Power amplifier

Abstract

The power amplifier includes an amplification transistor, a first resistor, a bias circuit, a second resistor, and a compensation circuit. The amplification transistor is used to amplify a radio frequency signal to output an amplified radio frequency signal. A control terminal of the amplification transistor receives the radio frequency signal, a first terminal of the amplification transistor is coupled to a first system voltage terminal and used to output the amplified radio frequency signal, and a second terminal of the amplification transistor is coupled to a first reference voltage terminal. The first resistor provides a first resistance value, and a second terminal of the first resistor is coupled to the control terminal of the amplification transistor. The bias circuit includes a bias transistor and is coupled to a first terminal of the first resistor. The second resistor provides a second resistance value smaller than the first resistance value, and a second terminal of the second resistor is coupled to the control terminal of the amplification transistor. The compensation circuit includes a compensation transistor, and an output terminal of the compensation circuit is coupled to a first terminal of the second resistor.

Description

Technical Field

[0001] This invention relates to a power amplifier, and more particularly to a power amplifier that maintains good power added efficiency (PAE) at higher back-off power. Background Technology

[0002] Amplifiers are common components in electronic devices, used to amplify signals to achieve the device's characteristics, such as gain, bandwidth, and linearity. Amplifiers have a wide range of applications, including active filters, buffers, analog-to-digital converters, and radio frequency transceivers. In wireless communication, power amplifiers are crucial components in radio frequency circuits, typically designed at the front end of antenna radiators. Their primary function is to amplify the output signal to a suitable amplitude.

[0003] In the prior art, power amplifiers typically have a bias resistor coupled to the control terminal of their power transistors. However, as the output power of the power amplifier increases, the current flowing through the bias resistor also increases, which results in the power amplifier's gain for high-power signals being less than expected. Summary of the Invention

[0004] One embodiment of the present invention provides a power amplifier comprising an amplifying transistor, a first resistor, a bias circuit, a second resistor, and a compensation circuit. The amplifying transistor amplifies a radio frequency (RF) signal to output an amplified RF signal. The control terminal of the amplifying transistor receives the RF signal, its first terminal is coupled to a first system voltage terminal, and its second terminal is coupled to a first reference voltage terminal. The first terminal of the amplifying transistor outputs the amplified RF signal. The first resistor provides a first resistance value, and its second terminal is coupled to the control terminal of the amplifying transistor. The bias circuit includes a bias transistor and is coupled to the first terminal of the first resistor. The second resistor provides a second resistance value less than the first resistance value, and its second terminal is coupled to the control terminal of the amplifying transistor. The compensation circuit includes a compensation transistor, and its output terminal is coupled to the first terminal of the second resistor.

[0005] Another embodiment of the present invention provides a power amplifier comprising an amplifying transistor, a first resistor, a bias circuit, and a compensation circuit. The amplifying transistor amplifies a radio frequency (RF) signal to output the amplified RF signal. The control terminal of the amplifying transistor receives the RF signal, a first terminal is coupled to a first system voltage terminal, and a second terminal outputs the amplified RF signal. The first resistor provides a first resistance value, and a second terminal of the first resistor is coupled to the control terminal of the amplifying transistor. The bias circuit includes a bias transistor and is coupled to the first terminal of the first resistor. The compensation circuit includes a compensation transistor, and the output terminal of the compensation circuit is coupled to the control terminal of the amplifying transistor. The resistance between the control terminal of the amplifying transistor and the bias transistor is greater than the resistance between the control terminal of the amplifying transistor and the compensation transistor. Attached Figure Description

[0006] Figure 1 This is a circuit diagram of a power amplifier according to an embodiment of the present invention.

[0007] Figure 2 The diagram in Figure 1 illustrates the relationship between the bias current and the compensation current and the output power of the power amplifier.

[0008] The relationship curve.

[0009] Figure 3 This is a circuit diagram of a power amplifier according to another embodiment of the present invention.

[0010] Figure 4 This is a circuit diagram of the bias circuit of a power amplifier according to another embodiment of the present invention.

[0011] Figure 5 This is a circuit diagram of a power amplifier according to another embodiment of the present invention.

