Feedforward amplifier circuit, audio amplifier and audio playback device

Abstract

A feedforward amplifier circuit, an audio amplifier, and an audio playback device relate to the field of feedforward amplifier circuits. The amplifier circuit comprises: a main amplifier circuit, an adder circuit, an auxiliary amplifier circuit, and a subtractor circuit. The main amplifier circuit adds distortion to an input signal to output a distorted signal, and inputs the distorted signal into the adder circuit and the subtractor circuit for feedforward correction. The auxiliary amplifier circuit amplifies the input signal and uses it as the positive input of the subtractor, so that the signal gain output by the subtractor equals the signal gain of the main amplifier. The subtractor circuit uses the distorted signal as a negative input, reversely amplifies the distorted signal, and then performs feedforward. The adder circuit superimposes the distorted signal output by the main amplifier circuit with the reversely amplified distorted signal output by the subtractor, and outputs a distortion-free signal. By eliminating the reliance on the open-loop frequency-amplitude characteristics and feedback loop of the main amplifier, the circuit structure and component parameter selection are simplified, and costs are saved.

Description

Technical Field

[0001] The present disclosure relates to the field of feedforward amplifier circuits, and in particular to a feedforward amplifier circuit, an audio amplifier, and an audio playback device. Background Art

[0002] In current feedforward amplifier circuits, when selecting circuit component parameters, it is necessary to consider the impact on the open-loop frequency-amplitude characteristics of the main amplifier and the feedback loop. This makes the process of determining circuit component parameters more complicated, the selected target circuit components may be more expensive, and the resulting feedforward amplifier circuit structure is more complex. Summary of the Invention

[0003] The present disclosure provides a feedforward amplifier circuit, an audio amplifier, and an audio playback device, which simplifies the circuit structure and component parameter selection and saves costs by getting rid of the dependence on the open-loop frequency-amplitude characteristics and feedback loop of the main amplifier.

[0004] The present disclosure provides a feedforward amplifier circuit, comprising: a main amplifier circuit, an adder circuit, an auxiliary amplifier circuit, and a subtractor circuit; the main amplifier circuit adds distortion to an input signal to output a distorted signal, and inputs the distorted signal into the adder circuit and the subtractor circuit for feedforward correction; the auxiliary amplifier circuit amplifies the input signal and uses it as the positive input of the subtractor, so that the signal gain output by the subtractor equals the signal gain of the main amplifier; the subtractor circuit uses the distorted signal as the negative input, reversely amplifies the distorted signal, and then performs feedforward; the adder circuit superimposes the distorted signal output by the main amplifier circuit with the reversely amplified distorted signal output by the subtractor, and outputs a distortion-free signal.

[0005] Optionally, the main amplifier circuit includes a main amplifier, an impedance Z1 and a first feedback impedance, the first feedback impedance includes an impedance r and an impedance R; the input signal enters from the positive input terminal of the main amplifier, the main amplifier output terminal is connected to one end of the impedance Z1, the other end of the impedance Z1 is connected to one end of the impedance r, the other end of the impedance r is respectively connected to one end of the impedance R and the negative input terminal of the main amplifier, and the other end of the impedance R is grounded.

[0006] Optionally, the auxiliary amplifier circuit includes an auxiliary amplifier and a second feedback impedance, the second feedback impedance includes an impedance r and an impedance R; the input signal enters from the positive input terminal of the auxiliary amplifier, the auxiliary amplifier output terminal is respectively connected to the subtractor and one end of the impedance r, the other end of the impedance r is respectively connected to one end of the impedance R and the negative input terminal of the auxiliary amplifier, and the other end of the impedance R is grounded.

