Gain-controlled amplifier, receiver circuit and radio communication device

• US 20060132235A1
• Filed: 08/06/2003
• Published: 06/22/2006
• Est. Priority Date: 08/06/2002
• Status: Active Grant

• Current Assignee: Sony Corporation (Sony Group Corp.)
• Original Assignee: Sony Corporation (Sony Group Corp.)
• Inventors: Ozawa, Miho
• Granted Patent: US 7,196,579 B2
• Time in Patent Office: Days
• US Class Current: 330/254
• CPC Class Codes: H03F 2200/372 Noise reduction and elimination in amplifier
• CPC Class Codes: H03F 2203/45082 the common mode signal being taken or deducted from the one or more outputs of the differential amplifier
• CPC Class Codes: H03F 2203/45101 Control of the DC level being present
• CPC Class Codes: H03F 2203/45286 the temperature dependence of a differential amplifier being controlled
• CPC Class Codes: H03F 3/45475 using IC blocks as the active amplifying circuit
• CPC Class Codes: H03F 3/45973 by using a feedback circuit
• CPC Class Codes: H03G 3/3036 in high-frequency amplifiers or in frequency-changers H03G3/3052, H03G3/32, H03G3/34 take precedence
• CPC Class Codes: H03G 3/3052 in bandpass amplifiers (H.F. or I.F.) or in frequency-changers used in a (super)heterodyne receiver H03G3/32, H03G3/34 take precedence
• CPC Class Codes: H03H 11/1291 Current or voltage controlled filters

Abstract

A gain-controlled amplifier capable of dealing with the system for performing the receiving operation continuously, and capable of correcting a change of a DC offset owing to an operation condition such as temperature; a receiver circuit using the gain-controlled amplifier; and a radio communication device installing the receiver circuit. In a gain-controlled amplifier composed of three GCA stages (11)-(13) connected by cascade connection, the center value of an output DC of each GCA stage (11)-(13) is kept to be constant by a common feedback circuit (16)-(18) provided correspondingly to each of the GCA stages (11)-(13), and a DC feedback quantity is made to be changed according to a gain control voltage VG by means of a DC feedback circuit (19) provided between an output side of a last stage of the GCA stages and an input side of a first stage of the GCA stages.

Claims

1. A gain-controlled amplifier, characterized by comprising:

a plurality of differential amplifier stages connected to each other by cascade connection, each of said differential amplifier stages performing gain control by a gain control voltage;

a plurality of common feedback circuits provided correspondingly to each of said plurality of differential amplifier stages, each of said common feedback circuits keeping a center value of an output DC of each of said differential amplifier stages to be constant; and

a DC feedback circuit provided between an output side of a last stage of said plurality of differential amplifier stages and an input side of a first stage of said differential amplifier stages, said DC feedback circuit changing a DC feedback quantity according to said gain control voltage.

2. The gain-controlled amplifier according to claim 1, characterized in that each of said plurality of differential amplifier stages comprises:

a differential amplifier in which a gain is changed according to said gain control voltage;

a first current source in which a current value is changed according to said gain control voltage; and

a Gilbert cell circuit provided between a load side of said differential amplifier and a power source, said Gilbert cell including a second current source constituting a current mirror with said first current source.

3. The gain-controlled amplifier according to claim 1, characterized in that each of said plurality of common feedback circuits comprises:

a first difference circuits for outputting a difference of each positive phase output of said plurality of differential amplifier stages to a predetermined reference voltage;

a second difference circuits for outputting a difference of each opposite phase output of said plurality of differential amplifier stages to said predetermined reference voltage; and

an adder for adding each difference output of said first difference circuit and said second difference circuit;

wherein a current value of a current source constituting each stage of said plurality of difference amplifier stages is controlled by an added output of said adder.

4. The gain-controlled amplifier according to claim 1, characterized in that said DC feedback circuit comprises:

a detector circuit for detecting an output voltage at a last stage of said plurality of differential amplifier stages; and

a variable gain amplifier for amplifying an output of said detector circuit by a gain in accordance with said gain control voltage;

wherein an output of said variable gain amplifier is added to an input of a first stage of said plurality of difference amplifier.

5. A receiver circuit, characterized by comprising a gain-controlled amplifier for adjusting an amplitude of a signal obtained by performing a frequency conversion of a received signal, wherein said gain-controlled amplifier has:

a plurality of differential amplifier stages connected to each other by cascade connection, each of said differential amplifier stages performing gain control by a gain control voltage;

a plurality of common feedback circuits provided correspondingly to each of said plurality of differential amplifier stages, each of said common feedback circuits keeping a center value of an output DC of each of the differential amplifier stages to be constant; and

a DC feedback circuit provided between an output side of a last stage of said plurality of differential amplifier stages and an input side of a first stage of said differential amplifier stages, the DC feedback circuit changing a DC feedback quantity according to said gain control voltage.

6. A radio communication device, characterized by comprising:

an antenna;

frequency converting means for performing a frequency conversion of a high frequency signal received by said antenna; and

a gain-controlled amplifier for adjusting an amplitude of a signal obtained by performing the frequency conversion of a received signal;

wherein said gain-controlled amplifier has;

a plurality of differential amplifier stages connected to each other by cascade connection, each of said differential amplifier stages performing gain control by a gain control voltage;

a plurality of common feedback circuits provided correspondingly to each of said plurality of differential amplifier stages, each of said common feedback circuits keeping a center value of an output DC of each of said differential amplifier stages to be constant; and

a DC feedback circuit provided between an output side of a last stage of said plurality of differential amplifier stages and an input side of a first stage of said differential amplifier stages, said DC feedback circuit changing a DC feedback quantity according to said gain control voltage.