CN113472315A - Active filter circuit based on operational amplifier chip - Google Patents
Active filter circuit based on operational amplifier chip Download PDFInfo
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- CN113472315A CN113472315A CN202110826675.1A CN202110826675A CN113472315A CN 113472315 A CN113472315 A CN 113472315A CN 202110826675 A CN202110826675 A CN 202110826675A CN 113472315 A CN113472315 A CN 113472315A
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- resistor
- operational amplifier
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H11/00—Networks using active elements
- H03H11/02—Multiple-port networks
- H03H11/04—Frequency selective two-port networks
- H03H11/12—Frequency selective two-port networks using amplifiers with feedback
- H03H11/1217—Frequency selective two-port networks using amplifiers with feedback using a plurality of operational amplifiers
Abstract
The invention relates to an active filter circuit based on an operational amplifier chip, which comprises the operational amplifier chip, a gain adjusting circuit, a direct current bias circuit, a first second-order circuit and a second-order circuit, wherein the first second-order circuit is connected with the second-order circuit; two operational amplifiers A and B are integrated in the operational amplifier chip; the gain adjusting circuit is connected with the input ends of the operational amplifiers A and B; the direct current bias circuit is connected with the first second-order circuit, and the first second-order circuit is connected with the input end and the output end of the operational amplifier; the second-order circuit is connected with the input end and the output end of the operational amplifier B. The invention does not need to introduce an inductor, and meets the requirement of working in a severe electromagnetic environment; by adopting a single chip, under the condition of the same filter order, compared with a circuit which is built by using two operational amplifier chips, the circuit has small area and is suitable for being used in a scene with limited volume such as a fuse; the advantage of LTC6229 high-gain bandwidth product is fully utilized, the use frequency reaches 11MHz, and reference is provided for subsequent intermediate frequency signal processing.
Description
Technical Field
The invention relates to the technical field of electronic devices, in particular to an active filter circuit based on an operational amplifier chip.
Background
The filter plays an important role in a medium radio frequency circuit as a frequency selection device. A passive filter and an active filter may be classified according to differences in constituent elements. The passive filter mainly comprises a capacitor and an inductor, is various in design form, large in frequency range, low in-band loss and low in adjustability. The active filter mainly comprises a resistor, a capacitor and an operational amplifier, and has gain in a band and high adjustability, but the applicable frequency is usually low, and new noise is easily introduced.
In electromagnetic weapons, due to the purpose of their combat and the specificity and complexity of the manner in which they are used, many technical problems are associated with the design of internal electronic circuits. Firstly, the electromagnetic weapon generates high-power electromagnetic wave interference and even permanently damages enemy communication facilities, which puts high electromagnetic compatibility requirements on an internal circuit of the weapon, and requires that an electromagnetic sensitive element such as an inductor cannot be used during circuit design, thereby bringing certain difficulty to the design of an intermediate frequency filter; secondly, the high-requirement filtering index can increase the order of the filter, and the occupied space is increased, which is in contradiction with the strict limitation of the circuit board area in the weapon. Third, if the intermediate frequency processing circuit often requires a gain of 50dB or more, a cascade of multiple intermediate frequency amplifiers is required, which not only increases the cost, but also complicates the peripheral circuits. Therefore, how to effectively solve the technical problems is extremely important.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides an active filter circuit based on an operational amplifier chip.
The purpose of the invention is realized by the following technical scheme: an active filter circuit based on an operational amplifier chip comprises the operational amplifier chip, a gain adjusting circuit, a direct current bias circuit, a first second-order circuit and a second-order circuit; two operational amplifiers A and B are integrated in the operational amplifier chip; the gain adjusting circuit is connected with the input ends of the operational amplifiers A and B to realize gain adjustment of the operational amplifier chip; the direct current bias circuit is connected with the first second-order circuit, the first second-order circuit is connected with the input end and the output end of the operational amplifier, and the direct current bias circuit provides direct current bias for input signals; the second-order circuit is connected with the input end and the output end of the operational amplifier B; and a signal is input from the input end of the operational amplifier A and is finally output from the output end of the operational amplifier B, so that the two-operational-amplifier four-order active filter circuit is obtained.