[0007] Optionally, the subtractor circuit includes a subtractor and a third feedback impedance, wherein the third feedback impedance includes impedance r2 and impedance r1; the positive input terminal of the subtractor is connected to the output terminal of the auxiliary amplifier in the auxiliary amplifier circuit, the negative input terminal of the subtractor is connected to one end of the impedance r1 and one end of the impedance r2, the other end of the impedance r1 is connected to the main amplifier circuit, and the other end of the impedance r2 is connected to the output terminal of the subtractor. Optionally, the adder circuit includes impedance Z1, impedance Z2, and impedance Z3; one end of the impedance Z1 is respectively connected to the output terminal of the main amplifier in the main amplifier circuit and the other end of the impedance r1 in the subtractor circuit, the other end of the impedance Z1 is respectively connected to one end of the impedance Z2 and one end of the main amplifier impedance r, the other end of the impedance Z2 is respectively connected to the output terminal and one end of the impedance Z3, and the other end of the impedance Z3 is connected to the output terminal of the subtractor in the subtractor circuit.

[0008] Optionally, the amplification factors of the first feedback impedance of the main amplifier circuit and the second feedback impedance of the auxiliary amplifier circuit are consistent or in the same proportion.

[0009] Optionally, the subtractor in the subtractor circuit has an amplification factor of 1 for the undistorted part of the distorted signal input to the negative input terminal, and has an amplification factor of -(r2 / r1) for the point distortion between the impedance Z1 and the output terminal of the main amplifier in the main amplifier circuit.

[0010] Optionally, the impedance in the adder circuit satisfies the following relationship: (r2 / r1)(Z1+Z2)=Z3

[0011] Optionally, the device further comprises an input terminal and an output terminal, wherein the input terminal is configured to provide the input signal, and the output terminal outputs an undistorted signal.

[0012] Optionally, if the resistance value of the impedance Z1 is 0, the main amplifier circuit, the auxiliary amplifier circuit, the subtractor circuit and the adder circuit are separate.

[0013] Optionally, an amplifier equivalent circuit is further included that is configured to equivalently replace the main amplifier circuit and the auxiliary amplifier circuit.

[0014] Optionally, the amplifier equivalent circuit includes an amplifier, an impedance r1, an impedance r2, and an impedance r3.

[0015] Optionally, the positive input terminal of the amplifier receives an input signal, the negative input terminal of the amplifier is respectively connected to one end of the impedance r1, one end of the impedance r2 and one end of the impedance r3, the input signal connected to the other end of the impedance r1 is the output signal of the main amplifier, the other end of the impedance r2 is connected to the output terminal of the amplifier, and the other end of the impedance r3 is grounded.

[0016] The present disclosure also provides an audio amplifier, comprising the feedforward amplifier circuit as described above.

[0017] The present disclosure also provides an audio playback device, comprising the audio amplifier as described above, and further comprising a processing chip and a playback component connected to the audio amplifier.

[0018] The present disclosure provides a feedforward amplifier circuit, an audio amplifier, and an audio playback device, which have the following beneficial effects.

[0019] The inputs of the main amplifier and the auxiliary amplifier are identical. The auxiliary amplifier output signal and the negative input signal from the main amplifier are combined after passing through a subtractor. The signal then passes through an adder circuit and is combined with the main amplifier output to form a total output signal, minimizing reliance on the main amplifier's negative feedback. Furthermore, equivalent impedances are located inside and outside the main amplifier feedback loop. The subtractor's negative input samples the signal between the impedance inside the loop and the main amplifier output. The impedance connected to the subtractor output and the impedance outside the loop form an adding circuit. The ratio of the equivalent impedance inside and outside the main amplifier feedback loop is equal to the subtractor's reverse amplification factor. When the subtractor output and the undistorted signal at the total output are at the same level, impedance Z3 experiences no undistorted signal voltage difference, meaning no undistorted current flows through impedance Z3. Consequently, no undistorted current is output from the subtractor output, achieving a zero-shunting subtractor. Furthermore, the impedances of the adder, auxiliary amplifier, and subtractor can be composed solely of resistors, achieving distortion suppression and minimizing excessive current shunting in the auxiliary circuit. The beneficial effects of the audio amplifier and audio playback device provided by the present disclosure relative to the prior art are the same as the beneficial effects of the above-mentioned feedforward amplifier circuit relative to the prior art, and will not be repeated here. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solution of the present disclosure, the drawings required for use will be briefly introduced below. It should be understood that the following drawings only illustrate certain implementation methods of the present disclosure and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without any creative work.

