ENVELOPE TRACKING INTEGRATED CIRCUIT OPERABLE WITH MULTIPLE TYPES OF POWER AMPLIFIERS

Abstract

An envelope tracking (ET) integrated circuit (ETIC) operable with multiple types of power amplifiers is provided. The ETIC is configured to provide one or more ET voltages to a power amplifier(s) for amplifying a radio frequency (RF) signal. In embodiments disclosed herein, the ETIC can be configured to generate the ET voltages at same or different voltage levels based on specific types of the power amplifier(s), such as multi-stage power amplifier and Doherty power amplifier, and for a wider modulation bandwidth of the RF signal. As such, the ETIC can be flexibly adapted to enable a variety of power management scenarios and/or topologies.

Claims

1. An envelope tracking (ET) integrated circuit (ETIC) comprising: a first voltage output and a second voltage output each coupled to a power amplifier configured to amplify a radio frequency (RF) signal to an output power; a first voltage circuit configured to generate a first ET voltage at the first voltage output; a second voltage circuit configured to generate a second ET voltage at the second voltage output; and a control circuit configured to: determine whether the power amplifier is one of a selected set of power amplifiers; and cause the second voltage circuit to generate the second ET voltage lower than or equal to the first ET voltage in response to determining that the power amplifier is one of the selected set of power amplifiers.

2. The ETIC of claim 1 wherein: the first voltage circuit is further configured to generate the first ET voltage based on a first ET target voltage; the second voltage circuit is further configured to generate the second ET voltage based on a second ET target voltage; and the control circuit is further configured to generate the first ET target voltage and the second ET target voltage to thereby cause the second voltage circuit to generate the second ET voltage lower than or equal to the first ET voltage.

3. The ETIC of claim 2 wherein the control circuit is further configured to: receive a time-variant ET target voltage that tracks a time-variant power envelope of the RF signal; and generate the first ET target voltage and the second ET target voltage based on the time-variant ET target voltage.

4. The ETIC of claim 3 wherein the control circuit is further configured to: generate the first ET target voltage based on a first analog lookup table (LUT) that correlates the time-variant ET target voltage with the first ET target voltage; and generate the first ET target voltage based on a second analog LUT that correlates the time-variant ET target voltage with the second ET target voltage.

5. The ETIC of claim 2 further comprising: a tracker circuit configured to provide a low-frequency current to the first voltage output; and a hybrid circuit coupled between the first voltage output and the second voltage output and configured to: operate as a closed switch to pass the low-frequency current from the first voltage output to the second voltage output; operate as an open switch to block the low-frequency current from the second voltage output; and operate as a low dropout (LDO) regulator to regulate the low-frequency current at the second voltage output.

6. The ETIC of claim 5 wherein the selected set of power amplifiers comprises a multi-stage power amplifier comprising a driver stage amplifier coupled to the second voltage output and an output stage amplifier coupled to the first voltage output.

7. The ETIC of claim 6 wherein the RF signal is modulated at a wide modulation bandwidth.

8. The ETIC of claim 6 wherein the control circuit is further configured to cause the hybrid circuit to operate as the LDO regulator.

9. The ETIC of claim 8 wherein the control circuit is further configured to cause the second voltage circuit to generate the second ET voltage lower than the first ET voltage to thereby drive the low-frequency current from the first voltage output toward the second voltage output.

10. The ETIC of claim 6 wherein the control circuit is further configured to: determine a temporal delay between the driver stage amplifier and the output stage amplifier; and generate the first ET target voltage with the determined temporal delay relative to the second ET target voltage to thereby cause the first ET voltage to be delayed from the second ET voltage by the determined temporal delay.

11. The ETIC of claim 5 wherein the selected set of power amplifiers comprises a Doherty power amplifier comprising a carrier amplifier coupled to the first voltage output and a peaking amplifier coupled to the second voltage output.

12. The ETIC of claim 11 wherein the control circuit is further configured to activate the first voltage circuit and deactivate the second voltage circuit in response to determining that the output power is lower than an average power of the RF signal.

13. The ETIC of claim 12 wherein the control circuit is further configured to cause the hybrid circuit to operate as the open switch.

