Dynamic Correction Of Gain Error In Current-Feedback Instrumentation Amplifiers

A method for gain error correction in a current-feedback instrumentation amplifier, said method comprising the steps of:

• providing an input transconductor comprising
• a first differential pair comprising first and second transistors,
• first and second tail current sources, and
• a first degeneration resistor coupled between the first and the second transistors;
• providing a feedback transconductor comprising
• a second differential pair comprising third and fourth transistors,
• third and fourth tail current sources, and
• a first degeneration resistor coupled between the third and the fourth transistors;
• and
• providing a first modulator circuit coupled between the first and third tail current sources, and the first and third transistors;
• providing a second modulator circuit coupled between the second and fourth tail current sources, and the second and fourth transistors;
• controlling the first and second modulator circuits by alternating first and second phase signals;
• wherein during the first phase signal comprises the steps of:
• coupling the first tail current source to the first transistor and the third tail current source to the third transistor with the first modulator circuit, and
• coupling the second tail current source to the second transistor and the fourth tail current to the fourth transistor with the second modulator circuit;
• wherein during the second phase signal comprises the steps of:
• coupling the first tail current source to the third transistor and the third tail current source to the first transistor with the first modulator circuit, and
• coupling the second tail current source to the fourth transistor and the fourth tail current to the second transistor with the second modulator circuit.
• whereby gain error caused by a difference between the tail current sources is averaged out.

A method for gain error correction in a current-feedback instrumentation amplifier, said method comprising the steps of:

• providing an input transconductor comprising
• a first differential pair of transistors, and
• a first tail current source;
• providing a feedback transconductor comprising
• a second differential pair of transistors, and
• a second tail current source;
• and
• providing a modulator circuit coupled between the first and second tail current sources, and the first and second differential pairs of transistors;
• controlling the modulator circuit by alternating first and second phase signals;
• wherein during the first phase signal comprises the steps of coupling the first tail current source to the first differential pair of transistors and the second tail current source to the second differential pair of transistors with the modulator circuit;
• and
• wherein during the second phase signal comprises the steps of coupling the first tail current source to the second differential pair of transistors, and the second tail current source to the first differential pair of transistors with the modulator circuit.

A current-feedback instrumentation amplifier having gain error correction, comprising:

• an input transconductor comprising
• a first differential pair of transistors,
• first degeneration resistors coupled to the first differential pair of transistors, and
• a first tail current source;
• a feedback transconductor comprising
• a second differential pair of transistors,
• second degeneration resistors coupled to the second differential pair of transistors, and
• a second tail current source;
• and
• a modulator circuit coupled between the first and second tail current sources, and the first and second degeneration resistors;
• wherein during a first phase state the modulator circuit couples the first tail current source to the first degeneration resistors and the second tail current source to the second degeneration resistors;
• and
• wherein during a second phase state the modulator circuit couples the first tail current source to the second degeneration resistors, and the second tail current source to the first degeneration resistors.

A current-feedback instrumentation amplifier having gain error correction, comprising:

• input transconductor comprising
• a differential pair comprising first and second transistors,
• first and second tail current sources, and
• a first degeneration resistor coupled between the first and the second transistors;
• a feedback transconductor comprising
• a differential pair comprising third and fourth transistors,
• third and fourth tail current sources, and
• a first degeneration resistor coupled between the third and the third transistors;
• and
• a first modulator circuit coupled between the first and third tail current sources, and the first and third transistors;
• a second modulator circuit coupled between the second and fourth tail current sources, and the second and fourth transistors;
• wherein during the first phase signal the first modulator circuit couples the first tail current source to the first transistor and the third tail current source to the third transistor, and the second modulator circuit couples the second tail current source to the second transistor and the fourth tail current to the fourth transistor;
• wherein during the second phase signal the first modulator circuit couples the first tail current source to the third transistor and the third tail current source to the first transistor, and the second modulator circuit couples the second tail current source to the fourth transistor and the fourth tail current to the second transistor.

A current-feedback instrumentation amplifier having gain error correction, comprising:

• an input transconductor comprising
• a first differential pair of transistors, and
• a first tail current source;
• a feedback transconductor comprising
• a second differential pair of transistors, and
• a second tail current source;
• and
• a modulator circuit coupled between the first and second tail current sources, and the first and second differential pairs of transistors;
• wherein during a first phase state the modulator circuit couples the first tail current source to the first differential pair of transistors and the second tail current source to the second differential pair of transistors;
• and
• wherein during a second phase state the modulator circuit couples the first tail current source to the second differential pair of transistors, and the second tail current source to the first differential pair of transistors.