[0021] Figure 1 This is a circuit diagram of a traditional non-feedforward audio amplifier.

[0022] Figure 2This is a circuit diagram of a traditional feedforward amplifier.

[0023] Figure 3 This is a circuit diagram of a feedforward amplifier provided by the present disclosure.

[0024] Figure 4 A schematic diagram of the circuit structure of a feedforward amplifier provided by the present disclosure.

[0025] Figure 5 This is a circuit structure diagram of an equivalent replacement circuit provided by the present disclosure.

[0026] Figure 6 A circuit structure diagram of another equivalent replacement circuit provided by the present disclosure.

[0027] Icons: 1-first circuit structure; 2-second circuit structure. DETAILED DESCRIPTION

[0028] To make the objectives, technical solutions, and advantages of the present disclosure more clear, the technical solutions of the present disclosure will be clearly and completely described below in conjunction with the accompanying drawings. It should be understood that the described embodiments are only some of the embodiments of the present disclosure, not all of them. The components of the present disclosure generally described and illustrated in the drawings herein can be arranged and designed in a variety of different configurations.

[0029] The terms "first," "second," and the like are used only to distinguish descriptions and should not be understood as indicating or implying relative importance. The terms "comprise," "include," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a process, method, article, or apparatus comprising a list of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus. In the absence of further limitations, an element defined by the phrase "comprising a..." does not preclude the presence of additional identical elements in the process, method, article, or apparatus comprising the element.

[0030] It should also be noted that, unless otherwise expressly specified or limited, terms such as "disposed" and "connected" should be understood broadly. For example, "connected" can mean a fixed connection, a detachable connection, or an integral connection; a mechanical connection or an electrical connection; a direct connection or an indirect connection through an intermediate medium; or internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in this disclosure based on specific circumstances.

[0031] The specific embodiments of the present disclosure are described in detail below with reference to the accompanying drawings.

[0032] Figure 1This is a common structure for audio amplifiers without feedforward. Output stage distortion can mostly be eliminated by large-loop negative feedback. For low-power amplifiers, the feedback of a high-performance operational amplifier can reduce distortion below 1kHz to very low levels, meeting application requirements. However, as frequency increases, the open-loop multiplier decreases rapidly, and the feedback decreases rapidly, causing distortion to increase. Furthermore, for high-power amplifiers, the output stage generates significant distortion when operating at high power in Class B or Class AB mode, making it difficult to reduce low-frequency distortion. Therefore, the effectiveness of this type of audio amplifier without feedforward is relatively limited.

[0033] Figure 2 In the above Figure 1 The amplifier shown here incorporates a feedforward circuit, along with impedances 1 and 2, and a secondary output stage. This structure was first used in the 1970s and 1980s. The feedforward circuit provides increased distortion suppression, and because its distortion suppression effect persists with increasing frequency, it is primarily used to compensate for the distortion reduction caused by negative feedback at high frequencies. The secondary output stage can be omitted or replaced with a separate amplifier.

[0034] The distortion suppression principle is as follows: the distortion at the output point of the output stage passes through the feedback loop (feedback loop 1 and feedback loop 2) and the input and amplification stages, and is converted into a signal whose phase and amplitude are related to the aforementioned path and is output by the secondary output stage. Then, the output signals of the two output stages pass through the adding circuit formed by impedance 1 and impedance 2 selected according to the aforementioned path, and a distortion-suppressed signal can be obtained at the output point. Ideally, the distortion can be completely eliminated.

[0035] According to the above existing feedforward principle, due to the reliance on the open-loop frequency-amplitude characteristics of the main amplifier and the feedback loop, the following disadvantages may occur in practice:

