Radio frequency front-end circuit

Abstract

A radio frequency (RF) front-end circuit is provided. A power management circuit is configured to output a first modulated voltage, a second modulated voltage, a first bias voltage, and a second bias voltage via a first voltage port(s), a second voltage port(s), a first bias voltage port(s), and a second bias voltage port(s), respectively. An amplifier circuit(s) is configured to amplify an RF signal based on a selected modulated voltage and a selected bias voltage outputted by a selected voltage port and a selected bias voltage port, respectively. The power management circuit can be controlled to dynamically increase the selected bias voltage at the selected bias voltage port in case the selected bias voltage drops below a defined bias voltage threshold. As such, it may be possible to maintain the selected bias voltage at a desirable level, thus enabling the amplifier circuit(s) to operate with improved linearity and efficiency.

Claims

1. A radio frequency (RF) front-end circuit comprising: a power management circuit configured to: output a first modulated voltage via a first voltage port; output a second modulated voltage via a second voltage port; output a first bias voltage via a first bias voltage port; and output a second bias voltage via a second bias voltage port; an amplifier circuit coupled to a selected voltage port among the first voltage port and the second voltage port and a selected bias voltage port among the first bias voltage port and the second bias voltage port, the amplifier circuit configured to: receive a selected modulated voltage and a selected bias voltage from the selected voltage port and the selected bias voltage port, respectively; and amplify an RF signal from an input power to an output power based on the selected modulated voltage and the selected bias voltage; and a control circuit coupled to the power management circuit and configured to: determine whether the selected bias voltage is lower than a defined bias voltage threshold; and cause the power management circuit to increase the selected bias voltage at the selected bias voltage port to the defined bias voltage threshold in response to the selected bias voltage being lower than the defined bias voltage threshold.

2. The RF front-end circuit of claim 1 wherein the power management circuit comprises: a first tracker coupled to the first voltage port and configured to generate the first modulated voltage; a second tracker coupled to the second voltage port and configured to generate the second modulated voltage; a first charge pump configured to receive a battery voltage and generate a first boosted voltage higher than the battery voltage; a second charge pump configured to receive the battery voltage and generate a second boosted voltage higher than the battery voltage; and a bias voltage circuit coupled to the first charge pump and the second charge pump, the bias voltage circuit configured to generate the selected bias voltage at the selected bias voltage port based on a selected input voltage among the first boosted voltage, the second boosted voltage, and the battery voltage.

3. The RF front-end circuit of claim 2 wherein the first boosted voltage and the second boosted voltage are both equal to two times the battery voltage.

4. The RF front-end circuit of claim 2 wherein: the first tracker is further configured to generate a first envelope tracking (ET) modulated voltage based on a first modulated target voltage; and the second tracker is further configured to generate a second ET modulated voltage based on a second modulated target voltage.

5. The RF front-end circuit of claim 2 wherein: the first tracker is further configured to generate a first average power tracking (APT) modulated voltage; and the second tracker is further configured to generate a second APT modulated voltage.

6. The RF front-end circuit of claim 2 wherein the bias voltage circuit comprises: a first multiplexer configured to: receive the first boosted voltage, the second boosted voltage, and the battery voltage; and output a selected one of the first boosted voltage, the second boosted voltage, and the battery voltage as the first bias voltage; a first regulator coupled to the first multiplexer and configured to regulate the first bias voltage to the defined bias voltage threshold; a second multiplexer configured to: receive the first boosted voltage, the second boosted voltage, and the battery voltage; and output a selected one of the first boosted voltage, the second boosted voltage, and the battery voltage as the second bias voltage; and a second regulator coupled to the second multiplexer and configured to regulate the second bias voltage to the defined bias voltage threshold.

7. The RF front-end circuit of claim 6 wherein the control circuit is further configured to selectively control at least one of the first multiplexer and the second multiplexer to output at least one of the first bias voltage and the second bias voltage.

8. The RF front-end circuit of claim 6 wherein the control circuit is further configured to determine whether the battery voltage is higher than or equal to the defined bias voltage threshold.

9. The RF front-end circuit of claim 8 wherein: the amplifier circuit is coupled to the first voltage port and the first bias voltage port; and the control circuit is further configured to: control the first multiplexer via a first control signal to output the battery voltage as the first bias voltage in response to the battery voltage being greater than or equal to the defined bias voltage threshold; and control the first multiplexer via the first control signal to output the first boosted voltage as the first bias voltage in response to the battery voltage being lower the defined bias voltage threshold.

