阅读说明：本技术 一种适用于低频微弱信号的信号放大电路 (Signal amplification circuit suitable for low-frequency weak signal ) 是由 包晓东 于 2020-06-23 设计创作，主要内容包括：本发明提供一种适用于低频微弱信号的信号放大电路,包括以下：前级放大电路、次级放大电路、滤波电路和跟踪电路；所述前级放大电路一端用于接收输入信号并进行初步放大,另一端与所述滤波电路电性连接；所述滤波电路与所述次级放大电路电性连接,用于消除基线漂移；所述跟踪电路与所述前级放大电路电性连接,用于消除微弱信号中存在的噪声。本发明提供的有益效果是：通过两级放大电路,实现微弱信号的放大,并通过滤波和反馈跟踪电路消除信号放大过程中的基线漂移与背景噪声,实现方法简单、成本低且通用性强。(The invention provides a signal amplification circuit suitable for low-frequency weak signals, which comprises the following components: the device comprises a preceding stage amplifying circuit, a secondary stage amplifying circuit, a filter circuit and a tracking circuit; one end of the pre-stage amplifying circuit is used for receiving an input signal and carrying out preliminary amplification, and the other end of the pre-stage amplifying circuit is electrically connected with the filter circuit; the filter circuit is electrically connected with the secondary amplifying circuit and is used for eliminating baseline drift; the tracking circuit is electrically connected with the preceding stage amplifying circuit and is used for eliminating noise existing in weak signals. The beneficial effects provided by the invention are as follows: the two-stage amplification circuit is used for amplifying weak signals, baseline drift and background noise in the signal amplification process are eliminated through the filtering and feedback tracking circuit, and the method is simple, low in cost and high in universality.)

1. A signal amplification circuit suitable for low-frequency weak signals is characterized in that: the method specifically comprises the following steps: the device comprises a preceding stage amplifying circuit, a secondary stage amplifying circuit, a filter circuit and a tracking circuit; one end of the pre-stage amplifying circuit is used for receiving an input signal and carrying out preliminary amplification, and the other end of the pre-stage amplifying circuit is electrically connected with the filter circuit; the filter circuit is electrically connected with the secondary amplifying circuit and is used for eliminating baseline drift; the tracking circuit is electrically connected with the preceding stage amplifying circuit and is used for eliminating noise in a weak signal;

the weak signal is preliminarily amplified through the pre-stage amplifying circuit and the tracking circuit, and noise is eliminated; and the baseline drift is eliminated through the filter circuit, and finally the signal is amplified again through the secondary amplifying circuit and output to the signal acquisition device.

2. A signal amplification circuit suitable for low frequency weak signals as claimed in claim 1, wherein: the preceding stage amplifying circuit specifically comprises: weak signal input terminal V_INThe resistor R1-the resistor R5, the preceding operational amplifier, the capacitor C1-the capacitor C3; the weak signal input end V_INIs connected with one end of a capacitor C1; the other end of the capacitor C1 is connected with one end of a resistor R1; the other end of the resistor R1 is respectively connected with a pin 2 of the preceding operational amplifier and one end of the resistor R2; the other end of the resistor R2 is connected with a pin 1 of the preceding operational amplifier; the 1 pin of the preceding operational amplifier is used as the output end V of the preceding amplifying circuit_OUT(ii) a The pin 1 of the preceding operational amplifier is also connected with one end of a capacitor C3; the other end of the capacitor C3 is connected with one end of a resistor R4; one end of a resistor R5 at the other end of the resistor R4 is connected with one end of a capacitor C2; the other end of the resistor R5 is connected with the other end of the capacitor C2 and is commonly connected with a pin 3 of the preceding operational amplifier and one end of the resistor R3; the other end of the resistor R3 is grounded; the 4 feet of the preceding operational amplifier are grounded; and the 5 pins of the preceding operational amplifier are electrically connected with the tracking circuit.

3. A signal amplification circuit suitable for low frequency weak signals as claimed in claim 2, wherein: the filter circuit specifically includes: a capacitor C4 and a resistor R6; the capacitor C4 and the resistor R6 jointly form a high-pass filter circuit; one end of the capacitor C4 is connected with the output end V of the pre-stage amplifying circuit_OUT(ii) a The other end of the resistor R6 is connected with one end of the secondary amplifying circuit; the other end of the resistor R6 is grounded.

