Systems and methods of dynamic bias switching for radio frequency power amplifiers
View Patent ↗A dynamic bias switching circuit is provided that includes a switching unit for switching between a first signal level and a second signal level based on a signal envelope of an input signal to an amplifier.
1. A dynamic bias switching circuit adapted to provide a first power supply level and a second power supply level, comprising:
an input signal having a signal envelope;
a detector adapted to extract the envelope from a sample of the multicarrier input signal;
a comparator circuit having a first input responsive to an output of the detector and a second input responsive to a reference input signal, wherein the comparator circuit generates an output by comparing, the output of the detector with the reference input signal, the comparator circuit comprising an operational amplifier having a first output voltage based on a first input voltage level and a second output voltage based on a second input voltage level; and
means for switching between the first power supply level and the second power supply level based on the signal envelope.
2. A dynamic bias switching circuit according to claim 1 , wherein the means for switching switches to the second power supply level when the signal envelope exceeds a threshold.
3. A dynamic bias switching circuit according to claim 1 , wherein the means for switching between a first power supply level and a second power supply level based on the signal envelope, comprises:
a switch unit that generates an output comprising one of the first power supply level and the second power supply level.
4. A dynamic bias switching circuit according to claim 3 , wherein the switch unit comprises:
a buffer switch; and
a first transistor coupled to a buffer output,
wherein the buffer switch enables switching of the first transistor to allow for tracking of variations of the envelope signal.
5. A dynamic bias switching circuit according to claim 4 , wherein the buffer switch comprises:
a complementary pair of transistors, wherein a gate of each of the pair of transistors is connected to the an output of a comparator circuit.
6. A dynamic bias switching circuit according to claim 4 , wherein the first power supply level is a discrete signal level (V L ) generated by a diode circuit that places the first transistor in an ON state.
7. A dynamic bias switching circuit according to claim 4 , wherein the second power supply level is a discrete signal level (V H ) that places the first transistor in an OFF state.
8. A dynamic bias switching circuit according to claim 1 wherein the second power supply level is greater than the first power supply level.
9. A dynamic bias switching circuit according to claim 1 , wherein the first power supply level is sufficient to operate the power amplifier for a first percentage of time.
10. A dynamic bias switching circuit according to claim 9 , wherein the first power supply level is insufficient to operate the power amplifier for a second percentage of time that is statistically less than the first percentage of time.
11. A dynamic bias switching circuit according to claim 9 , wherein during the first percentage of time an output waveform of the dynamic bias switching circuit is free from clipping.
12. A dynamic bias switching circuit according to claim 4 , further comprising:
an second transistor,
wherein the first transistor controls current between the power supply and a drain of the second transistor.
13. A dynamic bias switching circuit according to claim 12 , wherein a bias voltage of the first transistor is less than a preset threshold, and
wherein a drain voltage of the first transistor is switched to the second signal level to place the first transistor in an ON state and allow the second signal level to be applied to a drain of the second transistor when the signal envelope exceeds the preset threshold.
14. A power amplifier, comprising:
an amplifier that receives a multicarrier input signal; and
a dynamic bias switch unit having an input coupled to the amplifier input signal and an output coupled to the amplifier power supply, wherein the dynamic bias switch unit is adapted to switch a power supply level applied to the amplifier between a first power supply level and a second power supply level, wherein the dynamic bias switch unit comprises:
means for coupling a multicarrier input signal having a signal envelope;
means for determining the signal envelope; and
a buffer switch and a first transistor that generates an output for controlling selection of one of the first cower supply level and the second power supply level, wherein the buffer switch enables switching of the first transistor to allow for tracking of variations of the envelope signal.
15. A dynamic bias switching circuit according to claim 14 , wherein the buffer switch and first transistor switches to the second power supply level when the signal envelope exceeds a preset threshold.
16. A dynamic bias switching circuit according to claim 14 , wherein the means for determining the signal envelope, comprises:
a detector adapted to extract the envelope from a sample of the multicarrier input signal; and
a comparator circuit having a first input responsive to an output of the detector and a second input responsive to a reference input signal, wherein the comparator circuit generates an output by comparing the output of the detector with the reference input signal.
17. A dynamic bias switching circuit according to claim 16 , wherein the comparator circuit comprises:
an operational amplifier having a first output voltage based on a first input voltage level and a second output voltage based on a second input voltage level.
18. A dynamic bias switching circuit according to claim 14 , wherein the buffer switch comprises:
a complementary pair of transistors, wherein a drain of each of the pair of transistors is connected to the gate of the first transistor.
19. A dynamic bias switching circuit adapted to provide a first power supply level and a second power supply level, comprising:
an input signal having a signal envelope;
means for determining the signal envelope; and
a buffer switch and a first transistor coupled to a buffer output that generates an output comprising one of the first power supply level and the second power supply level based on the signal envelope, wherein the buffer switch enables switching of the first transistor to allow for tracking of variations of the envelope signal.
20. A dynamic bias switching circuit according to claim 19 , wherein the buffer switch provides a control signal to the first transistor to switch to the second power supply level when the signal envelope exceeds a threshold.
21. A dynamic bias switching circuit according to claim 19 , wherein the means for determining the signal envelope, comprises:
a detector adapted to extract the envelope from a sample of the multicarrier input signal; and
a comparator circuit having a first input responsive to an output of the detector and a second input responsive to a reference input signal, wherein the comparator circuit generates an output by comparing the output of the detector with the reference input signal.
22. A dynamic bias switching circuit according to claim 21 , wherein the comparator circuit comprises:
an operational amplifier having a first output voltage based on a first input voltage level and a second output voltage based on a second input voltage level.
23. A dynamic bias switching circuit according to claim 19 , wherein the buffer switch comprises:
a complementary pair of transistors, wherein a gate of each of the pair of transistors is connected to the an output of a comparator circuit.
24. A dynamic bias switching circuit according to claim 19 wherein the first power supply level is a discrete signal level (VL) generated by a diode circuit that places the first transistor in an ON state.
25. A dynamic bias switching circuit according to claim 19 , wherein the second power supply level is a discrete signal level (VH) that places the first transistor in an OFF state.
26. A dynamic bias switching circuit according to claim 19 , wherein the second power supply level is greater than the first power supply level.
27. A dynamic bias switching circuit according to claim 19 , wherein the first power supply level is sufficient to operate the power amplifier for a first percentage of time.
28. A dynamic bias switching circuit according to claim 27 , wherein the first power supply level is insufficient to operate the power amplifier for a second percentage of time that is statistically less than the first percentage of time.
29. A dynamic bias switching circuit according to claim 27 , wherein during the first percentage of time an output waveform of the dynamic bias switching circuit is free from clipping.