Circuit for power amplification

• US 20060066396A1
• Filed: 07/21/2003
• Published: 03/30/2006
• Est. Priority Date: 08/01/2002
• Status: Active Grant

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Brandt, Per-Olof
• Granted Patent: US 7,330,072 B2
• Time in Patent Office: Days
• US Class Current: 330/133
• CPC Class Codes: H03F 1/0261 with control of the polarisation voltage or current, e.g. gliding Class A
• CPC Class Codes: H03F 1/0272 by using a signal derived from the output signal
• CPC Class Codes: H03F 1/52 Circuit arrangements for protecting such amplifiers monitoring arrangements G01R31/28; increasing reliability in communication systems, e.g. using redundancy H04B1/74
• CPC Class Codes: H03F 2200/102 A non-specified detector of a signal envelope being used in an amplifying circuit
• CPC Class Codes: H03F 2200/451 the amplifier being a radio frequency amplifier
• CPC Class Codes: H03F 2200/99 A diode as rectifier being used as a detecting circuit in an amplifying circuit
• CPC Class Codes: H03F 3/19 with semiconductor devices only
• CPC Class Codes: H03G 3/3042 in modulators, frequency-changers, transmitters or power amplifiers transmission power control in bidirectional transmission systems H04W52/04

Abstract

A radio frequency (RF) power amplifier, including an external control loop and a protection circuit, which functions to maintain a constant output power during variations in impedance on the RF load. In the external control loop a collector current from an output transistor is detected and then regulated with respect to a reference current. The regulated signal is utilised to generate a bias control signal which is input to the base electrode of both a driver transistor and the output transistor. The protection circuit detects a voltage envelope at the collector electrode of the output transistor and utilises this signal to form a bias reduction signal which is input to the base electrode of the driver transistor.

Claims

1. A method of controlling output from a power amplifier which has a driver stage and an output stage, the method comprising:

detecting a first and a second electrical parameter at an output of the output stage;

processing the first parameter with a first reference signal to generate a bias control signal;

processing the second parameter with a second reference signal to generate a bias reduction signal;

feeding the bias control signal to an input of both the driver and the output stages;

feeding the bias reduction signal to an input of the driver stage.

2. The method of controlling output from a power amplifier as claimed in claim 1, wherein the first electrical parameter is an electrical current.

3. The method of controlling output from a power amplifier as claimed in claim 1, wherein the second electrical parameter is an output voltage envelope.

4. An electrical circuit comprising:

a power amplifier, an external control loop and a protection circuit;

wherein the protection circuit comprises;

detection means for detecting an electrical parameter at an output of the power amplifier;

bias reduction means for providing a bias signal at an input of the power amplifier;

a reference signal generator coupled to the bias reduction means.

5. The electrical circuit of claim 4, wherein the power amplifier has a driver stage and an output stage.

6. The electrical circuit of claim 5, wherein the detection means is coupled to the output of the output stage.

7. The electrical circuit of claim 6, wherein the bias reduction means is coupled to the input of the driver stage.

8. A mobile telecommunications device including the power amplification circuit as claimed in claims 4 to 7.