Browse Prior Art Database

Charge Coupled Device as a Nondestructive Serial Write, Parallel Read Device

IP.com Disclosure Number: IPCOM000081291D
Original Publication Date: 1974-May-01
Included in the Prior Art Database: 2005-Feb-27
Document File: 3 page(s) / 43K

Publishing Venue

IBM

Related People

Chai, HD: AUTHOR [+3]

Abstract

Moving charge packets (signals) in a charge-coupled device (CCD) can be nondestructively sensed by this circuit, resulting in a nondestructive serial-write, parallel-read device.

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Charge Coupled Device as a Nondestructive Serial Write, Parallel Read Device

Moving charge packets (signals) in a charge-coupled device (CCD) can be nondestructively sensed by this circuit, resulting in a nondestructive serial-write, parallel-read device.

The concept of nondestructive reading or sensing of charge packets will be explained using a metal-oxide semiconductor (MOS) capacitor shown in Fig. 1. Fig. 1a shows a MOS capacitor with a DC gate voltage V(GG). In the absence of inversion charges, the total capacitance C(t) is a series combination of the oxide capacitance C(ox) and an effective depletion capacitance C(d) given

(Image Omitted)

When a charge is injected at the S(i)-S(i)O(2) surface, (Fig. 1c), a screening effect takes place, and the total capacitance becomes

(Image Omitted)

This change in capacitance results in a current surge, i(sense) which can be detected by an appropriate means. Therefore, charge packets passing under the gate can be sensed. These charge packets can be thought of as logical 1's, while the absence of charge can be thought of as logical 0's.

Fig. 2 shows a three-gate/cell C:CD structure where two gates are used for clocking the 3rd gate for reading. Only two read gates (2 cells) are shown in the figure.

Data to be written is fed in at WRITE IV terminal at a speed determined by the clock frequency. The corresponding charge packets shift from one cell to the next at each clock cycle.

Fig. 3 shows the timing diagram necessary for charge transfer. As they pass under the READ gates, the gate capacitances change. This change causes current flow through the resistors....