CN101483420B - Switch capacitor band-pass filter and continuous time band-pass filter - Google Patents

Abstract

The present invention relates to a switch capacitance second order band-pass filter which is provided with four programmable capacitors, capacitance values of the four programmable capacitor being Alpha1C1, Alpha2C2, Alpha3C1, Alpha4C2, wherein, C1 and C2 are two integration capacitors, Alpha1-Alpha4 are coefficients, and Alpha1-Alpha4 satisfies: for example Alpha1=Alpha2=Omega0T, Alpha3=1/Q, Alpha4=KT, wherein Omega0 is filter center frequency, Q is filter figure of merit, and K is filter gain coefficient. Thereby the three parameters can be adjusted independently. The present invention also provides a continuous time RC structure and a difference structure of the above band-pass filter.

Description

Switched capacitor bandpass filter and continuous time band pass filter

Technical field

The present invention relates to a kind of filter circuit, relate in particular to a kind of switched capacitor bandpass filter and continuous time band pass filter.

Background technology

Band pass filter is a kind of application analog circuit very widely.Carrying out cascade with basic second-order bandpass filter is a kind of usual way that constitutes high-order band-pass filters.In this cascade system, seek the key that a kind of suitable second-order bandpass filter structure becomes technology.

In the application of filter,, often be necessary the filtering characteristic of filter is carried out programming Control for various needs.Sometimes be in order to proofread and correct because the skew of the characteristics such as frequency, Q value and gain that process deviation or design mismatch (Mismatch) are brought sometimes then is because filter itself needs controlled frequency characteristic (mainly referring to ripple and gain in band connection frequency, the band).

During this time, generally be the value of adjusting some resistance or electric capacity by external control signal, thus the frequency characteristic of control filters.So, by external control signal is programmed, just can realize the filter of different filtering characteristics, this will improve the efficient of filter greatly.

For a second-order bandpass filter, its typical transfer function is:

$H\left(s\right)=\frac{-K\·s}{s^2+\frac{{\mathrm{\ω}}_0}{Q}s+{{\mathrm{\ω}}_0}^2},$

ω wherein ₀Be the centre frequency of band pass filter, Q is a quality factor, and K is related to and only be related to gain, referred to herein as gain coefficient.

Figure 1 shows that a kind of low reactance-resistance ratio switching capacity second-order bandpass filter commonly used, wherein, just can obtain the implementation of its continuous time of RC, be not difficult to draw its z territory and pass letter as long as all switching capacities are converted into corresponding resistance:

$H\left(z\right)=-\frac{{\mathrm{\α}}_{4}z(z-1)}{(1+{\mathrm{\α}}_6)z^2+({\mathrm{\α}}_2{\mathrm{\α}}_5-{\mathrm{\α}}_6-2)z+1}$

In view of switching capacity filter generally all is that signal is carried out over-sampling, can suppose ω T＜＜1.So can hang down the equivalent s territory transfer function of Q structure:

$H\left(s\right)=-\frac{\frac{a_4}{T}s}{{\mathrm{<figure-callout\; id="2"\; label="s"\; filenames="S2008100323676E00031.png"\; state="\{\{state\}\}">s</figure-callout>}}^2+\frac{a_6}{T}s+\frac{a_2{a}_5}{{\mathrm{<figure-callout\; id="2"\; label="T"\; filenames="S2008100323676E00031.png"\; state="\{\{state\}\}">T</figure-callout>}}^2}}$

For obtaining good dynamic range, choose α ₂=α ₅So, have:

α ₂＝α ₅＝ω ₀T

${\mathrm{\&alpha;}}_6=\frac{{\mathrm{\&omega;}}_{0}T}{Q}$

α ₄＝KT

So, just can be by adjusting α simultaneously ₂And α ₅Come control centre's frequencies omega ₀, by adjusting α ₆Come controlling performance factor Q, and by adjusting α ₄Come ride gain.Certainly, these adjustment also can realize by the clock frequency of control switch electric capacity; But this adjusts relative complex, and the clock frequency variation can bring three parameters of filter all to change simultaneously, is unfavorable for independent control, so generally seldom use.Adjust α ₄, can adjust gain separately; Adjust α ₆, can adjust Q separately; Adjust α synchronously ₂, α ₅, can adjust ω ₀But because

Adjust α ₂, α ₅To adjust ω ₀The time, also adjusted Q, i.e. ω ₀And there is association between the Q, can't realizes ω ₀Independent the adjustment.

