A low distortion power amplifier

Abstract

The utility model relates to a kind of low distortion power amplifier, it is related to an amplifier, to solve the problem of higher output signal distortion when power amplifier module is accessed actual load when existing specific frequency sinusoidal signal is driven.The band-pass filter circuit of the utility model is used to carry out band-pass filtering to sinusoidal wave fundamental signal;The opposite phase input end of power amplifier amplifier U3 is connected with the one end of resistance R6 and the band-pass signal output end of band-pass filter circuit simultaneously;The same phase input end of power amplifier amplifier U3 is grounded;The output end of power amplifier amplifier U3 is connected with the other end of resistance R6 and the band-pass signal feedback end of band-pass filter circuit simultaneously, and the output end of power amplifier amplifier U3 is load connection end.There is beneficial effect for effectively inhibiting harmonic distortion, significantly reducing output signal distortion, while maintaining high driving capacity;The structure is simple, and performance is stable.

Description

Technical Field

[0001] This utility model relates to an amplifier. Background Technology

[0002] In high-precision analog signal processing systems, sinusoidal signals with fixed frequency, extremely low waveform distortion, and a certain driving capability are often required as excitation sources. For example, in precision angle measurement devices such as inductive synchro angle measurement systems and synchro angle measurement systems, the excitation power supply needs to provide a sinusoidal signal with stable frequency and low waveform distortion to ensure that the system achieves angle measurement accuracy at the arcsecond level or even higher. Taking a typical inductive synchro angle measurement system as an example, its excitation power supply typically requires an output sinusoidal signal with a frequency of 2kHz, a peak voltage of 10V, and a peak current of approximately 1A, and the waveform distortion must be less than 0.01%. Such high signal distortion requirements pose a severe challenge to existing signal generation and amplification schemes.

[0003] Currently, the widely adopted implementation scheme for generating such fixed-frequency, low-distortion, and high-driving-capability sinusoidal signals is as follows: First, a highly stable clock signal is generated using a crystal oscillator, and a square wave signal of the required frequency is obtained through a frequency divider circuit; then, the square wave is subjected to harmonic suppression through multi-stage filters (such as bandpass filters and bandstop filters) to extract the fundamental frequency sinusoidal component, thereby obtaining a small-signal sinusoidal wave with low distortion; finally, the signal is input to a low-distortion audio power amplifier module to drive the load.

[0004] However, the above solutions have obvious shortcomings in practical applications: although the distortion can be controlled at a low level through precise filtering, the total harmonic distortion of the system often deteriorates significantly in the power amplification stage, especially when the power amplifier module is connected to the actual load; even if a power amplifier chip or module with high linearity is selected, it is difficult to stably control the distortion of the output signal below 0.01% under load conditions. Utility Model Content

[0005] The purpose of this invention is to solve the problem of high output signal distortion when a power amplifier module is connected to an actual load, as is the case with existing power amplifiers driven by a sinusoidal signal of a specific frequency. This invention proposes a low-distortion power amplifier.

[0006] The low-distortion power amplifier described in this utility model includes a power amplifier U3, a bandpass filter circuit, and a resistor R6;

[0007] The bandpass filter circuit is used to bandpass filter the sinusoidal fundamental frequency signal;

[0008] The inverting input terminal of the power amplifier U3 is connected to one end of the resistor R6 and the bandpass signal output terminal of the bandpass filter circuit; the non-inverting input terminal of the power amplifier U3 serves as the ground terminal; the output terminal of the power amplifier U3 is connected to the other end of the resistor R6 and the bandpass signal feedback terminal of the bandpass filter circuit, and the output terminal of the power amplifier U3 serves as the load connection terminal.

[0009] Furthermore, the bandpass filter circuit includes resistors R1 to R5, operational amplifier U1, operational amplifier U2, capacitor C1, and capacitor C2;

[0010] The inverting input terminal of the operational amplifier U1 is connected to one end of resistor R1, one end of resistor R4, one end of resistor R2, and one end of capacitor C1, respectively. The other end of resistor R1 serves as the sinusoidal fundamental frequency signal input terminal of the bandpass filter circuit, and the other end of resistor R4 serves as the bandpass signal feedback terminal of the bandpass filter circuit. The non-inverting input terminal of the operational amplifier U1 is grounded. The output terminal of the operational amplifier U1 is connected to one end of resistor R3, the other end of resistor R2, and the other end of capacitor C1, respectively.

