TWI601374B - Power amplifier with feedback impedance for stable output - Google Patents

Description

Power amplifier with feedback impedance to stabilize the output [Cross-Reference to Related Applications]

This application claims the benefit of U.S. Provisional Patent Application No. 61/767,125, filed on Feb. 20, 2013, and U.S. Patent Application Serial No. 13/946,912, filed on Jul. 19, 2013, and filed on July 19, 2013 Priority is claimed in PCT/US13/51403, the entire contents of each of which are hereby incorporated by reference.

The present disclosure is generally directed to power amplification systems and methods, and more particularly to power amplification systems and methods having feedback impedance to stabilize the output.

The prior art descriptions provided herein are for the purpose of illustrating the context of the disclosure. The work of the inventors herein (as for the work described in this Background section) and the manner in which it may not be suitable as a prior art description of the prior art is neither express nor implied as prior to the disclosure. technology. The present disclosure relates generally to power amplification and more particularly to power amplification with feedback impedance for stable output in a wireless communication system.

FIG. 1 depicts an example of a power amplifier (PA) 100. A power amplifier (PA) 100 is coupled to a wideband transformer 101 that includes a transformer 102 and a load 104. Power amplifier 100 can be used as part of a wireless transmitter. In one example, the signal from power amplifier 100 is coupled through transformer 102 and transmitted through the antenna.

Power amplifier 100 includes a first amplifier in a feedback loop 108a, an inductor-capacitor (LC) resonant tank 110, a second amplifier 108b, and a resistor R1. The power amplifier 100 can become unstable. Input circuit 106 provides an input signal to power amplifier 100.

The dominant pole is introduced by amplifier 108a and LC resonant tank 110. This introduces a phase shift of approximately 90[deg.] (in unity gain points) on the signal output by power amplifier 100. Again, the phase shift introduced by amplifier 108b and transformer 102 can be small, such as 30°. In order to have a stable power amplifier, the total phase shift of the power amplifier 100 should be less than 180°. Therefore, the phase shift introduced by the feedback loop should be less than 60°.

The input impedance is shown as the impedance Z_ input and in this case is the parasitic capacitance of the transistor in amplifier 108a. The parasitic capacitance is modeled as a parasitic capacitor Cp. Since the feedback impedance Z_ feedback system resistance, the resistor-capacitor combination can introduce a phase shift greater than 60°. This can cause the power amplifier 100 to be unstable and the signal to oscillate. Again, the resistor-capacitor combination can create a pole that is within the operating bandwidth of the wireless transmitter. This may change the gain characteristics of the power amplifier 100.

In a particular embodiment, the device includes an amplifier circuit. The first feedback circuit can be coupled to the amplifier circuit. The first feedback circuit can include a capacitor. The components of the first feedback circuit can be selected based on the feedback factor. The input impedance of the amplifier circuit can have the same impedance characteristics as the feedback circuit impedance of the first feedback circuit.

In a particular embodiment, the device can include a second feedback circuit coupled to the amplifier circuit. In a particular embodiment, the second feedback circuit can include a capacitor. In a particular implementation, the components of the second feedback circuit can be selected based on the feedback factor. In a particular embodiment, the input impedance of the amplifier circuit can have the same impedance characteristics as the feedback circuit impedance of the second feedback circuit.

In a particular embodiment, the device can include a first feedforward circuit coupled to the amplifier. In a particular embodiment, the first feedforward circuit can include a capacitor. In a particular embodiment, the first feedforward can be selected based on a feedforward factor The components of the road. In a particular embodiment, the input impedance of the amplifier circuit can have the same impedance characteristics as the feedforward circuit impedance of the first feedforward circuit.

In a particular embodiment, the amplifier circuitry can include a first amplifier stage configured to amplify the signal. The system can include circuitry configured to receive signals from a first amplifier stage. The system can include a second amplifier stage configured to amplify signals from the circuit. The system can include a feedback circuit coupled to the second amplifier stage. The feedback circuit can include a capacitor. The components of the feedback circuit can be selected based on the feedback factor. The input impedance of the first amplifier stage can have the same impedance characteristics as the feedback circuit impedance of the feedback circuit. The system can include a transformer configured to receive signals from a second amplifier stage.

