CN112290902A - Low Pass Filters and Electronics - Google Patents
Low Pass Filters and Electronics Download PDFInfo
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- CN112290902A CN112290902A CN202011298419.1A CN202011298419A CN112290902A CN 112290902 A CN112290902 A CN 112290902A CN 202011298419 A CN202011298419 A CN 202011298419A CN 112290902 A CN112290902 A CN 112290902A
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
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- H03H7/01—Frequency selective two-port networks
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Abstract
本发明的实施例提供了一种低通滤波器和电子设备，涉及电子电路技术领域。该低通滤波器包括输入端口、输出端口以及至少两个滤波器，相互级联的所述至少两个滤波器电连接于所述输入端口和所述输出端口之间；所述至少两个滤波器包括至少一个前级滤波器和一个末级滤波器，所述前级滤波器与所述输入端口电连接，所述末级滤波器与所述输出端口电连接，末级滤波器的元器件参数的乘积等于预设值；其中，预设值为转折频率的倒数；前级滤波器的元器件参数的乘积小于预设值。其能够在不用运算放大器的情况下，达到运用运算放大器才能达到的效果。
Embodiments of the present invention provide a low-pass filter and an electronic device, and relate to the technical field of electronic circuits. The low-pass filter includes an input port, an output port and at least two filters, and the at least two filters cascaded with each other are electrically connected between the input port and the output port; the at least two filters The device includes at least one pre-stage filter and one final-stage filter, the pre-stage filter is electrically connected to the input port, the final-stage filter is electrically connected to the output port, and the components of the final-stage filter are The product of the parameters is equal to the preset value; wherein, the preset value is the reciprocal of the corner frequency; the product of the component parameters of the pre-filter is less than the preset value. It can achieve the effect that can be achieved by using an operational amplifier without using an operational amplifier.
Description
Technical Field
The invention relates to the technical field of electronic circuits, in particular to a low-pass filter and electronic equipment.
Background
In an electronic circuit, if a steeper attenuation is required for a low-pass filter, a plurality of low-pass filters need to be cascaded. If a plurality of low-pass filters are directly connected, the filtering characteristic effect is not good. Therefore, the existing solution is to insert a first-stage operational amplifier between two stages of filters for impedance transformation. However, in some occasions with higher frequency, the operational amplifier has higher price and introduces noise, and occupies the area of a circuit board.
Disclosure of Invention
The object of the present invention includes, for example, providing a low-pass filter and an electronic apparatus which can achieve an effect that can be achieved by using an operational amplifier without using the operational amplifier.
Embodiments of the invention may be implemented as follows:
in a first aspect, the present invention provides a low-pass filter, including an input port, an output port, and at least two filters, wherein the at least two filters in cascade connection are electrically connected between the input port and the output port; the at least two filters include at least a pre-filter electrically connected to the input port and a final filter electrically connected to the output port;
the product of the component parameters of the final filter is equal to a preset value; wherein the preset value is the reciprocal of the turning frequency;
and the product of the component parameters of the pre-stage filter is smaller than the preset value.
Optionally, each filter includes a resistor, a capacitor, an input terminal, an output terminal, and a ground terminal, the resistor is electrically connected to the capacitor, the resistor is disposed between the input terminal and the output terminal, the capacitor is disposed between the output terminal and the ground terminal, any one of the input terminal of the filter is electrically connected to the output terminal of the previous filter or the input port, and the output terminal is electrically connected to the input terminal of the next filter or the output port.
Optionally, a product of a resistance of the final filter and a capacitance of the final filter is equal to the preset value.
Optionally, a product of a resistance of the pre-filter and a capacitance of the pre-filter is smaller than the preset value.
Optionally, the value of the capacitance of the pre-filter is determined according to a reduction coefficient and an initial capacitance value;
the reduction coefficient is determined by the resistance value of the pre-filter and the resistance value of the next filter, and the initial capacitance value is determined by the resistance value of the pre-filter and the preset value.
Optionally, the reduction coefficient is calculated according to a formula k ═ 1-Rn/Rn +1, and n is greater than or equal to 1;
wherein k is the reduction coefficient, Rn is the resistance value of the preceding filter, and Rn +1 is the resistance value of the next filter.