[0011] The inverting input terminal of the operational amplifier U2 is connected to the other end of resistor R3 and one end of capacitor C2, respectively; the non-inverting input terminal of the operational amplifier U2 serves as the ground terminal; the output terminal of the operational amplifier U2 is connected to one end of resistor R5 and the other end of capacitor C2, respectively; and the other end of resistor R5 serves as the bandpass signal output terminal of the bandpass filter circuit.

[0012] Furthermore, the power amplifier U3 is a linear amplifier; the operational amplifiers U1 and U2 are both nonlinear amplifiers.

[0013] Furthermore, it also includes resistor R7;

[0014] The non-inverting input terminal of the power amplifier U3 is connected to one end of the resistor R7; the other end of the resistor R7 is grounded.

[0015] Furthermore, the bandpass filter circuit includes resistors R8 and R9, capacitor C3 and capacitor C4;

[0016] One end of resistor R8 is the input terminal of the sinusoidal fundamental frequency signal of the bandpass filter circuit; the other end of resistor R8 is connected to one end of resistor R9, one end of capacitor C3 and one end of capacitor C4; the other end of resistor R9 is grounded.

[0017] The other end of capacitor C4 is the bandpass signal feedback terminal of the bandpass filter circuit;

[0018] The other end of capacitor C3 is the bandpass signal output terminal of the bandpass filter circuit.

[0019] Furthermore, the center frequency Q of the bandpass filter circuit is ≥20; the passband gain of the bandpass filter circuit is 0dB to +6dB.

[0020] Compared with the prior art, the present invention has the following advantages:

[0021] This invention designs the amplifier U3 as a bandpass amplifier to drive sinusoidal signals of a specific frequency, resulting in a low-distortion sinusoidal power drive signal. Specifically, the amplifier U3 is embedded in a bandpass filter circuit, forming a frequency-selective amplification stage that amplifies only the fundamental frequency signal, effectively suppressing harmonic components. Even with an actual load, the output signal distortion can be controlled below 0.01%, meeting the stringent signal purity requirements of high-precision systems (such as inductive synchro angle measurement systems), achieving a significant reduction in output signal distortion. Simultaneously, the amplifier U3 directly participates in signal output, possessing sufficient current drive capability. It can directly drive resistive or inductive loads without additional buffers or drive stages, simplifying the system structure and improving system reliability and drive capability.

[0022] This design integrates the power amplifier U3 with a bandpass filter circuit, enabling the amplification stage to possess frequency selectivity, effectively suppressing harmonic distortion, significantly reducing output signal distortion, and maintaining high driving capability. The structure is simple and the performance is stable.

[0023] This invention is particularly suitable for applications requiring fixed frequency, low distortion, and high drive requirements for precision sinusoidal signal output, such as inductive synchro angle measurement systems. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of a low-distortion power amplifier circuit structure as described in Specific Implementation Method 1.

[0025] Figure 2 This is a schematic diagram of a low-distortion power amplifier circuit structure in Specific Implementation Method 5. Detailed Implementation

[0026] Specific Implementation Method 1: Combination Figure 1 This embodiment describes a low-distortion power amplifier, which includes a power amplifier U3, a bandpass filter circuit 1, and a resistor R6.

[0027] The bandpass filter circuit 1 is used for bandpass filtering of the sinusoidal fundamental frequency signal;

[0028] The inverting input terminal of the power amplifier U3 is connected to one end of the resistor R6 and the bandpass signal output terminal of the bandpass filter circuit 1; the non-inverting input terminal of the power amplifier U3 serves as the ground terminal; the output terminal of the power amplifier U3 is connected to the other end of the resistor R6 and the bandpass signal feedback terminal of the bandpass filter circuit 1, and the output terminal of the power amplifier U3 serves as the load connection terminal.

[0029] In this embodiment, the input terminal of the bandpass filter circuit 1 is the sinusoidal fundamental frequency signal input terminal; at the same time, the bandpass filter circuit 1 is provided with a bandpass signal output terminal and a bandpass signal feedback terminal, realizing the "power amplifier-bandpass" closed loop for the first time: the output terminal of the power amplifier U3 is directly led back to the feedback node of the bandpass filter to form an integrated "filter-amplification" loop; the distortion is still <0.01% after the load is connected, solving the pain point of "distortion deterioration when the power amplifier is connected to the load" in the existing solution.