In a particular embodiment. The system can include a feedforward circuit coupled to the amplifier circuit. In a particular implementation, the components of the feedforward circuit can be selected based on a feedforward factor. In a particular embodiment, the input impedance of the amplifier circuit can have the same impedance characteristics as the feedforward circuit impedance of the feedforward circuit. In a particular embodiment, the feedforward circuit can include a capacitor.

The detailed description and the annexed drawings are provided to provide a

[Prior technology]

100‧‧‧Power Amplifier

101‧‧‧Broadband transformer

102‧‧‧Transformers

104‧‧‧load

106‧‧‧Input circuit

108a‧‧‧First amplifier

108b‧‧‧second amplifier

110‧‧‧Resonance tank

C‧‧‧ capacitor

Cp‧‧‧ capacitor

L‧‧‧Inductors

R1‧‧‧Resistors

Z_ feedback ‧‧‧ feedback impedance

Z_ input ‧‧‧ input impedance

Vin‧‧‧Input voltage

[this invention]

200‧‧‧Power Amplifier

201‧‧‧Broadband transformer

202‧‧‧load

204‧‧‧Transformers

206‧‧‧Amplifier circuit

208‧‧‧ feedback circuit

210‧‧‧Input circuit

212‧‧‧ Common Gate

214‧‧‧second feedback circuit

216‧‧‧ Third feedback circuit

218‧‧‧ Common gate

220‧‧‧Feedback circuit

222‧‧‧ Common gate

224‧‧‧Feedback Circuit

302a‧‧‧First amplifier stage

302b‧‧‧second amplifier stage

302c‧‧‧current drive

302d‧‧‧third amplifier stage

304‧‧‧Resonance tank circuit

600‧‧‧Power Amplifier

700‧‧‧Power Amplifier

800‧‧‧Power Amplifier

900‧‧‧Power Amplifier

1000‧‧‧Power Amplifier

1100‧‧‧Power Amplifier

C‧‧‧ capacitor

C1‧‧‧ capacitor

Cin‧‧‧ capacitor

Cfb‧‧‧ capacitor

Cp‧‧‧ capacitor

Gm1‧‧‧Inductance

Gm2‧‧‧Inductance

Gm3‧‧‧Inductance

Gm4‧‧‧Inductance

L‧‧‧Inductors

L1‧‧‧Inductors

L2‧‧‧Inductors

R1‧‧‧Resistors

R2‧‧‧ resistor

Vin‧‧‧Input voltage

Z_ feedback ‧‧‧ feedback impedance

Z_Feedback_1‧‧‧Feedback impedance

Z_ feedback_2‧‧‧ feedback impedance

Z_ feedback _3‧‧‧ feedback impedance

Z_ input ‧‧‧ input impedance

Figure 1 shows an example of a power amplifier (PA).

2A shows an example of a power amplifier in accordance with one embodiment.

FIG. 2B shows a more detailed example of a power amplifier in accordance with one embodiment.

FIG. 3A illustrates an example of a power amplifier with a current input driver in accordance with one embodiment.

FIG. 3B illustrates a more detailed example of the current input driver shown in FIG. 3A in accordance with one embodiment.

4 illustrates power amplification using a voltage input driver in accordance with one embodiment An instance of the device.

FIG. 5 illustrates an example of a power amplifier using an inductor-capacitor-resistor circuit configured in series, in accordance with one embodiment.

6 illustrates an example of a power amplifier using an inductor-capacitor-resistor circuit configured in parallel, in accordance with one embodiment.

Figure 7 illustrates an example of a power amplifier using a common gate within a feedback loop, in accordance with one embodiment.

Figure 8 illustrates an example of a power amplifier using multiple feedback circuits, in accordance with one embodiment.

Figure 9 illustrates an additional example of a power amplifier using multiple feedback circuits in accordance with one embodiment.

Figure 10 illustrates an example of a power amplifier using a feedback circuit and a plurality of feedforward circuits, in accordance with one embodiment.

