Power amplifier having transformer
A power amplifier amplifying and compositing differential signals and capable of suppressing harmonics is provided. The power amplifier includes first amplifiers amplifying a first input signal and a second input signal, which are differential signals, a first coil receiving the first input signal and the second input signal amplified by the first amplifiers, a second coil magnetically coupled with the first coil and outputting a composite signal of the amplified first input signal and second input signal, a third coil magnetically coupled with the second coil, and a first capacitor coupled between both ends of the third coil, wherein one end of the first capacitor is coupled to a ground node.
1. A power amplifier comprising:
a first amplifier amplifying a first input signal and a second input signal, which are differential signals;
a first coil receiving the first input signal and the second input signal amplified by the first amplifier;
a second coil magnetically coupled with the first coil and outputting a composite signal of the amplified first input signal and second input signal;
a third coil magnetically coupled with the second coil;
a first capacitor coupled between both ends of the third coil; and
a semiconductor substrate;
wherein one end of the first capacitor is coupled to a ground node;
wherein the first coil and the second coil are provided over the main surface of the semiconductor substrate;
wherein over the main surface of the semiconductor substrate, there is formed a region with its entire circumference surrounded by the first coil and the second coil; and
wherein the third coil is provided in the region.
2. A power amplifier comprising:
a first amplifier amplifying a first input signal and a second input signal, which are differential signals;
a first coil receiving the first input signal and the second input signal amplified by the first amplifier;
a second coil magnetically coupled with the first coil and outputting a composite signal of the amplified first input signal and second input signal;
a third coil magnetically coupled with the second coil; and
a first capacitor coupled between both ends of the third coil,
wherein one end of the first capacitor is coupled to a ground node; and
wherein the first capacitor includes:
a first transistor having a first conductive electrode coupled to a first end of the third coil, a second conductive electrode, and a control electrode; and
a second transistor having a first conductive electrode coupled to a second end of the third coil, a second conductive electrode coupled to the second conductive electrode of the first transistor, and a control electrode coupled to the control electrode of the first transistor.
3. A power amplifier comprising:
a first amplifier amplifying a first input signal and a second input signal, which are differential signals;
a first coil receiving the first input signal and the second input signal amplified by the first amplifier;
a second coil magnetically coupled with the first coil and outputting a composite signal of the amplified first input signal and second input signal;
a third coil magnetically coupled with the second coil;
a first capacitor coupled between both ends of the third coil,
a fourth coil magnetically coupled with the first coil; and
a second capacitor coupled between both ends of the fourth coil;
wherein one end of the first capacitor is coupled to a ground node; and
wherein one end of the second capacitor is coupled to a ground node.
4. The power amplifier according to claim 3 , further comprising a semiconductor substrate,
wherein the first coil and the second coil are provided over the main surface of the semiconductor substrate;
wherein over the main surface of the semiconductor substrate, there is formed a region with its entire circumference surrounded by the first coil and the second coil;
wherein the third coil is provided in the region; and
wherein the fourth coil is provided over the main surface of the semiconductor substrate so as to surround the first coil and the second coil.
5. A power amplifier comprising:
a first amplifier amplifying a first input signal and a second input signal, which are differential signals;
a first coil receiving the first input signal and the second input signal amplified by the first amplifier;
a second coil magnetically coupled with the first coil and outputting a composite signal of the amplified first input signal and second input signal;
a third coil magnetically coupled with the second coil;
a first capacitor coupled between both ends of the third coil;
a second amplifier amplifying the first input signal and the second input signal;
a fifth coil receiving the first input signal and the second input signal amplified by the second amplifier;
a sixth coil magnetically coupled with the fifth coil and coupled with one end of the second coil;
a seventh coil magnetically coupled with the sixth coil and coupled with one end of the third coil; and
a third capacitor coupled between both ends of the seventh coil;
wherein one end of the first capacitor is coupled to a ground node; and
wherein a composite signal of the first input signal and the second input signal amplified by the first and second is output from the sixth coil.