Texas Instruments Corporation

Stephen Perry Emmons

Dennis D Buss

James B Barton

MOSFET structures are frequently used to establish the charge level in the first potential well of a CCD in accordance with an external voltage. When employed conventionally there exists a finite amount of charge under the MOSFET gate at the instant of turnoff. An indeterminate amount of this charge flows into the first potential well thereby giving rise to an uncertainty in the amount of charge in the well. Use of the invention disclosed eliminates this source of uncertainty.

CCD input and node preset method

It is frequently desirable to establish the level of charge in the first potential well of a CCD in accordance with an external electrical signal. Thermal noise associated with the output resistance of the external source gives rise to uncertainty in this charge level. The use of a floating diffused region as an intermediate receptacle for the charge introduced permits a substantial reduction in the magnitude of this uncertainty.

Use of floating diffusion for low-noise electrical inputs in CCD's

The specification discloses a technique for suppressing the effect of noise generated during the introduction of a charge into a potential well of a charge coupled device. The technique involves detecting the voltage appearing on a floating diffused region during the introduction of the charge through the floating diffused region into the CCD potential well. An error signal is developed from the detected voltage and is subsequently utilized to extract noise from the output electrical signal of the CCD.

Technique for reduction of electrical input noise in charge coupled

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.

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

The specification discloses a circuit for sampling charge stored adjacent a phase electrode in a charge coupled device and for selectively weighting the sampled charge. The circuit includes a first insulated gate field effect transistor connected at its source to one end of the phase electrode and connected at its drain to receive a clock. A predetermined first voltage is applied to the gate of the first transistor. A second insulated gate field effect transistor is connected to the other end of the phase electrode and is connected at its drain to receive a clock. A preselected second voltage is applied to the gate of the second transistor in order to control the percentage of charging current applied to the phase electrode through the second transistor. The preselected second voltage is equal to or less than the predetermined first voltage in order to maintain the clock voltage of the phase electrode at a predetermined set value. The amount of charging current applied to the phase electrode through each of the first and second transistors is detected in order to provide a weighted indication of the charge stored adjacent the phase electrode. The weighting applied to the sampled charge may be varied by varying the preselected second voltage.

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Dallas, TX, United States of America

Stephen Perry Emmons