Figure 11 shows a more detailed example of a power amplifier using the feedback circuit shown in Figure 10 and a plurality of feedforward circuits in accordance with one embodiment.

Figure 12 depicts a simplified flow diagram of a method for amplifying a signal, in accordance with one embodiment.

This article describes the technology of a power amplifier. In the following description, numerous examples and specific details are set forth Particular embodiments as defined by the scope of the claims may include only some or all of the features in the examples or described below Other features are combined, and may include modifications and equivalents of the features and concepts described herein.

FIG. 2A depicts an example of a power amplifier (PA) 200 in accordance with one embodiment. The power amplifier 200 drives an antenna (not shown) through a wideband transformer 201, which includes a transformer 204 and a load 202. For example, power amplifier 200 amplifies the signal from input circuit 210 for wireless transmission over a broadband wireless transmitter. However, power amplifier 200 can be part of other systems.

Power amplifier 200 includes an amplifier circuit 206 and a feedback circuit 208. The feedback loop is formed from the output of amplifier circuit 206, through feedback circuit 208, and into the input of amplifier circuit 206. The total phase shift of the feedback loop should be less than a threshold, such as 180°. The threshold can be determined, wherein a phase shift above the threshold can cause the power amplifier 200 to become unstable. For example, if the phase shift is greater than 180°, the output of power amplifier 200 can oscillate. Again, the feedback circuit 208 should not generate poles within the bandwidth range, such as the operating bandwidth of the transmitter. The poles within the operating bandwidth may change the gain characteristics of the power amplifier 200.

The feedback factor β is analyzed to determine if a pole has been generated or if a non-desired phase shift is caused. The feedback factor β is defined as: The Z_ input is the input impedance of the input node between the amplifier circuit 206 and the input circuit 210 and the feedback impedance of the Z_feedback feedback circuit 208. As will be described in more detail below, in a particular embodiment, the impedance Z_feedback has the same impedance characteristics as the impedance Z_ input. For example, impedance Z_feedback is equivalent to capacitance and impedance Z_ input is equivalent to capacitance. By having the same impedance characteristics, the poles can be generated by the feedback loop. Again, the phase shift caused by the feedback loop is less than the threshold at which the power amplifier 100 may become unstable. For example, when combined with the phase shift of amplifier circuit 206, the phase shift (or no phase shift) caused by feedback circuit 208 is less than a threshold of, for example, 180 degrees.

FIG. 2B depicts a more detailed example of power amplifier 200 in accordance with one embodiment. The amplifier circuit 206 includes a first amplifier 302a, a resonant tank circuit 304, and a second amplifier 302b. The resonant tank circuit 304 includes an inductor L1 and a capacitor C1. Other examples of resonant tanks can also be used. The transformer 204 and the load 202 are also included in the broadband transformer 201. The feedback circuit 208 includes a capacitor Cfb. The parasitic capacitance of the first amplifier 302a is modeled by the capacitor Cp.

The first amplifier 302a and the resonant tank circuit 304 can have a high quality factor (Q). For example, the quality factor can be greater than 10. The second amplifier 302b and the transformer 204 can have a low quality factor. For example, the quality factor of amplifier 302b and transformer 204 is lower than the quality factor of amplifier 302a and resonant tank circuit 304. The lower Q of amplifier 302b and transformer 204 allows power amplifier 200 to have a higher loop gain while the loop is still stable. Again, the higher Q of amplifier 302a means that a higher loop gain can be achieved while still stabilizing the loop. Again, in one embodiment, a low impedance coupling to the transformer 204 and the antenna is required. The amplifier 302b portion provides a low impedance due to a low quality factor.

Amplifier 302a and resonant tank circuit 304 provide a dominant pole in the frequency response of power amplifier 200. Amplifier 302b and transformer 204 provide another pole that is less dominant. When described herein, amplifier 302a can be described as introducing a dominant pole and amplifier 302b is described as introducing another pole. It will be appreciated that the poles may be introduced by a combination of amplifier 302a and resonant tank circuit 304 or a combination of amplifier 302b and the inductor of transformer 204. Other combinations can also be used to amplify the signal.

