Digital-to-analog converter having common adjustment means

Claim 2

A digital-to-analog converter comprising; (a) a digital-to-analog conversion circuit of a current output type; (b) a current-to-voltage conversion circuit for converting an anlog output current from said digital-to-analog conversion circuit into a voltage and producing the same; (c) a driving circuit for driving said digital-to-analog conversion circuit and said current-to-voltage conversion circuit with constant current; and (d) common adjustment means connected to said driving circuit to simultaneously change said constant current for driving, respectively, said digital-to-analog conversion circuit and said current-to-voltage conversion circuit.

Claim 3

A digital-to-analog converter according to claim 1, wherein the current-to-voltage conversion circuit has a reference input terminal biased to a voltage of 1/2 of a maximum output voltage.

Claim 4

A digital-to-analog converter according to claim 2, wherein said current-to-voltage conversion circuit includes an operational amplifier, and said operational amplifier has a non-inverting input terminal biased to the voltage of 1/2 of the maximum output voltage, and further has the output current of said digital-to-analog conversion circuit supplied to an inverting input terminal thereof.

Claim 5

A digital-to-analog converter according to claim 1, wherein said driving circuit includes a first current mirror circuit for driving said digital-to-analog conversion circuit with constant current, and a second current mirror circuit for driving said current-to-voltage conversion circuit with constant current.

Claim 6

A digital-to-analog converter according to claim 4, further comprising a first operational amplifier for controlling an amount of current of said first control mirror circuit, and a second operational amplifier for controlling an amount of current of said second current mirror circuit.

Claim 7

A digital-to-analog converter according to claim 1, wherein said digital-to-analog converter further comprises a single power source for driving said digital-to-analog conversion circuit and said current-to-voltage conversion circuit.

Claim 8

A digital-to-analog converter according to claim 1 or 6, wherein said current-to-voltage conversion circuit has an output voltage which is about equal to that of a power source voltage and is of unipolar nature.

Claim 9

A digital-to-analog converter according to claim 1, wherein said digital-to-analog conversion circuit, said current-to-voltage conversion circuit, and said driving circuit are formed into a monolithic integrated circuit (IC).

Claim 10

A digital-to-analog converter comprising: (a) a digital-to-analog conversion circuit of a current output type; (b) a current-to-voltage conversion circuit for converting an analog output current of said digital-to-analog conversion circuit into a voltage and producing the same; (c) a driving circuit for driving said digital-to-analog conversion circuit and said current-to-voltage conversion circuit with constant current; and (d) temperature compensation means connected to said driving circuit for simultaneously compensating changes due to temperature of said constant current for driving said digital-to-analog conversion circuit and said current-to-voltage conversion circuit, said temperature compensation means including a resistance element provided within said driving circuit so as to convert a reference voltage supplied from outside into a reference current, and a resistance element provided within said current-to-voltage conversion circuit, both said resistance elements having the same temperature characteristics.

Claim 11

A digital-to-analog converter comprising: (a) a digital-to-analog conversion circuit of a current output type; (b) a current-to-voltage conversion circuit for converting an analog output current of said digital-to-analog conversion circuit into a voltage and producing the same; (c) a driving circuit for driving said digital-to-analog conversion circuit and said current-to-voltage conversion circuit with constant current; and (d) temperature compensation means connected to said driving circuit for simultaneously compensating changes due to temperature of said constant current for driving said digital-to-analog conversion circuit and said current-to-voltage conversion circuit, said temperature compensation means including a resistance element provided within said driving circuit so as to convert a reference voltage supplied from outside into a reference current, and a resistance element provided within said current-to-voltage conversion circuit, both said resistance elements having the same temperature characteristics.

Claim 12

A digital-to-analog converter according to claim 9, wherein said current-to-voltage conversion circuit has a reference input terminal biased to a voltage of 1/2 of a maximum output voltage.

Claim 13

A digital-to-analog converter according to claim 10, wherein said current-to-voltage conversion circuit includes an operational amplifier, and said operational amplifier has a non-inverting input terminal biased to the voltage of 1/2 of the maximum output voltage, and has the output current of said digital-to-analog conversion circuit supplied to an inverting input terminal thereof.

Claim 14

A digital-to-analog converter according to claim 9, wherein said driving circuit includes a first current mirror circuit for driving said digital-to-analog conversion circuit with constant current, and a second current mirror circuit for driving said current-to-voltage conversion circuit with constant current.

Claim 15

A digital-to-analog converter according to claim 12, further comprising a first operational amplifier for controlling an amount of current of said first current mirror circuit, and a second operational amplifier for controlling an amount of current of said second current mirror circuit.

Claim 16

A digital-to-analog converter according to claim 9, wherein said digital-to-analog conversion circuit and said current-to-voltage conversion circuit are driven by a single power source.

Claim 17

A digital-to-analog converter according to claim 9 or claim 14, wherein said current-to-voltage conversion circuit has an output voltage which is about equal to that of a power source voltage and is of a unipolar nature.

Claim 18

A digital-to-analog converter according to claim 9, wherein said digital-to-analog conversion circuit, said current-to-voltage conversion circuit, and said driving circuit are formed into a monolithic integrated circuit (IC).

Claim 19

A digital-to-analog converter according to claim 9 wherein said resistance element provided within said driving circuit is a diffused resistor formed within said monolithic IC.