10. The RF front-end circuit of claim 8 wherein: the amplifier circuit is coupled to the second voltage port and the second bias voltage port; and the control circuit is further configured to: control the second multiplexer via a second control signal to output the battery voltage as the second bias voltage in response to the battery voltage being greater than or equal to the defined bias voltage threshold; and control the second multiplexer via the second control signal to output the second boosted voltage as the second bias voltage in response to the battery voltage being lower the defined bias voltage threshold.

11. The RF front-end circuit of claim 6 further comprising a second amplifier circuit, wherein: the amplifier circuit is coupled to the first voltage port and the first bias voltage port, the amplifier circuit configured to amplify the RF signal from the input power to the output power based on the first modulated voltage and the first bias voltage; and the second amplifier circuit is coupled to the second voltage port and the second bias voltage port, the second amplifier circuit configured to amplify a second RF signal from a second input power to a second output power based on the second modulated voltage and the second bias voltage.

12. The RF front-end circuit of claim 11 wherein the control circuit is further configured to control the first multiplexer and the second multiplexer to output the battery voltage as the first bias voltage and the second bias voltage, respectively, in response to the battery voltage being higher than or equal to the defined bias voltage threshold.

13. The RF front-end circuit of claim 11 wherein the control circuit is further configured to determine which of the output power and the second output power is higher in response to the battery voltage being lower than the defined bias voltage threshold.

14. The RF front-end circuit of claim 13 wherein the control circuit is further configured to: determine that the output power of the amplifier circuit is higher than the second output power of the second amplifier circuit in response to the output power being higher than a defined power threshold and the second output power being lower than or equal to the defined power threshold; and determine that the output power of the amplifier circuit is lower than the second output power of the second amplifier circuit in response to the output power being lower than or equal to the defined power threshold and the second output power being higher than the defined power threshold.

15. The RF front-end circuit of claim 14 wherein the defined power threshold is predetermined as being 3 decibels (dB) below a defined power ceiling for the RF front-end circuit.

16. The RF front-end circuit of claim 13 wherein, in response to the output power being higher than the second output power, the control circuit is further configured to: control the first multiplexer to output the second boosted voltage as the first bias voltage; and control the second multiplexer to output the battery voltage as the second bias voltage.

17. The RF front-end circuit of claim 13 wherein, in response to the output power being lower than the second output power, the control circuit is further configured to: control the first multiplexer to output the battery voltage as the first bias voltage; and control the second multiplexer to output the first boosted voltage as the second bias voltage.

18. The RF front-end circuit of claim 1 wherein the power management circuit and the control circuit are integrated into a power management integrated circuit (PMIC).

19. A radio frequency (RF) front-end circuit comprising: a power management circuit configured to: output a first modulated voltage via a first voltage port; output a second modulated voltage via a second voltage port; output a first bias voltage via a first bias voltage port; and output a second bias voltage via a second bias voltage port; an amplifier circuit coupled to a selected voltage port among the first voltage port and the second voltage port and a selected bias voltage port among the first bias voltage port and the second bias voltage port, the amplifier circuit configured to: receive a selected modulated voltage and a selected bias voltage from the selected voltage port and the selected bias voltage port, respectively; and amplify an RF signal from an input power to an output power based on the selected modulated voltage and the selected bias voltage; and wherein the power management circuit is further configured to: determine whether the selected bias voltage is lower than a defined bias voltage threshold; and increase the selected bias voltage at the selected bias voltage port to the defined bias voltage threshold in response to the selected bias voltage being lower than the defined bias voltage threshold.

20. The RF front-end circuit of claim 19 wherein the power management circuit comprises: a first tracker coupled to the first voltage port and configured to generate the first modulated voltage; a second tracker coupled to the second voltage port and configured to generate the second modulated voltage; a first charge pump configured to receive a battery voltage and generate a first boosted voltage higher than the battery voltage; a second charge pump configured to receive the battery voltage and generate a second boosted voltage higher than the battery voltage; and a bias voltage circuit coupled to the first charge pump and the second charge pump, the bias voltage circuit configured to generate the selected bias voltage at the selected bias voltage port based on a selected input voltage among the first boosted voltage, the second boosted voltage, and the battery voltage.