Amplifier 302a also introduces a larger phase shift than the phase shift introduced by amplifier 302b. For example, the phase shift of amplifier 302a can be about 90°. The second pole introduced by amplifier 302b may not be dominant. Since the frequency response is not sufficiently significant, the phase shift introduced by amplifier 302b can be about 30°.

In one embodiment, the total phase shift of power amplifier 200 should be less than a threshold to have a stable amplifier with the desired gain. For example, the total phase shift can be less than 180°. Thus, if the phase shift of amplifier 302a is 90° and the phase shift of amplifier 302b is 30°, feedback circuit 208 can result in a phase shift of less than 60°.

The phase shift of the feedback circuit 208 can be determined based on the feedback factor β . The feedback factor β can be as follows:

The feedback factor does not cause any phase shift in the signal. This is because the impedance Z_feedback and the Z_ input have the same impedance characteristics, and the resistor-capacitor circuit is not introduced in the feedback circuit 208. In contrast, the impedance characteristic of the feedback circuit 208 is the capacitor Cfb and the impedance characteristic of the Z_ input is the capacitor Cp. This does not introduce poles and phase shifts by the feedback factor.

The closed loop gain can be different based on the input circuit 210. Different input circuits 210 will be described below.

FIG. 3A depicts an example of a power amplifier 200 having a current input driver in accordance with one embodiment. Input circuit 210 includes a third amplifier 302c. In one embodiment, the third amplifier 302c includes a transconductance of Gm3. The first amplifier 302a includes the transconductance of Gm1 and the second amplifier 302b includes the transconductance of Gm2. The amplifiers 302a-302c can be transconductance amplifiers (Gm amplifiers) that output current proportional to the input voltage. The loop gain of the power amplifier 200 is: loop_gain=A(jω)* The β feedback factor is: As discussed above, the feedback factor β does not introduce a phase shift or pole. The closed loop gain can be as follows:

FIG. 3B illustrates a more detailed example of the current input driver shown in FIG. 3A, in accordance with one embodiment. As shown, input circuit 210 includes electricity Container Cin and transistor T. In one example, the transistor T is a bipolar junction transistor (BJT), although other types of transistors can be used.

The closed loop gain is a function of the transconductance Gm3 and frequency of the transistor T. A particular embodiment makes Gm3 a function of capacitance Cin. For example, Gm3 can be Vin/(the impedance of Cin). In this case, the closed loop gain can be equal to:

In the above case, when the capacitance of the capacitor Cp is changed, the closed loop gain can be affected. A voltage input driver can be used to maximize loop gain.

4 depicts an example of a power amplifier 200 that uses a voltage input driver in accordance with one embodiment. Input circuit 210 can include a capacitor Cin. In this case, Cp is kept small enough that the capacitor Cin is larger than the capacitor Cp (for example, Cin>>Cp). In this case, the feedback factor β is maximized and a higher loop gain for the closed loop gain is achieved.

The loop gain is: loop_gain=A(jω)* β. The feedback factor is: Where Cin>>Cp, the closed loop gain can be as follows:

Also, in this case, the feedback factor β does not introduce a phase shift or a pole.

FIG. 5 illustrates an additional example of a power amplifier 200 using an inductor-capacitor-resistor circuit configured in series, in accordance with one embodiment. As shown, the feedback circuit 208 includes an inductor L2, a capacitor Cfb, and a resistor R2 arranged in series. Input circuit 210 includes resistors R1, which are arranged in series Sensor L1 and capacitor Cin.

The loop gain is: loop_gain=A(jω)* β. The feedback factor is: The closed loop gain can be as follows:

The closed loop gain is the factor of resistors R2 and R1. This is because the feedback factor β is not a function of frequency because the inductor L and the capacitor C cancel each other if Cp is small. Thus, the closed loop gain is a function of the ratio of resistor R2 to resistor R1. The feedback factor also does not introduce phase shifts or poles.

