Method and apparatus for stabilizing RF power amplifiers
View Patent ↗A method and apparatus is provided for use in power amplifiers for reducing the peak voltage that transistors are subjected to. A power amplifier is provided with first and second switching devices and an inductor connected between the switching devices. The switching devices are driven such that the switching devices are turned on and off during the same time intervals. Differential RF power amplifiers are also provided with inductive networks coupled at various nodes of the power amplifiers. In some examples, techniques are used to stabilize differential power amplifiers by stabilizing common-mode feedback loops.
1. A differential RF power amplifier comprising:
a first differential amplifier having first and second switching devices coupled between a voltage differential;
a second differential amplifier having third and fourth switching devices coupled between a voltage differential, wherein the first and second differential amplifiers are configured to differentially drive a load, wherein an input of the first switching device is not shorted to an input of the third switching device, and wherein an input of the second switching device is not shorted to an input of the fourth switching device;
a first circuit element having a resistance coupled between the input of the first switching device and the input of the fourth switching device; and
a second circuit element having a resistance coupled between the input of the second switching device and the input of the third switching device.
2. The differential RF power amplifier of claim 1 , wherein the first and second circuit elements include first and second resistors, respectively.
3. The differential RF power amplifier of claim 1 , further comprising a first inductance coupled between the first and second switching devices, and a second inductance coupled between the third and fourth switching devices.
4. The differential RF power amplifier of claim 1 , wherein the differential RF power amplifier is configured such that the first and second switching devices are repeatedly turned on and off together, and the third and fourth switching devices are repeatedly turned on and off together.
5. The differential RF power amplifier of claim 4 , wherein the first, second, third, and fourth switching devices are driven by signals that repeatedly turn the switching devices on and off.
6. The differential RF power amplifier of claim 5 , wherein the signals driving the first and fourth switching devices are in phase with each other, and wherein the signals driving the second and third switching devices are in phase with each other.
7. The differential RF power amplifier of claim 1 , wherein the first and second differential amplifiers are implemented using a complementary metal oxide semiconductor (CMOS).
8. The differential RF power amplifier of claim 1 , wherein the differential RF power amplifier is suitable for use in a cellular telephone.
9. The differential RF power amplifier of claim 1 , further comprising a first pair of cross coupled switching devices coupled to inputs of the first and third switching devices.
10. The differential RF power amplifier of claim 9 , further comprising a second pair of cross coupled switching devices coupled to inputs of the second and fourth switching devices.
11. A method of stabilizing a differential RF power amplifier comprising:
coupling a first differential amplifier having first and second switching devices between a voltage differential;
coupling a second differential amplifier having third and fourth switching devices between a voltage differential, wherein an input of the first switching device is not shorted to an input of the third switching device, and wherein an input of the second switching device is not shorted to an input of the fourth switching device;
configuring the first and second differential amplifiers to differentially drive a load;
coupling a first circuit element between the input of the first switching device and the input of the fourth switching device to provide a desired resistance between the input of the first switching device and the input of the fourth switching device; and
coupling a second circuit element between the input of the second switching device and the input of the third switching device to provide a desired resistance between the input of the second switching device and the input of the third switching device.
12. The method of claim 11 , wherein the first and second circuit elements are resistors.
13. The method of claim 11 , further comprising coupling a first inductance between the first and second switching devices and a second inductance between the third and fourth switching devices.
14. The method of claim 11 , wherein the differential RF power amplifier is configured such that the first and second switching devices are repeatedly turned on and off together, and the third and fourth switching devices are repeatedly turned on and off together.
15. The method of claim 14 , wherein the first, second, third, and fourth switching devices are driven by signals that repeatedly turn the switching devices on and off.
16. The method of claim 15 , wherein the signals driving the first and fourth switching devices are in phase with each other, and wherein the signals driving the second and third switching devices are in phase with each other.
17. The method of claim 11 , wherein the first and second differential amplifiers are implemented using a complementary metal oxide semiconductor (CMOS).
18. A differential RF power amplifier comprising:
a first differential amplifier having first and second switching devices coupled between a voltage differential;
a second differential amplifier having third and fourth switching devices coupled between a voltage differential, wherein an input of the first switching device is not shorted to an input of the third switching device, and wherein an input of the second switching device is not shorted to an input of the fourth switching device;
a first resistor coupled between the first switching device and the fourth switching device; and
a second resistor coupled between the second switching device and the third switching device.
19. The differential RF power amplifier of claim 18 , wherein the first resistor is coupled between an input of the first switching device and an input of the fourth switching device, and the second resistor is coupled between an input of the second switching device and an input of the third switching device.
20. The differential RF power amplifier of claim 18 , wherein outputs of the first and second differential amplifiers are coupled together to differentially drive a load.