14. The ETIC of claim 11 wherein the control circuit is further configured to activate the first voltage circuit and the second voltage circuit to generate the first ET voltage and the second ET voltage, respectively, in response to determining that the output power is higher than or equal to an average power of the RF signal.

15. The ETIC of claim 14 wherein, in response to determining that the output power is lower than or equal to a peak power of the RF signal, the control circuit is further configured to: cause the first voltage circuit to generate the first ET voltage at a peak ET voltage level; and cause the second voltage circuit to generate the second ET voltage lower than the peak ET voltage level.

16. The ETIC of claim 15 wherein the control circuit is further configured to cause the hybrid circuit to operate at the LDO regulator.

17. The ETIC of claim 16 wherein the control circuit is further configured to control the hybrid circuit to regulate the low-frequency current based on a sense current generated by the second voltage circuit.

18. The ETIC of claim 15 wherein, in response to determining that the output power is higher than a peak power of the RF signal, the control circuit is further configured to: cause the first voltage circuit to increase the first ET voltage above the peak ET voltage level; and cause the second voltage circuit to increase the second ET voltage above the peak ET voltage level.

19. The ETIC of claim 18 wherein the control circuit is further configured to cause the hybrid circuit to operate as the closed switch.

20. The ETIC of claim 14 wherein the control circuit is further configured to: determine a temporal delay between the carrier amplifier and the peaking amplifier; and generate the second ET target voltage with the determined temporal delay to thereby cause the second ET voltage to be delayed from the first ET voltage by the determined temporal delay.

Description

BRIEF DESCRIPTION OF THE DRAWING FIGURES

[0008] The accompanying drawing figures incorporated in and forming a part of this specification illustrate several aspects of the disclosure, and together with the description serve to explain the principles of the disclosure.

[0009] FIG. 1 is a schematic diagram of an exemplary envelope tracking (ET) integrated circuit (ETIC) configured according to various embodiments of the present disclosure to support different types of power amplifiers;

[0010] FIG. 2 is a schematic diagram of an exemplary multi-stage power amplifier, which can be provided in the ETIC of FIG. 1 as one of the different types of power amplifiers;

[0011] FIG. 3 is a schematic diagram providing an exemplary illustration of the ETIC of FIG. 1 adapted to support the multi-stage power amplifier of FIG. 2;

[0012] FIG. 4A is a schematic diagram of an exemplary Doherty power amplifier, which can be provided in the ETIC of FIG. 1 as one of the different types of power amplifiers;

[0013] FIG. 4B is a graphic diagram providing an exemplary illustration of operating principles of the Doherty power amplifier in FIG. 4A;

[0014] FIG. 5 is a schematic diagram providing an exemplary illustration of the ETIC of FIG. 1 adapted to support the Doherty power amplifier of FIG. 4A; and

[0015] FIGS. 6A and 6B are graphic diagrams illustrating operating principles of the ETIC in FIG. 5.

DETAILED DESCRIPTION

[0016] The embodiments set forth below represent the necessary information to enable those skilled in the art to practice the embodiments and illustrate the best mode of practicing the embodiments. Upon reading the following description in light of the accompanying drawing figures, those skilled in the art will understand the concepts of the disclosure and will recognize applications of these concepts not particularly addressed herein. It should be understood that these concepts and applications fall within the scope of the disclosure and the accompanying claims.

[0017] It will be understood that, although the terms first, second, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element could be termed a second element, and, similarly, a second element could be termed a first element, without departing from the scope of the present disclosure. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items.

[0018] It will be understood that when an element such as a layer, region, or substrate is referred to as being “on” or extending “onto” another element, it can be directly on or extend directly onto the other element or intervening elements may also be present. In contrast, when an element is referred to as being “directly on” or extending “directly onto” another element, there are no intervening elements present. Likewise, it will be understood that when an element such as a layer, region, or substrate is referred to as being “over” or extending “over” another element, it can be directly over or extend directly over the other element or intervening elements may also be present. In contrast, when an element is referred to as being “directly over” or extending “directly over” another element, there are no intervening elements present. It will also be understood that when an element is referred to as being “connected” or “coupled” to another element, it can be directly connected or coupled to the other element or intervening elements may be present. In contrast, when an element is referred to as being “directly connected” or “directly coupled” to another element, there are no intervening elements present.

