two operational amplifiers oa 210 and 216 which are configured in a unity gain mode the oas 210 and 216 preferably include low noise large input swing devices indeed in the preferred embodiment they are constructed in such a way that their inputs can swing virtually from rail to rail furthermore the oas 210 and 216 are preferably mos devices in order to achieve very high input impedance and very low gate current the oas 210 and 216 drive the bases of two transistors 212 and 214 whose differential collector currents are proportional to the differential input voltages 118 and 116 in order to increase the dynamic range of the circuit 100 the overall circuit noise must be minimized this is accomplished by designing a low noise input stage operational amplifier a single p channel current source and a negative feedback around the input operational amplifiers in order to ensure that the outputs stay biased at the proper voltage level usually 1 2 the supply voltage the common mode feedback signal is applied to the pmos devices 222 and 226 in the complimentary output stage the common mode signal 224 adjusts itself to the variations of the input signal thereby suitably controlling the pmos drain current it is noted that the source of the common mode signal 224 has not been elaborated in fig2 for it is commonly known in the art the input ports 116 and 118 are differentially driven by the incoming signal.