Classifications

• • H—ELECTRICITY
  • H03—ELECTRONIC CIRCUITRY
  • H03F—AMPLIFIERS
  • H03F1/00—Details of amplifiers with only discharge tubes, only semiconductor devices or only unspecified devices as amplifying elements
  • H03F1/08—Modifications of amplifiers to reduce detrimental influences of internal impedances of amplifying elements
  • H03F1/083—Modifications of amplifiers to reduce detrimental influences of internal impedances of amplifying elements in transistor amplifiers
• • H—ELECTRICITY
  • H03—ELECTRONIC CIRCUITRY
  • H03F—AMPLIFIERS
  • H03F1/00—Details of amplifiers with only discharge tubes, only semiconductor devices or only unspecified devices as amplifying elements
  • H03F1/34—Negative-feedback-circuit arrangements with or without positive feedback
• • H—ELECTRICITY
  • H03—ELECTRONIC CIRCUITRY
  • H03F—AMPLIFIERS
  • H03F1/00—Details of amplifiers with only discharge tubes, only semiconductor devices or only unspecified devices as amplifying elements
  • H03F1/56—Modifications of input or output impedances, not otherwise provided for
• • H—ELECTRICITY
  • H03—ELECTRONIC CIRCUITRY
  • H03F—AMPLIFIERS
  • H03F3/00—Amplifiers with only discharge tubes or only semiconductor devices as amplifying elements
  • H03F3/189—High-frequency amplifiers, e.g. radio frequency amplifiers
  • H03F3/19—High-frequency amplifiers, e.g. radio frequency amplifiers with semiconductor devices only
  • H03F3/193—High-frequency amplifiers, e.g. radio frequency amplifiers with semiconductor devices only with field-effect devices
• • H—ELECTRICITY
  • H03—ELECTRONIC CIRCUITRY
  • H03F—AMPLIFIERS
  • H03F3/00—Amplifiers with only discharge tubes or only semiconductor devices as amplifying elements
  • H03F3/20—Power amplifiers, e.g. Class B amplifiers, Class C amplifiers
  • H03F3/24—Power amplifiers, e.g. Class B amplifiers, Class C amplifiers of transmitter output stages
  • H03F3/245—Power amplifiers, e.g. Class B amplifiers, Class C amplifiers of transmitter output stages with semiconductor devices only
• • H—ELECTRICITY
  • H03—ELECTRONIC CIRCUITRY
  • H03F—AMPLIFIERS
  • H03F2200/00—Indexing scheme relating to amplifiers
  • H03F2200/121—A transistor in common gate configuration being used in a feedback circuit of an amplifier stage
• • H—ELECTRICITY
  • H03—ELECTRONIC CIRCUITRY
  • H03F—AMPLIFIERS
  • H03F2200/00—Indexing scheme relating to amplifiers
  • H03F2200/138—Indexing scheme relating to amplifiers the feedback circuit comprising a parallel resonance circuit
• • H—ELECTRICITY
  • H03—ELECTRONIC CIRCUITRY
  • H03F—AMPLIFIERS
  • H03F2200/00—Indexing scheme relating to amplifiers
  • H03F2200/147—Indexing scheme relating to amplifiers the feedback circuit comprising a series resonance circuit
• • H—ELECTRICITY
  • H03—ELECTRONIC CIRCUITRY
  • H03F—AMPLIFIERS
  • H03F2200/00—Indexing scheme relating to amplifiers
  • H03F2200/153—Feedback used to stabilise the amplifier
• • H—ELECTRICITY
  • H03—ELECTRONIC CIRCUITRY
  • H03F—AMPLIFIERS
  • H03F2200/00—Indexing scheme relating to amplifiers
  • H03F2200/168—Two amplifying stages are coupled by means of a filter circuit
• • H—ELECTRICITY
  • H03—ELECTRONIC CIRCUITRY
  • H03F—AMPLIFIERS
  • H03F2200/00—Indexing scheme relating to amplifiers
  • H03F2200/541—Transformer coupled at the output of an amplifier

Definitions

• the present disclosure relates generally to power amplification systems and methods, and, more particularly, to systems and methods for power amplification with feedback impedance for stable output.
• the background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the inventors hereof, to the extent the work is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
• the present disclosure relates generally to power amplification, and, more particularly, to power amplification with feedback impedance for stable output in wireless communication systems.
• Fig. 1 depicts an example of a power amplifier (PA) 100.