[0019] Relative terms such as “below” or “above” or “upper” or “lower” or “horizontal” or “vertical” may be used herein to describe a relationship of one element, layer, or region to another element, layer, or region as illustrated in the Figures. It will be understood that these terms and those discussed above are intended to encompass different orientations of the device in addition to the orientation depicted in the Figures.

[0020] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises,” “comprising,” “includes,” and/or “including” when used herein specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

[0021] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. It will be further understood that terms used herein should be interpreted as having a meaning that is consistent with their meaning in the context of this specification and the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

[0022] Embodiments of the disclosure relate to an envelope tracking (ET) integrated circuit (ETIC) operable with multiple types of power amplifiers. The ETIC is configured to provide one or more ET voltages to a power amplifier(s) for amplifying a radio frequency (RF) signal. In embodiments disclosed herein, the ETIC can be configured to generate the ET voltages at same or different voltage levels based on specific types of the power amplifier(s), such as multi-stage power amplifier and Doherty power amplifier, and for a wider modulation bandwidth of the RF signal. As such, the ETIC can be flexibly adapted to enable a variety of power management scenarios and/or topologies.

[0023] In this regard, FIG. 1 is a schematic diagram of an exemplary ETIC 10 configured according to various embodiments of the present disclosure to support a power amplifier(s) 12 of different types. Although FIG. 1 shows only one of the power amplifier(s) 12, it should be appreciated that the ETIC 10 can support additional power amplifiers, either concurrently or independently.

[0024] The ETIC 10 includes a first voltage circuit 14A and a second voltage circuit 14B. The first voltage circuit 14A can be configured to generate a first ET voltage V.sub.CCA(t) at a first voltage output 16A and the second voltage circuit 14B can be configured to generate a second ET voltage V.sub.CCB(t) at a second voltage output 16B. The power amplifier(s) 12 is coupled to the first voltage output 16A and the second voltage output 16B and configured to amplify an RF signal 18 from an input power P.sub.IN(t) to an output power P.sub.OUT(t) based on one or more of the first ET voltage V.sub.CCA(t) and the second ET voltage V.sub.CCB(t).

[0025] The ETIC 10 further includes a control circuit 20, which can be a field-programmable gate array (FPGA), as an example. The control circuit 20 may cause the first voltage circuit 14A and/or the second voltage circuit 14B to adapt the first ET voltage V.sub.CCA(t) and/or the second ET voltage V.sub.CCB(t) base on specific types of the power amplifier(s) 12. As discussed in detail below, the control circuit 20 determines whether the power amplifier(s) 12 is one of a selected set of power amplifiers. If the power amplifier(s) 12 is one of the selected set of power amplifiers, the control circuit 20 can cause the second ET voltage V.sub.CCB(t) to be generated lower than or equal to the first ET voltage V.sub.CCA(t). In contrast, if the power amplifier(s) 12 is not among the selected set of power amplifiers, the control circuit 20 can further cause the ETIC 10 to generate the first ET voltage V.sub.CCA(t) and/or the second ET voltage V.sub.CCB(t) accordingly. As such, it is possible to flexibly configure the ETIC 10 to enable a variety of power management scenarios and/or topologies.

[0026] The first voltage circuit 14A includes a first voltage amplifier 22A and a first offset capacitor 24A. The first voltage amplifier 22A is configured to generate a first initial ET voltage V.sub.AMPA(t) based on a first supply voltage V.sub.SUPA. The first offset capacitor 24A is coupled between the first voltage amplifier 22A and the first voltage output 16A. The first offset capacitor 24A is configured to raise the first initial ET voltage V.sub.AMPA(t) by a first offset voltage V.sub.OFFA (e.g., 0.8 V) to generate the first ET voltage V.sub.CCA(t) at the first voltage output 16A. The first voltage circuit 14A also includes a first feedback loop 26A (denoted as “FB”) that provides a feedback of the first ET voltage V.sub.CCA(t) to the first voltage amplifier 22A and thereby makes the first voltage circuit 14A a closed-loop ET voltage circuit. Notably, the first voltage amplifier 22A is configured to generate the first initial ET voltage V.sub.AMPA(t) that tracks (e.g., rises and falls) a first ET target voltage V.sub.TGTA(t) over time. In this regard, it is possible to increase or decrease the first initial ET voltage V.sub.AMPA(t), and therefore the first ET voltage V.sub.CCA(t), by increasing or decreasing the first ET target voltage V.sub.TGTA(t).

