Charge transfer device with improved charge detection sensitivity
AssigneeNEC Corporation
InventorsNobuhiko Mutoh, Takashi Nakano
Life of this patent
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Abstract
In a charge transfer device, a floating gate is provided in an insulating film which is provided on a charge transfer channel layer. A buffer amplifier is connected with the floating gate, and detects signal charges in the charge transfer channel layer to generate a signal indicative of an output voltage corresponding to the signal charges. A bias gate is provided in the insulating film apart from the floating gate to cover at least a part of the floating gate. A bias applying unit applies a bias voltage to the bias gate in response to the output voltage signal such that an alternate current (AC) component of a voltage of the floating gate is substantially equal to an AC component of a voltage of the bias gate.
Claims17
A charge transfer device comprising:
- a floating gate provided in an insulating film which is provided on a charge transfer channel layer;
- a buffer amplifier connected with said floating gate, for detecting signal charges in said charge transfer channel layer to generate a signal indicative of an output voltage corresponding to said signal charges;
- a bias gate provided in said insulating film apart from said floating gate to cover at least a part of said floating gate;
- and
- a bias applying unit for applying a bias voltage to said bias gate in response to said output voltage signal such that an alternate current (AC) component of a voltage of said floating gate is substantially equal to an AC component of a voltage of said bias gate, and
- wherein said bias applying unit comprises a direct current bias voltage power supply for outputting a direct current (DC) voltage, and a bias feedback circuit for applying to said bias gate said bias voltage in which said DC voltage is added to said output voltage of said buffer amplifier,
- wherein said bias feedback circuit comprises a capacitor connected between an output of said buffer amplifier and a first node, and a resistor connected between said DC bias voltage power supply and said first node, said first node being connected to said bias gate so that a voltage between said resistor and said capacitor is applied to said bias gate as said bias voltage.
A charge transfer device comprising:
- a floating gate provided in an insulating film which is provided on a charge transfer channel layer;
- a buffer amplifier connected with said floating gate, for detecting signal charges in said charge transfer channel layer to generate a signal indicative of an output voltage corresponding to said signal charges;
- a bias gate provided in said insulating film apart from said floating gate to cover at least a part of said floating gate;
- and
- a bias applying unit for applving a bias voltage to said bias gate in response to said output voltage signal such that an alternate current (AC) component of a voltage of said floating gate is substantially equal to an AC component of a voltage of said bias gate,
- wherein said bias gate covers an entire surface of said floating gate other than a bottom surface thereof.
A method for transferring and detecting signal charges, comprising the steps of:
- transferring signal charges to a region of a charge transfer channel layer under a floating gate;
- applying a bias voltage to said bias gate, such that an alternate current (AC) component of a voltage of said floating gate is substantially equal to an AC component of a voltage of said bias gate;
- detecting said signal charges transferred in said charge transfer channel layer by use of said floating gate to generate an output signal;
- and
- controlling said bias voltage in response to said output signal,
- wherein said applying step includes the steps of,
- generating a direct current (DC) voltage,
- removing a DC component from said output signal to produce a DC component removed signal, and
- superimposing said DC component removed signal on said DC voltage to apply to said bias gate as said bias voltage.
A charge transfer device comprising:
- a floating gate in an insulating film on a charge transfer channel layer;
- a buffer amplifier connected to said floating gate;
- a direct current bias voltage power supply;
- a bias gate that is in said insulating film over a first surface of said floating gate opposite a second surface of said floating gate that faces said charge transfer channel layer;
- and
- a first node that is connected to said bias gate, to an output of said buffer amplifier through a capacitor, and to said direct current bias voltage power supply through a resistor.
Dependencies are inferred from the claim text.