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Charge Sensing Circuit using Charge Amplifications

IP.com Disclosure Number: IPCOM000085654D
Original Publication Date: 1976-May-01
Included in the Prior Art Database: 2005-Mar-02
Document File: 2 page(s) / 45K

Publishing Venue

IBM

Related People

Anantha, NG: AUTHOR [+4]

Abstract

The overflow of charge from a precharged potential well of a charge-coupled device (CCD) is used to amplify the output voltage of a CCD shift register. By making the charge capacity of the potential well large, a large amplification of signal results.

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Charge Sensing Circuit using Charge Amplifications

The overflow of charge from a precharged potential well of a charge-coupled device (CCD) is used to amplify the output voltage of a CCD shift register. By making the charge capacity of the potential well large, a large amplification of signal results.

The shift register N+ diffusion 1 is reset via field-effect transistor (FET) 2. The voltage V(GA) at gate 3 is then at approximately V(reset) -V(t), where V(t) is the threshold voltage of FET 4.

The charge amplifier N+ diffusion 5 is pulsed low and then high via FET 6 to fill the potential well under gate 3. V(block) on gate 7 is set to block charge flow. V(const) on gate 8 is a constant voltage.

The shift register output charge is transferred into N+ diffusion 1 causing a negative voltage. This voltage appears at gate 3 and causes charge stored in the underlying potential well to overflow into the N+ diffusion 5 in the charge amplifier. The overflow charge is then sensed by source follower 9 producing V(out).

By making gate 3 very large, the charge stored in the underlying potential well is large. Therefore, even a slight decrease in the potential at gate 3 causes a large output charge to flow into the N+ diffusion 5 of the charge amplifier. This large capacitance of the potential well under gate 3 gives the circuit a large gain.

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