• Power amplifier (PA) 100 is coupled to a wideband transformer 101 that includes a transformer 102 and a load 104.
• Power amplifier 100 may be part of a wireless transmitter.
• a signal from power amplifier 100 is coupled through transformer 102 and transmitted through an antenna.
• Power amplifier 100 includes a first amplifier 108a, an inductor-capacitor (LC) resonant tank 110, a second amplifier 108b, and a resistor Rl in a feedback loop. Power amplifier 100 may become unstable. An input circuit 106 provides an input signal to power amplifier 100.
• LC inductor-capacitor
• a dominant pole is introduced by amplifier 108a and LC resonant tank 110. This introduces a phase shift of around 90° (at a unity gain point) at the signal output by power amplifier 100. Also, a phase shift introduced by amplifier 108b and transformer 102 may be less, such as 30°. To have a stable power amplifier, a total phase shift for power amplifier 100 should be less than 180°. Thus, a phase shift introduced by the feedback loop should be less than 60°.
• the input impedance is shown as impedance Z input and in this case, is a parasitic capacitance of a transistor in amplifier 108a.
• the parasitic capacitance is modeled as a parasitic capacitor Cp.
• the resistor-capacitor combination may introduce a phase shift that is greater than 60°. This may cause power amplifier 100 to be unstable and the signal may oscillate. Also, the resistor-capacitor combination may create a pole that is within the working bandwidth of the wireless transmitter. This may alter the gain characteristics for power amplifier 100.
• an apparatus includes an amplifier circuit.
• a first feedback circuit may be coupled to the amplifier circuit.
• the first feedback circuit may include a capacitor. Components of the first feedback circuit may be selected based on a feedback factor.
• An input impedance to the amplifier circuit may have a same impedance characteristic as a feedback circuit impedance of the first feedback circuit.
• the apparatus may include a second feedback circuit connected to the amplifier circuit.
• the second feedback circuit may include a capacitor.
• components of the second feedback circuit may be selected based on the feedback factor.
• an input impedance to the amplifier circuit may have a same impedance characteristic as a feedback circuit impedance of the second feedback circuit
• the apparatus may include a first feedforward circuit connected to the amplifier.
• the first feedforward circuit may comprise a capacitor.
• components of the first feedforward circuit may be selected based on a feedforward factor.
• an input impedance to the amplifier circuit may have a same impedance characteristic as a feedforward circuit impedance of the first feedforward circuit.
• an amplifier circuit system may include a first amplifier stage configured to amplify a signal.
• the system may include a circuit configured to receive the signal from the first amplifier stage.
• the system may include a second amplifier stage configured to amplify the signal from the circuit.
• the system may include a feedback circuit coupled to the second amplifier stage.
• the feedback circuit may comprise a capacitor. Components of the feedback circuit may be selected based on a feedback factor.
• An input impedance to the first amplifier stage may have a same impedance characteristic as a feedback circuit impedance of the feedback circuit.
• the system may include a transformer configured to receive the signal from the second amplifier stage.
• the system may include a feedforward circuit coupled to the amplifier circuit.
• components of the feedforward circuit may be selected based on a feedforward factor.
• an input impedance to the amplifier circuit may have a same impedance characteristic as a feedforward circuit impedance of the feedforward circuit.
• the feedforward circuit may include a capacitor.
• Fig. 1 shows an example of a power amplifier (PA).
• PA power amplifier
• Fig. 2A shows an example of a power amplifier according to one embodiment.
• Fig. 2B shows a more detailed example of the power amplifier according to one embodiment.
• Fig. 3A shows an example of a power amplifier with a current input driver according to one embodiment.
• Fig. 3B shows a more detailed example of the current input driver shown in Fig. 3A according to one embodiment.
• Fig. 4 shows an example of a power amplifier using a voltage input driver according to one embodiment.
• Fig. 5 shows an example of a power amplifier using an inductor-capacitor- resistor circuit arranged in series according to one embodiment.
• Fig. 6 shows an example of a power amplifier using an inductor-capacitor- resistor circuit arranged in parallel according to one embodiment.
• Fig. 7 shows an example of a power amplifier using a common gate within a feedback loop according to one embodiment.
• Fig. 8 shows an example of a power amplifier using multiple feedback circuits according to one embodiment.
• Fig. 9 shows an additional example of a power amplifier using multiple feedback circuits according to one embodiment.
• Fig. 10 shows an example of a power amplifier using a feedback circuit and multiple feedforward circuits according to one embodiment.