4. A process as claimed in claim 3The signal amplification circuit suitable for the low-frequency weak signal is characterized in that: the tracking circuit specifically comprises: a tracking operational amplifier, resistor R7 and resistor R8; the resistor R7 and the resistor R8 are connected in parallel; one end of the resistor R7 and the 1-pin inverting input end V of the tracking operational amplifier_REFConnecting; 1-pin inverting input end V of tracking operational amplifier_REFThe power supply end is the power supply end of the preceding operational amplifier; the other end of the resistor R7 is connected with the 3-pin output end of the tracking operational amplifier; the homodromous input end of the tracking operational amplifier is grounded; the other two ends of the tracking operational amplifier are respectively connected with a +5V power supply and a-5V power supply.

5. The signal amplification circuit of claim 4, wherein the signal amplification circuit comprises: the secondary amplifying circuit specifically comprises: a secondary operational amplifier, a resistor R9 and a resistor R10; one end of the resistor R9 is connected with the 2-pin equidirectional input end of the secondary operational amplifier; the other end of the resistor R9 is grounded; the 2-pin equidirectional input end of the secondary operational amplifier is also connected with one end of a resistor R10; the other end of the resistor R10 is connected with the 3-pin output end of the secondary operational amplifier; the other two ends of the secondary operational amplifier are respectively connected with a +5V power supply and a-5V power supply.

6. A signal amplification circuit suitable for low frequency weak signals as claimed in claim 2, wherein: the gain of the preceding stage amplifying circuit is calculated according to the formula (1):

7. a signal amplification circuit suitable for low frequency weak signals as claimed in claim 3, wherein: the filter circuit is specifically a high-pass filter, and the frequency of the filter circuit is calculated as formula (2):

8. the signal amplification circuit of claim 4, wherein the signal amplification circuit comprises: the specific working principle of the tracking circuit is as follows: establishing common-mode negative feedback at the feedback end of the preceding operational amplifier and the ground end of a signal source, and simultaneously accessing a feedback signal of the tracking circuit to the feedback end of the preceding operational amplifier, namely V_REFTherefore, power frequency interference is suppressed.

9. The signal amplification circuit of claim 5, wherein the signal amplification circuit is adapted to amplify a low frequency weak signal, and comprises: the gain of the secondary amplifying circuit is calculated according to the formula (3):

Technical Field

The invention relates to the field of electronic circuits, in particular to a signal amplification circuit suitable for low-frequency weak signals.

Background

Weak signals generally have the following characteristics:

(1) the signal needs to be detected in a near field, and the signal cannot be detected when the signal is far away from a signal source;

(2) weak signal and energy below mV

(3) The interference is strong.

Aiming at the characteristics, the signal amplification circuit suitable for the low-frequency weak signal is designed, so that the low-frequency weak signal can be acquired by the device and can be greatly applied to certain specific fields in medical aspects and the like.

Disclosure of Invention

In view of this, the present invention provides a signal amplifying circuit suitable for low-frequency weak signals, which includes the following components:

the device comprises a preceding stage amplifying circuit, a secondary stage amplifying circuit, a filter circuit and a tracking circuit; one end of the pre-stage amplifying circuit is used for receiving an input signal and carrying out preliminary amplification, and the other end of the pre-stage amplifying circuit is electrically connected with the filter circuit; the filter circuit is electrically connected with the secondary amplifying circuit and is used for eliminating baseline drift; the tracking circuit is electrically connected with the preceding stage amplifying circuit and is used for eliminating noise in a weak signal;

the weak signal is preliminarily amplified through the pre-stage amplifying circuit and the tracking circuit, and noise is eliminated; and the baseline drift is eliminated through the filter circuit, and finally the signal is amplified again through the secondary amplifying circuit and output to the signal acquisition device.

Further, the pre-stage amplifying circuit specifically includes: weak signal input terminal V_INThe resistor R1-the resistor R5, the preceding operational amplifier, the capacitor C1-the capacitor C3; the weak signal input end V_INIs connected with one end of a capacitor C1; the other end of the capacitor C1 is connected with one end of a resistor R1; the other end of the resistor R1 is respectively connected with a pin 2 of the preceding operational amplifier and one end of the resistor R2; the other end of the resistor R2 is connected with a pin 1 of the preceding operational amplifier; the 1 pin of the preceding operational amplifier is used as the output end V of the preceding amplifying circuit_OUT(ii) a The pin 1 of the preceding operational amplifier is also connected with one end of a capacitor C3; the other end of the capacitor C3 is connected with one end of a resistor R4; one end of a resistor R5 at the other end of the resistor R4 is connected with one end of a capacitor C2; the other end of the resistor R5 is connected with the other end of the capacitor C2 and is commonly connected with a pin 3 of the preceding operational amplifier and one end of the resistor R3; the other end of the resistor R3 is grounded; the 4 feet of the preceding operational amplifier are grounded; and the 5 pins of the preceding operational amplifier are electrically connected with the tracking circuit.