[0012] Symbol Explanation

[0013] 10, 20, 30: Power amplifiers

[0014] 100, 100A, 100B: Bias circuit

[0015] 110: Reference current source

[0016] 200, 200A, 200B: Compensation circuit

[0017] 210: Detection circuit

[0018] 220A, 220B: Voltage regulation circuit

[0019] 300: Core Circuit

[0020] 510, 520: Relationship Curves

[0021] C: Isolation capacitor

[0022] C1, Ca, Cb, Cf, Cq: Capacitors

[0023] D1, Df: Diodes

[0024] GND: First reference voltage terminal

[0025] IREF: Reference Current

[0026] i B1 Bias current

[0027] i B2 Compensation current

[0028] LP1, LP2: Filters

[0029] R2, R3, R4, R5, R6, R7: Resistors

[0030] RB1, RB2, Ra, Rb, Rf, RE, Rx: Resistors

[0031] RFa: Amplified radio frequency signal

[0032] RFin: Radio frequency signal

[0033] Q3, T3, T4, T5: Transistors

[0034] QB1: Bias transistor

[0035] QB2: Compensation transistor

[0036] O1: Output terminal

[0037] Sc: Detection signal

[0038] T1: Amplifying transistor

[0039] V A Node voltage

[0040] V B Adjusting the voltage

[0041] V BT :bias

[0042] VBATT: Battery voltage terminal

[0043] VCC: First system voltage terminal

[0044] VDD: Device voltage terminal

[0045] VREF: Second reference voltage terminal Detailed Implementation

[0046] Figure 1This is a circuit diagram of a power amplifier 10 according to an embodiment of the present invention. The power amplifier 10 includes a bias circuit 100, a compensation circuit 200, and a core circuit 300. The core circuit 300 includes an amplifying transistor T1, resistors RB1 and RB2. The amplifying transistor T1 amplifies the radio frequency (RF) signal RFin to output an amplified RF signal RFa. The control terminal of the amplifying transistor T1 receives the RF signal RFin. The first terminal of the amplifying transistor T1 is coupled to the first system voltage terminal VCC to receive the first system voltage. The second terminal of the amplifying transistor is coupled to the first reference voltage terminal GND, which can be used to provide a ground voltage or other reference voltage lower than the first system voltage terminal VCC. The first terminal of the amplifying transistor T1 can be coupled to a matching circuit to output the amplified RF signal RFa or coupled to the next stage amplifier circuit. The first terminal of resistor RB1 is coupled to the output terminal of bias circuit 100, and the first terminal of resistor RB2 is coupled to the output terminal of compensation circuit 200. The second terminals of both resistors RB1 and RB2 are coupled to the control terminal of amplifying transistor T1. Resistor RB1 provides a first resistance value, and resistor RB2 provides a second resistance value. Furthermore, bias circuit 100 includes bias transistor QB1, which provides a bias current i. B1 The compensation circuit 200 includes a compensation transistor QB2, which can provide a compensation current i B2 The conduction and cutoff of the compensation transistor QB2 in the compensation circuit 200 can depend on the radio frequency signal RFin.

[0047] In some embodiments, the resistance between the control terminal of the amplifying transistor T1 and the bias transistor QB1 is greater than the resistance between the control terminal of the amplifying transistor T1 and the compensation transistor QB2. For example... Figure 1 As shown, the first resistance value of resistor RB1 is greater than the second resistance value of resistor RB2. For example, the first resistance value can be more than 100 times the second resistance value, but the present invention is not limited thereto. The ratio between the second resistance value and the first resistance value can be adjusted and optimized according to the specifications of the power amplifier 10.

[0048] In some embodiments, the first system voltage terminal VCC can provide a DC voltage, and the voltage provided by the first system voltage terminal VCC may not change with the power of the radio frequency signal RFin.

[0049] exist Figure 1In the illustrated embodiment, since the second terminals of resistors RB1 and RB2 are both coupled to the control terminal of amplifier transistor T1, resistors RB1 and RB2 are approximately connected in parallel. This makes the equivalent resistance of resistors RB1 and RB2 approximately equal to their parallel resistance, which is less than the first resistance of resistor RB1 and the second resistance of resistor RB2. In the case without compensation transistor QB2 and resistor RB2, the greater the power of the RF signal RFin, the greater the current flowing through bias transistor QB1. This causes an increase in the voltage across resistor RB1, thereby lowering node V. BT The voltage affects the operation of the amplifying transistor T1. In this embodiment, when the power of the RF signal RFin is high, both the bias transistor QB1 and the compensation transistor QB2 can be turned on, thereby providing a larger drive current. Furthermore, since the equivalent resistance formed by resistors RB1 and RB2 is small (smaller than the first resistance value of RB1 and smaller than the second resistance value of RB2), the control terminal of the power transistor T1, i.e., node V... BT The bias voltage can be kept relatively stable, thereby avoiding affecting the gain of the power amplifier 10 for the radio frequency signal RFin, and thus avoiding the decrease in the saturated output power of the power amplifier 10.