The gain adjusting circuit comprises a resistor R1, a resistor R2, a resistor R9, a capacitor C2 and a capacitor C6; the capacitor C2 is connected between the input end and the output end of the operational amplifier A, the resistor R2 is connected with the capacitor C2 in parallel, and the resistor R1 is connected with the resistor R2 in series and then grounded; the resistor R9 is connected between the input end and the output end of the operational amplifier B, and the capacitor C6 is connected with the resistor R9 in parallel.
The first two-stage circuit comprises a resistor R6, a resistor R7, a capacitor C4 and a capacitor C5; the capacitor C5 is connected between a power supply pin of the operational amplifier chip and the input end of the operational amplifier A, and the resistor R6 and the resistor R7 are connected in series and then connected to the input end of the operational amplifier A; one end of the capacitor C4 is connected between the resistor R6 and the resistor R7, and the other end is connected with the output end of the operational amplifier A.
The direct current bias circuit comprises a resistor R5 and a resistor R8; the resistor R5 and the resistor R8 are connected in series, the other end of the resistor R5 is connected with +5V voltage, the other end of the resistor R8 is grounded, and one end of the resistor R6 is connected between the resistor R5 and the resistor R8.
The second-order circuit comprises a resistor R3, a resistor R4, a capacitor C1 and a capacitor C3; one end of the capacitor C3 is connected with the output end of the operational amplifier B, the other end of the capacitor C3 is connected between the resistor R3 and the resistor R4 which are connected in series, the other end of the resistor R3 is connected with the output end of the operational amplifier A, the other end of the resistor R4 is connected with the input end of the operational amplifier B, one end of the capacitor C1 is connected with the input end of the operational amplifier B, and the other end of the capacitor C1 is grounded.
The invention has the following advantages: an active filter circuit based on an operational amplifier chip does not need to introduce an inductor, and meets the requirement of working in a severe electromagnetic environment; by adopting a single chip, under the condition of the same filter order, compared with a circuit which is built by using two operational amplifier chips, the circuit has small area and is suitable for being used in a scene with limited volume such as a fuse; the advantage of LTC6229 high-gain bandwidth product is fully utilized, the use frequency reaches 11MHz, and reference is provided for subsequent intermediate frequency signal processing; the single power supply is adopted for supplying power, the negative voltage stabilizer required by introducing dual power supplies is reduced, and the power supply has advantages in function, cost and size.
Drawings
FIG. 1 is a circuit block diagram of the present invention;
FIG. 2 is a diagram illustrating simulation results of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only a part of the embodiments of the present application, and not all the embodiments. The components of the embodiments of the present application, generally described and illustrated in the figures herein, can be arranged and designed in a wide variety of different configurations. Thus, the detailed description of the embodiments of the present application provided below in connection with the appended drawings is not intended to limit the scope of the claimed application, but is merely representative of selected embodiments of the application. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the present application without making any creative effort, shall fall within the protection scope of the present application. The invention is further described below with reference to the accompanying drawings.
As shown in fig. 1, the present invention relates to an active filter circuit based on an operational amplifier chip, which includes an operational amplifier chip, a gain adjusting circuit, a dc bias circuit, a first second-order circuit and a second-order circuit; two identical operational amplifiers A and B are integrated in the operational amplifier chip; the gain adjusting circuit is connected to the input ends of the operational amplifiers A and B in a negative feedback mode to realize gain adjustment of the operational amplifier chip; the direct current bias circuit is connected with the first second-order circuit, the first second-order circuit is connected with the input end and the output end of the operational amplifier, and the direct current bias circuit provides direct current bias for input signals; the second-order circuit is connected with the input end and the output end of the operational amplifier B; and a signal is input from the input end of the operational amplifier A and is finally output from the output end of the operational amplifier B, so that the two-operational-amplifier four-order active filter circuit is obtained.