• Fig. 11 shows a more detailed example of the power amplifier using a feedback circuit and multiple feedforward circuits shown in Fig. 10 according to one embodiment.
• Fig. 12 depicts a simplified flowchart of a method for amplifying a signal according to one embodiment.
• Fig. 2A depicts an example of a power amplifier (PA) 200 according to one embodiment.
• Power amplifier 200 drives an antenna (not shown) through a wideband transformer 201, which includes a transformer 204 and a load 202.
• PA power amplifier
• a wideband transformer 201 which includes a transformer 204 and a load 202.
• power amplifier 200 amplifies a signal from an input circuit 210 for wireless transmission through a wideband wireless transmitter.
• power amplifier 200 may be part of other systems.
• Power amplifier 200 includes an amplifier circuit 206 and a feedback circuit 208.
• a feedback loop is formed from an output of amplifier circuit 206, through feedback circuit 208, and into an input of amplifier circuit 206.
• the total phase shift of the feedback loop should be less than a threshold, such as 180°.
• the threshold may be determined where a phase shift above the threshold may cause power amplifier 200 to become unstable. For example, the output of power amplifier 200 may oscillate if the phase shift is greater than 180°.
• feedback circuit 208 should not create a pole within a bandwidth range, such as the working bandwidth of the transmitter. A pole within the working bandwidth might change the gain characteristics of power amplifier 200.
• a feedback factor ⁇ is analyzed to determine if a pole is created or an undesirable amount of phase shift is caused.
• the feedback factor ⁇ is defined as: ⁇ _ Z _ input
• Z input is the input impedance looking into an input node between amplifier circuit 206 and input circuit 210 and Z feedback is the feedback impedance of feedback circuit 208.
• the impedance Z feedback has the same impedance characteristic as the impedance Z input.
• the impedance Z feedback is equivalent to a capacitance and the impedance Z input is equivalent to a capacitance.
• a pole may not be created by the feedback loop.
• the phase shift caused by the feedback loop is less than the threshold in which power amplifier 100 may become unstable.
• Fig. 2B depicts a more detailed example of power amplifier 200 according to one embodiment.
• Amplifier circuit 206 includes a first amplifier 302a, a resonant tank circuit 304 and a second amplifier 302b.
• Resonant tank circuit 304 includes an inductor LI and a capacitor CI . Other examples of resonant tanks may also be used.
• Transformer 204 and load 202 are also included in wideband transformer 201.
• Feedback circuit 208 includes a capacitor Cfb.
• a parasitic capacitance of first amplifier 302a is modeled by a capacitor Cp.
• First amplifier 302a and resonant tank circuit 304 may have a high quality factor (Q).
• the quality factor may be greater than 10.
• Second amplifier 302b and transformer 204 may have a low quality factor.
• 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.
• the higher the Q of amplifier 302a means the higher loop gain can be achieved while still having the loop be stable.
• Amplifier 302b provides the low impedance in part because of the 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.
• amplifier 302a may be described as introducing the dominant pole and amplifier 302b as introducing another pole.
• the poles may be introduced by a combination of amplifier 302a with resonant tank circuit 304 or amplifier 302b with an inductor of transformer 204. Other combinations may also be used to amplify the signal.
• Amplifier 302a also introduces a larger phase shift than introduced by amplifier 302b. For example, the phase shift of amplifier 302a may be around 90°. The second pole introduced by amplifier 302b might not be dominant. Due to a frequency response that is not as sharp, the phase shift introduced by amplifier 302b may be around 30°.
• the total phase shift of power amplifier 200 should be less than a threshold to have a stable amplifier with the gain desired.
• a total phase shift may be less than 180°.
• the feedback circuit 208 should cause less than a 60° phase shift if the phase shift for amplifier 302a is 90° and the phase shift for amplifier 302b is 30°.
• the phase shift of feedback circuit 208 may be determined based on the feedback factor, ⁇ .
• the feedback factor ⁇ may be as follows:
• the feedback factor does not cause any phase shift in the signal. This is because the impedances Z feedback and Z input have the same impedance
• the impedance characteristic of feedback circuit 208 is capacitor Cfb and the impedance characteristic of Z input is capacitor Cp. This does not introduce a pole and a phase shift by the feedback factor.
• the closed loop gain may be different based on input circuit 210. The following will describe different input circuits 210.
• Fig. 3A depicts an example of power amplifier 200 with a current input driver according to one embodiment.
• Input circuit 210 includes a third amplifier 302c.
