Protection circuit for RF power amplifiers
AssigneeMotorola, Inc.
InventorBarry Jason
Life of this patent
Estimating the term…
Abstract
An improved power controller and protection circuit to regulate the RF output power of a radio transmitter and to protect its RF amplifier from overload damage. The controller features a floating input, voltage controlled current source with high common-mode rejection to provide feedback of the DC input current drawn by the RF power amplifier. The controller can use an arbitrary reference voltage, which allows its application universally with power amplifiers designed for different rated output powers and frequency ranges.
Claims6
In a feedback system for regulating the output power of a radio frequency (RF) power amplifier and for protecting the RF power amplifier from damage during operation, the feedback system comprising a control amplifier that minimizes the difference between a reference voltage and a feedback voltage related to a selected operating parameter of the RF power amplifier by controlling the gain of the RF power amplifier, an improved method of limiting a DC input current of the RF power amplifier comprising the steps of:
- developing a source current proportional to the DC input current of the power amplifier;
- developing a sink current proportional to a predetermined current limit;
- developing a feedback voltage related to the difference between the source and sink currents;
- and
- controlling the gain of the RF power amplifier to cause the feedback voltage to be substantially equal to or less than the reference voltage, whereby the DC input current of the RF power amplifier will be substantially equal to or less than the current limit.
In a feedback system for regulating the output power of a radio frequency (RF) power amplifier and for protecting the RF power amplifier from damage during operation, the feedback system comprising a control amplifier that minimizes the difference between a reference voltage and a feedback voltage related to a selected operating parameter of the RF power amplifier by controlling the gain of the RF power amplifier, an improved apparatus for limiting a DC input current of the RF power amplifier comprising:
- means for developing a source current proportional to the DC input current of the power amplifier;
- means for developing a sink current proportional to a predetermined current limit;
- means for developing a feedback voltage related to the difference between the source and sink currents;
- and
- means for controlling the gain of the RF power amplifier to cause the feedback voltage to be substantially equal to or less than the reference voltage, whereby the DC input current of the RF power amplifier will be substantially equal to or less than the current limit.
Dependencies are inferred from the claim text.