Further, the filter circuit specifically includes: a capacitor C4 and a resistor R6; the capacitor C4 and the resistor R6 jointly form high-pass filteringA circuit; one end of the capacitor C4 is connected with the output end V of the pre-stage amplifying circuit_OUT(ii) a The other end of the resistor R6 is connected with one end of the secondary amplifying circuit; the other end of the resistor R6 is grounded.

Further, the tracking circuit specifically includes: a tracking operational amplifier, resistor R7 and resistor R8; the resistor R7 and the resistor R8 are connected in parallel; one end of the resistor R7 and the 1-pin inverting input end V of the tracking operational amplifier_REFConnecting; 1-pin inverting input end V of tracking operational amplifier_REFThe power supply end is the power supply end of the preceding operational amplifier; the other end of the resistor R7 is connected with the 3-pin output end of the tracking operational amplifier; the homodromous input end of the tracking operational amplifier is grounded; the other two ends of the tracking operational amplifier are respectively connected with a +5V power supply and a-5V power supply.

Further, the secondary amplifying circuit specifically includes: a secondary operational amplifier, a resistor R9 and a resistor R10; one end of the resistor R9 is connected with the 2-pin equidirectional input end of the secondary operational amplifier; the other end of the resistor R9 is grounded; the 2-pin equidirectional input end of the secondary operational amplifier is also connected with one end of a resistor R10; the other end of the resistor R10 is connected with the 3-pin output end of the secondary operational amplifier; the other two ends of the secondary operational amplifier are respectively connected with a +5V power supply and a-5V power supply.

Further, the gain of the preceding stage amplifying circuit is calculated according to the following formula (1):

further, the filter circuit, specifically, the high-pass filter, has a frequency calculated as formula (2):

further, the tracking circuit specifically operates according to the following principle: establishing common-mode negative feedback between the feedback end of the preceding operational amplifier and the ground end of the signal source, and simultaneously enabling the tracking circuitThe feedback signal is connected to the feedback end of the preceding operational amplifier, i.e. V_REFTherefore, power frequency interference is suppressed.

The gain of the secondary amplifying circuit is calculated according to the formula (3):

the beneficial effects provided by the invention are as follows: the two-stage amplification circuit is used for amplifying weak signals, baseline drift and background noise in the signal amplification process are eliminated through the filtering and feedback tracking circuit, and the method is simple, low in cost and high in universality.

Drawings

FIG. 1 is a schematic diagram of a signal amplifying circuit suitable for low-frequency weak signals according to the present invention;

FIG. 2 is a schematic circuit diagram of a signal amplification circuit suitable for low frequency weak signals according to the present invention;

FIG. 3 is a schematic diagram of a pre-stage amplifying circuit of the signal amplifying circuit for low-frequency weak signals according to the present invention;

FIG. 4 is a schematic diagram of a filter circuit of a signal amplifying circuit for low frequency weak signals according to the present invention;

FIG. 5 is a schematic diagram of a tracking circuit of the signal amplification circuit of the present invention, which is suitable for low frequency weak signals;

fig. 6 is a schematic diagram of a secondary amplifying circuit of the signal amplifying circuit for low-frequency weak signals according to the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, embodiments of the present invention will be further described with reference to the accompanying drawings.

Referring to fig. 1, an embodiment of the present invention provides a signal amplifying circuit suitable for low-frequency weak signals, including the following:

the device comprises a preceding stage amplifying circuit, a secondary stage amplifying circuit, a filter circuit and a tracking circuit; one end of the pre-stage amplifying circuit is used for receiving an input signal and carrying out preliminary amplification, and the other end of the pre-stage amplifying circuit is electrically connected with the filter circuit; the filter circuit is electrically connected with the secondary amplifying circuit and is used for eliminating baseline drift; the tracking circuit is electrically connected with the preceding stage amplifying circuit and is used for eliminating noise in a weak signal;

the weak signal is preliminarily amplified through the pre-stage amplifying circuit and the tracking circuit, and noise is eliminated; and the baseline drift is eliminated through the filter circuit, and finally the signal is amplified again through the secondary amplifying circuit and output to the signal acquisition device.