[0036] 1. Because the impedance 1 and impedance 2 of the adder circuit are directly related to the parameters of the path from the feedback point to the output point of the input and output stages, the frequency-amplitude characteristic curve of the path should be as straight or regular as possible to facilitate the selection of impedance 1 and impedance 2. Assuming that the input and amplification stage is an operational amplifier with a very large open-loop multiplier, in order to obtain a straighter frequency-amplitude characteristic line, the feedback loop can be a resistor and a Miller capacitor. When the value is appropriate, the frequency-amplitude characteristic is the ratio of the capacitor impedance to the resistor. Since impedance 1 is directly connected to the output stage, it must withstand a very large current and cannot have large distortion. Therefore, its selection is basically limited to resistors and inductors. If impedance 1 is selected as a resistor, impedance 2 is preferably a pure capacitor, but this requires the secondary output stage to have a good capacitive load capacity, which makes the secondary output stage structure more complicated, or impedance 2 is selected as a small resistor and capacitor connected in series, which will affect the addition. The matching of the inductor circuit and the path requires compensation in the feedback path. If impedance 1 is chosen as an inductor, impedance 2 should be chosen as a resistor. However, the inductor inevitably has parasitic resistance that cannot be ignored in this case. This requires that impedance 2 be connected in series with a capacitor to match the parasitic resistance. In addition, inductors are commonly made of pure copper, and the parasitic resistance has a large temperature coefficient. Compensating with a capacitor with a corresponding temperature coefficient is impractical because the inductor generates heat and the capacitor is heated, and temperature changes are difficult to predict. Moreover, high-performance capacitors should not have such a large temperature coefficient. Therefore, the inductor needs to be connected in series with a resistor with a resistance an order of magnitude larger than the parasitic resistance to reduce the impact of the parasitic resistance temperature drift. Therefore, even if the input and output stages are relatively close to ideal open-loop op amps with large multipliers, the impedance selection still has many problems. In reality, the large errors in impedance, especially in capacitors and inductors, directly limit the distortion suppression.

[0037] 2. The above example uses an ideal op amp as the input amplifier stage. If this stage uses a custom discrete circuit, the frequency-amplitude characteristic line is likely to be curved. To achieve a straight frequency-amplitude characteristic line, the Miller capacitor must be large enough, which will significantly sacrifice feedback, making the gain unprofitable. The above example uses a single-pole compensation using a Miller capacitor. To extract more feedback, dual-pole compensation is required. To cope with the curved frequency-amplitude characteristic line produced by dual-pole compensation, the adder circuit will become more complex.

[0038] 3. According to the principle, the distortion at the output stage's output point will be amplified significantly. If the distortion is large, such as clipping, even slight clipping can cause the feedforward to malfunction. If the designed path has a small amplification factor, for example, replacing the Miller capacitor with a moderately large resistor, even large distortion can be corrected. A relatively flat frequency-amplitude characteristic line can also be obtained within the audio range, allowing the adder circuit to achieve distortion suppression with only two resistors. However, this sacrifices a significant amount of feedback, which is not worth the cost.

[0039] 4. The secondary output stage also needs to provide current to the load. The shunt ratio is the impedance ratio, which is the amplification factor of the above path. When the load is large and the current is also large, the output current of the secondary output stage is the distortion current plus the shunt current, so there are certain requirements for its current output capacity and scale.

[0040] 5. The existing method is highly dependent on negative feedback, so it has high requirements on the amount of feedback.

[0041] 6. The existing method requires that a point be taken from before the output stage. For an integral amplifier chip, it cannot be applied without adding an input amplifier stage and enclosing the amplifier chip with a feedback loop.

[0042] Based on this, the present disclosure provides a feedforward amplifier circuit, an audio amplifier, and an audio playback device, which can simplify the circuit structure and component parameter selection and save costs by getting rid of the dependence on the open-loop frequency-amplitude characteristics and feedback loop of the main amplifier.

[0043] Reference Figure 3 The present disclosure provides a feedforward amplifier circuit, comprising: a main amplifier circuit, an adder circuit, a sub-amplifier circuit, and a subtractor circuit. It should be noted that the impedances in the present disclosure are not limited to resistors, but can be suitable inductors, capacitors, resistors, or combinations thereof. The present disclosure assumes that all impedances in the circuit structure are resistors and that the amplifier has a large open-loop gain for illustration. For example, if all impedances can be resistors, the cost is low, the accuracy is high, the stability is high, and a wider range of values ​​can be selected.