[0027] The second voltage circuit 14B includes a second voltage amplifier 22B and a second offset capacitor 24B. In a non-limiting example, the second offset capacitor 24B has a smaller capacitance than the first offset capacitor 24A. The second voltage amplifier 22B is configured to generate a second initial ET voltage V.sub.AMPB(t) based on a second supply voltage V.sub.SUPB. The second offset capacitor 24B is coupled between the second voltage amplifier 22B and the second voltage output 16B. The second offset capacitor 24B is configured to raise the second initial ET voltage V.sub.AMPB(t) by a second offset voltage V.sub.OFFB (e.g., 0.8 V) to generate the second ET voltage V.sub.CCB(t) at the second voltage output 16B. The second voltage circuit 14B also includes a second feedback loop 26B (denoted as “FB”) that provides a feedback of the second ET voltage V.sub.CCB(t) to the second voltage amplifier 22B and thereby makes the second voltage circuit 14B a closed-loop ET voltage circuit. Notably, the second voltage amplifier 22B is configured to generate the second initial ET voltage V.sub.AMPB(t) that tracks (e.g., rises and falls) a second ET target voltage V.sub.TGTB(t) over time. In this regard, it is possible to increase or decrease the second initial ET voltage V.sub.AMPB(t), and therefore the second ET voltage V.sub.CCB(t), by increasing or decreasing the second ET target voltage V.sub.TGTB(t).

[0028] The ETIC 10 may include a supply voltage circuit 28. The supply voltage circuit 28 can be configured to generate the first supply voltage V.sub.SUPA and the second supply voltage V.sub.SUPB.

[0029] The control circuit 20 may receive a time-variant ET target voltage V.sub.TGT(t) from a transceiver circuit (not shown) that generates the RF signal 18. The time-variant ET target voltage V.sub.TGT(t) is so generated to track a time-variant power envelope ENV.sub.P(t) of the RF signal 18. In embodiments disclosed herein, the control circuit 20 may be configured to generate both the first ET target voltage V.sub.TGTA(t) and the second ET target voltage V.sub.TGTB(t) from the time-variant ET target voltage V.sub.TGT(t).

[0030] In a non-limiting example, the control circuit 20 can generate the first ET target voltage V.sub.TGTA(t) based on a first analog lookup table (LUT) that correlates the time-variant ET target voltage V.sub.TGT(t) with the first ET target voltage V.sub.TGTA(t). Likewise, the control circuit 20 may generate the second ET target voltage V.sub.TGTB(t) based on a first LUT that correlates the time-variant ET target voltage V.sub.TGT(t) with the second ET target voltage V.sub.TGTB(t). Notably, the first analog LUT may be the same as or different from the second analog LUT. As a result, the control circuit 20 can have more flexibility with respect to adapting the first ET target voltage V.sub.CCA(t) and/or the second ET target voltage V.sub.CCB(t) based on the output power P.sub.OUT(t) of the RF signal 18.

[0031] The ETIC 10 further includes a tracker circuit 30 that includes a multi-level charge pump 32 (denoted as “MCP”) and a power inductor 34. The multi-level charge pump 32 is configured to generate a low-frequency voltage V.sub.DC based on a battery voltage V.sub.BAT. The power inductor 34 is coupled between the multi-level charge pump 32 and the first voltage output 16A. The power inductor 34 is configured to induce a low-frequency current I.sub.DC based on the low-frequency voltage V.sub.DC and provide the low-frequency current I.sub.DC to the first voltage output 16A.

[0032] The ETIC 10 further includes a hybrid circuit 36 that is coupled between the first voltage output 16A and the second voltage output 16B. In embodiments disclosed herein, the hybrid circuit 36 may be controlled by the control circuit 20 to operate as a closed switch, an open switch, or a low dropout (LDO) regulator. When operating as the closed switch, the hybrid circuit 36 passes the low-frequency current I.sub.DC from the first voltage output 16A to the second voltage output 16B. When operating as the open switch, the hybrid circuit 36 blocks the low-frequency current I.sub.DC from the second voltage output 16B. When operating as the LDO regulator, the hybrid circuit 36 regulates (e.g., reduces) the low-frequency current I.sub.DC at the second voltage output 16B.

