JPH01303913A - Switched capacitor filter circuit - Google Patents

Switched capacitor filter circuit

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Publication number
JPH01303913A
JPH01303913A JP13588188A JP13588188A JPH01303913A JP H01303913 A JPH01303913 A JP H01303913A JP 13588188 A JP13588188 A JP 13588188A JP 13588188 A JP13588188 A JP 13588188A JP H01303913 A JPH01303913 A JP H01303913A
Authority
JP
Japan
Prior art keywords
output
operational amplifier
input
integrator
capacitor
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
JP13588188A
Other languages
Japanese (ja)
Other versions
JPH0770967B2 (en
Inventor
Katsuharu Kimura
克治 木村
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
NEC Corp
Original Assignee
NEC Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by NEC Corp filed Critical NEC Corp
Priority to JP63135881A priority Critical patent/JPH0770967B2/en
Publication of JPH01303913A publication Critical patent/JPH01303913A/en
Publication of JPH0770967B2 publication Critical patent/JPH0770967B2/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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Abstract

PURPOSE:To decrease the output sensitivity of a switched capacitor filter circuit(SC) with respect by an input offset of an operational amplifier by making the phases of the input/output signals opposite to each other for at least one of plural switched capacitors(SC) integration devices connected in cascade or over. CONSTITUTION:Four SC integration devices 100-400 of inverted phase and a noninverting phase SC integrator 500 are connected in cascade between an input terminal receiving an input signal Vin and an output terminal causing an output signal Vout. The SC integration device 100 receives an input signal through switches S1-S4 and a capacitor C11, the signal is given to an inverting input terminal of an operational amplifier E1 and an output V1 of the operational amplifier E1 is fed back negatively to an inverting input terminal through a capacitor C10. The other SC integration devices 200-500 are of nearly similar constitution and they are driven by clocks phi1, phi2 of inverted phase. Then switches S17, S18 between a capacitor C51 and the input terminal have only to be driven for only the SC integration device 500 by the clocks phi1, phi2 inverted from those of the other SC integrator 100-400 and the input offset of each operational amplifier is cancelled at the SCF output and reduced.

Description

【発明の詳細な説明】 〔産業上の利用分野〕 本発明はスイッチドキャパシタフィルタ回路（以下、Ｓ
ＣＦという）に関し、特にＳＣＦの構成に関する。[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a switched capacitor filter circuit (hereinafter referred to as S
(referred to as CF), and particularly relates to the configuration of SCF.

〔従来の技術〕[Conventional technology]

従来、この種のＳＣＦ型低域通過フィルタ（以下、ＬＰ
Ｆという）においてはスイッチドキャパシタ積分器（以
下、ＳＣ積分器という）を多数段従属接続している。こ
の時ＳＣ積分器の入出力は正相の関係にあるものか逆相
の関係にあるもののいずれかのみが用いられ、全体のス
イッチの総数が最小となるように構成されていた。Conventionally, this type of SCF type low-pass filter (hereinafter referred to as LP
In the SC integrator (hereinafter referred to as SC integrator), multiple stages of switched capacitor integrators (hereinafter referred to as SC integrator) are connected in series. At this time, the input/output of the SC integrator is configured so that either one in a positive phase relationship or one in a negative phase relationship is used, and the total number of switches is minimized.

〔発明が解決しようとする課題〕[Problem to be solved by the invention]

上述した従来のＳＣＦ型ＬＰＦは、全体でのスイッチの
総数を最小とする構成となっているので、必ずしもＳＣ
積分器中で使われる演算増幅器の入力オフセットに対す
る出力電圧の変動が最小にならないという欠点がある。The conventional SCF type LPF described above has a configuration that minimizes the total number of switches, so it is not necessary to
A disadvantage is that the output voltage variation with respect to the input offset of the operational amplifier used in the integrator is not minimized.

〔課題を解決するための手段〕[Means to solve the problem]

本発明によれば縦続接続されるＳＣ積分器の少なくとも
１つ以上は逆相ＳＣ積分器でその他は正相ＳＣ積分器で
あるスイッチドキャパシタフィルタを得る。According to the present invention, a switched capacitor filter is obtained in which at least one of the cascaded SC integrators is an anti-phase SC integrator and the others are positive-phase SC integrators.

