Read circuit, variable resistive element device, and imaging device

1. A read circuit comprising:

an integration circuit section configured to perform an integral operation and whose input is connected to an integration node; and

a bias circuit connected between a connection node to which a variable resistive element is connected and said integration node,

wherein said bias circuit comprises:

an integration transistor whose source is connected to said connection node and whose drain is connected to said integration node;

a first operational amplifier whose output is connected to a gate of said integration transistor, to whose first input a bias voltage is supplied, and whose second input is connected to said source of said integration transistor; and

at least one diode element that is connected between said gate and said source of said integration transistor and clips a gate-source voltage of said integration transistor.

2. The read circuit according to claim 1 , further comprising a bias cancel circuit connected to said integration node,

wherein said bias cancel circuit comprises:

a canceller transistor whose drain is connected to said integration node;

a canceller resistor and a canceller switch that are connected in series between a source of said canceller transistor and a node to which a power supply voltage or a ground voltage is supplied;

a second operational amplifier whose output is connected to a gate of said canceller transistor, to whose first input a bias cancel voltage is supplied, and whose second input is connected to said source of said canceller transistor; and

at least one diode element that is connected between said gate and said source of said canceller transistor and clips a gate-source voltage of said canceller transistor.

3. The read circuit according to claim 2 ,

wherein said bias cancel circuit further comprises: a second current switching circuit configured to provide or shut off a second current path, wherein said second current path is a current path through which a current flowing between said drain and said source of said canceller transistor flows without passing through said canceller resistor and said canceller switch.

4. The read circuit according to claim 3 ,

wherein said second current switching circuit comprises:

a second current switch; and

a second dummy resistor,

wherein said second current switch and said second dummy resistor are connected in series between said source of said canceller transistor and a node to which a power supply voltage or a ground voltage is supplied.

5. The read circuit according to claim 1 ,

wherein said bias circuit further comprises: a first current switching circuit configured to provide or shut off a first current path, wherein said first current path is a current path through which a current flowing between said drain and said source of said integration transistor flows without passing through said connection node.

6. The read circuit according to claim 5 ,

wherein said first current switching circuit comprises:

a first current switch; and

a first dummy resistor,

wherein said first current switch and said first dummy resistor are connected in series between said source of said integration transistor and a node to which a ground voltage or a power supply voltage is supplied.

7. The read circuit according to claim 1 ,

wherein said integration circuit section comprises:

an integration amplifier whose first input is connected to said integration node and to whose second input a predetermined voltage is supplied;

at least one integration capacitor connected between said first input and an output of said integration amplifier; and

a reset switch connected between said first input and said output of said integration amplifier.

8. A variable resistive element device comprising:

a read circuit; and

a variable resistive element connected to a connection node of said read circuit,

wherein said read circuit comprises:

an integration circuit section configured to perform an integral operation and whose input is connected to an integration node; and

a bias circuit connected between said connection node and said integration node,

wherein said bias circuit comprises:

an integration transistor whose source is connected to said connection node and whose drain is connected to said integration node;

an operational amplifier whose output is connected to a gate of said integration transistor, to whose first input a bias voltage is supplied, and whose second input is connected to said source of said integration transistor; and

at least one diode element that is connected between said gate and said source of said integration transistor and clips a gate-source voltage of said integration transistor.

9. The variable resistive element device according to claim 8 ,

wherein said bias circuit further comprises: a current switching circuit configured to provide or shut off a first current path, wherein said first current path is a current path through which a current flowing between said drain and said source of said integration transistor flows without passing through said connection node.

10. The variable resistive element device according to claim 8 ,

wherein said variable resistive element is any of a thermoelectric conversion element, a magnetoresistance element, a phase-change memory cell, a microwave/millimeter-wave detection element, a pressure sensor, a gas sensor and a flow sensor.

11. An imaging device comprising:

a plurality of thermoelectric conversion elements;

a read circuit; and

a selection circuit configured to connect a thermoelectric conversion element selected from said plurality of thermoelectric conversion elements with a connection node of said read circuit,

wherein said read circuit comprises:

an integration circuit section configured to perform an integral operation and whose input is connected to an integration node; and

a bias circuit connected between said connection node and said integration node,

wherein said bias circuit comprises:

an integration transistor whose source is connected to said connection node and whose drain is connected to said integration node;

an operational amplifier whose output is connected to a gate of said integration transistor, to whose first input a bias voltage is supplied, and whose second input is connected to said source of said integration transistor; and

at least one diode element that is connected between said gate and said source of said integration transistor and clips a gate-source voltage of said integration transistor.

12. The imaging device according to claim 11 ,

wherein said bias circuit further comprises: a current switching circuit configured to provide or shut off a first current path, wherein said first current path is a current path through which a current flowing between said drain and said source of said integration transistor flows without passing through said connection node.

13. The imaging device according to claim 12 , further comprising a plurality of signal lines respectively connected to said plurality of thermoelectric conversion elements,

wherein said selection circuit comprises switch circuits configured to switch a connection relationship between said plurality of signal lines and said connection node of said read circuit,

wherein a control signal is supplied to said current switching circuit,

said control signal is activated when said switch circuits disconnect all of said plurality of signal lines from said connection node, and

said current switching circuit provides said first current path when said control signal is activated.