[0044] The main amplifier circuit adds distortion to the input signal and outputs a distorted signal, which is then fed into an adder circuit and a subtractor circuit for feedforward correction. The auxiliary amplifier circuit amplifies the input signal and supplies it as the positive input to the subtractor circuit, ensuring that the signal gain of the subtractor output equals the signal gain of the main amplifier. The subtractor circuit receives the distorted signal as its negative input, reversely amplifies the distorted signal, and then feeds it forward. The adder circuit superimposes the distorted signal output by the main amplifier circuit with the reversely amplified distorted signal output by the subtractor, outputting an undistorted signal. In practical applications, the main amplifier circuit optionally outputs the distorted signal and feeds it forward, while the distorted signal and the signal obtained by amplifying the input signal by the auxiliary amplifier circuit are simultaneously input into the subtractor circuit. The subtractor reversely amplifies the distorted signal and feeds it forward. The distorted signal fed forward by the main amplifier is superimposed with the signal obtained by reversely amplifying and feeding it forward by the subtractor, outputting an undistorted signal. The present disclosure uses an independent feedforward circuit to amplify the signal and distortion, greatly reducing the dependence on the main amplifier circuit. A straight and regular frequency-amplitude characteristic line is not required to facilitate the matching of device parameters in the adder circuit. The main amplifier does not need to sacrifice too much feedback, and can even use double-pole compensation to further increase the feedback amount to improve performance. In addition, there is no need to take a point between the output stage and the amplification stage of the main amplifier to lead out to the adder, making the circuit more flexible and having a wider range of applications.

[0045] The signal gain effect of the auxiliary amplifier ensures that the signal gain of the main amplifier is equal to the signal gain of the subtractor. A distortion voltage difference exists between the output of the main amplifier circuit and the output of the subtractor circuit. The auxiliary amplifier circuit disclosed herein eliminates a signal voltage difference between the output of the main amplifier circuit and the output of the subtractor circuit, that is, eliminates a signal voltage difference across impedance Z3. If a voltage difference existed between the two, the auxiliary amplifier circuit would also become a load.

[0046] Based on the above embodiment, the gain of the auxiliary amplifier may also be higher or lower than the gain of the main amplifier output, and then attenuated or amplified to the gain of the main amplifier output in the subsequent circuit.

[0047] Optionally, in this embodiment, an input terminal and an output terminal are further included, the input terminal is configured to provide an input signal, and the output terminal outputs an undistorted signal.

[0048] The main amplifier circuit includes a main amplifier, an impedance Z1, and a first feedback impedance. The first feedback impedance includes impedances r and R. The input signal enters the positive input terminal of the main amplifier. The main amplifier output terminal is connected to one end of impedance Z1. The other end of impedance Z1 is connected to one end of impedance r. The other end of impedance r is connected to one end of impedance R and the negative input terminal of the main amplifier. The other end of impedance R is grounded. It can be understood that the first feedback impedance of the main amplifier circuit is composed of impedances r and R, and impedances r and R form a voltage divider circuit.

[0049] The open loop of the main amplifier can be a low open loop gain, in which case the impedance value needs to be changed accordingly to achieve no current diversion in the subtractor.

[0050] Exemplarily, the auxiliary amplifier circuit includes an auxiliary amplifier and a second feedback impedance, the second feedback impedance includes an impedance r and an impedance R; the input signal enters from the positive input terminal of the auxiliary amplifier, the auxiliary amplifier output terminal is respectively connected to the subtractor and one end of the impedance r, the other end of the impedance r is respectively connected to one end of the impedance R and the negative input terminal of the auxiliary amplifier, and the other end of the impedance R is grounded.

[0051] Optionally, the subtractor circuit includes a subtractor and a third feedback impedance, the third feedback impedance includes impedance r2 and impedance r1; the positive input end of the subtractor is connected to the output end of the auxiliary amplifier in the auxiliary amplifier circuit, the negative input end of the subtractor is connected to one end of the impedance r1 and one end of the impedance r2, the other end of the impedance r1 is connected to the main amplifier circuit, and the other end of the impedance r2 is connected to the output end of the subtractor.