The preceding stage amplifying circuit specifically comprises: weak signal input terminal V_INThe resistor R1-the resistor R5, the preceding operational amplifier, the capacitor C1-the capacitor C3; the weak signal input end V_INThe filter is sequentially connected with one end of a capacitor C1 and one end of a resistor R1, and C1 is used for filtering direct current signals in input signals; the other end of the resistor R1 is respectively connected with a pin 2 of the preceding operational amplifier and one end of the resistor R2; the other end of the resistor R2 is connected with a pin 1 of the preceding operational amplifier; the 1 pin of the preceding operational amplifier is used as the output end V of the preceding amplifying circuit_OUT(ii) a The pin 1 of the preceding operational amplifier is also connected with one end of a capacitor C3; the other end of the capacitor C3 is connected with one end of a resistor R4; one end of a resistor R5 at the other end of the resistor R4 is connected with one end of a capacitor C2; the other end of the resistor R5 is connected with the other end of the capacitor C2 and is commonly connected with a pin 3 of the preceding operational amplifier and one end of the resistor R3; the other end of the resistor R3 is grounded, and the resistor R3 is a balance resistor; the capacitor C3 is connected with the resistor R4 in series, the capacitor C2 is connected with the resistor R5 in parallel, and background noise with different frequencies existing in the input signal is absorbed by adjusting C2, C3, R4 and R5; the 4 feet of the preceding operational amplifier are grounded; and the 5 pins of the preceding operational amplifier are electrically connected with the tracking circuit.

The gain of the preceding stage amplifying circuit is calculated according to the formula (1):

the filter circuit specifically includes: a capacitor C4 and a resistor R6; the capacitor C4 and the resistor R6 are sharedA high-pass filter circuit is formed; one end of the capacitor C4 is connected with the output end V of the pre-stage amplifying circuit_OUT(ii) a The other end of the resistor R6 is connected with one end of the secondary amplifying circuit; the other end of the resistor R6 is grounded.

The filter circuit is specifically a high-pass filter, and the frequency of the filter circuit is calculated as formula (2):

the tracking circuit specifically comprises: a tracking operational amplifier, resistor R7 and resistor R8; the resistor R7 and the resistor R8 are connected in parallel; one end of the resistor R7 and the 1-pin inverting input end V of the tracking operational amplifier_REFConnecting; 1-pin inverting input end V of tracking operational amplifier_REFThe power supply end is the power supply end of the preceding operational amplifier; the other end of the resistor R7 is connected with the 3-pin output end of the tracking operational amplifier; the homodromous input end of the tracking operational amplifier is grounded; the other two ends of the tracking operational amplifier are respectively connected with a +5V power supply and a-5V power supply.

The specific working principle of the tracking circuit is as follows: establishing common-mode negative feedback at the feedback end of the preceding operational amplifier and the ground end of a signal source, and simultaneously accessing a feedback signal of the tracking circuit to the feedback end of the preceding operational amplifier, namely V_REFTherefore, power frequency interference is suppressed.

The secondary amplifying circuit specifically comprises: a secondary operational amplifier, a resistor R9 and a resistor R10; one end of the resistor R9 is connected with the 2-pin equidirectional input end of the secondary operational amplifier; the other end of the resistor R9 is grounded; the 2-pin equidirectional input end of the secondary operational amplifier is also connected with one end of a resistor R10; the other end of the resistor R10 is connected with the 3-pin output end of the secondary operational amplifier; the other two ends of the secondary operational amplifier are respectively connected with a +5V power supply and a-5V power supply.

The gain of the secondary amplifying circuit is calculated according to the formula (3):

the beneficial effects of the implementation of the invention are as follows: the two-stage amplification circuit is used for amplifying weak signals, baseline drift and background noise in the signal amplification process are eliminated through the filtering and feedback tracking circuit, and the method is simple, low in cost and high in universality.

In the embodiment of the invention, all components are uniformly explained and selected as follows:

the selection types of the preceding operational amplifier, the tracking operational amplifier and the secondary operational amplifier are OP07D, a resistor R1(27k omega), a resistor R2(68k omega), a resistor R3(8.2k omega), a resistor R4(10k omega), a resistor R5(1M omega), a resistor R6(1M omega), a resistor R7(2k omega), a resistor R8(10k omega), a resistor R9(3k omega), a resistor R10(1M omega), a capacitor C1(0.01uF), a capacitor C2(0.01uF), a capacitor C3(4.7uF) and a capacitor C4(4.7 uF).

In the embodiment of the invention, a LabVIEW experiment system is adopted, a low-frequency weak signal (the low-frequency weak signal refers to a signal of mV level or below) of 0.7mV and 1.5Hz is utilized for simulation, and the filtering frequency is calculated by a formula (2) and is 0.034 Hz; the final gain obtained from the formulas (1) and (3) is 839.4; and finally, the acquisition requirement of a signal device is met.

The features of the embodiments and embodiments described herein above may be combined with each other without conflict.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.