Low noise amplifier (LNA) gain switch circuitry
AssigneeBroadcom Corporation
InventorHooman Darabi
Life of this patent
Estimating the term…
Abstract
A circuit is formed to steer current in and out of an inductive load in a manner that enables an amplifier to provide a plurality of gain steps without modifying an LC time constant for the circuit and, therefore, without modifying the tuning or frequency of oscillation for the circuit. A first group of MOSFETs are coupled in parallel and define the circuit current flow. A second group of MOSFETs are coupled in parallel to each other and in series to an impedance device. A third group of MOSFETs coupled to steer current in and out of the impedance device to affect the output signal coupled to one end of the impedance device. The transistors in the second and third groups of MOSFETs are selectively activated to control the amount of current that goes through the impedance device.
Claims25
A method for adjusting a gain output in an amplifier, comprising:
- conducting current through an output inductive load device and through a number of branches of a first circuit portion operatively coupled downstream of the inductive output load device;
- selectively conducting current either through a second number of branches of a second circuit portion to increase an output gain by increasing current through the output inductive load device based upon a first logic state of a control signal or to decrease the output gain by decreasing current through the output inductive load device by increasing current conducted through the second number of branches of a third circuit portion based upon a second logic state of the control signal;
- and
- wherein a number of branches of the first circuit portion is always equal to a number of branches in the second and third branches that are conducting current and further wherein a frequency response defined at least in part by the output inductive load device and parasitic capacitance of MOSFET devices used to adjust the output gain remains substantially constant.
A low noise amplifier having selectable gain levels formed within an integrated circuit, comprising:
- 2*n1 total selectable branches in a first and second portion of an integrated circuit;
- 2*n2 total selectable branches in the first and second portions of the integrated circuit;
- a load device coupled in series with the first portion of the circuit wherein the load device and the first portion of the integrated circuit collectively are coupled in parallel with the second portion of the integrated circuit;
- and
- logic circuitry for selecting which of the 2*n1 and 2*n2 selectable branches are to conduct current and correspondingly, the amount of current flow through the load device wherein the output level of the amplifier formed within the integrated circuit corresponds to the amount of current in the load device.
A method for varying an amplifier output gain level, comprising:
- generating a first logic signal having a first logic state and producing the first logic signal to a first group of selectable MOSFETs;
- generating a second logic signal having either the first logic state or a second logic state and producing the second logic signal to a second group of selectable MOSFETs;
- generating a third logic signal having a logic state that is opposite of the first logic signal and producing the third logic signal to a third group of MOSFETs;
- generating a fourth logic signal having a logic state that is opposite of the second logic signal and producing the fourth logic signal to a fourth group of MOSFETs;
- conducting an amount of current through an inductive load wherein:
- a maximum amount of current is conducted if the first and second groups of MOSFETs receive the first and second logic signals being set to the first logic state at their gate terminals, respectively;
- and
- a minimum amount of current is conducted if the first and second groups of MOSFETs receive the first and second logic signals being set to the second logic state at their gate terminals, respectively.
A method for adjusting a gain output in an amplifier, comprising:
- conducting current through an output inductive load device to generate an output signal wherein an output frequency response is defined at least in part by the inductive load device and parasitic capacitance of active devices operatively coupled to the output inductive load device which active devices are operable to adjust a gain of the output signal;
- in a first mode, conducting a portion of the current away from the output inductive load device based upon a first control signal logic state;
- in a second mode, conducting the portion of the current through the output inductive load device based upon a second control signal logic state wherein the second control signal logic state is opposite of the first control signal logic state;
- operatively biasing a gain step MOSFET transistor coupled in series with the output inductive load device into an operational state to conduct the portion of the current through the output load device;
- and
- operatively turning off a current steering MOSFET transistor coupled across the output inductive load device to cause the current steering MOSFET to substantially stop conducting the portion of the current away from the output inductive load device.
Dependencies are inferred from the claim text.