Method and system for sensing charges at distributed points on a charge

Abstract

The specification discloses a technique for non-destructively sampling the charge stored adjacent distributed phase electrodes in a charge coupled device. A storage capacitor is provided with a capacitance in the range of the combined capacitance of the phase electrodes. A first switch is operable during a first clock period for connecting the capacitor to a source of reference voltage. A second switch is operable during the first clock period for connecting the phase electrodes to be sampled to circuit ground. An insulated gate field effect transistor is connected with its source and drain between the phase electrodes and the second switch. The gate of the transistor is biased at a voltage level less than the reference voltage. The first and second switches are then operable during a second clock period for coupling the charged capacitor through the field effect transistor to apply clock voltage to the phase electrodes, wherein the capacitor discharges by an amount proportional to the charge stored adjacent the phase electrodes. An output circuit is connected to the capacitor for detecting the amount of discharge of the capacitor to indirectly sample the charge.