Browse Prior Art Database

Charge Transfer Compensation Circuit

IP.com Disclosure Number: IPCOM000080916D
Original Publication Date: 1974-Mar-01
Included in the Prior Art Database: 2005-Feb-27
Document File: 2 page(s) / 27K

Publishing Venue

IBM

Related People

Heller, LG: AUTHOR [+2]

Abstract

This circuit provides compensation for signal distortion produced in charge-transfer circuits. It is well known that signals become distorted as they propagate through charge-coupled devices (CCD) and bucket brigade (BBD) shift registers. The present compensation technique can be used to reduce distortion in charge-transfer device (CTD) image sensors analog delay lines, and digital shift registers.

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Charge Transfer Compensation Circuit

This circuit provides compensation for signal distortion produced in charge- transfer circuits. It is well known that signals become distorted as they propagate through charge-coupled devices (CCD) and bucket brigade (BBD) shift registers. The present compensation technique can be used to reduce distortion in charge- transfer device (CTD) image sensors analog delay lines, and digital shift registers.

Typically, CTD shift registers display positive and negative unit step response characteristics. At the output, the leading edge of the step response has a response that is a fraction X of the input step amplitude, assuming unit amplitude input. The leading sample error is the fraction (1-X). Succeeding samples decrease the error by the factor X times the error in the preceding sample. The output distortion is substantially symmetrical; i.e., positive and negative step response, display an identical amount of distortion. From the theoretical standpoint. the symmetrical response is justified in the intrinsic case when a register is biased in the linear region. Distortion due to modulation index, channel length modulation, surface state effects and the threshold coupling effect, is probably also symmetrical.

The distortion compensation technique described here is a sensor that adjusts the output signal from a CTD register, in a way which significantly reduces the distortion. Since the distortion in any sample is related to the previ...