21. The RF front-end circuit of claim 20 wherein the bias voltage circuit comprises: a first multiplexer configured to: receive the first boosted voltage, the second boosted voltage, and the battery voltage; and output a selected one of the first boosted voltage, the second boosted voltage, and the battery voltage as the first bias voltage; a first regulator coupled to the first multiplexer and configured to regulate the first bias voltage to the defined bias voltage threshold; a second multiplexer configured to: receive the first boosted voltage, the second boosted voltage, and the battery voltage; and output a selected one of the first boosted voltage, the second boosted voltage, and the battery voltage as the second bias voltage; and a second regulator coupled to the second multiplexer and configured to regulate the second bias voltage to the defined bias voltage threshold.

Description

BRIEF DESCRIPTION OF THE DRAWING FIGURES

(1) 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.

(2) FIG. 1 is a schematic diagram of an exemplary radio frequency (RF) front-end circuit configured to improve linearity and efficiency of an amplifier circuit by providing a steady bias voltage to the amplifier circuit;

(3) FIG. 2 is a schematic diagram providing an exemplary illustration of a power management circuit provided in the RF front-end circuit of FIG. 1 and configured according to an embodiment of the present disclosure;

(4) FIG. 3 is a schematic diagram providing an exemplary illustration of a bias voltage circuit provided in the power management circuit of FIG. 2 according to an embodiment of the present disclosure;

(5) FIG. 4A is a schematic diagram providing an exemplary illustration of the power management circuit of FIG. 2 configured according to one embodiment of the present disclosure to enable single-transmit (STX) operation;

(6) FIG. 4B is a schematic diagram providing an exemplary illustration of the power management circuit of FIG. 2 configured according to another embodiment of the present disclosure to enable STX operation; and

(7) FIG. 5 is a schematic diagram of an exemplary RF front-end circuit 10A configured to support dual-transmit (DTX) operation.

DETAILED DESCRIPTION

(8) 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.

(9) 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.

(10) 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.

(11) 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.

(12) 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.

(13) 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.

(14) Embodiments of the disclosure relate to a radio frequency (RF) front-end circuit. A power management circuit is configured to output a first modulated voltage and a second modulated voltage via a first voltage port(s) and a second voltage port(s), respectively. The power management circuit is also configured to output a first bias voltage and a second bias voltage via a first bias voltage port(s) and a second bias voltage port(s), respectively. An amplifier circuit(s) is coupled to a selected voltage port among the first voltage port(s) and the second voltage port(s), and a selected bias port among the first bias port(s) and the second bias port(s). The amplifier circuit(s) is configured to amplify an RF signal based on a selected modulated voltage and a selected bias voltage outputted by the selected voltage port and the selected bias voltage port, respectively. The power management circuit can be controlled to dynamically increase the selected bias voltage at the selected bias voltage port in case the selected bias voltage drops below a defined bias voltage threshold. As such, it may be possible to maintain the selected bias voltage at a desirable level, thus enabling the amplifier circuit(s) to operate with improved linearity and efficiency.

(15) In this regard, FIG. 1 is a schematic diagram of an exemplary RF front-end circuit 10 configured to improve linearity and efficiency of an amplifier circuit 12 by providing a steady bias voltage to the amplifier circuit 12. In a non-limiting example, a power management circuit 14 includes at least one first voltage port 16A, at least one second voltage port 16B, at least one first bias voltage port 18A, and at least one second bias voltage port 18B. The first voltage port 16A and the second voltage port 16B are configured to output a first modulated voltage V.sub.CCA and a second modulated voltage V.sub.CCB, respectively. The first bias voltage port 18A and the second bias voltage port 18B are configured to output a first bias voltage V.sub.BIASA and a second bias voltage V.sub.BIASB, respectively.

(16) The amplifier circuit 12 can be coupled to a selected voltage port among the first voltage port 16A and the second voltage port 16B, and a selected bias voltage port among the first bias voltage port 18A and the second bias voltage port 18B. As shown in FIG. 1, the amplifier circuit 12 is coupled to the first voltage port 16A and the first bias voltage port 18A. In this regard, the first voltage port 16A and the first bias voltage port 18A are referred to hereinafter as the selected voltage port and the selected bias voltage port, respectively. In this regard, the amplifier circuit 12 receives the first modulated voltage V.sub.CCA and the first biased voltage V.sub.BIASA as a selected modulated voltage and a selected bias voltage, respectively. Accordingly, the amplifier circuit 12 amplifies an RF signal 20 from an input power P.sub.IN1 to an output power P.sub.OUT1 based on the selected modulated voltage and the selected bias voltage.