[0050] In one embodiment of the present invention, for example, when the power of the radio frequency signal RFin is a first power, the bias transistor QB1 is turned on, the compensation transistor QB2 can be turned off, and the compensation current i B2 Almost zero, bias current i B1 Greater than the compensation current i B2 When the power of the RF signal RFin increases, the conduction level of the compensation transistor QB2 can be increased to provide an appropriate compensation current i. B2 When the power of the RF signal RFin further increases to the second power, both the bias transistor QB1 and the compensation transistor QB2 are turned on. Since the first resistance of resistor RB1 is greater than the second resistance of the second resistor RB1, the bias current i B1 It can achieve a current less than the compensation current i B2 .

[0051] Figure 2 express Figure 1 The bias current i in B1 and compensation current i B2 Curves 510 and 520 show the relationship between the power amplifier 10 and its output power, respectively. In one embodiment of the present invention, when the power amplifier 10 is powered, the bias transistor QB1 can be turned on to provide a bias current i. B1When the power of the RF signal RFin is low, the compensation transistor QB2 can be turned off. When the power of the RF signal RFin is high, the output power of the power amplifier 10 can be high, and both the bias transistor QB1 and the compensation transistor QB2 can be turned on to provide bias current i respectively. B1 and compensation current i B2 Among them, the bias current i B1 The current flows through resistor RB1, and the compensation current i B2 The current flows through resistor RB2. For example... Figure 2 As shown, for example, when the output power of power amplifier 10 is less than 23dB, compensation transistor QB2 is turned off and bias transistor QB1 is turned on. At this time, the current used to drive amplifier transistor T1 is approximately equal to the bias current i. B1 When the output power of power amplifier 10 is approximately equal to or greater than 23dB, both bias transistor QB1 and compensation transistor QB2 are turned on. At this time, the current used to drive amplification transistor T1 is approximately equal to the bias current i. B1 With compensation current i B2 The sum (i.e., approximately equal to i) B1 +i B2 In this embodiment, the power amplifier 10 can operate in the back-off region, where the bias transistor QB1 is turned on and the compensation transistor QB2 is turned off. In this case, the power amplifier 10 can operate as a class-B amplifier to achieve better power-to-output (PAE). When the output power of the power amplifier 10 is high, both the bias transistor QB1 and the compensation transistor QB2 are turned on. In this case, the equivalent resistance formed by resistors RB1 and RB2 is relatively reduced, which can increase the saturation power of the power amplifier 10.

[0052] Figure 3 This is a circuit diagram of a power amplifier 30 according to an embodiment of the present invention. The power amplifier 30 includes a bias circuit 100A, a compensation circuit 200A, and a core circuit 300. The core circuit 300 and... Figure 1 The core circuit 300 has the same function and operation method, which can be referred to in the above description, and will not be repeated here. The following text further illustrates an example of the compensation circuit 200A.

[0053] like Figure 3As shown, the compensation circuit 200A includes a detection circuit 210, a voltage adjustment circuit 220A, and a compensation transistor QB2. The detection circuit 210 generates a detection signal Sc based on the radio frequency signal RFin (e.g., based on the power of the radio frequency signal RFin). In one embodiment of the invention, the detection circuit 210 includes a diode D1, the cathode of which is coupled to the input terminal of the detection circuit 210, and the anode of which is coupled to the output terminal of the detection circuit 210. In this embodiment, the diode D1 can chop the radio frequency signal RFin to generate the detection signal Sc. The detection circuit 210 may also include a capacitor C1, which can be coupled between the input terminal of the detection circuit 210 and the diode D1, or between the diode D1 and the output terminal of the detection circuit 210, to block the DC component of the radio frequency signal RFin.

[0054] like Figure 3 As shown, in one embodiment of the present invention, the input terminal of the voltage adjustment circuit 220A can be coupled to the output terminal of the detection circuit 210, and the output terminal of the voltage adjustment circuit 220A is used to output the adjustment voltage V. B This is directed to the control terminal of the compensation transistor QB2. Furthermore, based on the detection signal Sc, the voltage adjustment circuit 220A can adjust the voltage V. B Adjustments are made, and the compensation transistor QB2 adjusts according to the adjustment voltage V. B Turning off or on. For example, when compensation transistor QB2 is on, it can provide a compensation current i flowing to the control terminal of amplifier transistor T1. B2 In other words, the compensation transistor QB2 can be turned off or on based on the detection signal Sc, thereby selectively providing the compensation current i. B2 .