The intermediate frequency receiving module is applied to a fuse of a certain model, and is specifically used for amplifying and filtering an intermediate frequency receiving signal output by a down converter of a receiver, wherein the signal bandwidth is 10-11MHz, and the minimum attenuation is 20dB at 20 MHz. For this purpose, an operational amplifier chip LTC6229 from ADI was used. The chip is a dual-channel ultra-fast unit gain stable operational amplifier. The gain-bandwidth product is 890MHz and the slew rate is 500V/us.
Two operational amplifiers A and B are integrated in a chip LTC6229 in the circuit, pins-INA, + INA and OUTA are input and output of the operational amplifier A, and pins-INB, + INB and OUTB are input and output of the operational amplifier B. V + is power supply voltage, is connected with +5V and V-ground, and SHDNA and SHDNB are off pins which are suspended and not used.
Further, the gain adjustment circuit comprises a resistor R1, a resistor R2, a resistor R9, a capacitor C2 and a capacitor C6; the capacitor C2 is connected between the input end and the output end of the operational amplifier A, the resistor R2 is connected with the capacitor C2 in parallel, and the resistor R1 is connected with the resistor R2 in series and then grounded; the resistor R9 is connected between the input end and the output end of the operational amplifier B, and the capacitor C6 is connected with the resistor R9 in parallel. By adopting a second-order Sallen-Key low-pass filter structure, the gain can be effectively adjusted by changing the resistance values of the resistors R1, R2 and R9.
Further, the first two-stage circuit comprises a resistor R6, a resistor R7, a capacitor C4 and a capacitor C5; the capacitor C5 is connected between a power supply pin of the operational amplifier chip and the input end of the operational amplifier A, and the resistor R6 and the resistor R7 are connected in series and then connected to the input end of the operational amplifier A; one end of the capacitor C4 is connected between the resistor R6 and the resistor R7, and the other end is connected with the output end of the operational amplifier A.
Further, the dc bias circuit includes a resistor R5 and a resistor R8; the resistor R5 and the resistor R8 are connected in series, the other end of the resistor R5 is connected with +5V voltage, the other end of the resistor R8 is grounded, and one end of the resistor R6 is connected between the resistor R5 and the resistor R8. Resistors R5 and R8 divide the voltage to provide a dc bias to the input signal so that the amplitude of the output signal is within the gain range of the amplifier. Here, the dc voltages are equal, i.e., 2.5V.
Further, the second-order circuit comprises a resistor R3, a resistor R4, a capacitor C1 and a capacitor C3; one end of the capacitor C3 is connected with the output end of the operational amplifier B, the other end of the capacitor C3 is connected between the resistor R3 and the resistor R4 which are connected in series, the other end of the resistor R3 is connected with the output end of the operational amplifier A, the other end of the resistor R4 is connected with the input end of the operational amplifier B, one end of the capacitor C1 is connected with the input end of the operational amplifier B, and the other end of the capacitor C1 is grounded.
As shown in fig. 2, the filter has a gain of 10dB in the pass band and a relative attenuation of 20dB at 20MHz, which achieves the desired result. The invention does not need to introduce an inductor, and meets the requirement of working in a severe electromagnetic environment; by adopting a single chip, under the condition of the same filter order, compared with a circuit which is built by using two operational amplifier chips, the circuit has small area and is suitable for being used in a scene with limited volume such as a fuse; the advantage of LTC6229 high-gain bandwidth product is fully utilized, the use frequency reaches 11MHz, and reference is provided for subsequent intermediate frequency signal processing; the single power supply is adopted for supplying power, the negative voltage stabilizer required by introducing dual power supplies is reduced, and the power supply has advantages in function, cost and size.