(17) Notably, the amplifier circuit 12 may also be coupled to the second voltage port 16B and the second bias voltage port 18B. In this regard, the second voltage port 16B and the second bias voltage port 18B will become the selected voltage port and the selected bias voltage port, respectively. Accordingly, the second modulated voltage V.sub.CCB and the second bias voltage V.sub.BIASB will be the selected modulated voltage and the selected bias voltage, respectively.

(18) In a non-limiting example, the amplifier circuit 12 requires that the selected bias voltage be maintained at 3.15 volts (3.5 V) to help achieve desired linearity performance and efficiency. The selected bias voltage may initially be provided by a battery (not shown) capable of providing up to 4.4 V in voltage when fully charged. Given that the battery may also be powering other active components and/or circuits (e.g., transceiver, antenna, etc.), the voltage level of the battery will decrease over time, thus causing the selected bias voltage to drop as well.

(19) As such, the RF front-end circuit 10 further includes a control circuit 22, which can be provided as a microprocessor, for example. As discussed in detail below, the control circuit 22 is configured to dynamically determine whether the selected bias voltage is lower than a defined bias voltage threshold (e.g., 3.15 V). In response to the selected bias voltage being lower than the defined bias voltage threshold, the control circuit 22 is further configured to cause the power management circuit 14 to increase the selected bias voltage at the selected bias voltage port to the defined bias voltage threshold. By maintaining the selected bias voltage steadily at the defined bias voltage threshold, it may be possible to maintain linearity performance and efficiency of the amplifier circuit 12.

(20) In one embodiment, the control circuit 22 is separated from the power management circuit 14. In another embodiment, the control circuit 22 may be integrated with the power management circuit 14 in a power management integrated circuit (PMIC) 23. In another embodiment, functionalities of the control circuit 22 can be carried out by various components and/or circuitries in the power management circuit 14. As such, the RF front-end circuit 10 may not include an independent control circuit. It should be appreciated that the operational principles discussed hereinafter are independent from specific implementation of the control circuit 22.

(21) FIG. 2 is a schematic diagram providing an exemplary illustration of the power management circuit 14 of FIG. 1 configured according to an embodiment of the present disclosure. Common elements between FIGS. 1 and 2 are shown therein with common element numbers and will not be re-described herein.

(22) The power management circuit 14 includes a first tracker 24A and a second tracker 24B. The first tracker 24A is coupled to the first voltage port 16A and configured to generate the first modulated voltage V.sub.CCA at the first voltage port 16A based on a first supply voltage V.sub.SUPA. In a non-limiting example, the first tracker 24A is coupled to the first voltage port 16A via a first offset capacitor 26A, which is configured to raise the first modulated voltage V.sub.CCA (e.g., by 1 V) before outputting the first modulated voltage V.sub.CCA via the first voltage port 16A. In one example, the first tracker 24A can be configured to generate the first modulated voltage V.sub.CCA as a first envelope tracking (ET) modulated voltage based on a first modulated target voltage V.sub.TARGETA. In another example, the first tracker 24A can be configured to generate the first modulated voltage V.sub.CCA as a first average power tracking (APT) modulated voltage.

(23) The second tracker 24B is coupled to the second voltage port 16B and configured to generate the second modulated voltage V.sub.CCB at the second voltage port 16B based on a second supply voltage V.sub.SUPB. In a non-limiting example, the second tracker 24B is coupled to the second voltage port 16B via a second offset capacitor 26B, which is configured to raise the first modulated voltage V.sub.CCB (e.g., by 1 V) before outputting the second modulated voltage V.sub.CCB via the second voltage port 16B. In one example, the second tracker 24B can be configured to generate the second modulated voltage V.sub.CCB as a second ET modulated voltage based on a second modulated target voltage V.sub.TARGETB. In another example, the second tracker 24B can be configured to generate the second modulated voltage V.sub.CCB as a second APT modulated voltage.