Using a conventional power amplifier, the linear performance of power amplifier 200 can be about 27 dB gain. A particular embodiment provides a 30 dB loop gain resulting in a 3 dB improvement due to the feedback circuit 208 not adding a pole in the frequency response. The gain is also more linear because changes in gain result in greater linear performance variations.

In one example, the following can be used to determine Gm1 and Gm2 for the highest loop gain. The quality factor Q1 is the figure of merit of the amplifier 302a and the resonant tank circuit 304. The quality factor Q2 is the quality factor of the amplifier 302b and the transformer 204. For amplifier 302a, resonant phase circuit 304 impedance is a function of L when the phase shift is a unique function of resonant tank circuit 304 Q1, and when quality factor Q1 is fixed. For amplifier 302b, the phase shift is a function of the quality factor Q2 of transformer 204 and the impedance is a function of the resistance seen by transformer 204. Therefore, for a power amplifier 200 having a phase margin of 60 decibels, the following equation is found: Gm 1 * Z 1( jω , Q 1, L )* Gm 2 * Z 2( jω , Q 2,6 Ω)* β * α = 1 phase Z 1 ( jω , Q 1) + phase Z 2 ( jω , Q 2) = 120 dB where Z1 is the impedance of the resonant tank 302 and Z2 is the impedance of the transformer 204. α is also a variable based on the capacitance of the resonant tank 302. Also known as: This means that the impedance of amplifier 200 is less than 6.25 Ω. The maximum loop gain for the 60 phase margin is: loop gain = Gm 1 * Z 1 (2 GHz , Q 1, L ) * Gm 2 * Z 2 (6.25 Ω) * β * α Select Gm1 and Gm2 based on the above equation. For a particular phase margin, the highest loop gain is a function of Q1.

FIG. 6 illustrates an additional example of a power amplifier 600 that uses an inductor-capacitor-resistor circuit configured in parallel, in accordance with one embodiment. As shown, the feedback loop 208 includes an inductor L2, a capacitor Cfb, and a resistor R2 arranged in parallel. The input circuit 210 also includes a resistor R1, an inductor L1, and a capacitor Cin arranged in parallel. Configuring the inductor L1, capacitor Cin, and resistor R1 in parallel reduces the load on the driver circuit (such as current driver Gm3) and provides improved performance for RF implementation. As in Figures 1 to 5, the feedback factor can be calculated for use in Figure 6. The feedback factor can be used to select the components of the feedback circuit 208 and the input circuit 210 such that the feedback circuit 208 and the input circuit 210 have the same impedance characteristics. Any components of feedback circuit 208 and input circuit 210 can be selected such that the impedance characteristics of the feedback circuit are the same as the impedance characteristics of the input circuit. For example, the feedback circuit and the input circuit can include a capacitor.

7 shows an example of a power amplifier 700 that includes an input circuit 210, a feedback circuit 208, an amplifier circuit 206, a bandwidth transformer 201, and a common gate 212, which may be part of the amplifier circuit 206 or separately coupled to the amplifier Circuit 206. The amplifier circuit 206 can include a common gate 212, a first amplifier stage 302a having a transconductance Gm1, a resonant tank circuit 304, and a second amplifier stage 302b having a transconductance Gm2. The broadband transformer 201 can drive an antenna and includes a transformer 204 and a load 202. The common gate 212 can be located within the feedback loop to spread the bandwidth of the signal. The common gate 212 can have low impedance and thus can Can not affect the impedance characteristics of the circuit. The common gate 212 can also be used as a current buffer between any of the amplifier stages. As discussed with respect to FIG. 6, components of input circuit 210 and feedback circuit 208 may be selected based on feedback factors calculated for power amplifier circuits (eg, 600, 700). These components can be selected in any manner such that the feedback factor indicates that the input circuit 210 and the feedback circuit 208 have the same impedance characteristics.

