Signal amplifying circuit with reduced output signal noise by introducing coupling effect and related method thereof

• US 8,816,771 B2
• Filed: 09/10/2012
• Issued: 08/26/2014
• Est. Priority Date: 05/21/2012
• Status: Active Grant

• Current Assignee: Realtek Semiconductor Corp.
• Original Assignee: Realtek Semiconductor Corp.
• Inventors: Chen, Hsien-Ku, Chang, Chia-Jun, Chan, Ka-Un, Lin, Ying-Hsi
• Primary Examiner(s): Pascal, Robert
• Assistant Examiner(s): NGUYEN, KHIEM D
• Application Number:
  US13/607,830
• Publication Number:
  US 20130307620A1
• Time in Patent Office: 715 Days
• Field of Search: 330/253, 330/277, 330/195, 330/165, 330/302, 330/311
• US Class Current: 330/253
• CPC Class Codes: H03F 1/223 with MOSFET's
• CPC Class Codes: H03F 2200/294 the amplifier being a low noise amplifier [LNA]
• CPC Class Codes: H03F 2203/45562 the IC comprising a cross coupling circuit, e.g. comprising two cross-coupled transistors
• CPC Class Codes: H03F 2203/45638 the LC comprising one or more coils
• CPC Class Codes: H03F 3/45 Differential amplifiers differential sense amplifiers G11C7/062
• CPC Class Codes: H03F 3/45179 using MOSFET transistors as the active amplifying circuit H03F3/45278 takes precedence

Abstract

A signal amplifying circuit includes: an input stage circuit, arranged to receive an input signal; a first inductive device coupled between the input stage circuit and a first reference voltage; an output stage circuit arranged to generate an output signal according to the input signal; and a second inductive device coupled between the output stage circuit and a second reference voltage, wherein at least a part of a winding of the first inductive element is cross-coupled to at least a part of a winding of the second inductive element.

Claims

1. A signal amplifying circuit, comprising:

an input stage circuit, arranged for receiving an input signal;

a first inductive element, coupled between the input stage circuit and a first reference voltage, for receiving the input signal;

an output stage circuit, arranged for generating an output signal according to the input signal; and

a second inductive element, coupled between the output stage and a second reference voltage;

wherein at least a part of the winding of the first inductive element is cross-coupled to at least a part of the winding of the second inductive element.

2. The signal amplifying circuit of claim 1, wherein at least a part of the winding of the first inductive element is cross-coupled to at least a part of the winding of the second inductive element, thus a coupling effect is introduced between the first inductive element and the second inductive element.

3. The signal amplifying circuit of claim 2, wherein the first inductive element has a first inductance winding number, the second inductive element has a second inductance winding number, and a product of a ratio of the first inductance winding number to the second inductance winding number and a coupling coefficient corresponding to the coupling effect is not greater than 1.

4. The signal amplifying circuit of claim 3, wherein a first terminal of the first inductive element is coupled to the first reference voltage, and a second terminal is arranged for receiving the input signal;

wherein the input stage circuit comprises;

a first field effect transistor, comprising a first connection terminal coupled to the second terminal of the first inductive element, and a control terminal arranged for receiving a control signal;

wherein the output stage circuit comprises;

a second field effect transistor, comprising a first connection terminal coupled to a second connection terminal of the first field effect transistor, and a control terminal arranged for receiving a bias signal; and

wherein a first terminal of the second inductive element is coupled to a second connection terminal of the second field effect transistor and a second terminal arranged for coupling to the second reference voltage.

5. The signal amplifying circuit of claim 4, wherein the input stage circuit further comprises:

an amplifying circuit, comprising an input terminal coupled to the first connection terminal of the first field effect transistor, and an output terminal coupled to the control terminal of the first field effect transistor, the amplifying circuit arranged for providing a gain not greater than 0 to the input signal to generate the control signal.

6. The signal amplifying circuit of claim 3, wherein the first inductive element comprises a center-tapped terminal coupled to the first reference voltage;

wherein the input stage circuit comprises;

a first field effect transistor, comprising a first connection terminal coupled to a first terminal of the first inductive element and a first signal of the input signal, and a control terminal arranged for receiving a first control signal; and

a second field effect transistor, comprising a first connection terminal coupled to a second terminal of the first inductive element and a second signal of the input signal, and a control terminal arranged for receiving a second control signal;

wherein the second inductive element comprises a center-tapped terminal coupled to the second reference voltage;

wherein the output stage circuit comprises;

a third field effect transistor, comprising a first connection terminal coupled to a second connection terminal of the first field effect transistor, a control terminal arranged for receiving a first bias signal, a second connection terminal coupled to a first terminal of the second inductive element, and a first signal arranged for outputting the output signal; and

a fourth field effect transistor, comprising a first connection terminal coupled to a second connection terminal of the second field effect transistor, a control terminal arranged for receiving a second bias signal, a second connection terminal coupled to a second terminal of the second inductive element, and a second signal arranged for outputting the output signal.

7. The signal amplifying circuit of claim 6, wherein the input stage circuit further comprises:

a first amplifying circuit, comprising an input terminal coupled to the first connection terminal of the first field effect transistor, an output terminal coupled to the control terminal of the second field effect transistor, the first amplifying circuit arranged for providing a first gain to the first signal of the input signal to generate the second control signal.

8. The signal amplifying circuit of claim 7, wherein the input stage circuit further comprises:

a second amplifying circuit, comprising an input terminal coupled to the first connection terminal of the second field effect transistor, an output terminal coupled to the control terminal of the first field effect transistor, the second amplifying circuit arranged for providing a second gain to the second signal of the input signal to generate the first control signal.

9. The signal amplifying circuit of claim 8, wherein the first gain substantially equals to the second gain.

10. The signal amplifying circuit of claim 1, wherein the first reference voltage is a grounding voltage and the second reference voltage is a source voltage.

11. A signal amplifying method, comprising:

employing an input stage circuit to receive an input signal;

coupling a first inductive element between the input stage circuit and a first reference voltage for receiving the input signal;

employing an output stage circuit to generate an output signal according to the input signal;

coupling a second inductive element between the output stage circuit and a second reference voltage; and

cross-coupling at least a part of the winding of the first inductive element to at least a part of the winding of the second inductive element.

12. The signal amplifying method of claim 11, wherein at least a part of the winding of the first inductive element is cross-coupled to at least a part of the winding of the second inductive element, thus a coupling effect is introduced between the first inductive element and the second inductive element.

13. The signal amplifying method of claim 12, wherein the first inductive element has a first inductance winding number, the second inductive element has a second inductance winding number, and a product of a ratio of the first inductance winding number to the second inductance winding number and a coupling coefficient corresponding to the coupling effect is not greater than 1.

14. The signal amplifying method of claim 11, wherein the first reference voltage is a grounding voltage and the second reference voltage is a source voltage.