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Double-operational-amplifier elliptic function and inverse Chebyshev active low-pass filter circuit

An inverse Chebyshev, low-pass filter technology, applied in the field of analog microelectronics, can solve the problems of poor circuit symmetry and stability, small dispersion of component values, and large circuit volume, etc. The effect of cost, power consumption reduction, and circuit size reduction

Active Publication Date: 2021-05-07
王致华
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0004] In addition, the state variable elliptic function filter will change the shape of the frequency characteristic curve when the gain is changed. It is very inconvenient to use the filter for program-controlled gain amplification
[0005]Obviously, the performance of the elliptic function filter including three or more operational amplifiers is better, but its power consumption is larger, the circuit size is also larger, and the cost is higher ; and the symmetry and stability of the circuit of the elliptic function filter of the single op amp are not very good; therefore, there is a lack of a circuit to form a small number of op amps, and at the same time it has good stability, small component value dispersion, and circuit Elliptic function low-pass filter with high symmetry and independent gain programming

Method used

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  • Double-operational-amplifier elliptic function and inverse Chebyshev active low-pass filter circuit
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  • Double-operational-amplifier elliptic function and inverse Chebyshev active low-pass filter circuit

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Embodiment 1

[0034] A dual op amp elliptic function, anti-Chebyshev active low-pass filter circuit, including signal input terminal Vs, signal output terminal Vo and input and output signal common terminal GND, is characterized in that, also includes resistance Rq1, resistance Rq2, resistance Ra, resistor Rb, resistor Rd, resistor Ri, resistor Ro, capacitor Ca, capacitor Cb, operational amplifier U1A and operational amplifier U1B, one end of resistor Rq1, resistor Ri and capacitor Ca is connected to node p1; as an input terminal connected to the input signal Vi; the other end of the resistor Rq1, the other end of the capacitor Ca, one end of the resistor Rq2 and the resistor Ra, and the non-inverting input end of the operational amplifier U1A are connected to the node p2; the other end of the resistor Rq2 is connected to the input and output signal common terminal GND; the resistor Ra The other end of the capacitor Cb, one end of the capacitor Cb, and the output of the op amp U1B are connec...

Embodiment 2

[0065] The present embodiment is the detailed circuit parameter example of 1KHz elliptic function low-pass filter:

[0066] A 5th-order elliptic function low-pass filter-amplifier, its cut-off frequency fc: 1KHz; passband fluctuation: 0.1dB; stopband attenuation: 60dB; transition bandwidth: 1.044fc; gain: maximized;

[0067] Obviously, you can use Figure 7 The scheme is realized, and the parameters of each filter section are as follows:

[0068] The first filter section: Op-amp isolation first-order RC low-pass filter section, circuit diagram: Figure 4 ;

[0069] Rs1=27K; C1=10nF

[0070] The second filter section: dual op amp second-order elliptic function low-pass filter section, circuit diagram: figure 1 ;

[0071] Ri=Ro=4.99K; Ca=Cb=10nF;

[0072] Ra=Rb=6.42K; Rd=7.96k; Rq1=Rq2=113K;

[0073] The third filter section: dual op amp second-order elliptic function low-pass filter section, circuit diagram: figure 1 ;

[0074] Ri=Ro=4.99K; Ca=Cb=10nF;

[0075] Ra=Rb=...

Embodiment 3

[0079] The present embodiment is the detailed circuit parameter example of 1KHz elliptic function low-pass filter:

[0080] Realize a 5th-order elliptic function low-pass filter with unity gain, 1KHz cut-off frequency, 0.1dB passband fluctuation, 60dB stopband attenuation, and excess bandwidth equal to 1.044 times the cut-off frequency.

[0081] use Figure 9 Scheme, the value of the second-order filter section circuit components is the same as that of embodiment 2, and the first-order filter section adopts Figure 5circuit, the attenuation of the first-order filter section is equal to the total gain of all second-order filter sections, and the unity gain filter is obtained, and its circuit element values ​​are: C1=10nF; Rs1=1665K; Rs2=27.5K;

[0082] Will Figure 11 The curve of is shifted down to the gain of 0 dB, that is, shifted down by 35.6 dB to obtain the frequency characteristic of this embodiment.

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Abstract

The invention discloses an inverse Chebyshev active low-pass filter circuit with a double-operational-amplifier elliptic function. The circuit comprises a signal input end Vs, a signal output end Vo and an input and output signal common end GND, and is characterized by further comprising a resistor Rq1, a resistor Rq2, a resistor Ra, a resistor Rb, a resistor Rd, a resistor Ri, a resistor Ro, a capacitor Ca, a capacitor Cb, an operational amplifier U1A and an operational amplifier U1B, and one end of the resistor Rq1, one end of the resistor Ri and one end of the capacitor Ca are connected to a node p1, which serves as the input end which is connected to an input signal Vi; the other end of the resistor Rq1, the other end of the capacitor Ca, one end of the resistor Rq2, one end of the resistor Ra and the in-phase input end of the operational amplifier U1A are connected to a node p2; and the other end of the resistor Rq2 is connected to the input and output signal common end GND. The circuit is good in symmetry, stable in performance and easy to design and use, one to two operational amplifiers are saved compared with a 3 or 4 operational amplifier state variable elliptic function filter, power consumption is reduced, the size of the circuit is reduced, and the cost of the filter and the circuit is reduced.

Description

technical field [0001] The invention relates to the technical field of analog microelectronics, in particular to a circuit using two operational amplifiers to form an elliptic function and an inverse Chebyshev active filter. Background technique [0002] Active filters are an important part of electronic circuit signal conditioning technology, and are widely used in electronic circuits such as communication technology, instrumentation, industrial measurement and control, and military electronics to eliminate out-of-band noise of signals and electronic equipment. The transfer function forms of active filters mainly include Butterworth filter, Chebyshev filter, inverse Chebyshev filter, and elliptic function filter, and their frequency characteristics can be divided into low-pass filter, high-pass filter, band-pass filter, band-stop filter. Its circuit composition is divided into single op amp circuit, double op amp circuit, three op amp circuit, and four op amp circuit accor...

Claims

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Application Information

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IPC IPC(8): H03H11/46
CPCH03H11/46
Inventor 王致华
Owner 王致华
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