Except low Q structure shown in Figure 1, also have another high Q structure commonly used, also can be used for realizing band pass filter.Shown in Figure 2ly be high Q switching electric capacity second-order bandpass filter, wherein as long as all switching capacities are converted into corresponding resistance, just can obtain the implementation of its continuous time of RC, the z territory transfer function of being not difficult to draw high Q structure is:

$H\left(z\right)=-\frac{{\mathrm{\&alpha;}}_3{\mathrm{\&alpha;}}_5(z-1)}{z^2+({\mathrm{\&alpha;}}_4{\mathrm{\&alpha;}}_5+{\mathrm{\&alpha;}}_2{\mathrm{\&alpha;}}_5-2)z+(1-{\mathrm{\&alpha;}}_4{\mathrm{\&alpha;}}_5)}$

In view of switching capacity filter generally all is to equalisation of over-sampled signals, can do hypothesis ω T＜＜1.Pass letter so can get the equivalent s territory of high Q structure:

$H\left(s\right)=-\frac{\frac{a_3{\mathrm{\&alpha;}}_5}{T}s}{s^2+\frac{{\mathrm{\&alpha;}}_4{a}_5}{T}s+\frac{a_2{a}_5}{{\mathrm{<figure-callout\; id="2"\; label="T"\; filenames="S2008100323676E00031.png"\; state="\{\{state\}\}">T</figure-callout>}}^2}}$

For obtaining good dynamic range, choose α ₂=α ₅So, have:

α ₂＝α ₅＝ω ₀T

${\mathrm{\&alpha;}}_4=\frac{1}{Q}$

${\mathrm{\&alpha;}}_3=\frac{K}{{\mathrm{\&omega;}}_0}$

So, adjust α ₃, can adjust gain separately; Adjust α ₄, can adjust Q separately; Adjust α synchronously ₂, α ₅, can adjust ω ₀But because

Adjust α ₂, α ₅To adjust ω ₀The time, also adjusted K, i.e. ω ₀And there is association between the K, can't realizes ω ₀Independent the adjustment.

Therefore, thirst for having and a kind ofly can realize ω ₀,

The second-order bandpass filter that each parameter of K is independently adjusted.

Summary of the invention

Technical problem to be solved by this invention provides a kind of programmable switch electric capacity second-order bandpass filter structure, and each centre frequency, quality factor and gain coefficient can independently be adjusted.

In addition, the present invention proposes a kind of continuous time of band pass filter, and each centre frequency, quality factor and gain coefficient can independently be adjusted.

The present invention solves the problems of the technologies described above the technical scheme that adopts to provide a kind of switched capacitor bandpass filter, comprising: first operational amplifier, have first input end, second input and output, and wherein this second input connects an electronegative potential; First integral electric capacity, the one end is connected in the first input end of this first operational amplifier, and the other end is connected in the output of this first operational amplifier; Second operational amplifier has first input end, second input and output, and wherein this second input connects an electronegative potential, and this output is exported an output signal; Second integral electric capacity, the one end is connected in the first input end of this second operational amplifier, and the other end is connected in the output of this second operational amplifier; First switched capacitor, the one end is connected in the first input end of this first operational amplifier, and the other end is connected in the output of this second operational amplifier; The second switch capacitor, the one end is connected in the output of this first operational amplifier, and the other end is connected in the first input end of this second operational amplifier; The 3rd switched capacitor, the one end connects an input signal, and the other end is connected in the first input end of this second operational amplifier; And adjustment electric capacity, the one end is connected in the first input end of this first operational amplifier, and the other end is connected in the output of this second operational amplifier.Wherein, if this first integral capacitance is C1, this second integral capacitance is C2, and then the capacitance of this first switched capacitor is α ₁C1, the capacitance of this second switch capacitor are α ₂C2, the capacitance of the 3rd switched capacitor are α ₄C2, this adjustment capacitance is α ₃C1.

In the above-mentioned switched capacitor bandpass filter, α ₁～α ₄For example satisfy:

α ₁＝α ₂＝ω ₀T

${\mathrm{\&alpha;}}_3=\frac{1}{Q}$

α ₄＝KT

Wherein, ω ₀Be the centre frequency of this switched capacitor bandpass filter, Q is a quality factor, and K is a gain coefficient, and T is the time cycle of clock signal.

