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:
Oct. 28, 2003
Filed:
Jan. 23, 2002
Yuuichi Aoki, Tokyo, JP;
NEC Corporation, , JP;
Abstract
There is disclosed a variable-gain amplifier circuit comprising an adjustable impedance circuit part including a bipolar transistor having a base connected to a control terminal for receiving a controlled bias voltage, a collector connected to a positive power supply voltage terminal, and an emitter connected to ground through a diode in such a manner that an anode of the diode is connected to the emitter of the transistor and a cathode of the diode is connected to the ground. The variable-gain amplifier circuit further comprises a variable-gain amplifying circuit part having an amplifying circuit having an input coupled through an DC blocking capacitor to an input terminal for receiving an input signal and an output connected to an output terminal. The emitter of the bipolar transistor is connected to a node between the input terminal and the DC blocking capacitor. By controlling the bias voltage applied to the base of the transistor, it is possible to adjust the gain of the whole circuit by action of the adjustable impedance circuit part, and at the same time, it is possible to allow the amplifying circuit having a high S/N ratio, to operate under a low power supply voltage with a low noise factor.