Mobile wireless communications device including sensing transistor and hysteretic comparator and related methods
View Patent ↗A mobile wireless communications device may include a portable housing, and a supply modulator carried by the portable housing. The supply modulator may include an output node, a linear amplifier coupled to the output node, and a switching amplifier also coupled to the output node. The switching amplifier may include at least one sensing transistor configured to sense current output from the linear amplifier and generate a drive voltage, and a hysteretic comparator coupled to the at least one sensing transistor and configured to be driven by the drive voltage. The mobile wireless communications device may also include a radio frequency (RF) power amplifier coupled to the output node of the supply modulator, and a wireless transceiver carried by the portable housing and coupled to the RF power amplifier.
1. A mobile wireless communications device comprising:
a portable housing;
a supply modulator carried by said portable housing and comprising
an output node,
a linear amplifier coupled to said output node, and
a switching amplifier also coupled to said output node and comprising
at least one sensing transistor configured to sense current output from said linear amplifier and generate a drive voltage, and
a hysteretic comparator coupled to said at least one sensing transistor and configured to be driven by the drive voltage;
a radio frequency (RF) power amplifier coupled to said output node of said supply modulator; and
a wireless transceiver carried by said portable housing and coupled to said RF power amplifier.
2. The mobile wireless communications device of claim 1 , wherein said switching amplifier further comprises at least one current conveyor circuit coupled to said at least one sensing transistor and configured to control a bias of said at least one sensing transistor.
3. The mobile wireless communications device of claim 1 , wherein said linear amplifier comprises an operational transconductance amplifier and at least one transistor coupled thereto.
4. The mobile wireless communications device of claim 1 , wherein said switching amplifier further comprises a buffer coupled between said hysteretic comparator and said output node.
5. The mobile wireless communications device of claim 4 , wherein said buffer comprises a pair of transistors having respective control terminals coupled to each other.
6. The mobile wireless communications device of claim 4 , wherein said switching amplifier further comprises at least one inductor coupled between said output node and said buffer.
7. The mobile wireless communications device of claim 1 , wherein said wireless transceiver comprises a cellular transceiver.
8. A supply modulator to be carried by a portable housing of a mobile wireless communications device comprising a radio frequency (RF) power amplifier and a wireless transceiver carried by the portable housing and coupled to the RF power amplifier, the supply modulator comprising:
an output node coupled to be coupled to the RF power amplifier;
a linear amplifier coupled to said output node; and
a switching amplifier also coupled to said output node and comprising
at least one sensing transistor configured to sense current output from said linear amplifier and generate a drive voltage, and
a hysteretic comparator coupled to said at least one sensing transistor and configured to be driven by the drive voltage.
9. The supply modulator of claim 8 , wherein said switching amplifier further comprises at least one current conveyor circuit coupled to said at least one sensing transistor and configured to control a bias of said at least one sensing transistor.
10. The supply modulator of claim 8 , wherein said linear amplifier comprises an operational transconductance amplifier and at least one transistor coupled thereto.
11. The supply modulator of claim 8 , wherein said switching amplifier further comprises a buffer coupled between said hysteretic comparator and said output node.
12. The supply modulator of claim 11 , wherein said buffer comprises a pair of transistors having respective control terminals coupled to each other.
13. The supply modulator of claim 11 , wherein said switching amplifier further comprises at least one inductor coupled between said output node and said buffer.
14. A method of operating a supply modulator for a power amplifier of a mobile wireless communications device, the supply modulator comprising an output node, a linear amplifier coupled to the output node, and a switching amplifier coupled to the linear amplifier, method comprising:
using the switching amplifier to
sense current output from the linear amplifier via at least one sensing transistor,
generate a drive voltage via the at least one sensing transistor, and
drive a hysteretic comparator coupled to the at least one sensing transistor with the drive voltage.
15. The method of claim 14 , wherein the switching amplifier further comprises at least one current conveyor circuit coupled to the at least one sensing transistor; and wherein the switching amplifier is used to control a bias of the at least one sensing transistor.
16. The method of claim 14 , wherein the switching amplifier further comprises a buffer coupled between the hysteretic comparator and the output node.
17. The method of claim 16 , wherein the buffer comprises a pair of transistors having respective control terminals coupled to each other.
18. The method of claim 16 , wherein the switching amplifier further comprises at least one inductor coupled between the output node and the buffer.