A method, comprising: receiving at a gain circuit a gain signal, the gain signal based on a predetermined amplitude for an analog signal representative of a barcode; generating a linear response to the gain signal; applying the analog signal to a positive input of a first operational amplifier (U3A); and applying the linear response to the gain signal to a negative input of the first operational amplifier (U3A); wherein the gain circuit comprises: a second operational amplifier, adapted to buffer the gain signal and to drive first and second gain elements (Q7, Q4); a first gain element adapted to receive the buffered gain signal and respond according to its characteristic curve providing a first equivalent resistance, that resistance determining in part the linear response applied to the negative input of the first operational amplifier (U3A); and a second gain element adapted to receive the buffered gain signal and respond according to its characteristic curve providing a second equivalent resistance, the second gain element being in the regulating feedback loop of the second operational amplifier, and wherein the first and second gain elements are matched and similarly loaded in impedance so as to provide the linear response to the gain signal. receiving at a gain circuit a gain signal, the gain signal based on a predetermined amplitude for an analog signal representative of a barcode; generating a linear response to the gain signal; applying the analog signal to a positive input of a first operational amplifier (U3A); and applying the linear response to the gain signal to a negative input of the first operational amplifier (U3A); wherein the gain circuit comprises: a second operational amplifier, adapted to buffer the gain signal and to drive first and second gain elements (Q7, Q4); a first gain element adapted to receive the buffered gain signal and respond according to its characteristic curve providing a first equivalent resistance, that resistance determining in part the linear response applied to the negative input of the first operational amplifier (U3A); and a second gain element adapted to receive the buffered gain signal and respond according to its characteristic curve providing a second equivalent resistance, the second gain element being in the regulating feedback loop of the second operational amplifier, and wherein the first and second gain elements are matched and similarly loaded in impedance so as to provide the linear response to the gain signal. a second operational amplifier, adapted to buffer the gain signal and to drive first and second gain elements (Q7, Q4); a first gain element adapted to receive the buffered gain signal and respond according to its characteristic curve providing a first equivalent resistance, that resistance determining in part the linear response applied to the negative input of the first operational amplifier (U3A); and a second gain element adapted to receive the buffered gain signal and respond according to its characteristic curve providing a second equivalent resistance, the second gain element being in the regulating feedback loop of the second operational amplifier, and wherein the first and second gain elements are matched and similarly loaded in impedance so as to provide the linear response to the gain signal.