Amplifier with active bias compensation and method for adjusting quiescent current

An amplifier with active bias compensation, comprising:

• a first amplification element having a bias terminal, and a current supply terminal coupled to a first voltage supply conductor via a sensing resistor;
• an active bias compensation circuit having a first input and a second input coupled across the sensing resistor for sensing a quiescent current in the first amplification element, and an output coupled to the bias terminal of the first amplification element, wherein the active bias compensation circuit includes:
• a first transistor having a control electrode coupled to the first input of the active bias compensation circuit, a first current conducting electrode, and a second current conducting electrode coupled to the output of the active bias compensation circuit;
• a second transistor having a control electrode coupled for receiving a reference voltage, a first current conducting electrode coupled to the first current conducting electrode of the first transistor, and a second current conducting electrode;
• a first resistor having a first electrode coupled to a first voltage supply conductor and a second electrode coupled to the first current conducting electrode of the first transistor;
• and
• a second resistor having a first electrode coupled to the second current conducting electrode of the first transistor and a second electrode coupled to the second input of the active bias compensation circuit;
• and
• a third resistor having a first electrode coupled to the second current conducting electrode of the second transistor and a second electrode coupled to the second input of the active bias compensation circuit;
• and
• a second amplification element having a quiescent current tracking the quiescent current in the first amplification element.

A radio frequency (RF) power amplifier, comprising:

• a sensing resistor having a first electrode coupled to a first operating potential, and a second electrode;
• a difference amplifier having a first input coupled to the first electrode of the sensing resistor, a second input coupled to the second electrode of the sensing resistor, and an output;
• a first amplification element having a bias terminal coupled to the output of the difference amplifier via at least one passive circuit element and no active elements and a current supply terminal coupled to the second electrode of the sensing resistor;
• and
• a second amplification element having a current supply terminal coupled to the first operating potential.

A radio frequency (RF) power amplifier, comprising:

• a sensing resistor having a first electrode coupled to a first operating potential, and a second electrode;
• a difference amplifier having a first input coupled to the first electrode of the sensing resistor, a second input coupled to the second electrode of the sensing resistor, and an output;
• a first amplification element having a bias terminal coupled to the output of the difference amplifier, a current supply terminal coupled to the second electrode of the sensing resistor, an RF signal input coupled for receiving an RF signal of the RF power amplifier, and an RF signal output;
• and
• a second amplification element having a current supply terminal coupled to the first operating potential, a bias terminal coupled to the output of the difference amplifier, an RF signal input coupled to the RF signal output of the first amplification element and an RF signal output.

A radio frequency (RF) power amplifier, comprising:

• a sensing resistor having a first electrode coupled to a first operating potential, and a second electrode;
• a difference amplifier having a first input coupled to the first electrode of the sensing resistor, a second input coupled to the second electrode of the sensing resistor, and an output;
• a first amplification element having a bias terminal coupled to the output of the difference amplifier and a current supply terminal coupled to the second electrode of the sensing resistor, wherein the first amplification element is a quiescent current bias reference element;
• and
• a second amplification element having a current supply terminal coupled to the first operating potential, a bias terminal coupled to the output of the difference amplifier, and an RF signal input coupled for receiving an RF signal input to the RF power amplifier and an RF signal output.

A radio frequency (RF) power amplifier, comprising:

• a sensing resistor having a first electrode coupled to a first operating potential, and a second electrode;
• a difference amplifier having a first input coupled to the first electrode of the sensing resistor, a second input coupled to the second electrode of the sensing resistor, and an output;
• a first amplification element having a bias terminal coupled to the output of the difference amplifier and a current supply terminal coupled to the second electrode of the sensing resistor, wherein the first amplification element includes:
• a first transistor having a control electrode coupled for receiving a first RF input signal, a first current conducting electrode, and a second current conducting electrode;
• a first alternating current signal blocking element having a first electrode coupled to the bias terminal of the first amplification element and a second electrode coupled to the control electrode of the first transistor;
• and
• a first resistor having a first electrode coupled to the first current conducting electrode of the first transistor and a second electrode coupled to the current supply terminal of the first amplification element;
• and
• a second amplification element having a current supply terminal coupled to the first operating potential.

A radio frequency (RF) power amplifier, comprising:

• a sensing resistor having a first electrode coupled to a first operating potential, and a second electrode;
• a difference amplifier having a first input coupled to the first electrode of the sensing resistor, a second input coupled to the second electrode of the sensing resistor, and an output, wherein the difference amplifier includes:
• a first resistor having a first electrode coupled to the first input of the difference amplifier, and a second electrode;
• a first transistor having a control electrode coupled to the second input of the difference amplifier, a first current conducting electrode coupled to the second electrode of the first resistor, and a second current conducting electrode;
• a second transistor having a control electrode coupled for receiving a reference voltage, a first current conducting electrode coupled to the second electrode of the first resistor, and a second current conducting electrode coupled to the output of the difference amplifier;
• and
• a second resistor having a first electrode coupled to the second current conducting electrode of the first transistor and a second electrode coupled to a second operating potential;
• a first amplification element having a bias terminal coupled to the output of the difference amplifier and a current supply terminal coupled to the second electrode of the sensing resistor;
• and
• a second amplification element having a current supply terminal coupled to the first operating potential.

A radio frequency (RF) power amplifier, comprising:

• a sensing resistor having a first electrode coupled to a first operating potential, and a second electrode;
• a difference amplifier having a first input coupled to the first electrode of the sensing resistor, a second input coupled to the second electrode of the sensing resistor, and an output, wherein the difference amplifier includes:
• a first transistor having a control electrode coupled to the second input of the difference amplifier, a first current conducting electrode, and a second current conducting electrode coupled to the output of the difference amplifier;
• a second transistor having a control electrode coupled for receiving a reference voltage, a first current conducting electrode coupled to the first current conducting electrode of the first transistor, and a second current conducting electrode;
• a first resistor having a first electrode coupled to the second current conducting electrode of the first transistor and a second electrode coupled to a second operating potential;
• a second resistor having a first electrode coupled to the second current conducting electrode of the second transistor and a second electrode coupled to the second electrode of the first resistor;
• and
• a third resistor having a first electrode coupled to the first input of the difference amplifier and a second electrode coupled to the first current conducting electrode of the first transistor;
• a first amplification element having a bias terminal coupled to the output of the difference amplifier and a current supply terminal coupled to the second electrode of the sensing resistor;
• and
• a second amplification element having a current supply terminal coupled to the first operating potential.

A method for adjusting a quiescent current, comprising:

• serially coupling a sensing resistor with a conduction path of a first amplification element;
• establishing the quiescent current flowing through the conduction path of the first amplification element;
• generating a sensing voltage across the sensing resistor;
• generating a bias signal applied to a bias terminal of the first amplification element in accordance with the sensing voltage to adjust the quiescent current by applying the sensing voltage to a control electrode of a first transistor;
• applying a reference voltage to a control electrode of a second transistor;
• and adjusting the quiescent current flowing in the first amplification element to match a current flowing in the first transistor and a current flowing in the second transistor;
• establishing a second quiescent current flowing through a conduction path of a second amplification element;
• and
• adjusting the second quiescent current flowing through the conduction path of the second amplification element in accordance with the quiescent current flowing through the conduction path of the first amplification element.