On the other hand, an embodiment of the present application further provides an electronic device, including a low-pass filter, where the low-pass filter includes an input port, an output port, and at least two filters, and the at least two filters in cascade connection are electrically connected between the input port and the output port; the at least two filters comprise at least one pre-filter and a final filter, the pre-filter is electrically connected with the input port, and the product of the parameters of components of the final filter electrically connected with the output port is equal to a preset value; wherein the preset value is the reciprocal of the turning frequency;
and the product of the component parameters of the pre-stage filter is smaller than the preset value.
Optionally, each filter includes a resistor, a capacitor, an input terminal, an output terminal, and a ground terminal, the resistor is electrically connected to the capacitor, the resistor is disposed between the input terminal and the output terminal, the capacitor is disposed between the output terminal and the ground terminal, any one of the input terminal of the filter is electrically connected to the output terminal of the previous filter or the input port, and the output terminal is electrically connected to the input terminal of the next filter or the output port.
Optionally, the value of the capacitance of the pre-filter is determined according to a reduction coefficient and an initial capacitance value;
the reduction coefficient is determined by the resistance value of the pre-filter and the resistance value of the next filter, and the initial capacitance value is determined by the resistance value of the pre-filter and the preset value.
The low-pass filter and the electronic equipment provided by the embodiment of the invention have the beneficial effects that: the low-pass filter comprises an input port, an output port and at least two filters, wherein the at least two filters which are cascaded with each other are electrically connected between the input port and the output port; the at least two filters comprise at least one pre-filter and a final filter, the pre-filter is electrically connected with the input port, the final filter is electrically connected with the output port, and the product of the component parameters of the final filter is equal to a preset value; wherein the preset value is the reciprocal of the turning frequency; and the product of the component parameters of the preceding-stage filter is smaller than the preset value. Because the latter stage affects the load of the former stage, the low-pass filter can achieve the same effect as the operational amplifier by changing the component parameters of the former stage filter and the last stage filter. The circuit has the advantages of cost saving, simple circuit, circuit board area saving and the like.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present invention and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained according to the drawings without inventive efforts.
Fig. 1 is a schematic structural diagram of an electronic device according to an embodiment of the present invention;
fig. 2 is a schematic structural diagram of another electronic device according to an embodiment of the present invention;
FIG. 3 is a schematic circuit diagram of a filter according to an embodiment of the present invention;
FIG. 4 is a circuit diagram of a low pass filter according to an embodiment of the present invention;
FIG. 5 is a circuit diagram of another low pass filter according to an embodiment of the present invention;
FIG. 6 is a diagram illustrating simulation results of a low-pass filter provided in the prior art;
FIG. 7 is a diagram illustrating simulation results of another low-pass filter provided in the prior art;
FIG. 8 is a circuit schematic of another low pass filter provided by the prior art;
FIG. 9 is a diagram illustrating simulation results of still another low-pass filter provided by the prior art;
FIG. 10 is a diagram illustrating simulation results of still another low-pass filter provided by the prior art;
FIG. 11 is a circuit diagram of a low pass filter provided in the prior art;
FIG. 12 is a diagram illustrating simulation results of still another low-pass filter provided by the prior art;
fig. 13 is a diagram illustrating simulation results of a low-pass filter according to an embodiment of the present invention;
fig. 14 is a diagram illustrating simulation results of another low-pass filter according to an embodiment of the present invention.
Icon: 10-an electronic device; 100-a low-pass filter; 110-input port; 120-output port; 130-a pre-filter; 140-final filter.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. The components of embodiments of the present invention generally described and illustrated in the figures herein may be arranged and designed in a wide variety of different configurations.
Thus, the following detailed description of the embodiments of the present invention, presented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
It should be noted that: like reference numbers and letters refer to like items in the following figures, and thus, once an item is defined in one figure, it need not be further defined and explained in subsequent figures.
In the description of the present invention, it should be noted that if the terms "upper", "lower", "inside", "outside", etc. indicate an orientation or a positional relationship based on that shown in the drawings or that the product of the present invention is used as it is, this is only for convenience of description and simplification of the description, and it does not indicate or imply that the device or the element referred to must have a specific orientation, be constructed in a specific orientation, and be operated, and thus should not be construed as limiting the present invention.
Furthermore, the appearances of the terms "first," "second," and the like, if any, are used solely to distinguish one from another and are not to be construed as indicating or implying relative importance.
It should be noted that the features of the embodiments of the present invention may be combined with each other without conflict.