[0052] Among them, the subtractor theoretically only outputs or absorbs distortion current and does not need to provide current to the load, so its current output capability requirement is relatively small. When the open-loop multiple of the main amplifier is large and the impedance Z2 is greater than the impedance Z1, the distortion current is approximately equal to Figure 1 In the figure, the distortion voltage at the output of the main amplifier without feedforward is divided by Z2. Because the subtractor does not require current shunting, the reverse gain and Z3 do not need to be large. Therefore, even if the main amplifier circuit has large distortion, it can still be fed forward normally after amplification, and distortion suppression can also be achieved even when the main amplifier has mild clipping.

[0053] Optionally, the adder circuit includes an impedance Z1, an impedance Z2, and an impedance Z3; one end of the impedance Z1 is respectively connected to the output end of the main amplifier in the main amplifier circuit and the other end of the impedance r1 in the subtractor circuit, the other end of the impedance Z1 is respectively connected to one end of the impedance Z2 and one end of the main amplifier impedance r, the other end of the impedance Z2 is respectively connected to the output end and one end of the impedance Z3, and the other end of the impedance Z3 is connected to the output end of the subtractor in the subtractor circuit.

[0054] Optionally, the amplification factors of the first feedback impedance of the main amplifier circuit and the second feedback impedance of the auxiliary amplifier circuit are consistent or in the same proportion. The main amplifier can also be reverse amplification, and correspondingly, the auxiliary amplifier should be changed to reverse amplification.

[0055] For example, the subtractor in the subtractor circuit has an amplification factor of 1 for the undistorted signal, while the amplification factor for the distorted portion between impedance Z1 and the output of the main amplifier in the main amplifier circuit is -(r2 / r1). Impedances Z1 to Z3 in the adder circuit satisfy the following relationship: (r2 / r1)×(Z1+Z2)=Z3. Furthermore, the impedances in the adder circuit may also have the following relationship: Z2 / Z1=r2 / r1. Impedances Z1 and Z2 generally have relatively small impedance values ​​because they must carry large currents.

[0056] When only (r2 / r1)×(Z1+Z2)=Z3 is satisfied, but Z2 / Z1=r2 / r1 is not satisfied, there is still a good distortion correction effect, but the secondary output stage will participate in the shunting.

[0057] Since the present disclosure greatly reduces the reliance on the feedback of the main amplifier, the impedance does not need to be strictly determined according to the properties of the main amplifier. For a main amplifier with a large open-loop gain, it is only necessary to know its closed-loop gain. The reverse gain of the subtractor can be set by itself, and the value of the adder circuit is also the simple relationship described above.

[0058] When the impedance satisfies the above relationship and it is assumed that the auxiliary amplifier and the subtractor have no distortion on the input signal, the distorted signal at the output end of the main amplifier is amplified by the subtractor and the positive and negative cancellation is performed by the adder, and the output point is distortion-free; assuming that the output current of the main amplifier is I, the input is u, and the undistorted part of the distorted signal output at the negative feedback point is U, then the voltage drop of Z1 is I×Z1, and the voltage drop of Z2 is I×Z2, that is, I×(r2 / r1)×Z1, so the output signal is (UI×(r2 / r1)×Z1), and the voltage drop of Z1 is amplified by (r2 / r1) times in the reverse direction by the subtractor, then the output undistorted signal of the subtractor is (UI×(r2 / r1)×Z1), which is the same as the output point, so the subtractor does not output the current of the distortion-free signal or is not loaded.

[0059] Optionally, if the resistance value of impedance Z1 is 0, the main amplifier circuit, auxiliary amplifier circuit, subtractor circuit and adder circuit are independent of each other, and the subtractor point is actually outside the main amplifier loop and has no dependence on the negative feedback of the main amplifier.

[0060] When Z1 is 0 and (r2 / r1)Z2=Z3, there is still a good distortion correction effect and it is completely independent of the negative feedback of the main amplifier. Therefore, the distortion correction of the output stage can be performed separately and then a negative feedback loop can be added.

[0061] In this disclosure, Figure 4 As shown, the feedforward amplifier circuit can be divided into two parts, including a first circuit structure 1 and a second circuit structure 2.