[0055] like Figure 3 As shown, in this embodiment, the voltage adjustment circuit 220A includes a resistor R3, a transistor T3, a resistor R4, and a transistor T4. The first terminal of resistor R3 is coupled to the second reference voltage terminal VREF, the second terminal of resistor R3 is coupled to the first terminal of transistor T3, the second terminal of transistor T3 is coupled to the first reference voltage terminal GND, and the control terminal of transistor T3 is configured to be coupled to the input terminal of the voltage adjustment circuit 220A, thereby receiving the detection signal Sc. Figure 3 As shown, the first terminal of transistor T3 can be coupled to the output terminal of voltage adjustment circuit 220A to output the adjusted voltage V. BThe first end of resistor R4 is coupled to the second reference voltage terminal VREF, and the second end of resistor R4 is coupled to the first end of transistor T4. The second end of transistor T4 is coupled to the first reference voltage terminal GND, and the control terminal of transistor T4 can be coupled to the first end of transistor T4. In other words, the second end of resistor R4, the first end of transistor T4, and the control terminal of transistor T4 can be coupled together and can be further coupled to the input terminal of voltage adjustment circuit 220A. In other embodiments, voltage adjustment circuit 220A also includes resistor R7, the first end of which can be coupled to the control terminal of transistor T4, and the second end of which can be coupled to the input terminal of voltage adjustment circuit 220A. Figure 3 As shown, the first terminal of transistor T4 and the control terminal can be coupled together via resistor R7.

[0056] like Figure 3 As shown, in one embodiment of the present invention, the voltage adjustment circuit 220A includes a filter LP1. The filter LP1 can be coupled between the input terminal of the voltage adjustment circuit 220A and the control terminal of the transistor T3. Further, the filter LP1 may include a resistor Ra and a capacitor Ca. One end of the resistor Ra is coupled to the input terminal of the voltage adjustment circuit 220A, and the other end is coupled to the control terminal of the transistor T3. One end of the capacitor Ca is coupled to the control terminal of the transistor T3, and the other end is coupled to the first reference voltage terminal GND. The voltage adjustment circuit 220A may also include a filter LP2, which may include a resistor Rb and a capacitor Cb. The filter LP2 can be coupled between the first terminal of the transistor T3 and the output terminal of the voltage adjustment circuit 220A; that is, the first terminal of the transistor T3 can be coupled to the output terminal of the voltage adjustment circuit 220A via the filter LP2. Furthermore, one end of the resistor Rb of filter LP2 can be coupled to the first terminal of transistor T3, and the other end can be coupled to the output terminal of voltage adjustment circuit 220B. One end of capacitor Cb is coupled to the other end of resistor Rb, and the other end of capacitor Cb is coupled to the first reference voltage terminal GND. In some embodiments, filter LP1 and / or filter LP2 can be low-pass filters, which allow signals with lower frequency values ​​to pass through. In the above embodiments, the capacitance value of capacitor Cb can be greater than the capacitance value of capacitor Ca. For example, the capacitance value of capacitor Ca can be 1 to 2 picofarads (1pF to 2pF), while the capacitance value of capacitor Cb can be 8 picofarads (8pF). However, the present invention is not limited thereto, and the capacitance values ​​of capacitor Ca and capacitor Cb can be adjusted according to the specifications of voltage adjustment circuit 220A.

[0057] In one embodiment of the present invention, the compensation circuit 200A may further include a compensation capacitor Cq, which is coupled between the first terminal of the compensation transistor QB2 and the first reference voltage terminal GND.

[0058] like Figure 3As shown, in one embodiment of the present invention, the first terminal of the compensation transistor QB2 can be coupled to the device voltage terminal VDD, the second terminal can be coupled to the first terminal of the resistor RB2, and the control terminal can be coupled to the output terminal of the voltage adjustment circuit 220A to receive the adjustment voltage V. B In a further embodiment, the compensation circuit 200A may further include a compensation resistor R2, with its first end coupled to the device voltage terminal VDD and its second end coupled to the first end of the compensation transistor QB2. In other embodiments, the first end of the compensation resistor R2 may also be coupled to the second reference voltage terminal VREF (e.g., ...). Figure 5 (As shown).

[0059] In some embodiments, when the power of the radio frequency signal RFin changes, the detection signal Sc generated by the detection circuit 210 changes accordingly. For example, when the power of the radio frequency signal RFin increases, due to the chopping effect of the reverse diode D1 in the detection circuit 210 on the radio frequency signal RFin, the average voltage of the detection signal Sc output by the detection circuit 210 decreases. Figure 3 As shown, after rectification by filter LP1, node V... A The voltage at the control terminal of transistor T3 decreases, thus reducing the conduction level of transistor T3. In this situation, the current flowing between the first and second terminals of transistor T3 decreases, causing the voltage difference across resistor R3 to decrease. Therefore, the voltage at the first terminal of transistor T3 increases, thereby increasing the adjustment voltage V of the voltage adjustment circuit 220A. B Increase. When adjusting voltage V B When the value increases to a value greater than the predetermined value, the compensation transistor QB2 turns on, at which point the compensation transistor QB2 can provide a compensation current i flowing to the control terminal of the amplification transistor T1. B2 .