• a third amplifier 302c includes a transductance of Gm3.
• First amplifier 302a includes a transductance of Gml and second amplifier 302b includes a
• Amplifiers 302a-302c may be transductance amplifiers (Gm amplifiers) that output a current proportional to the input voltage.
• the loop gain of power amplifier 200 is:
• Loop Gain A jco * ⁇ .
• the feedback factor is:
• the closed loop gain may be as follows: Gm3
• Fig. 3B shows a more detailed example of the current input driver shown in
• input circuit 210 includes a capacitor Cin and a transistor T.
• transistor T is a bipolar junction transistor (BJT) but other types of transistors may be used.
• the closed loop gain is a function of the transductance Gm3 of transistor T and frequency.
• Gm3 be a function of the capacitance Cin.
• Gm3 may be Vin/(impedance of Cin).
• the closed loop gain may be equal to:
• a voltage input driver may be used to maximize loop gain.
• Fig. 4 depicts an example of power amplifier 200 using a voltage input driver according to one embodiment.
• Input circuit 210 may include a capacitor Cin.
• Cp is kept sufficiently small such that capacitor Cin is greater than capacitor Cp (e.g., Cin » Cp).
• the feedback factor ⁇ is maximized and a higher loop gain is achieved for the closed loop gain.
• the loop gain is:
• Loop Gain A(jco) * ⁇ .
• the feedback factor is:
• the closed loop gain may be as follows:
• feedback factor ⁇ also does not introduce a phase shift or pole.
• Fig. 5 shows an additional example of power amplifier 200 using an inductor- capacitor-resistor circuit arranged in series according to one embodiment.
• feedback circuit 208 includes an inductor L2, a capacitor Cfb, and a resistor R2 in a series arrangement.
• Input circuit 210 includes a resistor Rl, inductor LI, and capacitor Cin in a series arrangement.
• the loop gain is:
• Loop Gain A jco * ⁇ .
• the feedback factor is:
• the closed loop gain may be as follows: R2.
• the closed loop gain is a factor of resistors R2 and Rl . This is because the feedback factor ⁇ is not a function of frequency since inductor L and capacitor C cancel each other out if Cp is small. Thus, a closed loop gain is a function of the ratio of resistor R2 to resistor Rl . The feedback factor also does not introduce a phase shift or pole.
• the linear performance of power amplifier 200 may be about a 27dB gain using conventional power amplifiers.
• Particular embodiments may provide a loop gain of 30dB for a 3dB improvement due to feedback circuit 208 not adding a pole in the frequency response.
• the gain is also more linear as changes in gain result in more linear performance changes.
• Quality factor Ql is a quality factor of amplifier 302a and resonant tank circuit 304.
• Quality factor Q2 is a quality factor for amplifier 302b and transformer 204.
• the phase shift is the only function of resonant tank circuit 304 Ql, and resonant tank circuit 304 impedance is a function of L when quality factor Ql is fixed.
• the phase shift is a function of quality factor Q2 of transformer 204 and the impedance is a function of the resistance seen by transformer 204.
• PhaseZ ⁇ j ⁇ , Ql) + phaseZ2 ⁇ jco, Q2) I20dec
• Zl is the impedance of resonant tank 302
• Z2 is the impedance of transformer 204.
• a is also a variable based a capacitance of resonant tank 302. Also known is: l- « 6.25 ⁇
• LoopGain Gml * Zl(2GHz, Ql, L) * Gm2 * ⁇ 2(6.25 ⁇ ) * ⁇ * a
• Fig. 6 shows an additional example of a power amplifier 600 using an inductor- capacitor-resistor circuit arranged in parallel according to one embodiment.
• feedback circuit 208 includes an inductor L2, a capacitor Cfb, and a resistor R2 in a parallel arrangement.
• Input circuit 210 also includes a resistor Rl, inductor LI, and capacitor Cin in a parallel arrangement. Arranging the inductor LI, capacitor Cin, and resistor Rl in parallel may reduce the load on a driver circuit, such as current driver Gm3, and provide improved performance for radio-frequency implementation.
• a driver circuit such as current driver Gm3, and provide improved performance for radio-frequency implementation.
• a feedback factor may be computed for Fig. 6.
• the feedback factor may be used to select components for feedback circuit 208 and input circuit 210 such that the feedback circuit 208 and input circuit 210 have the same impedance characteristic. Any components of feedback circuit 208 and input circuit 210 may be selected such that an impedance characteristic of the feedback circuit is the same as an impedance characteristic of the input circuit.