[0033] In a non-limiting example, the second voltage circuit 14B may generate a sense current I.sub.SENSE to indicate a current surplus or deficit at the second voltage output 16B. Accordingly, the control circuit 20 can determine how much of the low-frequency current I.sub.DC needs to be forwarded to the second voltage output 16B based on the sense current I.sub.SENSE generated by the second voltage circuit 14B.

[0034] In one embodiment, the selected set of power amplifiers includes a multi-stage power amplifier. In this regard, FIG. 2 is a schematic diagram of an exemplary multi-stage power amplifier 38, which can be provided in the ETIC 10 of FIG. 1 as the power amplifier(s) 12.

[0035] In a non-limiting example, the multi-stage power amplifier 38 includes a driver stage amplifier 40 and an output stage amplifier 42 that collectively amplify the RF signal 18 from the input power P.sub.IN(t) to the output power P.sub.OUT(t). The driver stage amplifier 40 operates based on a driver voltage V.sub.D(t) and the output stage amplifier 42 operates based on an output voltage V.sub.O(t) that is typically higher than the driver voltage V.sub.D(t). Given that the driver stage amplifier 40 is placed in front of the output stage amplifier 42, the RF signal 18 received by the output stage amplifier 42 will be delayed by a temporal delay ΔT relative to the RF signal 18 received by the driver stage amplifier 40.

[0036] FIG. 3 is a schematic diagram providing an exemplary illustration of the ETIC 10 of FIG. 1 adapted to support the multi-stage power amplifier 38 of FIG. 2. Common elements between FIGS. 1, 2 and 3 are shown therein with common element numbers and will not be re-described herein.

[0037] In one embodiment, the output stage amplifier 42 is coupled to the first voltage output 16A and the driver stage amplifier 40 is coupled to the second voltage output 16B. In this regard, the output stage amplifier 42 receives the first ET voltage V.sub.CCA(t) as the output voltage V.sub.O(t) and the driver stage amplifier 40 receives the second ET voltage V.sub.CCB(t) as the driver voltage V.sub.D(t).

[0038] As mentioned earlier, the output voltage V.sub.O(t) is typically higher than the driver voltage V.sub.D(t). As such, the control circuit 20 is configured to generate the first ET target voltage V.sub.TGTA(t) and the second ET target voltage V.sub.TGTB(t) to thereby cause the first ET voltage V.sub.CCA(t) to always be generated higher than the second ET voltage V.sub.CCB(t). In a non-limiting example, the control circuit 20 can cause the first ET voltage V.sub.CCA(t) to always be generated higher than the second ET voltage V.sub.CCB(t) when the RF signal 18 is modulated to a wide modulation bandwidth (e.g., ≥200 MHz).

[0039] Notably, by generating the first ET voltage V.sub.CCA(t) to always be higher than the second ET voltage V.sub.CCB(t), it is possible to drive the low-frequency current I.sub.DC from the first voltage output 16A toward the second voltage output 16B. As such, the control circuit 20 may control the hybrid circuit 36 to operate as the LDO regulator to regulate the low-frequency current I.sub.DC that flows from the first voltage output 16A toward the second voltage output 16B.

[0040] As discussed in FIG. 2, the RF signal 18 may be delayed by the temporal delay ΔT when it arrives at the output stage amplifier 42. In this regard, the control circuit 20 may be further configured to determine the temporal delay ΔT (e.g., based on configuration) and generate the first ET target voltage V.sub.TGTA(t) with the temporal delay ΔT relative to the second ET target voltage V.sub.TGTB(t). In other words, the first ET target voltage V.sub.TGTA(t) will be delayed from the second ET target voltage V.sub.TGTB(t) by the temporal delay ΔT. As a result, the first ET voltage V.sub.CCA(t) will be delayed from the second ET voltage V.sub.CCB(t) by the determined temporal delay ΔT to ensure proper alignment to the time-variant power envelope ENV.sub.P(t) of the RF signal 18.