[0060] like Figure 3 As shown, in one embodiment of the present invention, the bias circuit 100A is similar to... Figure 1The difference in the bias circuit 100 is that, in addition to the bias transistor QB1, the bias circuit 100A may also include a reference current source 110, a reference resistor Rf, diodes Df (shown as two diodes Df in the diagram), and a capacitor Cf. The reference current source 110 provides a reference current IREF. The first end of the reference resistor Rf is coupled to the reference current source IREF, and the second end is coupled to the control terminal of the bias transistor QB1. In this embodiment, there are two diodes Df, but the invention is not limited to this; the bias circuit 100A may include three or more diodes Df connected in series. The diodes Df of the bias circuit 100A are coupled between the second end of the reference resistor Rf and the first reference voltage terminal GND, used to control the bias voltage of the control terminal of the bias transistor QB1, so as to provide a bias current i from the output terminal O1 of the bias circuit 100A. B1 The capacitor Cf can be coupled between the control terminal of the bias transistor QB1 and the first reference voltage terminal GND.

[0061] Figure 4 This is a circuit diagram of the bias circuit 100B of a power amplifier according to another embodiment of the present invention. The bias circuit 100B can be used to replace... Figure 3 The bias circuit 100A is included. The bias circuit 100B includes a bias transistor QB1, a reference current source 110, and a transistor Q3. The reference current source 110 provides a reference current IREF, and its output is coupled to the control terminal of the bias transistor QB1. The first terminal of transistor Q3 is coupled to the output terminal of the reference current source 110, the second terminal is coupled to the first reference voltage terminal GND, and the control terminal is coupled to the second terminal of the bias transistor QB1 and the output terminal O1 of the bias circuit 100B. In this embodiment, the first terminal of the bias transistor QB1 can be coupled to the battery voltage terminal VBATT, and the battery voltage terminal VBATT can be used to receive the voltage provided by an external battery. In other embodiments, the first terminal of the bias transistor QB1 can also be coupled to the device voltage terminal VDD (e.g., ...). Figure 3 (As shown). In a further embodiment, the bias circuit 100B may further include a resistor Rx, the first end of which is coupled to the control terminal of transistor Q3, and the second end of which is coupled to the second terminal of bias transistor QB1. In this embodiment, the output terminal O1 of the bias circuit 100B may be coupled to resistor RB1 (as shown). Figure 3 The first end (as shown).

[0062] Figure 5This is a circuit diagram of a power amplifier 20 according to another embodiment of the present invention. The power amplifier 20 includes a bias circuit 100A, a compensation circuit 200B, and a core circuit 300. The compensation circuit 200B includes a detection circuit 210, a voltage adjustment circuit 220B, and a compensation transistor QB2. In this embodiment, the bias circuit 100A, the core circuit 300, the detection circuit 210 of the compensation circuit 200B, and the compensation transistor QB2 of the compensation circuit 200B are similar to... Figure 3 The above explanation is provided for reference and will not be repeated here. The following section further illustrates an example of the voltage adjustment circuit 220B of the compensation circuit 200B.

[0063] like Figure 5 As shown, in one embodiment of the present invention, the voltage adjustment circuit 220B includes a resistor R5, a transistor T5, and a resistor R6. The first terminal of resistor R5 is coupled to the second reference voltage terminal VREF, and the second terminal is coupled to the first terminal of transistor T5. The second terminal of transistor T5 is coupled to the first reference voltage terminal GND, and the control terminal is coupled to the input terminal of the voltage adjustment circuit 220B, thereby receiving the detection signal Sc. Figure 5 As shown, the first terminal of transistor T5 can be coupled to the output terminal of voltage adjustment circuit 220B to output the adjusted voltage V. B The first terminal of resistor R6 is coupled to the bias circuit 100A, specifically, to the second terminal of the bias transistor QB1 in the bias circuit 100A. The second terminal of resistor R6 is coupled to the input terminal of the voltage adjustment circuit 220B.

