US Patent 7348910 Reference module apparatus and method therefor

A Root Mean Square (RMS) detector circuit includes a first differential pair circuit arranged to operate in a common mode. The detector circuit also includes a compensation circuit unit having a second differential pair circuit to duplicate an unwanted base current drawn by the first differential pair circuit. The compensation circuit unit is arranged to generate an offset voltage using the duplicated base current. The compensation circuit unit also has an operational amplifier coupled to an NMOS transistor so as to generate a corrective current corresponding to the offset voltage, the corrective current being mirrored by a current mirror and provided as a compensatory current to an input of the first differential pair circuit.