In the above-mentioned switched capacitor bandpass filter, first switched capacitor comprises: first capacity cell and first to fourth switch, first end of this first capacity cell is connected in the first input end of this first operational amplifier through this first switch, second end of this first capacity cell is connected in the output of this second operational amplifier through this second switch, the 3rd switch is connected between first end and an electronegative potential of this first capacity cell, the 4th switch is connected between second end and this electronegative potential of this first capacity cell, wherein this first and second switch connects a second switch signal, and this third and fourth switch connects one first switching signal.

In the above-mentioned switched capacitor bandpass filter, the second switch capacitor comprises: second capacity cell and the 5th closes to octavo, first end of this second capacity cell is connected in the output of this first operational amplifier through the 5th switch, second end of this second capacity cell is connected in the first input end of this second operational amplifier through the 6th switch, this minion is closed and is connected between first end and an electronegative potential of this first capacity cell, this octavo is closed and is connected between second end and this electronegative potential of this first capacity cell, wherein the 5th close with octavo and to be connected one first switching signal, the 6th is connected a second switch signal with the minion pass.

In the above-mentioned switched capacitor bandpass filter, the 3rd switched capacitor comprises: the 3rd capacity cell and first to fourth switch, first end of the 3rd capacity cell connects this input signal through this first switch, second end of the 3rd capacity cell is connected in the first input end of this second operational amplifier through the 3rd switch, the 3rd switch is connected between first end and an electronegative potential of the 3rd capacity cell, the 4th switch is connected between second end and this electronegative potential of the 3rd capacity cell, wherein this first and second switch connects a second switch signal, and this third and fourth switch connects one first switching signal.

In the above-mentioned switched capacitor bandpass filter, described electronegative potential is an earthing potential.

In the above-mentioned switched capacitor bandpass filter, first end of first operational amplifier and/or second operational amplifier is a positive terminal, and second end is a negative phase end.

The present invention also proposes a kind of continuous time of band pass filter, comprising: first operational amplifier, have first input end, second input and output, and wherein this second input connects an electronegative potential; First integral electric capacity, the one end is connected in the first input end of this first operational amplifier, and the other end is connected in the output of this first operational amplifier; Second operational amplifier has first input end, second input and output, and wherein this second input connects an electronegative potential, and this output is exported an output signal; Second integral electric capacity, the one end is connected in the first input end of this second operational amplifier, and the other end is connected in the output of this second operational amplifier; First resistor, the one end is connected in the first input end of this first operational amplifier, and the other end is connected in the output of this second operational amplifier; Second resistor, the one end is connected in the output of this first operational amplifier, and the other end is connected in the first input end of this second operational amplifier; The 3rd resistor, the one end connects an input signal, and the other end is connected in the first input end of this second operational amplifier; And adjustment electric capacity, the one end is connected in the first input end of this first operational amplifier, and the other end is connected in the output of this second operational amplifier.Wherein, the resistance of this first to the 3rd resistor is respectively 1/ ω ₀,-1/ ω ₀, 1/K, this adjustment capacitance is 1/Q, wherein, ω ₀Be the centre frequency of this of band pass filter, Q is a quality factor continuous time, and K is a gain coefficient.

In the above-mentioned continuous time band pass filter, first end of first operational amplifier and/or second operational amplifier is a positive terminal, and second end is a negative phase end.

In the above-mentioned continuous time band pass filter, described electronegative potential is an earthing potential.

The present invention also proposes by above-mentioned switched capacitor bandpass filter and difference type filter that continuous time, band pass filter was formed.

Switching capacity second-order bandpass filter of the present invention or its continuous time reinforced concrete structure, can independently adjust the parameters such as centre frequency, quality factor and gain coefficient of filtering, so can carry out independent programming Control to one of them parameter or Several Parameters easily.The present invention can be used to form higher order filter.

Description of drawings

For above-mentioned purpose of the present invention, feature and advantage can be become apparent, below in conjunction with accompanying drawing the specific embodiment of the present invention is elaborated, wherein:

Fig. 1 is existing a kind of low reactance-resistance ratio switching capacity second-order bandpass filter circuit diagram;

Fig. 2 is existing a kind of high Q value switching capacity second-order bandpass filter circuit diagram;

Fig. 3 be one embodiment of the invention switching capacity second-order bandpass filter circuit diagram;

Fig. 4 be another embodiment of the present invention switching capacity second-order bandpass filter circuit diagram;

Fig. 5 is second-order bandpass filter circuit diagram continuous time of one embodiment of the invention.