[0064] like Figure 5 As shown, in one embodiment of the present invention, the voltage adjustment circuit 220B includes filters LP1 and / or LP2. Filter LP1 is coupled between the input terminal of the voltage adjustment circuit 220A and the control terminal of transistor T5, and / or filter LP2 is coupled between the first terminal of transistor T5 and the output terminal of the voltage adjustment circuit 220B. Filters LP1 and / or LP2 can be similar to... Figure 3 Please refer to the above explanation, and it will not be repeated here.

[0065] Basically, when the voltage of the detection signal Sc increases, the conduction level of transistor T5 increases, the current flowing between the first and second terminals of transistor T5 increases, and the voltage difference across resistor R5 increases. Therefore, the voltage at the first terminal of transistor T5 decreases, thereby increasing the adjustment voltage V of the voltage adjustment circuit 220B. B Decrease. When adjusting voltage V B When the current drops below a predetermined value, compensation transistor QB2 is turned off. At this time, compensation transistor QB2 does not provide compensation current i flowing to the control terminal of amplification transistor T1. B2 When the voltage of the detection signal Sc drops, it is similar to... Figure 3 According to the relevant description, the conduction level of transistor T5 decreases, which in turn causes the adjustment voltage V to... B It should be noted that the detection signal Sc is generated by truncating the RF signal RFi through diode D1. Diode D1 cuts off the upper part of the RF signal RFi's swing; therefore, the higher the power of the RF signal RFi, the larger the swing. While the upper part of the RF signal's swing is cut off by diode D1, the lower part of the swing is also larger, which reduces the average voltage of the detection signal Sc, and the node V... A The voltage at that point therefore decreases. When the node voltage V A When the voltage drops, the conduction level of transistor T5 decreases, causing the current flowing through resistor R5 to decrease. As the current flowing through resistor R5 decreases, the voltage difference across resistor R5 also decreases, thus affecting the adjustment voltage V. B The voltage increases, causing the compensation transistor QB2 to turn on and provide the compensation current i. B2 Furthermore, the reference voltage provided by the second reference voltage terminal VREF can be adjusted according to the characteristics of the components of the voltage adjustment circuit 220B (e.g., resistance value), so that the voltage adjustment circuit 220B can adjust at node V. A When the voltage drops to a default voltage (correspondingly, adjust the voltage V), B When the value increases to a value greater than the predetermined value, the compensation transistor QB2 turns on to provide the compensation current i. B2 .

[0066] In the above embodiments, it is noteworthy that the input terminal of the detection circuit 210 is coupled to a power amplifier of the same level (e.g., using...). Figure 3 For example, the input terminal of the core circuit 300 of the power amplifier 30) receives the radio frequency signal RFin, but the present invention is not limited thereto. In other embodiments, the input terminal of the detection circuit 210 may also be coupled to the input terminal of the pre-amplifier or the power amplifier to receive the input radio frequency signal of the pre-amplifier or the power amplifier. Similarly, in other further embodiments, the input terminal of the detection circuit 210 may also be coupled to the output terminal of the power amplifier, for example, the output terminal of the same stage, the pre-amplifier, and / or the power amplifier, to receive the output radio frequency signal of the same stage, the pre-amplifier, or the power amplifier (e.g., using...). Figure 3 For example, the power amplifier 30 amplifies the radio frequency signal RFa. In this case, since the input and output radio frequency signals of the preamplifier, the same stage, or the subsequent stage power amplifier can be correlated, for example, positively correlated, the detection signal Sc generated by the detection circuit 210 can be transmitted to the voltage adjustment circuit to further control the operation of the compensation transistor QB2.

[0067] In one embodiment of the present invention, the core circuit 300 also includes an isolation capacitor C, coupled between the input terminal of the power amplifier and the control terminal of the amplifying transistor T1, to block the direct current (DC) signal in the radio frequency signal RFin. In another embodiment of the present invention, the core circuit 300 may further include a resistor RE, coupled between the second terminal of the amplifying transistor T1 and the first reference voltage terminal GND.

[0068] In other embodiments of the present invention, the resistor RB2 described above can be omitted, and the second terminal of the compensation transistor QB2 is coupled to the control terminal of the amplifying transistor T1. For example, a wire can be used instead of resistor RB2 between the second terminal of the compensation transistor QB2 and the control terminal of the amplifying transistor T1.

[0069] According to the various embodiments of the present invention described above, when the output power of the power amplifier is low, the bias transistor is turned on, while the compensation transistor is turned off. When the output power of the power amplifier is high, both the bias transistor and the compensation transistor are turned on, thereby providing a larger drive current. Because the equivalent resistance of the two resistors coupled to the bias transistor and the compensation transistor is less than the resistance of either of the two resistors, the bias voltage at the control terminal of the amplifying transistor can be kept relatively stable. Therefore, even if the power amplifier outputs a large power, the present invention can still maintain the gain of the power amplifier and maintain the stability of the power of the amplified RF signal output by the power amplifier. Embodiments of the present invention can provide good power-added efficiency.