[0041] In another embodiment, the selected set of power amplifiers includes a Doherty power amplifier. In this regard, FIG. 4A is a schematic diagram of an exemplary Doherty power amplifier 44, which can be provided in the ETIC 10 of FIG. 1 as the power amplifier(s) 12. Common elements between FIGS. 1 and 4A are shown therein with common element numbers and will not be re-described herein.

[0042] The Doherty power amplifier 44 includes a carrier amplifier 46 and a peaking amplifier 48. In a non-limiting example, the carrier amplifier 46 is coupled to a load R.sub.L (e.g., an antenna port) via an impedance inverter 50 (denoted as “Ka”). The carrier amplifier 46 is associated with a carrier current I.sub.M and configured to amplify the RF signal 18 based on a carrier voltage V.sub.M(t). The peaking amplifier 48 is associated with a peaking current j*I.sub.P and configured to amplify the RF signal 18 based on a peaking voltage V.sub.P(t).

[0043] FIG. 4B is a graphic diagram providing an exemplary illustration of operating principles of the Doherty power amplifier 44 in FIG. 4A. Assuming that the RF signal 18 has a peak-to-average ratio (PAR) of 6 dB, when the output power P.sub.OUT(t) is below an average power P.sub.AVG of the output power P.sub.OUT(t), which corresponds to one-half (½) of the output power P.sub.OUT(t), the carrier amplifier 46 is activated while the peaking amplifier 48 is deactivated. Accordingly, the carrier amplifier 46 amplifies the RF signal 18 from the input power P.sub.IN(t) to the output power P.sub.OUT(t) based on the carrier voltage V.sub.M(t). When the output power P.sub.OUT(t) is in between of the average power P.sub.AVG and a peak power P.sub.PEAK of the output power P.sub.OUT(t), the carrier amplifier 46 continues to amplify the RF signal 18 based on the carrier voltage V.sub.M(t), which is maintained at a maximum voltage V.sub.MAX. In the meantime, the peaking amplifier 48 is also activated to amplify the RF signal 18 based on the peaking voltage V.sub.P(t).

[0044] As shown in FIG. 4B, before the output power P.sub.OUT(t) reaches the peak power P.sub.PEAK, the carrier voltage V.sub.M(t) is higher than the peaking voltage V.sub.P(t). However, when the output power P.sub.OUT(t) reaches the peak power P.sub.PEAK, the carrier voltage V.sub.M(t) and the peaking voltage V.sub.P(t) become equal. In this regard, for the PAR of 6 dB, it can be said that the carrier voltage V.sub.M(t) is greater than or equal to the peaking voltage V.sub.P(t).

[0045] Assuming now that the RF signal 18 has a PAR of 8 dB, the output power P.sub.OUT(t) is higher than the peak power P.sub.PEAK in a region 52. In this regard, the carrier volage V.sub.M(t) and the peaking voltage V.sub.P(t) will be increased concurrently and equally toward a higher maximum voltage V.sub.MAX1. Accordingly, the carrier amplifier 46 and the peaking amplifier 48 are both activated to amplify the RF signal 18.

[0046] Several operating principles of the Doherty power amplifier 44 can be observed from FIG. 4B. First, it can be observed that only the carrier voltage V.sub.M(t) is needed when the output power P.sub.OUT(t) is below the average power P.sub.AVG. Second, it can be observed that the carrier voltage V.sub.M(t) is always higher than the peaking voltage V.sub.P(t) when the output power P.sub.OUT(t) is higher than the average power P.sub.AVG but lower than the peak power P.sub.PEAK. Third, it can be further observed that the carrier voltage V.sub.M(t) equals the peaking voltage V.sub.P(t) when the output power P.sub.OUT(t) is higher than or equal to the peak power P.sub.PEAK. As discussed below in FIG. 5, it is possible to adapt the ETIC 10 of FIG. 1 to support the Doherty power amplifier 44 of FIG. 4A based on the operating principles observed in FIG. 4B.

[0047] In this regard, FIG. 5 is a schematic diagram providing an exemplary illustration of the ETIC 10 of FIG. 1 adapted to support the Doherty power amplifier 44 of FIG. 4A. Common elements between FIGS. 1, 4A, 4B, and 5 are shown therein with common element numbers and will not be re-described herein.