Fig. 6 is the differential configuration switched capacitor bandpass filter circuit diagram of one embodiment of the invention.

Fig. 7 is the differential configuration band pass filter circuit continuous time figure of one embodiment of the invention.

Embodiment

Embodiments of the invention have been described and a kind ofly can have been realized ω ₀, Independently the programme second order filter of linear programming of K.

Please refer to shown in Figure 3, the second order filter of one embodiment of the invention mainly is made up of following element: first and second operational amplifiers (hereinafter to be referred as amplifier) OP1, OP2, two integrating capacitor C1, C2, first to the 3rd switched capacitor 301～303, is adjusted electric capacity 304.Wherein C1, C2 also represent the capacitance of integrating capacitor.And the capacitance of capacity cell is α in first switched capacitor 301 ₁C1, the capacitance of capacity cell is α in the second switch capacitor 302 ₂C2, the capacitance of capacity cell is α in the 3rd switched capacitor 303 ₄C2, the capacitance of adjusting electric capacity 304 is α ₃C1.At this α ₁～α ₄Be called first to fourth and adjust coefficient.

The first amplifier Op1 has two inputs (be anode+and negative terminal-) and an output, and wherein to connect one for example be the electronegative potential of earthing potential to negative terminal.The cross-over connection of first integral capacitor C 1 is between the anode and output of this first amplifier OP1.

The second amplifier Op2 has two inputs (be anode+and negative terminal-) and an output, and wherein negative to connect one for example be the electronegative potential of earthing potential, and this output is exported an output signal Vout ^e(Z).2 cross-over connections of second integral capacitor C are between the anode and output of the big Op2 of this second fortune.

One end of first switched capacitor 301 is connected in the anode of the first amplifier Op1, and the other end is connected in the output of the first amplifier Op2.This first switched capacitor 301 comprises that further capacitance is α ₁First capacity cell of C1, and first to fourth K switch, 1～K4, first end of first capacity cell connects the anode of the first amplifier Op1 through K switch 1, second end connects the output of the second amplifier Op2 through K switch 2, and K switch 3 is connected between this first end and the electronegative potential (as earthing potential), and K switch 4 is connected between this second end and this electronegative potential.Wherein, this first and second K switch 1, K2 connect a second switch signal psi 2, and this third and fourth K switch 3, K4 connect one first switching signal φ 1.Wherein, the not conducting simultaneously of the first switching signal φ 1 and second switch signal psi 2, the two for example is anti-phase.

One end of second switch capacitor 302 is connected in the output of the first amplifier Op1, and the other end is connected in the anode of the second amplifier Op2.This second switch capacitor 302 comprises that further capacitance is α ₂Second capacity cell of c2, and first to fourth K switch, 5～K8, first end of second capacity cell connects the output of the first amplifier Op1 through K switch 5, second end connects the anode of the second amplifier Op2 through K switch 6, and K switch 7 is connected between this first end and the electronegative potential (as earthing potential), and K switch 8 is connected between this second end and this electronegative potential.Wherein, this first is connected the first switching signal φ 1 with the 4th K switch 5, K8, and this second is connected second switch signal psi 2 with the 3rd K switch 6, K7.

One end of the 3rd switched capacitor 303 connects an input signal Vin ^e(Z), the other end is connected in the anode of this second amplifier Op2.This 3rd switched capacitor 303 comprises that further capacitance is α ₄The 3rd capacity cell of C2, and first to fourth K switch, 9～K12, first end of the 3rd capacity cell connects this input signal Vin through K switch 9 ^e(Z), second end is through the anode of the K switch 10 connections second amplifier Op2, and K switch 11 is connected between this first end and the electronegative potential (as earthing potential), and K switch 12 is connected between this second end and this electronegative potential.Wherein, this first and second K switch 9, K10 connect second switch signal psi 2, and this third and fourth K switch 11, K12 connect the first switching signal φ 1.

Adjust the anode that electric capacity 304 1 ends are connected in this first amplifier Op1, the other end is connected in the output of this second amplifier Op2.