[0062] Optionally, the first circuit structure 1 can be combined with Figure 5 The circuit structure shown in is equivalently replaced. At this time, the impedance has the following relationship: (r1 / (r1+r2))×Z=Z1, (r2 / (r1+r2))×Z=Z2, r=r1 / / r2, where r1 / / r2 represents the value of impedance r1 and impedance r2 in parallel.

[0063] Optionally, the second circuit structure 2 can also be connected to Figure 6 The amplifier equivalent circuit shown in the figure is replaced. The amplifier equivalent circuit is configured to equivalently replace the main amplifier circuit and the auxiliary amplifier circuit. The amplifier equivalent circuit includes an amplifier, an impedance r1, an impedance r2, and an impedance r3. The positive input terminal of the amplifier receives the input signal, and the negative input terminal of the amplifier is connected to one end of impedance r1, one end of impedance r2, and one end of impedance r3, respectively. The input signal received by the other end of impedance r1 is the output signal of the main amplifier. The other end of impedance r2 is connected to the output terminal of the amplifier, and the other end of impedance r3 is grounded. At this time, the impedances in the auxiliary amplifier have the following relationship: r = r2, R = r1 / / r3.

[0064] Optionally, the auxiliary amplifier or the subtractor may also be connected in parallel in an equivalent manner to achieve a corresponding equivalent replacement effect.

[0065] Optionally, both the main amplifier and the auxiliary amplifier may adopt an inverting input or a differential input.

[0066] The present disclosure also provides an audio amplifier, including the feedforward amplifier circuit as described above, which is applied to the technical field of audio amplification. It solves the same technical problems and achieves the same technical effects as the aforementioned feedforward amplifier circuit, and will not be described in detail here.

[0067] The present disclosure also provides an audio playback device comprising the audio amplifier described above, a processing chip connected to the audio amplifier, and a playback component. The processing chip sends a control signal to control the audio signal to be output without distortion after passing through the audio amplifier, and then played by the playback component, thereby achieving a distortion-free audio playback effect.

[0068] Finally, it should be noted that the above-described embodiments are only specific implementation methods of the present disclosure, which are used to illustrate the technical solutions of the present disclosure, rather than to limit them. The scope of protection of the present disclosure is not limited thereto. Although the present disclosure has been described in detail with reference to the above-described embodiments, those skilled in the art should understand that any person skilled in the art can modify or easily conceive of changes to the technical solutions described in the above-described embodiments within the technical scope disclosed in the present disclosure, or replace some of the technical features therein with equivalents. Such modifications, changes, or replacements do not deviate from the spirit and scope of the technical solutions of the embodiments of the present disclosure, and should be included in the scope of protection of the present disclosure. Therefore, the scope of protection of the present disclosure shall be subject to the scope of protection of the claims.

[0069] Industrial Applicability

[0070] The feedforward amplifier circuit disclosed herein includes a main amplifier circuit, an adder circuit, a sub-amplifier circuit, and a subtractor circuit. The inputs of the main amplifier and the sub-amplifier are consistent. The output signal of the sub-amplifier and the negative input signal output from the main amplifier are output after passing through the subtractor, and then combined with the output of the main amplifier through the adder circuit to form a total output signal. This circuit has low reliance on the negative feedback of the main amplifier.