Referring to fig. 1 and fig. 2, the present embodiment provides an implementable structural schematic diagram of an electronic device 10, the electronic device 10 includes a low-pass filter 100, the low-pass filter 100 includes an input port 110, an output port 120 and at least two filters, at least two filters cascaded with each other are electrically connected between the input port 110 and the output port 120; the at least two filters include at least one pre-filter 130 and one final filter 140, the pre-filter 130 is electrically connected to the input port 110, the final filter 140 is electrically connected to the output port 120, and the at least one pre-filter 130 is not electrically connected to the output port 120.
In the present embodiment, the product of the component parameters of the final filter 140 is equal to a preset value; wherein the preset value is the reciprocal of the turning frequency; the product of the component parameters of the pre-filter 130 is smaller than a preset value.
It is understood that the at least two filters may be two, three, 32 or more. That is, as shown in fig. 1, the pre-filter 130 may be one; alternatively, as shown in fig. 2, there may be two pre-filters 130, and of course, there may be 31 or more pre-filters 130.
Optionally, referring to fig. 3, each filter includes a resistor R, a capacitor C, an input end, an output end, and a ground end, the resistor is electrically connected to the capacitor, the resistor is disposed between the input end and the output end, and the capacitor is disposed between the output end and the ground end, so that each filter forms an RC filter through an internal circuit. The input terminal of any one of the filters is electrically connected to the output terminal of the previous filter or the input port 110, the output terminal of any one of the filters is electrically connected to the input terminal of the next filter or the output port 120, and the ground lines of the adjacent two filters are electrically connected.
For example, referring to fig. 4, the number of the pre-filters 130 is three, one end of the resistor R1 of the first pre-filter 130 is electrically connected to the input port 110, and the other end is electrically connected to the capacitor C1 and one end of the resistor R2 of the second pre-filter 130; the other end of the resistor R2 of the second pre-filter 130 is electrically connected to one end of the capacitor C2 and one end of the resistor R3 of the third pre-filter 130, the other end of the resistor R3 of the third pre-filter 130 is electrically connected to one end of the capacitor C3 and one end of the resistor Rx of the final filter 140, and the other end of the resistor Rx is electrically connected to the capacitor Cx and the output port 120. Meanwhile, the ground terminals of all the filters are electrically connected.
It is understood that when the number of the front-stage filters 130 is more or less, the connection relationship of the low-pass filter 100 is similar, and will not be described herein.
In the present embodiment, the product of the resistance value of the resistor Rx of the final stage filter 140 and the capacitance value of the capacitor Cx of the final stage filter 140 is equal to a preset value. The product of the resistance value and the capacitance value of the pre-filter 130 is smaller than the predetermined value.
It is understood that the value of the capacitance of the pre-filter 130 is determined according to the reduction coefficient and the initial capacitance value; the reduction coefficient is determined by the resistance of the pre-filter 130 and the resistance of the next filter, and the initial capacitance is determined by the resistance of the pre-filter 130 and a predetermined value.
In this embodiment, the reduction coefficient is calculated according to the formula k ═ 1-Rn/Rn + 1, where n is greater than or equal to 1; where k is the reduction coefficient, Rn is the resistance of any preceding filter 130, and Rn +1 is the resistance of the next filter. When the number of the preceding stage filters 130 is only 1, the final stage filter 140 is the next stage filter of the preceding stage filters 130, and Rn +1 is Rx.
In this embodiment, the ratio of the resistance value of the next filter to the resistance value of the previous filter 130 is a positive number greater than 2. The resistance value of the post-stage filter can be kept larger than that of the former-stage filter, and the increasing relation is met. Meanwhile, the capacitance value of the post-stage filter is smaller than that of the former-stage filter, and the decreasing relation is met. In other words, in the present application, the resistance and the capacitance in the low-pass filter 100 satisfy the relationship R1> R2. > Rx, C1< C2. < Cx.
It is understood that the ratio of the resistances between at least two filters, and each adjacent two filters, may be the same or different. For example, if the number of the pre-filters 130 is three, the resistance value of the resistor R2 of the second pre-filter 130 may be 5 times the resistance value of the resistor R1 of the first pre-filter 130, the resistance value of the resistor Rx of the final filter 140 may be 10 times the resistance value of the resistor R2 of the second pre-filter 130, and of course, the resistance value of the resistor Rx of the final filter 140 may be 5 times the resistance value of the resistor R2 of the second pre-filter 130.
In the present embodiment, the transition frequency is 1/RC according to the formula ω, where ω is the transition frequency, R is the resistance of the resistor Rx of the final filter 140, and Cx is the capacitance of the capacitor Cx of the final filter 140.