(its capacitance is α respectively for capacity cell in above-mentioned first to the 3rd capacitor 301～303 ₁C1, α ₂C2, α ₄And adjust electric capacity 304 (its capacitance is α C2), ₃C1) all can programme, to adjust adjustment factor alpha wherein by capacitor array ₁～α ₄

Switching capacity second-order bandpass filter structure as shown in Figure 3.Can derive, its z territory transfer function is:

$H\left(z\right)=-\frac{{\mathrm{\&alpha;}}_{4}z(z-1)}{{\mathrm{<figure-callout\; id="2"\; label="z"\; filenames="S2008100323676E00031.png"\; state="\{\{state\}\}">z</figure-callout>}}^2+({\mathrm{\&alpha;}}_1{\mathrm{\&alpha;}}_2+{\mathrm{\&alpha;}}_2{\mathrm{\&alpha;}}_3-2)z+(1-{\mathrm{\&alpha;}}_1{\mathrm{\&alpha;}}_2)}$

In view of switching capacity filter generally all is to the passband signal over-sampling, can do hypothesis ω T＜＜1.So can get equivalent s territory transfer function:

$H\left(s\right)=-\frac{\frac{{\mathrm{\&alpha;}}_4}{T}s}{{\mathrm{<figure-callout\; id="2"\; label="s"\; filenames="S2008100323676E00031.png"\; state="\{\{state\}\}">s</figure-callout>}}^2+\frac{{\mathrm{\&alpha;}}_2{a}_3}{T}s+\frac{a_1{a}_2}{{\mathrm{<figure-callout\; id="2"\; label="T"\; filenames="S2008100323676E00031.png"\; state="\{\{state\}\}">T</figure-callout>}}^2}}$

For obtaining good dynamic range, choose α ₁=α ₂So, have:

α ₁＝α ₂＝ω ₀T

${\mathrm{\&alpha;}}_3=\frac{1}{Q}$

α ₄＝KT

So, just can be by adjusting α simultaneously ₁And α ₂Come control centre's frequencies omega ₀, by adjusting α ₃Come controlling performance factor Q, and by adjusting α ₄Control K.

What be different from tradition low Q structure commonly used and high Q structure is α in the new construction ₁, α ₂With centre frequency ω ₀, α ₃And Q, α ₄And all one-to-one relationship independently between the K: adjust α simultaneously ₁And α ₂Come control centre's frequencies omega ₀The time, can not have influence on Q or K; By adjusting α ₃When coming controlling performance factor Q, can not have influence on ω ₀Perhaps K; By adjusting α ₄When controlling K, can not have influence on ω ₀Perhaps Q.Be ω ₀, between Q and the K three without any association, being suitable for very much independent programming and adjusting.

Simultaneously, under the constant situation of clock cycle T, α ₁, α ₂With centre frequency ω ₀, α ₃With

α ₄And all linear relationship between the K.If capacitor array is to factor alpha ₁, α ₂, α ₃And α ₄Carry out linear programming, can realize ω ₀, the independent linearity adjustment control of Q and K.

Fig. 4 be another embodiment of the present invention switching capacity second-order bandpass filter circuit diagram.As shown in Figure 4, be with the difference of last embodiment shown in Figure 3, omit K switch 8 and K10, and a wherein end of second switch capacitor 302 is passed through K switch 12 ground connection, and a wherein end of second switch capacitor 302 is connected to the negative input end of the second amplifier Op2 by K switch 7.Therefore can simplify circuit structure by switch multiplexing.Other structures of present embodiment are identical with last embodiment, are not described in detail at this.

In addition, because switching capacity equivalence itself is a resistance, thereby those skilled in the art as can be known, and this structure also can convert RC filter continuous time to very easily, equally can very simple realization ω ₀, Q and K independent programming Control.Fig. 5 is the circuit diagram of band pass filter continuous time of the present invention.As Fig. 5, this filter comprises first and second amplifier Op1 and the Op2, two integrating capacitor C1, C2, first to the 3rd resistor 501～503, and an adjustment electric capacity 504.Wherein the resistance value of first resistor 501 is 1/ ω ₀, second resistor 502 resistance value be-1/ ω ₀, the 3rd resistor 503 resistance value be 1/K, the capacitance of adjusting electric capacity 504 is 1/Q.Since first resistor 501 and second resistor 502 only with centre frequency ω ₀Relevant, the 3rd resistor 503 is only relevant with gain coefficient K, and it is only relevant with quality factor q to adjust electric capacity 504, therefore can independently adjust these filter parameters by the programming said elements.

Further, can release its differential configuration pattern by aforesaid two kinds of band pass filters.