FIG. 8 shows an example of a power amplifier 800 that includes multiple feedback circuits. The power amplifier 800 includes an input circuit 210, a first feedback circuit 208, a second feedback circuit 214, a first amplifier stage 302a having an inductance value Gm1, a second amplifier stage 302b having an inductance value Gm2, and a broadband transformer 201. The first amplifier stage 302a can be coupled to the second amplifier stage 302b. Power amplifier 800 can also include a common gate 212. In one embodiment, the first feedback circuit 208 can be coupled to an amplifier circuit including a second feedback circuit 214 coupled as in FIG. 8, a first amplifier stage 302a, and a second amplifier stage 302b. The first feedback circuit 208 has a feedback impedance of Z_feedback_1, and the second feedback circuit 214 has a feedback impedance of Z_feedback_2. Multiple feedback circuits save physical space in the power amplifier design. For example, multiple feedback circuits can be included to replace the resonant tank circuit in the amplifier circuit. In addition, adding another feedback circuit expands the bandwidth and increases the signal gain. However, additional feedback circuits can reduce the stability of the circuit and/or increase the phase shift of the signal. The feedback circuit can be connected to different locations along amplifier stages 302a-c and a common gate. For example, the first feedback circuit 208 can be coupled from the output of the second amplifier stage 302b to the input of the common gate 212. As discussed with respect to Figures 6 and 7, the components of input circuit 210 and feedback circuits 208, 214 are selected based on feedback factors calculated for power amplifier circuits (e.g., 600, 700, 800). These components can be selected in any manner such that the feedback factor indicates that the input circuit 210 and the first feedback circuit 208 have the same impedance characteristics.

FIG. 9 shows an example of a power amplifier 900 similar to the power amplifier 800 shown in FIG. Power amplifier 900 can include a third feedback circuit 216 in addition to the functions and features of power amplifier 800. The power amplifier 900 includes an input circuit 210, a common gate 212, a first amplifier stage 302a, The second amplifier stage 302b, the third amplifier stage 302c, the first feedback circuit 208, the second feedback circuit 214, and the third feedback circuit 216. The first feedback circuit 208 has a feedback impedance of Z_feedback_1. The second feedback circuit 214 has a feedback impedance of Z_feedback_2. The feedback circuit 216 has a feedback impedance of Z_feedback_3. Adding a third feedback circuit 216 to the power amplifier 800 shown in Figure 9 can be used to further spread the bandwidth and increase the gain of the signal. The feedback circuit can be connected to different locations along amplifier stages 302a-c and a common gate. For example, the first feedback circuit 208 can be coupled from the output of the third amplifier stage 302c to the input of the common gate 212. The first feedback circuit 208 can be coupled to an amplifier circuit including a second feedback circuit 214, a third feedback circuit 216, a first amplifier stage 302a, a second amplifier stage 302b, and a third amplifier stage 302d coupled as in FIG. The second feedback circuit 214 can be coupled from the output of the first amplifier stage 302a to the input of the first amplifier stage 302a. The third feedback circuit 216 can be coupled from the output of the second amplifier stage 302b to the input of the first amplifier stage 302a.

To address the reduction in stability caused by the additional feedback circuit, one or more feedforward circuits can be added to the power amplifier. FIG. 10 shows an example of a power amplifier 1000 that includes a feedback circuit 208 and feedforward circuits 220, 224. In particular, power amplifier 1000 includes an input circuit 210 having an input impedance Z_ input, a first amplifier stage 302a having a transconductance Gm1, a resonant tank circuit 304, a second amplifier stage 302b having a transconductance Gm2, having a Z_feedback The feedback impedance feedback circuit 208, the first feedforward circuit 220, the second feedforward circuit 224, and the broadband transformer 201. The common gates 218, 222 can be included as part of the feedforward circuits 220, 224, or external to the feedforward circuits 220, 224. The feedback circuit 208 can include a plurality of feedback circuits similar to the circuits shown in Figures 8 and 9. Each of the feedback circuits of power amplifier 1000 (e.g., 208 and/or a feedback circuit (not shown) included in 208) can have the same performance as each of the feedback circuits (e.g., 220, 224) in power amplifier 1000. Impedance characteristics. Each of the one or more feedback circuits of the power amplifier 1000 and each of the one or more feedforward circuits may be selected based on a feedforward factor such that the feedback circuit has the same impedance characteristics as the feedforward circuit. These components can include capacitors, inductors, One or more of a resistor and any other suitable component. In one example, components in one or more of the feedback circuits 208 within the power amplifier 1000 can include capacitors. Additionally, components in one or more of the feedforward circuits 220, 224 within the power amplifier 1000 can also include capacitors. Input circuit 210, feedback circuit 208, and components of one or more feedforward circuits 220, 224 may be selected based on the calculated parameters. For example, the calculated parameter can be a feedback factor. The feedback factor can be calculated using the impedance characteristics of the input circuit 210, the feedback circuit 208, and/or the feedforward circuits 220, 224. For example, the feedback factor may indicate that the impedance characteristic of the feedback circuit 208 is the same as the impedance characteristic of the input circuit 210. In another example, the calculated parameter can be a feed forward factor. The feed forward factor can calculate the impedance characteristics of the input circuit 210, the feedback circuit 208, and/or the feedforward circuits 220, 224. For example, the feed forward factor may indicate that the impedance characteristics of the feedforward circuits 220, 224 are the same as the impedance characteristics of the input circuit 210, and may also be the same as the impedance characteristics of the feedback circuit 208.