〔実施例〕〔Example〕

次に、図面を参照して本発明をより詳細に説明する。 Next, the present invention will be explained in more detail with reference to the drawings.

第１図は本発明の一実施例を示すもので、リープフロッ
プタイプの５次ＬＰＦであり、入出力抵抗を正規化して
いる。入力信号Ｖｉｎを受ける入力端子と出力信号Ｖｏ
ｕｔを生じる出力端子との間に４つの逆相ＳＣ積分器１
００〜４００と１つの正相ＳＣ積分器５００を縦続接続
している各ＳＣ積分器１００〜５００は同様の構成をし
ており、入力信号をスイッチＳｌ、Ｓ２．Ｓ３．Ｓ４と
容量Ｃ１、で受け、演算増幅器Ｅ１の反転入力端子−に
与え、この演算増幅器Ｅ１の出力ｖ１は容量Ｃ１゜で反
転入力端子−に負帰還されている。他のＳＣ積分器２０
０〜５００もほぼ同様の構成をしており、互いに逆相の
クロックφ１．φ２で駆動されている。FIG. 1 shows an embodiment of the present invention, which is a leap-flop type fifth-order LPF, and has normalized input and output resistances. Input terminal receiving input signal Vin and output signal Vo
4 anti-phase SC integrators 1 between the output terminals that produce ut
Each of the SC integrators 100 to 500, in which one positive-phase SC integrator 500 is cascade-connected to each other, has a similar configuration, and input signals are passed through switches Sl, S2 . S3. S4 and the capacitor C1 and applied to the inverting input terminal of the operational amplifier E1, and the output v1 of the operational amplifier E1 is negatively fed back to the inverting input terminal by the capacitor C1. Other SC integrator 20
0 to 500 have almost the same configuration, and the clocks φ1. It is driven by φ2.

逆相ＳＣ積分器１００〜４００ではスイッチＳ１と８４
がクロックφ１を受はスイッチＳ２とＳ３とがクロック
φ２を受けて入出力が逆相となるように動作するが、正
相ＳＣ積分器５００ではスイッチＳｚａとＳ２゜がクロ
ックφ１を受はスイッチＳ１７とＳ１９がクロックφ２
を受けて入出力が正（同）相となるように動作している
。更に、各ＳＣ積分器間でも容量Ｃ１１１ＣＩ３ＩＣ２
□等とスイッチＳ２．。In the anti-phase SC integrators 100 to 400, switches S1 and 84
When receiving clock φ1, switches S2 and S3 receive clock φ2 and operate so that the input and output are in opposite phases. However, in the positive phase SC integrator 500, when switches Sza and S2゜ receive clock φ1, switch S17 receives clock φ1. and S19 are clock φ2
In response to this, the input and output are in positive (same) phase. Furthermore, the capacitance C111CI3IC2 is also between each SC integrator.
□ etc. and switch S2. .

８２４等で帰還が施されている。Feedback is performed with 824 etc.

いま、各演算増幅器Ｅｌｌ　Ｅ２．Ｅ３．Ｅ４．Ｅｓの
出力電圧をｖ、、Ｖ’＝、ｖ、、Ｖ４．Ｖｓとするとと
表わせる。ここで、ＬＬ、Ｃ２，Ｌ３．Ｃ４゜Ｌ５はＬ
Ｃラダー形ＬＰＦの定数を示す。Now, each operational amplifier Ell E2. E3. E4. Let the output voltage of Es be v,,V'=,v,,V4. It can be expressed as Vs. Here, LL, C2, L3. C4゜L5 is L
The constants of the C-ladder type LPF are shown.

０〜０式かられかるように各演算増幅器は順次正相で接
続されている。従って、正相ＳＣ積分器１００’〜５０
０′のみを５段縦続接続すれば入出力間が同相（正相）
の５次ＬＰＦが得られる。As can be seen from equations 0 to 0, each operational amplifier is sequentially connected in positive phase. Therefore, the positive phase SC integrators 100' to 50
If only 0' is connected in cascade in 5 stages, the input and output will be in the same phase (positive phase)
A fifth-order LPF is obtained.

これを第３図に示す。スイッチを駆動するクロックφ１
．φ２の与え方のみが第１図と異なるので、回路構成の
説明は省略する。This is shown in FIG. Clock φ1 that drives the switch
．． Since only the way in which φ2 is given differs from FIG. 1, a description of the circuit configuration will be omitted.