[0048] In this embodiment, the carrier amplifier 46 is coupled to the first voltage output 16A to receive the first ET target voltage V.sub.TGTA(t). The peak amplifier 48 is coupled to the second voltage output 16B via a voltage feeder circuit 54 (denoted as “V.sub.CC feed”). The voltage feeder circuit 54 is configured to introduce a 90° phase shift in the second ET target voltage V.sub.TGTB(t).

[0049] In accordance with the operating principles observed in FIG. 4B, the control circuit 20 activates the first voltage circuit 14A and deactivates the second voltage circuit 14B when the control circuit 20 determines that the output power P.sub.OUT(t) of the RF signal 18 is lower than the average power P.sub.AVG of the RF signal 18. The control circuit 20 may also control the hybrid circuit 36 to operate as the open switch to thereby block the low-frequency current I.sub.DC from the second voltage output 16B.

[0050] When the control circuit 20 determines that the output power P.sub.OUT(t) is higher than or equal to the average power P.sub.AVG of the RF signal 18, the control circuit 20 activates the second voltage circuit 14B. More specifically, if the control circuit 20 determines that the output power P.sub.OUT(t) is lower than or equal to the peak power P.sub.PEAK (e.g., 6 dB PAR), the control circuit 20 controls the first voltage circuit 14A to maintain the first ET voltage V.sub.CCA(t) at a peak ET voltage level V.sub.CC-MAX (e.g., 5.5 V). Concurrently, the control circuit 20 controls the second voltage circuit 14B to generate the second ET voltage V.sub.CCB(t) lower than the ET voltage V.sub.CCA(t). By keeping the first ET voltage V.sub.CCA(t) higher than the second ET voltage V.sub.CCB(t), the low-frequency current I.sub.DC can flow from the first voltage output 16A toward the second voltage output 16B. The control circuit 20 may control the hybrid circuit 36 to operate as the LDO regulator to regulate the low-frequency current I.sub.DC that flows from the first voltage output 16A toward the second voltage output 16B. In a non-limiting example, the control circuit 20 can increase or decrease the low-frequency current I.sub.DC based on the sense current I.sub.SENSE generated by the second voltage circuit 14B.

[0051] The first ET voltage V.sub.CCA(t) and the second ET voltage V.sub.CCB(t) will become equal when the output power P.sub.OUT(t) reaches the peak power P.sub.PEAK. As a result, the carrier amplifier 46 and the peaking amplifier 48 each produces ½ of the peak power P.sub.PEAK.

[0052] When the control circuit 20 determines that the output power P.sub.OUT(t) is higher than the peak power P.sub.PEAK (e.g., 8 dB PAR), the control circuit 20 may control the first voltage circuit 14A and the second voltage circuit 14B to increase the first ET voltage V.sub.CCA(t) and the second ET voltage V.sub.CCB(t), respectively, to a higher peak ET voltage level V.sub.CC-MAX1 (V.sub.CC-MAX1>V.sub.CC-MAX). Accordingly, the control circuit 20 may control the hybrid circuit 36 to operate as the closed switch.

[0053] The control circuit 20 may further determine whether there exists the temporal delay ΔT between the carrier amplifier 46 and the peaking amplifier 48. If the control circuit 20 determines that such temporal delay ΔT exists, for example in the peaking amplifier 48, the control circuit 20 may generate the second ET target voltage V.sub.TGTB(t) with the determined temporal delay ΔT relative to the first ET target voltage V.sub.TGTA(t) to thereby cause the second ET voltage V.sub.CCB(t) to be delayed by the determined temporal delay ΔT.

[0054] FIGS. 6A and 6B are graphic diagrams illustrating operating principles of the ETIC 10 in FIG. 5. Specifically, FIG. 6A illustrates operation of the ETIC 10 when the RF signal 18 is associated with the 6 dB PAR, and FIG. 6B illustrates operation of the ETIC 10 when the RF signal 18 is associated with the 8 dB PAR.

[0055] Those skilled in the art will recognize improvements and modifications to the preferred embodiments of the present disclosure. All such improvements and modifications are considered within the scope of the concepts disclosed herein and the claims that follow.