The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Sep. 19, 1995
Filed:
Feb. 22, 1994
Takumi Kawai, Kawasaki, JP;
Chikara Tsuchiya, Kawasaki, JP;
Fujitsu Limited, Kawasaki, JP;
Abstract
A preamplifying circuit to amplify signals detected by a magnetoresistance device for a magnetic head. Two terminals of the magnetoresistance device are connected via a first resistor to a power source line Vcc and via a second resistor to a current input terminal of a constant current source having an output terminal which is connected to a ground line, respectively. A first capacitor is connected between the power source line Vcc and an input terminal of the constant current source. The two terminals of the magnetoresistance device are connected to bases of first and second transistors, respectively, in a differential amplification circuit. With this, because the input impedances at both terminals of the magnetoresistance device are equal, the external noise added to both of the terminals of the magnetoresistance device via parasitic capacitance become inphase. Also, the noise from the constant current source added to the base of the second transistor via the second resistor and the noise from the constant current source added to the base of the first transistor via the first capacitor and the first resistor become in-phase.