(24) The power management circuit 14 includes a first charge pump 28A and a second charge pump 28B. The first charge pump 28A is configured to receive a battery voltage V.sub.BAT and generate a first boosted voltage V.sub.BOOSTA higher than the battery voltage V.sub.BAT. In a non-limiting example, the first boosted voltage V.sub.BOOSTA can equal up to two times the battery voltage V.sub.BAT (V.sub.BOOSTA=2V.sub.BAT). The second charge pump 28B is configured to receive the battery voltage V.sub.BAT and generate a second boosted voltage V.sub.BOOSTB higher than the battery voltage V.sub.BAT. In a non-limiting example, the second boosted voltage V.sub.BOOSTB can equal up to two times the battery voltage V.sub.BAT (V.sub.BOOSTB=2V.sub.BAT).

(25) The power management circuit 14 includes a bias voltage circuit 30. The bias voltage circuit 30 is coupled to the first charge pump 28A, the second charge pump 28B, the first bias voltage port 18A, and the second bias voltage port 18B. The bias voltage circuit 30 is configured to generate the selected bias voltage (e.g., the first bias voltage V.sub.BIASA or the second bias voltage V.sub.BIASB) based on a selected input voltage among the first boosted voltage V.sub.BOOSTA, the second boosted voltage V.sub.BOOSTB, and the battery voltage V.sub.BAT.

(26) FIG. 3 is a schematic diagram providing an exemplary illustration of the bias voltage circuit 30 of FIG. 2 according to an embodiment of the present disclosure. The bias voltage circuit 30 includes a first multiplexer 32A and a second multiplexer 32B. The first multiplexer 32A receives the first boosted voltage V.sub.BOOSTA, the second boosted voltage V.sub.BOOSTB, and the battery voltage V.sub.BAT. The control circuit 22 of FIG. 2 (not shown) may control the first multiplexer 32A via a first control signal 34A to output a selected one of the first boosted voltage V.sub.BOOSTA, the second boosted voltage V.sub.BOOSTB, and the battery voltage V.sub.BAT as the first bias voltage V.sub.BIASA. The second multiplexer 32B receives the first boosted voltage V.sub.BOOSTA, the second boosted voltage V.sub.BOOSTB, and the battery voltage V.sub.BAT. The control circuit 22 of FIG. 2 (not shown) may control the second multiplexer 32B via a second control signal 34B to output a selected one of the first boosted voltage V.sub.BOOSTA, the second boosted voltage V.sub.BOOSTB, and the battery voltage V.sub.BAT as the second bias voltage V.sub.BIASB. In this regard, the control circuit 22 may selectively control the first multiplexer 32A and/or the second multiplexer 32B to output the first bias voltage V.sub.BIASA and/or the second bias voltage V.sub.BIASB via the first control signal 34A and/or the second control signal 34B.

(27) As previously discussed, the first boosted voltage V.sub.BOOSTA and the second boosted voltage V.sub.BOOSTB may each equal up to two times the battery voltage V.sub.BAT. Assuming that the amplifier circuit 12 of FIG. 1 (not shown) requires the selected bias voltage to be maintained at 3.15 V and the battery voltage V.sub.BAT currents to stand at 2.5 V, the first multiplexer 32A would output the first bias voltage V.sub.BIASA at about 5 V, which is higher than the 3.15 V bias voltage needed by the amplifier circuit 12. As such, the bias voltage circuit 30 may further include a first regulator 36A to regulate the first bias voltage V.sub.BIASA before providing the first bias voltage V.sub.BIASA to the first bias voltage port 18A of FIG. 2 (not shown). Similarly, the bias voltage circuit 30 may further include a second regulator 36B to regulate the second bias voltage V.sub.BIASB before providing the second bias voltage V.sub.BIASB to the second bias voltage port 18B of FIG. 2 (not shown).

(28) With reference back to FIG. 2, the power management circuit 14 may further include a first switcher 38A and a second switcher 38B. The first switcher 38A is coupled to the first voltage port 16A via a first inductor 40A. The second switcher 38B is coupled to the second voltage port 16B via a second inductor 40B. Notably, the first switcher 38A and the second switcher 38B can be implemented based on any number, type, and layout of switches without affecting functionalities of the first switcher 38A and the second switcher 38B. In a non-limiting example, the first switcher 38A and the second switcher 38B each includes a single-pole three-throw (SP3T) switch.

(29) The first switcher 38A is configured to receive the battery voltage V.sub.BAT and the first boosted voltage V.sub.BOOSTA. In this regard, the first switcher 38A can be controlled to selectively output one of the battery voltage V.sub.BAT, the first boosted voltage V.sub.BOOSTA, or zero volt voltage. The voltage outputted by the first switcher 38A causes the first inductor 40A to induce a first current I.sub.CCA at the first voltage port 16A. The first current I.sub.CCA can be a direct current, an alternating current, or a combination of both.