Now, the analysis and explanation are performed according to the simulation result after the actual parameter configuration. If the resistance value of the resistor Rx of the final stage filter 140 is set to 1K Ω, the capacitance value of the capacitor Cx of the final stage filter 140 is set to 1 uF. As shown in fig. 5, then, when there is one of the at least two filters, i.e., the at least two filters include only the final stage filter 140, the resistor R3 of the final stage filter 140 has one end electrically connected to the input port 110 and the other end electrically connected to both the capacitor C3 of the final stage filter 140 and the output port 120.
The frequency characteristics of the simulated output of the final filter 140 are shown in fig. 6; at a frequency of 159Hz, the corresponding attenuation value is-3 dB. The frequency of the final filter 140 can be calculated according to the formula f ω/2 pi 159 Hz.
When a faster attenuation characteristic is required, two or more stages are required. If the two stages are directly connected, i.e. at least two filters comprise a pre-filter 130 and a final filter 140, the pre-filter 130 and the final filter 140 are connected in series between the input port 110 and the output port 120. Since the final stage filter 140 has an influence on the load of the preceding stage filter 130, if the values of the resistor R1 and the capacitor C1 of the preceding stage filter 130 and the values of the resistor Rx and the capacitor Cx of the final stage filter 140 are set to be the same. As shown in fig. 7, at a frequency of 159Hz, the corresponding attenuation value is-9.5 dB. It can be seen that the attenuation characteristics are different from the desired value-6 dB for the direct cascade.
As shown in fig. 8, when the first operational amplifier U1 is inserted between the pre-stage filter 130 and the final stage filter 140, one end of the resistor R1 of the pre-stage filter 130 is electrically connected to the input port 110, the other end is electrically connected to both the capacitor C1 of the pre-stage filter 130 and the non-inverting input port 110 of the first operational amplifier U1, both the inverting input port 110 and the output port 120 of the first operational amplifier U1 are electrically connected to one end of the resistor Rx of the final stage filter 140, and the other end of the resistor R3 of the final stage filter 140 is electrically connected to both the capacitor Cx of the final stage filter 140 and the output port 120.
As shown in fig. 9, at a frequency of 159Hz, the corresponding attenuation value is-6 dB. In accordance with the cascade operation of the filters, when the pre-filter 130 and the post-filter 140 are used in cascade, the corresponding transfer function is the product of the two transfer functions, and the corresponding decibels are directly added, so that the corresponding attenuation value should be-6 dB at 159 Hz.
If the three stages are directly connected, i.e., at least two filters include two pre-stage filters 130 and one final-stage filter 140, the pre-stage filters 130 and the final-stage filter 140 are sequentially connected in series between the input port 110 and the output port 120. As shown in fig. 10, at a frequency of 159Hz, the corresponding attenuation value is-16 dB.
As shown in fig. 11, if the first operational amplifier U1 is inserted between the first pre-filter 130 and the second pre-filter 130, and a second operational amplifier U2 is inserted between the second pre-filter 130 and the final filter 140, one end of a resistor R1 of the pre-filter 130 is electrically connected to the input port 110, the other end is electrically connected to both the capacitor C1 and the non-inverting input port 110 of the first operational amplifier U1, the inverting input and the output of the first operational amplifier U1 are electrically connected to one end of a resistor R2 of the second pre-filter 130, the other end of a resistor R2 of the second pre-filter 130 is electrically connected to both the capacitor C2 and the non-inverting input port 110 of the second operational amplifier U2, the inverting input and the output of the second operational amplifier U2 are electrically connected to one end of a resistor Rx of the final filter 140, and the other end of the resistor Rx of the final filter 140 is electrically connected to both the capacitor Cx of the final filter 140 and the output port 120.
As shown in fig. 12, at a frequency of 159Hz, the corresponding attenuation value is-9 dB. It can be concluded that multiple stages of the same filter cascade, and the filter characteristics will change if no op-amp is inserted in between. In the embodiment of the application, the parameters of the resistor and the capacitor of the filter can be changed to achieve the same effect as that of using the operational amplifier.
