CONTROLLING AMPLIFIER INPUT IMPEDANCE

• US 20100201450A1
• Filed: 04/10/2008
• Published: 08/12/2010
• Est. Priority Date: 04/13/2007
• Status: Active Grant

• Current Assignee: Qualcomm technologies international, ltd. (Qualcomm, Inc.)
• Original Assignee: Cambridge Silicon Radio Limited (Qualcomm, Inc.)
• Inventors: MacFarthing, Antony Lawrence
• Granted Patent: US 8,314,659 B2
• Time in Patent Office: Days
• US Class Current: 330/302
• CPC Class Codes: H03F 1/26 Modifications of amplifiers to reduce influence of noise generated by amplifying elements
• CPC Class Codes: H03F 1/56 Modifications of input or output impedances, not otherwise provided for
• CPC Class Codes: H03F 2200/222 A circuit being added at the input of an amplifier to adapt the input impedance of the amplifier
• CPC Class Codes: H03F 2200/294 the amplifier being a low noise amplifier [LNA]
• CPC Class Codes: H03F 2200/372 Noise reduction and elimination in amplifier
• CPC Class Codes: H03F 2200/451 the amplifier being a radio frequency amplifier
• CPC Class Codes: H03F 2200/489 A coil being added in the source circuit of a common source stage, e.g. as degeneration means
• CPC Class Codes: H03F 2200/492 A coil being added in the source circuit of a transistor amplifier stage as degenerating element
• CPC Class Codes: H03F 2200/75 the amplifier stage being a common source configuration MOSFET
• CPC Class Codes: H03F 3/195 in integrated circuits
• CPC Class Codes: H03H 7/38 Impedance-matching networks

Abstract

An amplifier (22) containing an arrangement of capacitive elements (26, 28) in place of a source degeneration inductor arrangement to set the real part of the amplifier'"'"'s input impedance.

Claims

1. An amplifier containing an arrangement of capacitive elements to provide the function of a source degeneration inductor arrangement in determining the real part of the amplifier'"'"'s input impedance.

2. An amplifier according to claim 1, wherein at least one capacitive element is provided at least in part by an intrinsic capacitance of a transistor within the amplifier.

3. An amplifier according to claim 1 or 2, wherein at least one capacitive element is provided at least in part by a capacitor external to a transistor within the amplifier.

8. An amplifier according to claim 1, wherein the amplifier is a LNA.

9. An integrated circuit containing the amplifier of claim 1.

10. A radio receiver containing the amplifier of claim 1.

4. An amplifier comprising a transistor, having first, second and third terminals, and first and second capacitive elements, wherein the first capacitive element is located between the first terminal and one of the other two terminals and the second capacitive element is located between the second and third terminals such that the capacitive elements co-operate such that the real part of the amplifier'"'"'s input impedance is substantially provided by reactive elements.

5. An amplifier according to claim 4, wherein the first, second and third terminals are gate, source and drain terminals, respectively.

6. An amplifier according to claim 4, wherein at least one capacitive element is provided at least in part by an intrinsic capacitance of the transistor.

7. An amplifier according to claim 4, wherein at least one capacitive element is provided at least in part by a capacitor external to the transistor.