Gain boosting in power amplifiers using RF-coupled feedback
A power amplifier comprises a first amplification stage having an input terminal receiving a radio frequency (RF) signal to be amplified and having a first coupling unit, a second amplification stage outputting an amplified radio frequency signal and having a second coupling unit and a third coupling unit providing RF feedback to the input terminal of the first amplification stage through an RF feedback path, the second coupling unit being coupled to the first coupling unit, and the third coupling unit being coupled to the first coupling unit.
1 . A power amplifier comprising:
a first amplification stage having an input terminal receiving a radio frequency signal to be amplified and having a first coupling unit on a die with a first width;
a second amplification stage outputting an amplified radio frequency signal and having a second coupling unit on the die that is inductively coupled with the first coupling unit; and
a third coupling unit on the die inductively coupled with the first coupling unit, the third coupling unit provides radio frequency-coupled feedback to the input terminal of the first amplification stage through a radio frequency-coupled feedback path, the third coupling unit is shielded from the second coupling unit by routing the third coupling unit completely under the first coupling unit with the third coupling unit having a second width that is narrower than the first width.
2 . The power amplifier of claim 1 wherein the first, second and third coupling units respectively include at least one coil.
3 . The power amplifier of claim 1 wherein the first amplification stage includes a bipolar transistor having a base, a collector, and an emitter.
4 . The power amplifier of claim 1 wherein the second amplification stage includes two amplifier portions in push-pull arrangement.
5 . The power amplifier of claim 4 wherein the second amplification stage operates on differential signals.
6 . The power amplifier of claim 5 wherein the first amplification stage operates on single-ended signals.
7 . The power amplifier of claim 6 wherein the first and second coupling units form an inter-stage balun between the first and second amplification stages to convert a single-ended first amplification stage signal into a differential signal to drive the second amplification stage.
8 . The power amplifier of claim 3 further comprising a first stage power supply terminal and a ground terminal, the first coupling unit being connected between the first stage power supply terminal and the collector of the bipolar transistor.
9 . The power amplifier of claim 8 wherein the third coupling unit is connected between the ground terminal and the base of the bipolar transistor.
10 . The power amplifier of claim 9 further comprising a first capacitor and a second capacitor, the first capacitor being provided between the collector and the base of the bipolar transistor and the second capacitor being provided in the radio frequency-coupled feedback path between the third coupling unit and the base of the bipolar transistor.
11 . The power amplifier according to claim 7 further comprising a die, the inter-stage balun being an on-die balun for converting the single-ended first amplification stage signal into the differential signal.
12 . A method for boosting gain in a power amplifier, the method comprising:
amplifying a radio frequency signal by a first amplification stage on a die having an input terminal for receiving the radio frequency signal and having a first coupling unit with a first width;
inductively coupling on the die the first coupling unit with a second coupling unit of a second amplification stage;
amplifying the amplified radio frequency signal with a second amplification stage coupled to the second coupling unit and outputting the amplified radio frequency signal from the second amplification stage;
inductively coupling on the die a third coupling unit to the first coupling unit, the third coupling unit is shielded from the second coupling unit by routing the third coupling unit completely under the first coupling unit with the third coupling unit having a second width that is narrower than the first width; and
providing radio frequency feedback to the input terminal of the first amplification stage through a radio frequency feedback path from the third coupling unit to the first coupling unit.
13 . The method of claim 12 further comprising operating the second amplification stage on differential signals.
14 . The method of claim 13 further comprising operating the first amplification stage on single-ended signals.
15 . The method of claim 12 further comprising converting a single-ended first amplification stage signal into a differential signal to drive the second amplification stage.
16 . The method of claim 12 further comprising connecting the first coupling unit between a ground terminal and a collector of a bipolar transistor.
17 . The method of claim 12 further comprising connecting the third coupling unit between a ground terminal and a base of a bipolar transistor in the first amplification stage.
18 . The method of claim 17 further comprising providing a first capacitor between a collector and the base of the bipolar transistor and a second capacitor in the radio frequency feedback path between the third coupling unit and the base of the bipolar transistor.
19 . A mobile device comprising:
a transceiver configured to generate a radio frequency signal;
a first amplification stage on a die having an input terminal receiving a radio frequency signal to be amplified and having a first coupling unit with a first width;
a second amplification stage on the die outputting an amplified radio frequency signal and having a second coupling unit that is inductively coupled with the first coupling unit; and
a third coupling unit on the die inductively coupled with the first coupling unit, the third coupling unit provides radio frequency-coupled feedback to the input terminal of the first amplification stage through a radio frequency-coupled feedback path, the third coupling unit is shielded from the second coupling unit by routing the third coupling unit completely under the first coupling unit with the third coupling unit having a second width that is narrower than the first width.
20 . The mobile device of claim 19 wherein the first and second coupling units form an inter-stage balun between the first and second amplification stages to convert a single-ended first amplification stage signal into a differential signal to drive the second amplification stage.