With reference to Fig. 6, the difference type switched capacitor bandpass filter of this structure is by reconfiguration shown in Figure 4, wherein two amplifier Op1 and Op2 change the first differential amplifier Op3 and the second differential amplifier Op4 into, and they respectively have two inputs and two outputs.A pair of first integral capacitor C 1, (promptly "-" holds in the first input end of the first differential amplifier Op3 in cross-over connection respectively, to call negative input end in the following text) (promptly "+" holds with first output, to call positive output end in the following text) between, and second input (i.e. "+" end, to call positive input terminal in the following text) with second output (i.e. "-" hold, to call negative output terminal in the following text) between.A pair of second integral capacitor C 2 is distinguished cross-over connection between the negative input end and positive output end of the second differential amplifier Op4, and between the positive input terminal (+) and negative output terminal of Op4.

The Op4 positive output end of one of them connection of a pair of first switched capacitor 601 and the negative input end of Op3, another then connects the negative output terminal of Op4 and the positive input terminal of Op3.

One of them of a pair of second switch capacitor 602 connects the positive output end of Op3 and the negative input end of Op4; Another then connects the negative output terminal of Op3 and the negative input end of Op4.

One of them of a pair of the 3rd switched capacitor 603 connects the negative input end of first input signal (as positive input signal Vip) and Op4, and another then connects the positive input terminal of one second input signal (as negative input signal Vin) and Op4.Two outputs of second differential amplifier are exported first differential output signal (being negative output signal Von) and second differential output signal (being positive output signal Vop).

One of them of a pair of adjustment electric capacity 604 connects the positive output end of Op4 and the negative input end of Op3, and another then connects the negative output terminal of Op4 and the positive input terminal of Op3.

Wherein, still establishing this first integral capacitance is C1, and this second integral capacitance is C2, and the capacitance of this first switched capacitor 601 is α ₁C1, the capacitance of this second switch capacitor 602 are α ₂C2, the capacitance of the 3rd switched capacitor 603 are α ₄C2, this adjustment capacitance is α ₃C1.Wherein, α ₁～α ₄Still satisfy:

α ₁＝α ₂＝ω ₀T

${\mathrm{\&alpha;}}_3=\frac{1}{Q}$

α ₄＝KT

Wherein, ω ₀Be the centre frequency of this switched capacitor bandpass filter, Q is a quality factor, and K is a gain coefficient, and T is the time cycle of clock signal.

Have under the condition of four switch cooperatings at satisfied capacity cell, above-mentioned switched capacitor 601～603 required switch elements all can carry out as required such as merging multiplexing such optimal design, these optimal design or without the structure of switch multiplexing or part switch multiplexing, all in practical range of the present invention.

Please refer to shown in Figure 7, difference type band pass filter continuous time of this structure is by reconfiguration shown in Figure 5, perhaps be considered as the equivalent structure of structure shown in Figure 6, first resistor to the, three resistors 701～703 wherein, and adjust electric capacity 704 and be equipped with a pair ofly, connect according to difference pattern symmetry.The resistance of this first to the 3rd resistor 701～703 still is respectively 1/ ω ₀,-1/ ω ₀, 1/K, this adjusts capacitance still is 1/Q, wherein, ω ₀Be the centre frequency of this of band pass filter, Q is a quality factor continuous time, and K is a gain coefficient.Other structures in the present embodiment have been described in detail among other above-mentioned embodiment, and those skilled in the art do not repeat them here when can easily understanding and reproduce present embodiment with reference to the description of preamble.

Switching capacity second-order bandpass filter of the present invention or its continuous time reinforced concrete structure, can independently adjust the parameters such as centre frequency, quality factor and gain coefficient of filtering, so can carry out independent programming Control to one of them parameter or Several Parameters easily.

Though the present invention discloses as above with preferred embodiment; right its is not in order to qualification the present invention, any those skilled in the art, without departing from the spirit and scope of the present invention; when can doing a little modification and perfect, so protection scope of the present invention is when with being as the criterion that claims were defined.

