1. Field of the Invention
The invention relates to a power circuit for a power amplifier, and more particularly to a power circuit for a power amplifier applied in a communication system.
2. Description of the Related Art
In current communication systems, before a transmission signal is broadcasted through an antenna, the power of the transmission signal has to be amplified by a power amplifier. Among elements of a communication system, a power amplifier consumes a great amount of current from a system power supply when the power amplifier is active. Thus, in such cases, remaining current may not be sufficient for other elements to operate. In efforts to provide sufficient power for all elements to operate when a power amplifier is activated, a communication system requires a system power supply that provides a large amount of total current.
However, for some applications, the total amount of current provided by a system power supply is limited. For example a USB dongle device is limited to a specific power specification of 500 mA (2.5 W). Thus, it is desired to provide a low current power circuit to drive a power amplifier in a low powered device.