US 6,320,466 B1 · Amplifier circuit

Abstract

The object of the invention is to realize an MR amplifier circuit that is operable with a single power supply voltage, and in which the CMRR can be maintained large. Current supply circuit (10) supplies a prescribed current (IB) to MR element (20) in response to a control signal (SD), the current of resistive element (R2) that is connected between node (ND2) and ground potential is set by means of the equivalent current circuit (40), the current that flows in resistive element (R2) is controlled in response to potential changes of node (ND2) when a noise is applied to MR element (20), and current changes of MR element (20) are suppressed. Due to the fact that a voltage drop that is generated in MR element (20) is amplified by amplifier (30) that is operated with a single power supply voltage, and since the resistance changes of MR element (20) accompanying changes in the magnetic field are detected, an amplifier circuit can be realized wherein the strength of the magnetic field can be detected, the CMRR can be kept high, and the effects due to in-phase noise can be minimized.

Claims12

Dependent claims

An amplifier circuit comprising:

a magneto-resistive (MR) element in which the resistance value changes in response to the strength of a magnetic field,
a current supply means that supplies a prescribed current to the first terminal of the MR element,
a resistive element that is connected between a second terminal of the MR element and ground potential,
a current control means responsive to changes in a potential of the second terminal for supplying a current to the second terminal that opposes the current change in the MR element generated by an in-phase noise signal, for minimizing changes in said predetermined current flow through said MR element,
and an amplifying means that amplifies the voltage difference of the first terminal and second terminal, and outputs an amplified signal.

2 more elements

An amplifier circuit comprising:

a magneto-resistive (MR) element in which the resistance value changes in response to the strength of a magnetic field,
a current supply means that supplies a prescribed current to the first terminal of the MR element,
a resistive element that is connected between a second terminal of the MR element and ground potential,
a current control means that, when the potential of the second terminal changes, supplies a current to the second terminal that is equivalent to the current change amount of the resistive element that is generated by means of the potential change of the terminal,
and an amplifying means that amplifies the voltage difference of the first terminal and second terminal, and outputs an amplified signal, wherein:
the current control means has a first current source and a first transistor that are series-connected between a supply line for the power supply voltage and the second terminal,
a second current source, a second transistor, and a second resistive element that are series-connected between the supply line for the power supply voltage and the ground potential,
a third resistive element that is connected between the connecting point for the first current source and first transistor and the connecting point for the second current source and second transistor,
and a second current supply means that supplies an equivalent current as the current supply means to a connecting point between the second transistor and the second resistive element,
wherein the control terminal of the first transistor is connected to the connecting point between the second transistor and the second resistive element, and the control terminal for the second transistor is connected to the second terminal.

7 more elements

Dependencies are inferred from the claim text.

Amplifier circuit

Life of this patent

Amplifier circuit

Life of this patent

Abstract

Claims12