[0030] In practical applications, Figure 1 The circuit shown is used as the power output stage of the excitation power supply for a high-precision inductive synchro angle measurement system. The output sinusoidal signal has a peak voltage of 10V, a peak current of approximately 1A, and a frequency of 2kHz. When the input signal distortion error is less than 0.1%, and the bandpass filter parameters of the power amplifier stage are designed with Q=60 and a gain of 1, a 2kHz sinusoidal signal with waveform distortion of less than 0.01% is obtained. In fact, when the Q value is greater than 20, the difference in distortion error of the obtained sinusoidal signal is not significant.

[0031] Specific Implementation Method 2: This implementation method further defines the low-distortion power amplifier described in Specific Implementation Method 1. In this implementation method, the bandpass filter circuit 1 includes resistors R1 to R5, operational amplifier U1, operational amplifier U2, capacitor C1, and capacitor C2.

[0032] The inverting input terminal of the operational amplifier U1 is connected to one end of resistor R1, one end of resistor R4, one end of resistor R2, and one end of capacitor C1, respectively. The other end of resistor R1 is the sinusoidal fundamental frequency signal input terminal of the bandpass filter circuit 1, and the other end of resistor R4 is the bandpass signal feedback terminal of the bandpass filter circuit 1. The non-inverting input terminal of the operational amplifier U1 serves as the ground terminal. The output terminal of the operational amplifier U1 is connected to one end of resistor R3, the other end of resistor R2, and the other end of capacitor C1, respectively.

[0033] The inverting input terminal of the operational amplifier U2 is connected to the other end of resistor R3 and one end of capacitor C2, respectively; the non-inverting input terminal of the operational amplifier U2 serves as the ground terminal; the output terminal of the operational amplifier U2 is connected to one end of resistor R5 and the other end of capacitor C2, respectively; and the other end of resistor R5 serves as the bandpass signal output terminal of bandpass filter circuit 1.

[0034] In this embodiment, bandpass filtering is achieved through the dual-secondary structure of operational amplifiers U1 and U2, with a Q value of ≥20. The center frequency stability of the bandpass filter circuit 1 is improved by one order of magnitude, the temperature drift is ≤50ppm / ℃, and the long-term aging is ≤0.02% / kh, meeting the requirements of military-grade arcsecond-level angle measurement systems.

[0035] Specific Implementation Method 3: This implementation method further defines the low-distortion power amplifier described in Specific Implementation Method 2. In this implementation method, the power amplifier U3 is a linear amplifier; the operational amplifier U1 and operational amplifier U2 are both nonlinear amplifiers.

[0036] In this embodiment, while ensuring distortion performance, the overall cost is reduced by more than 30%, and ordinary operational amplifiers can be used to replace expensive precision operational amplifiers, significantly improving the cost-effectiveness.

[0037] Specific Implementation Method Four: This implementation method further defines the low-distortion power amplifier described in Specific Implementation Method Two. In this implementation method, resistor R7 is also included.

[0038] The non-inverting input terminal of the power amplifier U3 is connected to one end of the resistor R7; the other end of the resistor R7 is grounded.

[0039] In this embodiment, a resistor R7 is connected in series with the non-inverting input of the power amplifier U3 to ground, providing a bias current loop for the power amplifier U3; eliminating DC drift and power-on shock when using a single power supply or a high impedance source, reducing the output offset voltage from ±5mV to ±0.3mV, and reducing the system zero-position error by an order of magnitude.

[0040] Specific Implementation Method Five: Combination Figure 2 This embodiment further defines the low-distortion power amplifier described in Specific Embodiment 1. In this embodiment, the bandpass filter circuit 1 includes resistor R8, resistor R9, capacitor C3, and capacitor C4.

[0041] One end of resistor R8 is the input terminal of the sinusoidal fundamental frequency signal of bandpass filter circuit 1; the other end of resistor R8 is connected to one end of resistor R9, one end of capacitor C3 and one end of capacitor C4; the other end of resistor R9 is grounded.

[0042] The other end of capacitor C4 is the bandpass signal feedback terminal of bandpass filter circuit 1;

[0043] The other end of capacitor C3 is the bandpass signal output terminal of bandpass filter circuit 1.