That is, as described above, if two stages are directly connected, that is, at least two filters include the pre-stage filter 130 and the final-stage filter 140, the pre-stage filter 130 and the final-stage filter 140 are connected in series between the input port 110 and the output port 120. If the value of the resistor R1 of the pre-filter 130 is set to a, the value of the resistor Rx of the final filter 140 is set to N ﹡ a, the value of the capacitor C1 of the pre-filter 130 is set to (1-1/N) ﹡ C, and the value of the capacitor Cx of the final filter 140 is set to C/N. Where N is the ratio of the resistance Rx of the final filter 140 to the resistance R1 of the pre-filter 130, (1-1/N) is the reduction factor, and C is the initial capacitance value. If A is 1 K.OMEGA.C is 1uF and N is 10. Then the value of the resistor R1 of the front filter 130 is 1K Ω, the value of the resistor R3 of the final filter 140 is 10K Ω, the value of the capacitor C1 of the front filter 130 is 0.9uF, and the value of the capacitor C3 of the final filter 140 is 0.1 uF. As shown in fig. 13, in order to set the resistance and capacitance values of the pre-stage filter 130 and the final stage filter 140 according to the foregoing values, the simulation results were obtained as follows: at a frequency of 159Hz, the corresponding attenuation value is-6 dB. It can be seen that the effect of the two-stage filter cascaded by the operational amplifier is the same.
If the three stages are directly connected, i.e., at least two filters include two pre-stage filters 130 and one final-stage filter 140, the two pre-stage filters 130 and the final-stage filter 140 are sequentially connected in series between the input port 110 and the output port 120. If the value of the resistor R1 of the first pre-filter 130 is set to a, the value of the resistor R2 of the second pre-filter 130 is set to N ﹡ a, the value of the resistor Rx of the final filter 140 is set to N ﹡ N ﹡ a, the value of the capacitor C1 of the first pre-filter 130 is set to (1-1/N) ﹡ C, the value of the capacitor C2 of the second pre-filter 130 is set to (1-1/N) ﹡ C/N, and the value of the capacitor Cx of the final filter 140 is set to C/(N ﹡ N). Where N is the ratio of the resistor Rx of the final filter 140 to the resistor R2 of the second pre-filter 130 and the ratio of the resistor R2 of the second pre-filter 130 to the resistor R1 of the first pre-filter, (1-1/N) is a reduction coefficient, C is the initial capacitance of the capacitor C1 of the first pre-filter 130, and C/N is the initial capacitance of the capacitor C2 of the second pre-filter 130. The product of the value of the resistor R1 of the first pre-filter 130 and the initial capacitance value of the capacitor C1 is equal to a predetermined value, and the product of the value of the resistor R2 of the second pre-filter 130 and the initial capacitance value of the capacitor C2 is equal to a predetermined value.
If A is 1 K.OMEGA.C is 1uF and N is 10. Then the resistance R1 of the first pre-filter 130 has a value of 1K Ω, the resistance R2 of the second pre-filter 130 has a value of 10K Ω, the resistance Rx of the final filter 140 has a value of 100K Ω, the capacitance C1 of the first pre-filter 130 has a value of 0.9uF, the capacitance C2 of the second pre-filter 130 has a value of 0.09uF, and the capacitance Cx of the final filter 140 has a value of 0.01 uF. As shown in fig. 14, in order to set the resistance and capacitance values of the intermediate stage filter and the final stage filter 140 of the preliminary filter according to the foregoing values, the simulation results were obtained as follows: at a frequency of 159Hz, the corresponding attenuation value is-9 dB. It can be seen that the effect of the three-stage filter cascaded by the operational amplifier is the same.
It can be seen that through the optimized design of the parameters of the low-pass filter 100, the mutual influence of the front and rear stages when the filters are cascaded is avoided, so that an operational amplifier is omitted, the cost is saved, the introduction of additional noise by using the operational amplifier is avoided, the area of a circuit board is saved, and the energy consumption is saved.
In summary, the low-pass filter and the electronic device provided by the embodiment of the invention have the beneficial effects that: the low-pass filter comprises an input port, an output port and at least two filters, wherein the at least two filters which are cascaded with each other are electrically connected between the input port and the output port; the at least two filters comprise at least one pre-filter and a final filter, the pre-filter is electrically connected with the input port, the final filter is electrically connected with the output port, and the product of the component parameters of the final filter is equal to a preset value; wherein the preset value is the reciprocal of the turning frequency; and the product of the component parameters of the preceding-stage filter is smaller than the preset value. Because the latter stage affects the load of the former stage, the low-pass filter can achieve the same effect as the operational amplifier by changing the component parameters of the former stage filter and the last stage filter. The circuit has the advantages of cost saving, simple circuit, circuit board area saving and the like.
The above description is only for the specific embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the appended claims.