(30) The second switcher 38B is configured to receive the battery voltage V.sub.BAT and the second boosted voltage V.sub.BOOSTB. In this regard, the second switcher 38B can be controlled to selectively output one of the battery voltage V.sub.BAT, the second boosted voltage V.sub.BOOSTB, and 0 V voltage. The voltage outputted by the second switcher 38B causes the second inductor 40B to induce a second current I.sub.ccB at the second voltage port 16B. The second current I.sub.CCB can be a direct current, an alternating current, or a combination of both.

(31) In one embodiment, the amplifier circuit 12 of FIG. 1 (not shown) may be coupled to the first voltage port 16A and the first bias voltage port 18A, as shown in FIG. 4A. In this regard, FIG. 4A is a schematic diagram providing an exemplary illustration of the power management circuit 14 of FIG. 2 configured according to one embodiment of the present disclosure to enable single-transmit (STX) operation. Common elements between FIGS. 1, 2, and 4A are shown therein with common element numbers and will not be re-described herein.

(32) As shown in FIG. 4A, the amplifier circuit 12 is coupled to the first voltage port 16A and the first bias voltage port 18A to receive the first modulated voltage V.sub.CCA and the first bias voltage V.sub.BIASA, respectively. The control circuit 22 is configured to determine whether the first bias voltage V.sub.BIASA is higher than or equal to the defined bias voltage threshold. If the first bias voltage V.sub.BIASA is higher than or equal to the defined bias voltage threshold, the control circuit 22 controls the first multiplexer 32A (not shown) in the bias voltage circuit 30 via the first control signal 34A to output the battery voltage V.sub.BAT to the first regulator 36A (not shown) and, thus, the first bias voltage port 18A. In contrast, if the first bias voltage V.sub.BIASA is lower than the defined bias voltage threshold, the control circuit 22 controls the first multiplexer 32A in the bias voltage circuit 30 via the first control signal 34A to output the second boosted voltage V.sub.BOOSTB to the first regulator 36A and, thus, the first bias voltage port 18A. The control circuit 22 may not provide the second control signal 34B to the second multiplexer 32B (not shown) in the bias voltage circuit 30. As such, the second bias voltage V.sub.BIASB will not be provided to the second regulator 36B and the second bias voltage port 18B. The control circuit 22 may further control the second switcher 38B to decouple the second charge pump 28B from the second voltage port 16B.

(33) In another embodiment, the amplifier circuit 12 of FIG. 1 (not shown) may be coupled to the second voltage port 16B and the second bias voltage port 18B, as shown in FIG. 4B. In this regard, FIG. 4B is a schematic diagram providing an exemplary illustration of the power management circuit 14 of FIG. 2 configured according to another embodiment of the present disclosure to enable STX operation. Common elements between FIGS. 1, 2, and 4B are shown therein with common element numbers and will not be re-described herein.

(34) As shown in FIG. 4B, the amplifier circuit 12 is coupled to the second voltage port 16B and the second bias voltage port 18B to receive the second modulated voltage V.sub.CCB and the second bias voltage V.sub.BIASB, respectively. The control circuit 22 is configured to determine whether the second bias voltage V.sub.BIASB is higher than or equal to the defined bias voltage threshold. If the second bias voltage V.sub.BIASB is higher than or equal to the defined bias voltage threshold, the control circuit 22 controls the second multiplexer 32B (not shown) in the bias voltage circuit 30 via the second control signal 34B to output the battery voltage V.sub.BAT to the second regulator 36B (not shown) and, thus, the second bias voltage port 18B. In contrast, if the second bias voltage V.sub.BIASB is lower than the defined bias voltage threshold, the control circuit 22 controls the second multiplexer 32B in the bias voltage circuit 30 via the second control signal 34B to output the first boosted voltage V.sub.BOOSTA to the second regulator 36B and, thus, the second bias voltage port 18B. The control circuit 22 may not provide the first control signal 34A to the first multiplexer 32A (not shown) in the bias voltage circuit 30. As such, the first bias voltage V.sub.BIASA will not be provided to the first regulator 36A and the first bias voltage port 18A. The control circuit 22 may further control the first switcher 38A to decouple the first charge pump 28A from the first voltage port 16A.