[0070] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made within the scope of the claims of the present invention should be included within the scope of the present invention.

Claims

1. A power amplifier, characterized in that, Include: An amplifying transistor is used to amplify a radio frequency (RF) signal to output an amplified RF signal. A control terminal of the amplifying transistor receives the RF signal. A first terminal of the amplifying transistor is coupled to a first system voltage terminal, and a second terminal of the amplifying transistor is coupled to a first reference voltage terminal. The first terminal of the amplifying transistor is used to output the amplified RF signal. A first resistor has a first terminal and a second terminal for providing a first resistance value, and the second terminal of the first resistor is coupled to the control terminal of the amplifying transistor. A bias circuit includes a bias transistor, the bias circuit being coupled to the first terminal of the first resistor; A second resistor, having a first terminal and a second terminal, is used to provide a second resistance value less than the first resistance value, and the second terminal of the second resistor is coupled to the control terminal of the amplifying transistor; and A compensation circuit includes a compensation transistor, and an output terminal of the compensation circuit is coupled to a first terminal of the second resistor; When the power of the radio frequency signal is a first power, the bias transistor is turned on and the compensation transistor is turned off; and When the power of the radio frequency signal is the second power, both the bias transistor and the compensation transistor are turned on.

2. The power amplifier as described in claim 1, characterized in that, The compensation circuit further includes a compensation resistor coupled between a device voltage terminal and a first terminal of the compensation transistor.

3. The power amplifier as described in claim 1, characterized in that, The voltage at the voltage terminal of the first system does not change with the change in the power of the radio frequency signal.

4. The power amplifier as described in claim 1, characterized in that, The bias circuit provides a bias current, and the compensation circuit provides a compensation current. Wherein, when the power of the radio frequency signal is the first power, the bias current is greater than the compensation current; and When the power of the radio frequency signal is the second power, the bias current is less than the compensation current, and the second power is greater than the first power.

5. The power amplifier as described in claim 1, characterized in that, The first resistance value is more than 100 times the second resistance value.

6. The power amplifier as described in claim 1, characterized in that, The power amplifier further includes a resistor coupled between the second terminal of the amplifying transistor and the first reference voltage terminal.

7. A power amplifier, characterized in that, Include: An amplifying transistor is used to amplify a radio frequency (RF) signal to output an amplified RF signal. A control terminal of the amplifying transistor receives the RF signal. A first terminal of the amplifying transistor is coupled to a first system voltage terminal, and a second terminal of the amplifying transistor is coupled to a first reference voltage terminal. The first terminal of the amplifying transistor is used to output the amplified RF signal. A first resistor has a first terminal and a second terminal for providing a first resistance value, and the second terminal of the first resistor is coupled to the control terminal of the amplifying transistor. A bias circuit includes a bias transistor, the bias circuit being coupled to the first terminal of the first resistor; A second resistor, having a first terminal and a second terminal, is used to provide a second resistance value less than the first resistance value, and the second terminal of the second resistor is coupled to the control terminal of the amplifying transistor; and A compensation circuit includes a compensation transistor, and an output terminal of the compensation circuit is coupled to a first terminal of the second resistor; The compensation circuit further includes a detection circuit for providing a detection signal based on the power of the radio frequency signal, and the compensation transistor provides a compensation current based on the detection signal.

8. The power amplifier as described in claim 7, characterized in that, The detection circuit includes a diode, the cathode of which is coupled to an input terminal of the detection circuit, and the anode of which is coupled to an output terminal of the detection circuit.

9. The power amplifier as described in claim 8, characterized in that, The detection circuit further includes a capacitor coupled between the input terminal of the detection circuit and the diode, or coupled between the diode and the output terminal of the detection circuit.

10. The power amplifier as claimed in claim 7, characterized in that, The compensation circuit further includes a voltage adjustment circuit. An input terminal of the voltage adjustment circuit is coupled to the detection circuit, and an output terminal of the voltage adjustment circuit is used to provide an adjustment voltage to a control terminal of the compensation transistor. The voltage adjustment circuit adjusts the adjustment voltage according to the detection signal.

11. The power amplifier as claimed in claim 10, characterized in that, The compensation transistor is turned off or on according to the adjustment voltage, wherein when the compensation transistor is on, the compensation transistor provides the compensation current flowing to the control terminal of the amplifying transistor.

