Automatic power output control circuit
View Patent ↗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.
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;
an output voltage detection section which detects an output voltage of the power amplifier; and
a 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 and comprising 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, and a selection circuit which selects one of outputs of the plurality of transistors having the different sizes.