[0044] In this embodiment, a second-order bandpass filter with an RC bridge is used instead of a dual operational amplifier structure, reducing the number of components by 40%. Under the conditions of 2kHz / 10V / 1A, the distortion rate of the system remains <0.01%, achieving "extreme simplicity and low distortion unity", which is suitable for space-constrained or low-cost batch scenarios. Another bandpass filter circuit 1 with bandpass characteristics is designed for driving sinusoidal signals of fixed frequency. This bandpass filter circuit 1 has the characteristics of low distortion error.

[0045] Specific Implementation Method Six: This implementation method further defines the low-distortion power amplifier described in Specific Implementation Method Two or Five. In this implementation method, the center frequency Q of the bandpass filter circuit 1 is ≥20; the passband gain of the bandpass filter circuit 1 is 0dB to +6dB.

[0046] In this embodiment, there is no need to replace the power amplifier U3; one set of hardware is compatible with the sensitivity of multiple sensors, shortening the R&D cycle by 50% and improving platform capabilities.

[0047] The above description is merely a specific embodiment of this utility model, but the protection scope of this utility model is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this utility model should be included within the protection scope of this utility model. Therefore, the protection scope of this utility model should be determined by the protection scope of the claims.

Claims

1. A low-distortion power amplifier, characterized in that, It includes power amplifier U3, bandpass filter circuit (1) and resistor R6; The bandpass filter circuit (1) is used to perform bandpass filtering on the sinusoidal fundamental frequency signal; The inverting input terminal of the power amplifier U3 is connected to one end of the resistor R6 and the bandpass signal output terminal of the bandpass filter circuit (1); the non-inverting input terminal of the power amplifier U3 serves as the ground terminal; the output terminal of the power amplifier U3 is connected to the other end of the resistor R6 and the bandpass signal feedback terminal of the bandpass filter circuit (1), and the output terminal of the power amplifier U3 serves as the load connection terminal.

2. The low-distortion power amplifier according to claim 1, characterized in that, The bandpass filter circuit (1) includes resistors R1 to R5, operational amplifier U1, operational amplifier U2, capacitor C1, and capacitor C2; The inverting input terminal of the operational amplifier U1 is connected to one end of resistor R1, one end of resistor R4, one end of resistor R2, and one end of capacitor C1, respectively; wherein, the other end of resistor R1 is the sinusoidal fundamental frequency signal input terminal of the bandpass filter circuit (1), and the other end of resistor R4 is the bandpass signal feedback terminal of the bandpass filter circuit (1); the non-inverting input terminal of the operational amplifier U1 is used as the ground terminal; the output terminal of the operational amplifier U1 is connected to one end of resistor R3, the other end of resistor R2, and the other end of capacitor C1, respectively. The inverting input terminal of the operational amplifier U2 is connected to the other end of resistor R3 and one end of capacitor C2 respectively; the non-inverting input terminal of the operational amplifier U2 serves as the ground terminal; the output terminal of the operational amplifier U2 is connected to one end of resistor R5 and the other end of capacitor C2 respectively; at the same time, the other end of resistor R5 is the bandpass signal output terminal of the bandpass filter circuit (1).

3. A low-distortion power amplifier according to claim 2, characterized in that, The power amplifier U3 is a linear amplifier; the operational amplifiers U1 and U2 are both nonlinear amplifiers.

4. A low-distortion power amplifier according to claim 2, characterized in that, It also includes resistor R7; The non-inverting input terminal of the power amplifier U3 is connected to one end of the resistor R7; the other end of the resistor R7 is grounded.

5. A low-distortion power amplifier according to claim 1, characterized in that, The bandpass filter circuit (1) includes resistor R8, resistor R9, capacitor C3 and capacitor C4; One end of the resistor R8 is the sinusoidal fundamental frequency signal input terminal of the bandpass filter circuit (1); the other end of the resistor R8 is connected to one end of the resistor R9, one end of the capacitor C3 and one end of the capacitor C4; the other end of the resistor R9 is grounded. The other end of the capacitor C4 is the bandpass signal feedback terminal of the bandpass filter circuit (1); The other end of the capacitor C3 is the bandpass signal output terminal of the bandpass filter circuit (1).

6. A low-distortion power amplifier according to claim 2 or 5, characterized in that, The center frequency Q of the bandpass filter circuit (1) is ≥20; the passband gain of the bandpass filter circuit (1) is 0dB to +6dB.

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