12. The power amplifier as claimed in claim 10, characterized in that, The voltage adjustment circuit includes: A third resistor, wherein a first terminal of the third resistor is coupled to a second reference voltage terminal; A first transistor, a first terminal of which is coupled to a second terminal of the third resistor, a second terminal of which is coupled to the first reference voltage terminal, and a control terminal of which is coupled to the input terminal of the voltage adjustment circuit; A fourth resistor, a first terminal of which is coupled to the second reference voltage terminal; A second transistor, a first terminal of which is coupled to a second terminal of the fourth resistor, a second terminal of which is coupled to the first reference voltage terminal, and a control terminal of which is coupled to the input terminal of the voltage adjustment circuit and the first terminal of the second transistor; as well as At least one filter is coupled between the input terminal of the voltage adjustment circuit and the control terminal of the first transistor, or between the first terminal of the first transistor and the output terminal of the voltage adjustment circuit, wherein the adjustment voltage increases when the voltage of the detected signal decreases.

13. The power amplifier as claimed in claim 12, characterized in that, The at least one filter includes: A first filter is coupled between the input terminal of the voltage regulation circuit and the control terminal of the first transistor; and A second filter is coupled between the first terminal of the first transistor and the output terminal of the voltage adjustment circuit.

14. The power amplifier as claimed in claim 12, characterized in that, The bias circuit further includes: A reference current source is used to provide a reference current; A reference resistor, a first end of which is coupled to the reference current source, and a second end of which is coupled to a control terminal of the bias transistor; At least one diode is coupled between the second terminal of the reference resistor and the first reference voltage terminal; as well as A capacitor is coupled between the control terminal of the bias transistor and the first reference voltage terminal.

15. The power amplifier as claimed in claim 12, characterized in that, The bias circuit further includes: A reference current source for providing a reference current, and an output terminal of the reference current source coupled to a control terminal of the bias transistor; and A third transistor, a first terminal of which is coupled to the output terminal of the reference current source, a second terminal of which is coupled to the first reference voltage terminal, and a control terminal of which is coupled to a second terminal of the bias transistor and the first terminal of the first resistor.

16. The power amplifier as claimed in claim 12, characterized in that, The voltage regulation circuit further includes: A fifth resistor is coupled between the input terminal of the voltage adjustment circuit and the control terminal of the second transistor.

17. The power amplifier as claimed in claim 10, characterized in that, The voltage adjustment circuit includes: A fifth resistor, wherein a first terminal of the fifth resistor is coupled to a second reference voltage terminal; A fifth transistor, a first terminal of which is coupled to a second terminal of the fifth resistor, a second terminal of which is coupled to a first reference voltage terminal, and a control terminal of which is coupled to the input terminal of the voltage adjustment circuit; A sixth resistor, a first terminal of which is coupled to a second terminal of the bias transistor, and a second terminal of which is coupled to the input terminal of the voltage regulation circuit; and At least one filter is coupled between the input terminal of the voltage adjustment circuit and the control terminal of the fifth transistor, or between the first terminal of the fifth transistor and the output terminal of the voltage adjustment circuit, wherein the adjustment voltage increases when the voltage of the detected signal decreases.

18. The power amplifier as claimed in claim 17, characterized in that, The at least one filter includes: A first filter is coupled between the input terminal of the voltage regulation circuit and the control terminal of the fifth transistor; and A second filter is coupled between the first terminal of the fifth transistor and the output terminal of the voltage adjustment circuit.

19. A power amplifier, characterized in that, Include: An amplifying transistor is used to amplify a radio frequency (RF) signal to output an amplified RF signal. A control terminal of the amplifying transistor receives the RF signal, a first terminal of the amplifying transistor is coupled to a first system voltage terminal, and the first terminal of the amplifying transistor is used to output the amplified RF signal. A first resistor has a first terminal and a second terminal for providing a first resistance value, and the second terminal of the first resistor is coupled to the control terminal of the amplifying transistor. A bias circuit, comprising a bias transistor coupled to a first terminal of the first resistor; and A compensation circuit includes a compensation transistor, an output terminal of the compensation circuit being coupled to the control terminal of the amplifying transistor, wherein the resistance between the control terminal of the amplifying transistor and the bias transistor is greater than the resistance between the control terminal of the amplifying transistor and the compensation transistor. When the power of the radio frequency signal is a first power, the bias transistor is turned on and the compensation transistor is turned off; and When the power of the radio frequency signal is the second power, both the bias transistor and the compensation transistor are turned on.

20. The power amplifier as claimed in claim 19, characterized in that, The power amplifier further includes a resistor coupled between a second terminal of the amplifying transistor and a first reference voltage terminal.

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