Claims

1. A feedforward amplifier circuit, characterized in that: include: a main amplifier circuit, an adder circuit, a sub-amplifier circuit, and a subtractor circuit; The main amplifier circuit adds distortion to the input signal to output a distorted signal, and inputs the distorted signal into the adder circuit and the subtractor circuit for feedforward correction. The main amplifier circuit includes a main amplifier, an impedance Z1, and a first feedback impedance, wherein the first feedback impedance includes a main amplifier impedance r and an impedance R. The input signal enters the positive input terminal of the main amplifier, the main amplifier output terminal is connected to one end of the impedance Z1, the other end of the impedance Z1 is connected to one end of the main amplifier impedance r, the other end of the main amplifier impedance r is respectively connected to one end of the impedance R in the first feedback impedance and the negative input terminal of the main amplifier, and the other end of the impedance R in the first feedback impedance is grounded. The auxiliary amplifier circuit amplifies the input signal and uses it as a positive input of the subtractor circuit, so that the signal gain of the subtractor output in the subtractor circuit is equal to the signal gain of the main amplifier in the main amplifier circuit; The subtractor circuit takes the distorted signal as a negative input, reversely amplifies the distorted signal, and then performs feedforward. The subtractor circuit includes a subtractor and a third feedback impedance, wherein the third feedback impedance includes an impedance r2 and an impedance r1. The positive input end of the subtractor is connected to the output end of the auxiliary amplifier in the auxiliary amplifier circuit, the negative input end of the subtractor is connected to one end of the impedance r1 and one end of the impedance r2, the other end of the impedance r1 is connected to the main amplifier circuit, and the other end of the impedance r2 is connected to the output end of the subtractor. The adder circuit superimposes the distorted signal output by the main amplifier circuit with the distorted signal after reverse amplification output by the subtractor, and outputs an undistorted signal. The adder circuit includes the impedance Z1, the impedance Z2, and the impedance Z3. One end of the impedance Z1 is also connected to the other end of the impedance r1 in the subtractor circuit. The other end of the impedance Z1 is also connected to one end of the impedance Z2. The other end of the impedance Z2 is respectively connected to the output end and one end of the impedance Z3. The other end of the impedance Z3 is connected to the subtractor output end of the subtractor circuit. The impedances in the adder circuit satisfy the relationship (r2 / r1)×(Z1+Z2)=Z3. When Z1 approaches 0, the relationship (r2 / r1)Z2=Z3 is satisfied.

2. The feedforward amplifier circuit according to claim 1, wherein: The auxiliary amplifier circuit includes an auxiliary amplifier and a second feedback impedance, wherein the second feedback impedance includes an impedance r and an impedance R; The input signal enters from the positive input terminal of the auxiliary amplifier, the output terminal of the auxiliary amplifier is respectively connected to the subtractor and one end of the impedance r, the other end of the impedance r is respectively connected to one end of the impedance R and the negative input terminal of the auxiliary amplifier, and the other end of the impedance R is grounded.

3. The feedforward amplifier circuit according to claim 1, wherein: The amplification factors of the first feedback impedance of the main amplifier circuit and the second feedback impedance of the auxiliary amplifier circuit are consistent or in the same proportion.

4. The feedforward amplifier circuit according to claim 1, wherein: The subtractor in the subtractor circuit has an amplification factor of 1 for the undistorted portion of the distorted signal input to the negative input terminal, and has an amplification factor of -(r2 / r1) for the point distortion between the impedance Z1 and the output terminal of the main amplifier in the main amplifier circuit.

5. The feedforward amplifier circuit according to claim 1, wherein: The device further includes an input terminal and an output terminal, wherein the input terminal is configured to provide the input signal and the output terminal outputs an undistorted signal.

6. The feedforward amplifier circuit according to claim 1, wherein: If the resistance value of the impedance Z1 is 0, the main amplifier circuit, the auxiliary amplifier circuit, the subtractor circuit, and the adder circuit are each separate.

7. The feedforward amplifier circuit according to claim 1, wherein: Also included is an amplifier equivalent circuit configured to equivalently replace the main amplifier circuit and the sub-amplifier circuit.

8. The feedforward amplifier circuit according to claim 7, wherein: The amplifier equivalent circuit includes an amplifier, an impedance r1 , an impedance r2 , and an impedance r3 .

9. The feedforward amplifier circuit according to claim 8, wherein: The positive input terminal of the amplifier receives an input signal, the negative input terminal of the amplifier is respectively connected to one end of the impedance r1, one end of the impedance r2 and one end of the impedance r3, the input signal connected to the other end of the impedance r1 is the output signal of the main amplifier, the other end of the impedance r2 is connected to the output terminal of the amplifier, and the other end of the impedance r3 is grounded.

10. An audio amplifier, characterized in that: The invention comprises a feedforward amplifier circuit as claimed in any one of claims 1 to 9.

11. An audio playback device, characterized in that: The invention comprises the audio amplifier as claimed in claim 10, and further comprises a processing chip and a playback component connected to the audio amplifier.

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