Claims (11)

1. switched capacitor bandpass filter is characterized in that comprising:

First operational amplifier has first input end, second input and output, and wherein this second input connects an electronegative potential;

First integral electric capacity, the one end is connected in the first input end of this first operational amplifier, and the other end is connected in the output of this first operational amplifier;

Second operational amplifier has first input end, second input and output, and wherein this second input connects an electronegative potential, and this output is exported an output signal;

Second integral electric capacity, the one end is connected in the first input end of this second operational amplifier, and the other end is connected in the output of this second operational amplifier;

First switched capacitor, the one end is connected in the first input end of this first operational amplifier, and the other end is connected in the output of this second operational amplifier;

The second switch capacitor, the one end is connected in the output of this first operational amplifier, and the other end is connected in the first input end of this second operational amplifier;

The 3rd switched capacitor, the one end connects an input signal, and the other end is connected in the first input end of this second operational amplifier; And

Adjust electric capacity, the one end is connected in the first input end of this first operational amplifier, and the other end is connected in the output of this second operational amplifier;

Wherein, if this first integral capacitance is C1, this second integral capacitance is C2, and then the capacitance of this first switched capacitor is α ₁C1, the capacitance of this second switch capacitor are α ₂C2, the capacitance of the 3rd switched capacitor are α ₄C2, this adjustment capacitance is α ₃C1, α ₁～α ₄Satisfy:

α ₁＝α ₂＝ω ₀T

${\mathrm{\&alpha;}}_3=\frac{1}{Q}$

α ₄＝KT

Wherein, ω ₀Be the centre frequency of this switched capacitor bandpass filter, Q is a quality factor, and K is a gain coefficient, and T is the time cycle of clock signal.

2. switched capacitor bandpass filter as claimed in claim 1, it is characterized in that, described first switched capacitor comprises: first capacity cell and first to fourth switch, first end of this first capacity cell is connected in the first input end of this first operational amplifier through this first switch, second end of this first capacity cell is connected in the output of this second operational amplifier through this second switch, the 3rd switch is connected between first end and an electronegative potential of this first capacity cell, the 4th switch is connected between second end and this electronegative potential of this first capacity cell, wherein this first and second switch connects a second switch signal, and this third and fourth switch connects one first switching signal.

3. switched capacitor bandpass filter as claimed in claim 2, it is characterized in that, described second switch capacitor comprises: second capacity cell and the 5th closes to octavo, first end of this second capacity cell is connected in the output of this first operational amplifier through the 5th switch, second end of this second capacity cell is connected in the first input end of this second operational amplifier through the 6th switch, this minion is closed and is connected between first end and an electronegative potential of this first capacity cell, this octavo is closed and is connected between second end and this electronegative potential of this first capacity cell, wherein the 5th close with octavo and to be connected this first switching signal, the 6th is connected this second switch signal with the minion pass.

4. switched capacitor bandpass filter as claimed in claim 1, it is characterized in that, described the 3rd switched capacitor comprises: the 3rd capacity cell and first to fourth switch, first end of the 3rd capacity cell connects this input signal through this first switch, second end of the 3rd capacity cell is connected in the first input end of this second operational amplifier through the 3rd switch, the 3rd switch is connected between first end and an electronegative potential of the 3rd capacity cell, the 4th switch is connected between second end and this electronegative potential of the 3rd capacity cell, wherein this first and second switch connects a second switch signal, and this third and fourth switch connects one first switching signal.

5. as each described switched capacitor bandpass filter of claim 1～4, it is characterized in that described electronegative potential is an earthing potential.

6. switched capacitor bandpass filter as claimed in claim 1 is characterized in that, first end of described first operational amplifier and/or second operational amplifier is a positive terminal, and second end is a negative phase end.

One kind continuous time band pass filter, it is characterized in that comprising:

First operational amplifier has first input end, second input and output, and wherein this second input connects an electronegative potential;

First integral electric capacity, the one end is connected in the first input end of this first operational amplifier, and the other end is connected in the output of this first operational amplifier;

Second operational amplifier has first input end, second input and output, and wherein this second input connects an electronegative potential, and this output is exported an output signal;

Second integral electric capacity, the one end is connected in the first input end of this second operational amplifier, and the other end is connected in the output of this second operational amplifier;

First resistor, the one end is connected in the first input end of this first operational amplifier, and the other end is connected in the output of this second operational amplifier;

Second resistor, the one end is connected in the output of this first operational amplifier, and the other end is connected in the first input end of this second operational amplifier;

The 3rd resistor, the one end connects an input signal, and the other end is connected in the first input end of this second operational amplifier; And

Adjust electric capacity, the one end is connected in the first input end of this first operational amplifier, and the other end is connected in the output of this second operational amplifier;

Wherein the resistance value of this first to the 3rd resistor is respectively 1/ ω ₀,-1/ ω ₀, 1/K, this adjustment capacitance is 1/Q, wherein, ω ₀Be the centre frequency of this of band pass filter, Q is a quality factor continuous time, and K is a gain coefficient.

