -40 to 120degC.