The linearity and stability of an amperometric sensor can be affected by the size of the double layer capacitor (???) in the electrode. A working electrode (WE) with millimeter size area can have a ??? larger than 10nF, whereas a WE in nanometer range show tens of femto-Farad ???. We propose an amperometric sensors that is immune to the negative effect introduced by a wide variance of ???, but does not require and additional mismatch calibration. By using dynamic current mirrors, the resolution of the sensor is increased to over 9bits. We perform extensive simulation to determine linearity (??>?.???), DNL and noise floor all within acceptable limits.