US 7,746,169 B2 · LNA having a post-distortion mode and a high-gain mode

Abstract

A differential low noise amplifier (LNA) is operable in a selectable one of two modes. The LNA includes a first transistor, a second transistor, a third transistor and a fourth transistor. In the first mode (PDC mode), the four transistors are configured to operate as a post-distortion cancellation (PDC) LNA. The third and fourth transistors operate as cancel transistors that improve linearity, but reduce LNA gain somewhat. In the second mode (high gain mode), the third and fourth transistors are configured so that amplified versions of the LNA input signal that they output are added to amplified versions of the LNA input signal that are output by the first and second main transistors, resulting in increased gain. Multiplexing circuits are provided within the LNA so that the LNA is configurable into a selectable one of the two modes by controlling a digital mode control signal supplied to the LNA.

Claims22

Dependent claims

A low noise amplifier (LNA) having a first differential input node and a second differential input node, the LNA comprising:

a first transistor biased in the saturation region, wherein a gate of the first transistor is coupled to the first differential input node, wherein the first transistor generates a first distortion signal onto a drain of the first transistor;
a second transistor biased in the saturation region, wherein a gate of the second transistor is coupled to the second differential input node, wherein the second transistor generates a second distortion signal onto a drain of the second transistor;
a third transistor having a gate that is switchably selectively couplable to either a drain of the first transistor or to a drain of the second transistor;
and
a fourth transistor having a gate that is switchably selectively couplable to either the drain of the second transistor or to the drain of the first transistor.

2 more elements

A differential low noise amplifier (LNA) that receives a desired signal, the LNA comprising:

a first transistor biased in the saturation region, wherein the first transistor generates a first amplified version of the desired signal and a first distortion signal;
a second transistor biased in the saturation region, wherein the second transistor generates a second amplified version of the desired signal and a second distortion signal;
a third transistor;
a fourth transistor;
and
means for configuring the first, second third and fourth transistors together such that the LNA operates in a selectable one of two modes, wherein in a first of the two modes post-distortion cancellation is utilized to cancel at least some of the first and second distortion signals, and wherein in a second of the two modes the third transistor generates a third amplified version of the desired signal that is in-phase with the first amplified version of the desired signal and is summed with the first amplified version of the desired signal, and wherein in the second of the two modes the fourth transistor generates a fourth amplified version of the desired signal that is in-phase with the second amplified version of the desired signal and is summed with the second amplified version of the desired signal.

3 more elements

A method comprising:

(a) receiving a control signal;
(b) if the control signal received in (a) has a first digital logic value then coupling a first transistor, a second transistor, a third transistor and a fourth transistor of a low-noise amplifier (LNA) together such that the LNA operates as a post-distortion cancellation LNA, wherein when the LNA operates as the post-distortion cancellation LNA the third transistor generates distortion that cancels distortion generated by the first transistor, and wherein when the LNA operates as the post-distortion cancellation LNA the fourth transistor generates distortion that cancels distortion generated by the second transistor;
and
(c) if the control signal received in (a) has a second digital logic value then coupling the first, second, third and fourth transistors together such that the third transistor contributes to the gain of the LNA and such that the fourth transistor contributes to the gain of the LNA.

1 more element

A method comprising:

providing a low-noise amplifier (LNA) that is configurable to operate in a switchably selectable one of two modes, wherein in the first mode the LNA employs a post-distortion cancellation technique to cancel distortion generated in the LNA, wherein the LNA has exhibits a signal first gain when the LNA is operating in the first mode, wherein in the second mode the LNA has a second gain that is higher than the first gain, and wherein in the second mode the LNA is less linear that it is when the LNA is operating in the first mode.

Dependencies are inferred from the claim text.

LNA having a post-distortion mode and a high-gain mode

Life of this patent

LNA having a post-distortion mode and a high-gain mode

Life of this patent

Abstract

Claims22