The foregoing is illustrative of the preferred embodiments of this invention, and it is to be understood that the invention is not limited to the precise form disclosed herein and that various other combinations, modifications, and environments may be resorted to, falling within the scope of the concept as disclosed herein, either as described above or as apparent to those skilled in the relevant art. And that modifications and variations may be effected by those skilled in the art without departing from the spirit and scope of the invention as defined by the appended claims.
Claims (5)
1. An active filter circuit based on operational amplifier chip, its characterized in that: the circuit comprises an operational amplifier chip, a gain adjusting circuit, a direct current bias circuit, a first second-order circuit and a second-order circuit; two operational amplifiers A and B are integrated in the operational amplifier chip; the gain adjusting circuit is connected with the input ends of the operational amplifiers A and B to realize gain adjustment of the operational amplifier chip; the direct current bias circuit is connected with the first second-order circuit, the first second-order circuit is connected with the input end and the output end of the operational amplifier, and the direct current bias circuit provides direct current bias for input signals; the second-order circuit is connected with the input end and the output end of the operational amplifier B; and a signal is input from the input end of the operational amplifier A and is finally output from the output end of the operational amplifier B, so that the two-operational-amplifier four-order active filter circuit is obtained.
2. The active filter circuit based on the operational amplifier chip as claimed in claim 1, wherein: the gain adjusting circuit comprises a resistor R1, a resistor R2, a resistor R9, a capacitor C2 and a capacitor C6; the capacitor C2 is connected between the input end and the output end of the operational amplifier A, the resistor R2 is connected with the capacitor C2 in parallel, and the resistor R1 is connected with the resistor R2 in series and then grounded; the resistor R9 is connected between the input end and the output end of the operational amplifier B, and the capacitor C6 is connected with the resistor R9 in parallel.
3. The active filter circuit based on the operational amplifier chip as claimed in claim 1, wherein: the first two-stage circuit comprises a resistor R6, a resistor R7, a capacitor C4 and a capacitor C5; the capacitor C5 is connected between a power supply pin of the operational amplifier chip and the input end of the operational amplifier A, and the resistor R6 and the resistor R7 are connected in series and then connected to the input end of the operational amplifier A; one end of the capacitor C4 is connected between the resistor R6 and the resistor R7, and the other end is connected with the output end of the operational amplifier A.
4. The active filter circuit based on the operational amplifier chip as claimed in claim 3, wherein: the direct current bias circuit comprises a resistor R5 and a resistor R8; the resistor R5 and the resistor R8 are connected in series, the other end of the resistor R5 is connected with +5V voltage, the other end of the resistor R8 is grounded, and one end of the resistor R6 is connected between the resistor R5 and the resistor R8.
5. The active filter circuit based on the operational amplifier chip as claimed in claim 1, wherein: the second-order circuit comprises a resistor R3, a resistor R4, a capacitor C1 and a capacitor C3; one end of the capacitor C3 is connected with the output end of the operational amplifier B, the other end of the capacitor C3 is connected between the resistor R3 and the resistor R4 which are connected in series, the other end of the resistor R3 is connected with the output end of the operational amplifier A, the other end of the resistor R4 is connected with the input end of the operational amplifier B, one end of the capacitor C1 is connected with the input end of the operational amplifier B, and the other end of the capacitor C1 is grounded.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202110826675.1A CN113472315A (en) | 2021-07-21 | 2021-07-21 | Active filter circuit based on operational amplifier chip |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202110826675.1A CN113472315A (en) | 2021-07-21 | 2021-07-21 | Active filter circuit based on operational amplifier chip |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN113472315A true CN113472315A (en) | 2021-10-01 |
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Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202110826675.1A Pending CN113472315A (en) | 2021-07-21 | 2021-07-21 | Active filter circuit based on operational amplifier chip |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN113472315A (en) |
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2021
- 2021-07-21 CN CN202110826675.1A patent/CN113472315A/en active Pending
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