AUTOMATIC POWER OUTPUT CONTROL CIRCUIT

Abstract

This invention includes a gain control section 13 capable of changing an APC loop gain according to a power output level set in a power amplifier to allow suppression of variation in power output level when the power output level is low and suppression of occurrence of ringing when the power output level is high by making the loop gain high when the power output level is low and making the loop gain low when the power output level is high.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing an example of the configuration of a power amplifier according to an embodiment;

FIG. 2 is a diagram showing an example of the configuration of a pre-driver according to this embodiment;

FIG. 3 is a diagram showing an example of the configuration of a power setting circuit according to this embodiment;

FIG. 4 is a diagram showing an example of the configuration of an APC circuit according to this embodiment;

FIG. 5A is a graph showing the control characteristic when a set power output level is low, and there is no variation between devices;

FIG. 5B is a graph showing the control characteristic of this embodiment when a set power output level is low, and there is variation between devices;

FIG. 5C is a graph showing the control characteristic of a conventional case when a set power output level is low, and there is variation between devices;

FIG. 5D is a graph showing the control characteristic of this embodiment when the set power output level is high, and there is variation between devices; and

FIG. 5E is a graph showing the control characteristic of the conventional case when the set power output level is high, and there is variation between devices.

Claims

1. An automatic power output control circuit applied to a power amplifier capable of changing a setting of a power output level by changing an idling current of a driver, comprising: a gain control section which changes a loop gain for automatic power output control according to the power output level set in the power amplifier.

2. The automatic power output control circuit according to claim 1, further comprising: an output voltage detection section which detects an output voltage of the power amplifier; anda comparator which compares the output voltage detected by the output voltage detection section with a reference voltage and performs differential amplification operation on the basis of a difference between the output voltage and the reference voltage,wherein the gain control section comprises a circuit capable of changing a gain of the comparator according to the power output level set in the power amplifier.

3. The automatic power output control circuit according to claim 2, wherein the circuit capable of changing the gain of the comparator comprises: a current mirror circuit which is connected to an output of a differential amplifier circuit of the comparator and in which each of a plurality of transistors having different sizes is current-mirror connected to a transistor; anda selection circuit which selects one of outputs from the plurality of transistors having the different sizes.