Controlling amplifier input impedance

• US 8,314,659 B2
• Filed: 04/10/2008
• Issued: 11/20/2012
• 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: McFarthing, Anthony Lawrence
• Primary Examiner(s): Choe, Henry
• Application Number:
  US12/595,470
• Publication Number:
  US 20100201450A1
• Time in Patent Office: 1,685 Days
• Field of Search: 330/302, 330/277, 330/292, 330/67
• 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 capacitors to provide a function of a source degeneration inductor arrangement in determining a real part of the amplifier'"'"'s input impedance, and a transistor, having first, second and third terminals, and the arrangement of capacitors comprising first and second capacitors, wherein the first capacitor is located between the first terminal and another one of the terminals and the second capacitor is located between the second and third terminals, and at least one of the capacitors is a non-parasitic capacitor.

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

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

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

2. An amplifier comprising a transistor, having first, second and third terminals, and first and second capacitors, wherein the first capacitor is located between the first terminal and another one of the terminals and the second capacitor is located between the second and third terminals such that the capacitors cooperate such that the real part of the amplifier'"'"'s input impedance is substantially provided by reactive elements, wherein at least one of the capacitors is a non-parasitic capacitor.

3. An amplifier according to claim 2, wherein the first, second and third terminals are gate, source and drain terminals, respectively.