Abstract: An analog signal sampler with improved correlated double sampling (CDS) performance for imaging systems includes a dual mode input amplifier, a switched capacitor network and a differential amplifier. The dual mode input amplifier has a high input impedance and allows for receiving either positive-going contact image sensor (CIS) or negative-going charge couple device (CCD) image signals as desired. The switched capacitor network and differential amplifier together perform an improved CDS of the image signal and convert the unipolar input image signal to a bipolar differential output signal with an improved dynamic signal range. The CDS technique used relies upon simultaneous charging of the coupling and sample and hold capacitances with charge transfer from the coupling capacitance to the sample and hold capacitance. The gain of the sampler can be programmed by appropriate selection of the ratio of the coupling capacitance to the sample and hold capacitance.

Abstract: A MOSFET amplifier includes an amplifier stage with a boosted transconductance and a differential current mirror. The amplifier stage with a boosted transconductance includes complementary MOSFETs cross-connected with a fixed current source whereby the drain-to-source current and, therefore, the gate-to-source voltage, of the input MOSFET is fixed by the current source, while the drain-to-source current of the other MOSFET is dependent upon the input signal voltage. The differential current mirror includes a multiple branch differential input stage with a bridging resistor connected between the differential branches. The bridging resistor conducts a bridging current which equals one half of the difference between the differential branch currents, is substantially zero when the differential input voltage is zero and is nonzero when the differential input voltage is nonzero.