US 7,202,738 B1Granted

Accurate voltage to current converters for rail-sensing current-feedback instrumentation amplifiers

AssigneeMaxim Integrated Products, Inc.

InventorsJohan Hendrik Huijsing, Behzad Shahi

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Abstract

Accurate voltage to current converters for rail-sensing current-feedback instrumentation amplifiers using folded cascode transistors. Embodiments using various degrees of cascoding, as well as using bootstrapped folded cascoded input transistors are disclosed. Circuits for sensing around the negative rail are disclosed, though circuits for sensing around the positive rail may be readily achieved by use of complementary devices.

Claims7

Dependent claims

A differential voltage to current converter comprising:

first and second transistors of a first conductivity type and third through sixth transistors of a second conductivity type, each transistor having first and second terminals and a control terminal, the conduction between the first and second terminal being controlled by the voltage between the control terminal and the first terminal;
first through fifth current sources;
first through fourth resistors each having first and second terminals;
the second current source being coupled between a first power supply terminal and the first terminals of the first and second resistors, the second terminals of the first and second resistors being coupled to the first terminals of the first and second transistors, respectively, the second terminals of the first and second transistors being coupled to a second power supply terminal through fourth and fifth current sources, respectively, and to the first terminals of the fifth and sixth transistors, respectively;
the first and third current sources being coupled between the first power supply terminal and the control terminals of the third and fourth transistors, respectively, and to the second terminals of the fifth and sixth transistors, respectively;
the third and fourth transistors having their second terminals coupled to the second terminals of the first and second resistors, respectively, and their first terminals coupled through the third and fourth resistors to the second power supply terminals, respectively, the first terminals of the third and fourth transistors also being coupled to first and second output terminals of the differential voltage to current converter;
the control terminals of the fifth and sixth transistors being coupled to a first reference voltage;
the control terminals of the first and second transistors being coupled to first and second input terminals, respectively, of the differential voltage to current converter.

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Dependencies are inferred from the claim text.

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Abstract

A differential voltage to current converter comprising:

first and second transistors of a first conductivity type and third through sixth transistors of a second conductivity type, each transistor having first and second terminals and a control terminal, the conduction between the first and second terminal being controlled by the voltage between the control terminal and the first terminal;
first through fifth current sources;
first through fourth resistors each having first and second terminals;
the second current source being coupled between a first power supply terminal and the first terminals of the first and second resistors, the second terminals of the first and second resistors being coupled to the first terminals of the first and second transistors, respectively, the second terminals of the first and second transistors being coupled to a second power supply terminal through fourth and fifth current sources, respectively, and to the first terminals of the fifth and sixth transistors, respectively;
the first and third current sources being coupled between the first power supply terminal and the control terminals of the third and fourth transistors, respectively, and to the second terminals of the fifth and sixth transistors, respectively;
the third and fourth transistors having their second terminals coupled to the second terminals of the first and second resistors, respectively, and their first terminals coupled through the third and fourth resistors to the second power supply terminals, respectively, the first terminals of the third and fourth transistors also being coupled to first and second output terminals of the differential voltage to current converter;
the control terminals of the fifth and sixth transistors being coupled to a first reference voltage;
the control terminals of the first and second transistors being coupled to first and second input terminals, respectively, of the differential voltage to current converter.

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