• the feedback circuit and input circuit may include a capacitor.
• Fig. 7 shows an example of a power amplifier 700 which includes an input circuit 210, a feedback circuit 208, an amplifier circuit 206, a wideband transformer 201, and a common gate 212 which may be part of amplifier circuit 206 or separately coupled to amplifier circuit 206.
• Amplifier circuit 206 may include the common gate 212, first amplifier stage 302a having a transductance Gml, a resonant tank circuit 304, and a second amplifier stage 302b having a transductance Gm2.
• the wideband transformer 201 may drive an antenna and includes a transformer 204 and a load 202.
• the common gate 212 may be located within the feedback loop to extend the bandwidth of a signal.
• the common gate 212 may have a low impedance and therefore may not affect the impedance characteristic of a circuit.
• the common gate 212 may also be used as a current buffer between any of the amplifier stages.
• components for input circuit 210 and feedback circuit 208 may be selected based on a feedback factor computed for the power amplifier circuit (e.g., 600, 700). These components may be selected in any way such that the feedback factor indicates that input circuit 210 and feedback circuit 208 have the same impedance characteristic.
• Fig. 8 shows an example of a power amplifier 800 which includes multiple feedback circuits.
• 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 Gml, a second amplifier stage 302b having an inductance Gm2, and a wideband transformer 201.
• First amplifier stage 302a may be connected to second amplifier stage 302b.
• Power amplifier 800 may also include a common gate 212.
• first feedback circuit 208 may be connected to an amplifier circuit comprising second feedback circuit 214, first amplifier state 302a, and second amplifier stage 302b, as coupled in Fig. 8.
• First feedback circuit 208 has a feedback impedance of Z feedback l
• second feedback circuit 214 has a feedback impedance of
• Multiple feedback circuits may conserve physical space in the power amplifier design. For example, multiple feedback circuits may be included to replace a resonant tank circuit in the amplifier circuit. Furthermore, the addition of another feedback circuit may extend the bandwidth and increase the gain of a signal. However, additional feedback circuits may decrease stability of a circuit and/or increase phase shift of the signal. Feedback circuits may be connected to different locations along the amplifier stages 302a-c and common gate. For example, first feedback circuit 208 may be connected from an output of the second amplifier stage 302b to the input of the common gate 212. As discussed in relation to Fig.
• components for input circuit 210 and feedback circuits 208, 214 are selected based on a feedback factor computed for the power amplifier circuit (e.g., 600, 700, 800). These components may be selected in any way such that feedback factor indicates that input circuit 210 and first feedback circuit 208 have the same impedance characteristic.
• Fig. 9 shows an example of a power amplifier 900 similar to power amplifier 800 shown in Fig. 8.
• Power amplifier 900 may include a third feedback circuit 216, in addition to functionalities and features of power amplifier 800.
• Power amplifier 900 includes an input circuit 210, a common gate 212, a first amplifier stage 302a, a second amplifier stage 302b, a third amplifier stage 302c, first feedback circuit 208, second feedback circuit 214, and third feedback circuit 216.
• First feedback circuit 208 has a feedback impedance of Z feedback l .
• Second feedback circuit 214 has a feedback impedance of Z_feedback_2.
• Feedback circuit 216 has a feedback impedance of Z_feedback_3.
• first feedback circuit 208 may be connected from the output of third amplifier stage 302c to the input of the common gate 212.
• First feedback circuit 208 may be connected to an amplifier circuit comprising second feedback circuit 214, third feedback circuit 216, first amplifier stage 302a, second amplifier stage 302b, and third amplifier stage 302d, as coupled in Fig. 9.
• Second feedback circuit 214 may be connected from the output of the first amplifier stage 302a to the input of the first amplifier stage 302a.
• Third feedback circuit 216 may be connected from the output of the second amplifier stage 302b to the input of the first amplifier stage 302a.
• Fig. 10 shows an example of a power amplifier 1000 which includes a feedback circuit 208 and feedfoward circuits 220, 224.
• power amplifier 1000 includes an input circuit 210 having input impedance Z input, a first amplifier stage 302a having a transductance Gml, a resonant tank circuit 304, a second amplifier stage 302b having a transductance Gm2, a feedback circuit 208 having a feedback impedance of Z feedback, a first feedforward circuit 220, a second feedforward circuit 224, and a wideband transformer 201.
• Common gates 218, 222 may be included as part of the feedforward circuits 220, 224 or external to feedforward circuits 220, 224.
