Amplifier circuit and method for reducing noise therein
AssigneeMotorola, Inc.
InventorsWilliam E. Main, Danielle L. Coffing
Life of this patent
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Abstract
A transconductance amplifier (67) includes a multiple-stage amplifier (99) for amplifying an Intermediate Frequency (IF) signal. The transconductance amplifier includes a feedback path (103) having a resistance (105) for providing a feedback signal from an output of the multiple-stage amplifier (99) to an input of the multiple-stage amplifier (99). The resistance (105) of the feedback path (103) is selected so that an input impedance of the transconductance amplifier is equal to a source impedance at an input terminal (82) of the transconductance amplifier (67) and an output impedance of the transconductance amplifier (67) is equal to a load impedance at an output terminal (84) of the transconductance amplifier (67).
Claims19
An amplifier circuit, comprising:
- a transconductance amplifier having a transconductance, an input coupled to an input of the amplifier circuit, and an output coupled to an output of the amplifier circuit;
- a feedback path having a resistance for providing a feedback signal from the output of the transconductance amplifier to the input of the transconductance amplifier;
- wherein the resistance of the feedback path is a function of the transconductance of the transconductance amplifier;
- and
- wherein the resistance of the feedback path is chosen so that an input impedance of the amplifier circuit is substantially equal to a source impedance at the input of the amplifier circuit and an output impedance of the amplifier circuit is substantially equal to a load impedance at the output of the amplifier circuit.
An integrated circuit, comprising:
- a multiple-stage transconductance amplifier having a first input coupled for receiving a bias signal, a second input coupled to an input of the integrated circuit for receiving a voltage signal, and an output for providing a current signal to an output of the integrated circuit;
- a feedback path for transmitting a feedback signal from the output of the multiple-stage transconductance amplifier to the second input of the multiple-stage transconductance amplifier;
- wherein the feedback path is devoid of a decoupling capacitor so that the feedback signal includes an Alternating Current (AC) component for reducing noise in the integrated circuit;
- and
- wherein the multiple-stage transconductance amplifier includes a current mirror circuit coupled to the output of the integrated circuit.
A method for reducing noise and power dissipation in a transconductance amplifier circuit, comprising the steps of:
- providing a feedback path for transmitting a feedback signal from an output of the transconductance amplifier circuit to an input of the transconductance amplifier circuit, wherein the feedback signal has a Direct Current (DC) component and an Alternating Current (AC) component for reducing noise in the transconductance amplifier circuit;
- and
- setting a resistance of the feedback path so that an input impedance of the transconductance amplifier circuit is substantially equal to a source impedance at the input of the transconductance amplifier circuit and an output impedance of the transconductance amplifier circuit is substantially equal to a load impedance at the output of the transconductance amplifier circuit.
Dependencies are inferred from the claim text.