Voltage generating circuit

A digital-to-analog conversion circuit comprising:

• a voltage dividing circuit including a first impedance element connected to a first supply line, a second impedance element connected to a second supply line, the second impedance element having substantially the same impedance as the first impedance element, and a third impedance element connected between the first and second impedance elements, having a predetermined impedance, wherein the third impedance element includes a plurality of sub-impedance elements for dividing a voltage between the first and second impedance elements to generate a plurality of divided voltages at nodes between the sub-impedance elements;
• a first current source connected to a first node between the first and third impedance elements and a second current source connected to a second node between the second and third impedance elements, the first and second current sources supplying first and second currents having substantially identical values to the first and second nodes, respectively;
• a selecting unit that selects one of the nodes between the sub-impedance elements and outputs the node voltage as a selected voltage on the basis of the first and second currents and the impedances of the first to third impedance elements;
• and
• a control circuit that receives the selected voltage and a predetermined reference voltage, compares the selected voltage with the predetermined reference voltage, and, on the basis of the compared result, controls the first and second currents supplied from the first and second current sources to bring the selected voltage to a substantial equivalence with the reference voltage, wherein the first and second node voltages are used for generating an analog voltage signal.

A constant current circuit comprising:

• first and second transistors connected in parallel between first and second supply lines, which have gates connected with each other, wherein the first and second transistors are different sizes;
• an output transistor having a gate connected to the gates of the first and second transistors;
• and
• a control circuit that controls the voltage applied to the gates of the first and second transistors so that drain currents having substantially the same value flow through the first and second transistors, wherein the drain current of the output transistor is constant.

A digital-to-analog conversion circuit comprising:

• a voltage dividing circuit including a first impedance element connected to a first supply line, a second impedance element connected to a second supply line, the second impedance element having substantially the same impedance as the first impedance element, and a third impedance element connected between the first and second impedance elements, the third impedance element having a predetermined impedance, wherein the third impedance element includes a plurality of sub-impedance elements for dividing a voltage between the first and second impedance elements to generate a plurality of divided voltages at nodes between the sub-impedance elements;
• a first current source connected to a first node between the first and third impedance elements, and a second current source connected to a second node between the second and third impedance elements, which supply first and second currents having substantially the same value to the first node and the second node, respectively;
• a selecting unit that selects one of the nodes between the sub-impedance elements and outputs the selected node voltage as a selected voltage on the basis of the first and second currents and the impedances of the first through third impedance elements;
• and
• a first control circuit including a comparing circuit that receives the selected voltage and a predetermined reference voltage and compares the selected voltage with the predetermined reference voltage, the first control circuit controlling, on the basis of the compared result, the first and second currents supplied from the first and second current sources so as to bring the selected voltage to a substantial equivalence with the reference voltage, wherein voltages at the first and second nodes are used for generating an analog voltage signal, the comparing circuit includes a constant current circuit for generating a bias current used in the comparing circuit, and the constant current circuit includes,
• first and second transistors connected in parallel between the first and second supply lines, the gates of the first and second transistors being connected to each other and wherein the first and second transistors have different sizes,
• an output transistor having a gate connected to the gates of the first and second transistors, and
• a second control circuit that controls voltages applied to the gates of the first and second transistors so that drain currents having a substantially same value flow through the first and second transistors, wherein the drain current flows through the output transistor as the bias current.

A current generating circuit comprising:

• a first voltage dividing circuit, connected between first and second supply lines, which divides a differential voltage between first and second voltages to generate a first divided voltage;
• a second voltage dividing circuit including a first impedance element connected to the first supply line, a second impedance element connected to the second supply line, the second impedance element having substantially the same impedance as the first impedance element, and a third impedance element connected between the first and second impedance elements, the third impedance element having a predetermined impedance, wherein the third impedance element includes a plurality of sub-impedance elements for generating a plurality of second divided voltages at nodes between the sub-impedance elements;
• a first current source connected to a first node between the first and third impedance elements and a second current source connected to a second node between the second and third impedance elements, which supply a first current and a second current having substantially the same value to the first node and the second node, respectively;
• a differential circuit that receives the first divided voltage and one of the plurality of the second divided voltages and controls the first and second currents supplied from the first and second current sources so as to bring the first divided voltage to a substantial equivalence with the selected second divided voltage;
• and
• a third current source connected to the differential circuit which generates a third current having a value substantially equal to the first and second currents, wherein the third current is an output current of the current generating circuit.