(35) In another embodiment, the RF front-end circuit 10 of FIG. 1 may include a second amplifier circuit to support dual-transmit (DTX) operation, such as carrier aggregation, as shown in FIG. 5. In this regard, FIG. 5 is a schematic diagram of an exemplary RF front-end circuit 10A configured to support dual-transmit (DTX) operation. Common elements between FIGS. 1, 2, and 5 are shown therein with common element numbers and will not be re-described herein.

(36) The RF front-end circuit 10A includes a second amplifier circuit 42. In this regard, the amplifier circuit 12 is coupled to the first voltage port 16A and the first bias voltage port 18A, while the second amplifier circuit 42 is coupled to the second voltage port 16B and the second bias voltage port 18B. Accordingly, the amplifier circuit 12 receives the first modulated voltage V.sub.CCA and the first bias voltage V.sub.BIASA, and the second amplifier circuit 42 receives the second modulated voltage V.sub.CCB and the second bias voltage V.sub.BIASB. Accordingly, the second amplifier circuit 42 amplifies a second RF signal 44 from a second input power P.sub.IN2 to a second output power P.sub.OUT2 based on the second modulated voltage V.sub.CCB and the second bias voltage V.sub.BIASB.

(37) The control circuit 22 determines whether the battery voltage V.sub.BAT is higher than or equal to the defined bias voltage threshold. If the battery voltage V.sub.BAT is higher than or equal to the defined bias voltage threshold, the control circuit 22 controls the first multiplexer 32A (not shown) and the second multiplexer 32B (not shown) via the first control signal 34A and the second control signal 34B to output the battery voltage V.sub.BAT to the first bias voltage port 18A and the second bias voltage port 18B, respectively.

(38) In the event that the battery voltage V.sub.BAT is lower than the defined bias voltage threshold, the control circuit 22 is further configured to determine which of the output power P.sub.OUT1 and the second output power P.sub.OUT2 is higher. More specifically, the control circuit 22 determines that the output power P.sub.OUT1 is higher than the second output power P.sub.OUT2 if the output power P.sub.OUT1 is higher than a defined power threshold and the second output power P.sub.OUT2 is low than or equal to the defined power threshold. In contrast, the control circuit 22 determines that the second output power P.sub.OUT2 is higher than the output power P.sub.OUT1 if the second output power P.sub.OUT2 is higher than the defined power threshold and the output power P.sub.OUT1 is lower than or equal to the defined power threshold. In a non-limiting example, the defined power threshold is 3 decibels (3 dB) below a defined power ceiling for the RF front-end circuit 10A (defined power threshold=defined power ceiling3 dB).

(39) If the output power P.sub.OUT1 is determined to be higher than the second output power P.sub.OUT2, the control circuit 22 controls the first multiplexer 32A to output the second boosted voltage V.sub.BOOST2 at the first bias voltage port 18A as the first bias voltage V.sub.BIASA. In this regard, the first bias voltage V.sub.BIASA is maintained at the defined bias voltage threshold. Concurrently, the control circuit 22 controls the second multiplexer 32B to output the battery voltage V.sub.BAT at the second bias voltage port 18B as the second bias voltage V.sub.BIASB. Although the second amplifier circuit 42 receives the second bias voltage V.sub.BIASB lower than the defined bias voltage threshold, operation of the second amplifier circuit 42 may not be negatively impacted since the second output power P.sub.OUT2 of the second amplifier circuit 42 is lower than the output power P.sub.OUT1 of the amplifier circuit 12.

(40) In contrast, if the second output power P.sub.OUT2 is determined to be higher than the output power P.sub.OUT1, the control circuit 22 controls the first multiplexer 32A to output the battery voltage V.sub.BAT at the first bias voltage port 18A as the first bias voltage V.sub.BIASA. Although the amplifier circuit 12 receives the first bias voltage V.sub.BIASA lower than the defined bias voltage threshold, operation of the amplifier circuit 12 may not be negatively impacted since the output power P.sub.OUT1 of the amplifier circuit 12 is lower than the second output power P.sub.OUT2 of the second amplifier circuit 42. Concurrently, the control circuit 22 controls the second multiplexer 32B to output the first boosted voltage V.sub.BOOSTA at the second bias voltage port 18B as the second bias voltage V.sub.BIASB. In this regard, the second bias voltage V.sub.BIASB is maintained at the defined bias voltage threshold.

(41) 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.