The feedforward circuit introduces zero in the frequency response of the power amplifier. Introducing zero to the frequency response improves the phase margin and overall stability of the amplifier. Feedforward circuits 220, 224 can be connected to different locations along the amplifier circuit. For example, feedforward circuit 220 can be coupled from an input circuit to an input of resonant tank circuit 304. Feedforward circuit 224 can be coupled from input circuit 210 to the input of second amplifier stage 302b.

Figure 11 shows a more detailed embodiment of a power amplifier 1100 comprising both a feedback circuit and a feedforward circuit. Input circuit 210 can include current driver 302c, a resonant tank, or both. As discussed with respect to FIG. 10, feedback circuit 208 and feedforward circuits 220, 224 can include capacitors, resonant tank circuits, or any other suitable components that can be selected based on the calculated parameters.

FIG. 12 depicts a simplified flowchart 1200 of a method for amplifying a signal, in accordance with one embodiment. At 1202, the signals are coupled through input circuit 210. At 1204, the signal is amplified by amplifier 302a. At 1206, the signals are coupled through a resonant tank circuit 304. Amplifier 302a and resonant tank circuit 304 introduce a phase shift into the signal.

At 1208, the signal is amplified by amplifier 302b. At 1210, Signals are coupled through transformer 204 for wireless transmission. Amplifier 302a and transformer 204 introduce a second phase shift into the signal.

At 1210, the signals are coupled through feedback circuit 208. The feedback circuit 208 includes a capacitor and does not introduce a phase shift into the signal or introduces a phase shift if the total phase shift is less than a threshold for stable operation.

At 1212, the signals are coupled through one or more feedforward circuits 220, 224. Each feedforward circuit 220, 224 may include a capacitor and will not introduce a phase shift into the signal or introduce a phase shift if the total phase shift is less than a threshold for stable operation. Each feedforward circuit can include a resonant tank. Each feedforward circuit can include a common gate. Each feedforward circuit can include a high frequency wide circuit or a low frequency wide circuit. The components of the feedforward circuit can be selected based on the feedforward factor. The input impedance of the amplifier circuit can have the same impedance characteristics as the feedforward circuit impedance of the feedforward circuit.

The process 1200 of Figure 12 is merely illustrative. Any of the steps in the program 1200 can be modified (e.g., performed in a different order), combined or removed, and any additional steps can be added to the program 1200 without departing from the scope of the present disclosure.

Thus, certain embodiments use capacitors or inductor-capacitor-resistor feedback circuits. This results in a minimum phase shift in the feedback circuit 208 and a non-oscillating and stable power amplifier gain output. The phase shift of the entire loop is less than 180°, which means that the power amplifier 200 is stable.

&quot;an&quot; and &quot;the&quot; are used in the <RTIgt; </ RTI> <RTIgt; </ RTI> <RTIgt; And &quot;in,&quot; and &quot;in,&quot;

The above description illustrates various embodiments of the invention and examples of how the aspects of the invention can be implemented. The above examples and embodiments are to be considered in all respects as illustrative and illustrative of the nature of the invention as claimed. Based on the above disclosure and the following patent application Other configurations, embodiments, embodiments, and equivalents may be used without departing from the scope of the invention as defined by the scope of the claims.

