A circuit for measuring absolute spread in capacitors implemented in planary technology using a charge pump (CP) supplying a charge current to an internal capacitor (Cint), the voltage across the internal capacitor (Cint) being coupled through a comparator (COM) for comparing said voltage with first and second threshold levels to a bistable multivibrator (BM) for reversing the direction of the charge current to charge the internal capacitor (Cint) when said voltage decreases below the second threshold level and to decharge the internal capacitor (Cint), when said voltage increases above the first threshold level, the charge current being determined by a reference voltage being provided across an external resistor (Rext), said first and second threshold levels defining a voltage range being proportional to the reference voltage, an output signal of the bistable multivibrator being coupled to frequency measuring means (CFM) to compare the repetition frequency thereof with a reference frequency.