Claims (10)
1. A low-pass filter is characterized by comprising an input port, an output port and at least two filters, wherein the at least two filters which are cascaded with each other are electrically connected between the input port and the output port; the at least two filters include at least a pre-filter electrically connected to the input port and a final filter electrically connected to the output port;
the product of the component parameters of the final filter is equal to a preset value; wherein the preset value is the reciprocal of the turning frequency;
and the product of the component parameters of the pre-stage filter is smaller than the preset value.
2. The low pass filter according to claim 1, wherein each of the filters includes a resistor, a capacitor, an input terminal, an output terminal, and a ground terminal, the resistor is electrically connected to the capacitor, the resistor is disposed between the input terminal and the output terminal, the capacitor is disposed between the output terminal and the ground terminal, the input terminal of any one of the filters is electrically connected to the output terminal of the previous filter or the input port, and the output terminal is electrically connected to the input terminal of the next filter or the output port.
3. A low-pass filter as claimed in claim 2, characterized in that the product of the resistance of the final filter and the capacitance of the final filter is equal to the predetermined value.
4. The low pass filter according to claim 2, wherein a product of a resistance of the pre-filter and a capacitance of the pre-filter is smaller than the preset value.
5. A low-pass filter as claimed in claim 4, characterized in that the value of the capacitance of the pre-filter is determined in dependence on a reduction factor and an initial capacitance value;
the reduction coefficient is determined by the resistance value of the pre-filter and the resistance value of the next filter, and the initial capacitance value is determined by the resistance value of the pre-filter and the preset value.
6. A low-pass filter as claimed in claim 5, characterized in that said reduction factor is calculated according to the formula k ═ 1-Rn/Rn +1, n ≧ 1;
wherein k is the reduction coefficient, Rn is the resistance value of the preceding filter, and Rn +1 is the resistance value of the next filter.
7. A low-pass filter as claimed in claim 6, characterized in that the ratio of the resistance of the following filter stage to the resistance of the preceding filter stage is a positive number greater than 2.
8. An electronic device, comprising a low-pass filter, wherein the low-pass filter comprises an input port, an output port and at least two filters, and the at least two filters which are cascaded with each other are electrically connected between the input port and the output port; the at least two filters comprise at least one pre-filter and a final filter, the pre-filter is electrically connected with the input port, and the product of the parameters of components of the final filter electrically connected with the output port is equal to a preset value; wherein the preset value is the reciprocal of the turning frequency;
and the product of the component parameters of the pre-stage filter is smaller than the preset value.
9. The electronic device according to claim 8, wherein each of the filters includes a resistor, a capacitor, an input terminal, an output terminal, and a ground terminal, the resistor is electrically connected to the capacitor, the resistor is disposed between the input terminal and the output terminal, the capacitor is disposed between the output terminal and the ground terminal, the input terminal of any one of the filters is electrically connected to the output terminal of the previous filter or the input port, and the output terminal is electrically connected to the input terminal of the next filter or the output port.
10. The electronic apparatus according to claim 9, wherein a value of a capacitance of the pre-stage filter is determined in accordance with a reduction coefficient and an initial capacitance value;
the reduction coefficient is determined by the resistance value of the pre-filter and the resistance value of the next filter, and the initial capacitance value is determined by the resistance value of the pre-filter and the preset value.
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| CN210642833U (en) * | 2019-11-06 | 2020-06-02 | 广东科贸职业学院 | A smart bracelet for ECG monitoring |
| CN213342162U (en) * | 2020-11-19 | 2021-06-01 | 江苏海湾电气科技有限公司 | Low-pass filter and electronic device |
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2020
- 2020-11-19 CN CN202011298419.1A patent/CN112290902A/en active Pending
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| CN1346538A (en) * | 2000-02-08 | 2002-04-24 | 三菱电机株式会社 | Multistage amplifier |
| US6812794B1 (en) * | 2000-02-08 | 2004-11-02 | Mitsubishi Denki Kabushiki Kaisha | Multistage amplifier |
| JP2014204286A (en) * | 2013-04-04 | 2014-10-27 | ルネサスモバイル株式会社 | Multistage active filter and reception device |
| CN208548873U (en) * | 2018-09-05 | 2019-02-26 | 深圳市山田微电子有限公司 | A kind of low-noise filter |
| CN210642833U (en) * | 2019-11-06 | 2020-06-02 | 广东科贸职业学院 | A smart bracelet for ECG monitoring |
| CN213342162U (en) * | 2020-11-19 | 2021-06-01 | 江苏海湾电气科技有限公司 | Low-pass filter and electronic device |
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