200‧‧‧Power Amplifier

201‧‧‧Broadband transformer

202‧‧‧load

204‧‧‧Transformers

206‧‧‧Amplifier circuit

208‧‧‧ feedback circuit

210‧‧‧Input circuit

Cp‧‧‧ capacitor

Vin‧‧‧Input voltage

Z_ feedback ‧‧‧ feedback impedance

Z_ input ‧‧‧ input impedance

Claims (23)

An apparatus having a feedback amplifier for stabilizing an output power amplifier, comprising: an amplifier circuit; a first feedback circuit coupled to the amplifier circuit, the first feedback circuit comprising a capacitor; and a second feedback circuit Connected to the amplifier circuit, wherein: the component of the first feedback circuit is selected based on a feedback factor, and one of the input impedances of the amplifier circuit has an impedance characteristic that is the same as a feedback circuit impedance of the first feedback circuit. The device of claim 1, wherein the amplifier circuit comprises a common gate. The device of claim 1, wherein the second feedback circuit comprises a capacitor. The apparatus of claim 1, wherein the component of the second feedback circuit is selected based on the feedback factor. The device of claim 1, wherein the input impedance of one of the amplifier circuits has the same impedance characteristic as the feedback circuit of one of the second feedback circuits. The apparatus of claim 1, further comprising a first feedforward circuit coupled to the amplifier circuit. The device of claim 6, wherein the first feedforward circuit comprises a capacitor. The device of claim 6, wherein the first feedforward circuit is a low frequency wide circuit or a high frequency wide circuit. The apparatus of claim 6, wherein the component of the first feedforward circuit is selected based on a feedforward factor. The device of claim 9, wherein the input impedance of one of the amplifier circuits has one of the same impedance characteristics as the feedforward circuit impedance of one of the first feedforward circuits. The device of claim 6 further comprising a second feedforward circuit coupled to one of the amplifier circuits at a second location. The device of claim 11, wherein the second feedforward circuit comprises a capacitor. The device of claim 11, wherein the second feedforward circuit comprises a common gate. The device of claim 11, wherein the second feedforward circuit comprises a resonant tank circuit. An amplifier circuit system comprising: a first amplifier stage configured to amplify a signal; a circuit configured to receive a signal from the first amplifier stage; a second amplifier stage grouped State to amplify the signal from the circuit; a feedback circuit coupled to the second amplifier stage, the feedback circuit including a capacitor; and a second feedback circuit coupled to the first amplifier stage, wherein: Selecting a component of the feedback circuit based on a feedback factor, and One of the input impedances of the first amplifier stage has one of the same impedance characteristics as the feedback circuit of one of the feedback circuits; and a transformer configured to receive the signal from the second amplifier stage. A system of claim 15 further comprising a feedforward circuit coupled to one of the amplifier circuits. The system of claim 16 wherein the component of the feedforward circuit is selected based on a feedforward factor. The system of claim 16 wherein the input impedance of the first amplifier stage has one of the same impedance characteristics as the feedforward circuit impedance of one of the feedforward circuits. The system of claim 15 wherein the feedforward circuit comprises a capacitor. A method of a power amplifier having a feedback impedance for stabilizing an output, comprising: amplifying a signal through an amplifier circuit; coupling the signal through a feedback circuit; and connecting to the amplifier circuit via a second feedback circuit, wherein: The feedback factor selects a component of the feedback circuit, one of the input impedances of the amplifier circuit having one of the same impedance characteristics as the feedback circuit of one of the feedback circuits, and the feedback circuit includes a capacitor. The method of claim 20, further comprising coupling the signal through a feedforward circuit. The method of claim 21, wherein the component of the feedforward circuit is selected based on a feedforward factor. The method of claim 22, wherein the input impedance of the amplifier circuit has one of the same impedance characteristics as the feedforward circuit impedance of one of the feedforward circuits.