• Feedback circuit 208 may comprise multiple feedback circuits, similar to the circuits shown in Fig. 8 and Fig. 9. Each feedback circuit (e.g., 208 and/or feedback circuits included in 208 (not shown)) in power amplifier 1000 may have the same impedance characteristic as each feedforward circuit (e.g., 220, 224) in power amplifier 1000. Components for each of one or more feedback circuits and each of one or more feedforward circuits of power amplifier 1000 may be selected based on a feedforward factor such that the impedance characteristic of the feedback circuit and feedforward circuit(s) are the same.
• components in one or more feedback circuits 208 within power amplifier 1000 may comprise a capacitor.
• components in one or more feedforward circuits 220, 224 within power amplifier 1000 may also comprise a capacitor.
• Components of the input circuit 210, feedback circuit 208, and one or more feedforward circuits 220, 224 may be selected based on a calculated parameter.
• the calculated parameter may be a feedback factor.
• the feedback factor may be calculated using the impedance characteristics of an input circuit 210, a feedback circuit 208, and/or a feedforward circuit 220, 224.
• the feedback factor may indicate that an impedance characteristic of a feedback circuit 208 is the same as an impedance characteristic of an input circuit 210.
• the calculated parameter may be a feedforward factor.
• the feedforward factor may compute the impedance characteristics of an input circuit 210 a feedback circuit 208, and/or a feedforward circuit 220, 224.
• the feedforward factor may indicate that an impedance characteristic of a feedforward circuit 220, 224 is the same as an impedance characteristic of an input circuit 210, which may also be the same as an impedance characteristic of feedback circuit 208.
• a feedforward circuit may introduce a zero in the frequency response of the power amplifier. The introduction of a zero to the frequency response may improve the phase margin and overall stability of the amplifier.
• Feedforward circuits 220, 224 may be connected to different locations along the amplifier circuit. For example, feedforward circuit 220 may be connected from the input circuit to the input of resonant tank circuit 304. Feedforward circuit 224 may be connected from the input circuit 210 to the input of the second amplifier stage 302b.
• Fig. 11 shows a more detailed embodiment of a power amplifier 1100 that includes both feedback and feedforward circuits.
• Input circuit 210 may include current driver 302c, a resonant tank, or both.
• feedback circuit 208 and feedforward circuit(s) 220, 224 may include a capacitor, resonant tank circuit, or any other appropriate component that are selected based on a calculated parameter.
• Fig. 12 depicts a simplified flowchart 1200 of a method for amplifying a signal according to one embodiment.
• a signal is coupled through input circuit 210.
• the signal is amplified by amplifier 302a.
• the signal is coupled through resonant tank circuit 304.
• Amplifier 302a and resonant tank circuit 304 introduce a phase shift into the signal.
• the signal is amplified by amplifier 302b.
• the signal is coupled through transformer 204 for wireless transmission.
• Amplifier 302a and transformer 204 introduce a second phase shift into the signal.
• the signal is coupled through feedback circuit 208.
• Feedback circuit 208 includes a capacitor and does not introduce a phase shift into the signal or introduces a phase shift where a total phase shift is less than a threshold for stable operation.
• each feedforward circuit 220, 224 may include a capacitor and does not introduce a phase shift into the signal or introduces a phase shift where a total phase shift is less than a threshold for stable operation.
• Each feedforward circuit may include a resonant tank.
• Each feedforward circuit may include a common gate.
• Each feedforward circuit may include a high bandwidth circuit or a low bandwidth circuit. Components of the feedforward circuit may be selected based on a feedforward factor.
• An input impedance to the amplifier circuit may have a same impedance characteristic as a feedforward circuit impedance of the feedforward circuit.
• process 1200 may be modified (e.g., performed in a different order), combined, or removed, and any additional steps may be added to process 1200, without departing from the scope of the present disclosure.
• particular embodiments use a capacitor or inductor-capacitor- resistor feedback circuit. This results in a minimal phase shift in feedback circuit 208 and a power amplifier gain output that does not oscillate and is stable. The phase shift of the entire loop is less than 180°, which means power amplifier 200 is stable.

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  • 2013-07-19 CN CN201380075255.8A patent/CN105075113B/zh not_active Expired - Fee Related
  • 2013-07-19 WO PCT/US2013/051403 patent/WO2014130075A1/en active Application Filing
  • 2013-07-19 EP EP13844567.1A patent/EP2959577A1/en not_active Withdrawn

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