8. continuous time as claimed in claim 7, band pass filter is characterized in that first end of described first operational amplifier and/or second operational amplifier is a positive terminal, and second end is a negative phase end.

As claim 7 or 8 described continuous time band pass filter, it is characterized in that described electronegative potential is an earthing potential.

10. switched capacitor bandpass filter is characterized in that comprising:

First differential amplifier has first input end, second input and first output, second output;

A pair of first integral electric capacity is distinguished cross-over connection between the first input end and first output of this first differential amplifier, and between second input and second output of this first differential amplifier;

Second differential amplifier has first input end, second input and first output, second output, and wherein this first output is exported one first output signal, and this second output is exported one second output signal;

A pair of second integral electric capacity is distinguished cross-over connection between the first input end and first output of this second differential amplifier, and between second input and second output of this second differential amplifier;

A pair of first switched capacitor, wherein one first switched capacitor connects first output of this second differential amplifier and the first input end of this first differential amplifier, and another first switched capacitor connects second output of this second differential amplifier and second input of this first differential amplifier;

A pair of second switch capacitor, wherein a second switch capacitor connects first output of this first differential amplifier and the first input end of this second differential amplifier; Another second switch capacitor connects second output of this first differential amplifier and second input of this second differential amplifier;

A pair of the 3rd switched capacitor, wherein one the 3rd switched capacitor connects the first input end of one first input signal and this second differential amplifier, and another the 3rd switched capacitor connects second input of one second input signal and this second differential amplifier; And

A pair of adjustment electric capacity, wherein an adjustment electric capacity connects first output of this second differential amplifier and the first input end of this first differential amplifier, and another is adjusted electric capacity and connects second output of this second differential amplifier and second input of this first differential amplifier;

Wherein, if this first integral capacitance is C1, this second integral capacitance is C2, and then the capacitance of this first switched capacitor is α ₁C1, the capacitance of this second switch capacitor are α ₂C2, the capacitance of the 3rd switched capacitor are α ₄C2, this adjustment capacitance is α ₃C1, α ₁～α ₄Satisfy:

α ₁＝α ₂＝ω ₀T

${\mathrm{\&alpha;}}_3=\frac{1}{Q}$

α ₄＝KT

Wherein, ω ₀Be the centre frequency of this switched capacitor bandpass filter, Q is a quality factor, and K is a gain coefficient, and T is the time cycle of clock signal.

11. one kind continuous time band pass filter, it is characterized in that comprising:

First differential amplifier has first input end, second input and first output, second output;

A pair of first integral electric capacity is distinguished cross-over connection between the first input end and first output of this first differential amplifier, and between second input and second output of this first differential amplifier;

Second differential amplifier has first input end, second input and first output, second output, and wherein this first output is exported one first output signal, and this second output is exported one second output signal;

A pair of second integral electric capacity is distinguished cross-over connection between the first input end and first output of this second differential amplifier, and between second input and second output of this second differential amplifier;

A pair of first resistor, wherein one first resistor connects first output of this second differential amplifier and the first input end of this first differential amplifier, and another first resistor connects second output of this second differential amplifier and second input of this first differential amplifier;

A pair of second resistor, wherein one second resistor connects first output of this first differential amplifier and the first input end of this second differential amplifier; Another second resistor connects second output of this first differential amplifier and second input of this second differential amplifier;

A pair of the 3rd resistor, wherein one the 3rd resistor connects the first input end of one first input signal and this second differential amplifier, and another the 3rd resistor connects second input of one second input signal and this second differential amplifier; And

A pair of adjustment electric capacity, wherein an adjustment electric capacity connects first output of this second differential amplifier and the first input end of this first differential amplifier, and another is adjusted electric capacity and connects second output of this second differential amplifier and second input of this first differential amplifier;

Wherein the resistance of this first to the 3rd resistor is respectively 1/ ω ₀,-1/ ω ₀, 1/K, this adjustment capacitance is 1/Q, wherein, ω ₀Be the centre frequency of this of band pass filter, Q is a quality factor continuous time, and K is a gain coefficient.

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