CURRENT SWITCH CIRCUIT AND D/A CONVERTER, SEMICONDUCTOR INTEGRATED CIRCUIT, AND COMMUNICATION DEVICE USING THE SAME
First Claim
1. A current switch circuit comprising a current source and a differential switch connected to an output terminal of the current source, whereinthe current source includes at least one transistor having a gate terminal to which a bias voltage is applied that determines a value of a current to conduct,the differential switch includes first and second transistors, each of the transistors having source terminals connected to the output terminal of the current source in parallel, drain terminals as first and second output terminals respectively, and gate terminals to which complementary signals are inputted, andthe current switch circuit further comprises a threshold voltage control circuit for outputting a substrate voltage to a substrate terminal of each of the first and second transistors to adjust a threshold voltage of the first and second transistors.
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Accused Products
Abstract
[Means for Solving the Problem] In a current switch circuit A used for a current steering D/A converter, a current switch basic circuit 1 includes first and second transistors Tr121 and Tr122 included in a differential switch 12. A threshold voltage control circuit 5 has an output terminal Vbout controlling the substrate voltage to be outputted to the substrate terminal of each of the two transistors Tr121 and Tr122 included in the differential switch 12 for controlling the threshold voltage of the two transistors of the differential switch. Accordingly, the present invention improves the decrease in the dynamic range of the current switch basic circuit 1 dependent on the threshold of each of the two transistors in the differential switch 12 and realizes a wider output voltage range without causing deterioration in properties even in a case that the power voltage is reduced in the current switch basic circuit 1.
41 Citations
17 Claims
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1. A current switch circuit comprising a current source and a differential switch connected to an output terminal of the current source, wherein
the current source includes at least one transistor having a gate terminal to which a bias voltage is applied that determines a value of a current to conduct, the differential switch includes first and second transistors, each of the transistors having source terminals connected to the output terminal of the current source in parallel, drain terminals as first and second output terminals respectively, and gate terminals to which complementary signals are inputted, and the current switch circuit further comprises a threshold voltage control circuit for outputting a substrate voltage to a substrate terminal of each of the first and second transistors to adjust a threshold voltage of the first and second transistors.
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6. A current switch circuit comprising a current source and a differential switch connected to an output terminal of the current source, wherein
the current source includes at least one transistor having a gate terminal to which a bias voltage is applied that determines a value of a current to conduct, the differential switch includes first and second transistors, the transistors having source terminals connected to an output terminal of the current source in parallel, drain terminals as first and second output terminals respectively, and gate terminals to which complementary signals are inputted, and the first and second transistors of the differential switch has the threshold voltage determined to have an absolute value greater than an absolute value of a threshold voltage of the transistor included in the current source.
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17. A threshold voltage control circuit comprising:
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a reference voltage generating circuit; a first transistor; a substrate voltage control circuit for controlling a substrate voltage of the first transistor in such a way that a voltage difference between a reference voltage generated in the reference voltage generating circuit and a bias voltage becomes a threshold voltage of the first transistor; and a second transistor having the same threshold voltage characteristics as that of the first transistor and including a substrate terminal to which an output voltage of the substrate voltage control circuit is input.
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Specification