例えばここで各演算増幅器の出力レベルが同一レベルと
なるように設定された５次ベッセルフィルタを考える。For example, consider a fifth-order Bessel filter in which the output levels of each operational amplifier are set to be the same level.

このときに各演算増幅器Ｅｌｌ　Ｅｅｌ　Ｅｓｒ　Ｅｅ
ｌＥ、に入カニｔ　７　セラ）　ＶＯ９１１ＶＯ３２１
ＶＯＪ３＋　ＶＯ９４＋ｖ０８５が生じたとすると出力
電圧Ｖ。ＴＩＴ　”　Ｖ　Ｓとの関係はシュミレーショ
ンによれば １２　ＶｏｕＴ／　２　￥ｏｓｌｌ　”＝　３　　　　
　−・・・■１２Ｖｏｕア／２Ｖ。３□１≠２　　　　
　・・・・・・■１２　Ｖｏｔ＋Ｔ／　２　Ｖｏｓｓ　
ｌ　＃２　　　　　　”””■１２　Ｖｏｕｔ／　２　
ＶＯ３４１”＝　１．５　　　　　＝・・・・■１２　
ＹｏｕＴ／　２　Ｖｏｓｓ　Ｉ　＃　１．５　　　　　
”・・■と近似出来る。At this time, each operational amplifier Ell Eel Esr Ee
lE, nirikani t 7 Sera) VO911VO321
If VOJ3+ VO94+v085 occurs, the output voltage is V. According to the simulation, the relationship with TIT ” VS is 12 VouT/ 2 ¥osll ” = 3
-...■12Voua/2V. 3□1≠2
・・・・・・■12 Vot+T/2 Voss
l #2 ”””■12 Vout/ 2
VO341”= 1.5 =・・・■12
YouT/2 Voss I #1.5
”...It can be approximated as ■.

従って第３図に示す回路では各演算増幅器のオフセット
はＳＣＦ出力のオフセット感度をＳ　Ｏ！ｌ０ＵＴとお
くと ５ｏｓｏｕ丁”Σ　（２Ｖｏｕｒ／　２　ＶｏＳＩ）＃
３＋２＋２＋１．５＋１．５＝１０　　　・・・・・・
■一方、第１図に示す回路では Ｓ　０３ＯＵＴ＝Σ（２ＶｏｕＴ／　２　Ｖｏｓ）哄−
３＋２−２＋１．５＋１．５＝Ｏ・・・・・・■となり
、各演算増幅器の入力オフセットはＳＣＦ出力ではそれ
ぞれ相殺されて低減されると期待される。Therefore, in the circuit shown in FIG. 3, the offset of each operational amplifier is the offset sensitivity of the SCF output. If 10UT is set, 5osoud”Σ (2Vour/2 VoSI)#
3+2+2+1.5+1.5=10...
■On the other hand, in the circuit shown in Figure 1, S03OUT=Σ(2Vout/2Vos) -
3+2-2+1.5+1.5=O...■, and the input offsets of each operational amplifier are expected to be canceled and reduced at the SCF output.

第１図の実施例においては入出力間を逆相とするＳＣ積
分器５００のみは入力端子とキャパシタ０５１間のスイ
ッチ３１７１　Ｓ１８をそれぞれ他のＳＣ積分器１００
〜４００のものとは逆相のクロックφ１．φ２で駆動す
れば良い。In the embodiment shown in FIG. 1, only the SC integrator 500 whose input and output are in reverse phase has the switch 3171 S18 between the input terminal and the capacitor 051 connected to each other SC integrator 100.
The clock φ1.~400 has a reverse phase. It is sufficient to drive with φ2.

第２図は本発明の他の実施例を示す回路図である。入力
抵抗が零の４次ＬＰＦで逆相ＳＣ積分器６００．８００
と正相ＳＣ積分器７００，９００とを交互に縦続接続し
ている。各演算増幅器の出力電圧ｖｌ、Ｖ２．ｖ３．ｖ
ｔとすると、と表わせる。ここでＬｌ、Ｃ２，Ｌ３．Ｃ
４はＬＣラダ形ＬＰＦの定数を示す。FIG. 2 is a circuit diagram showing another embodiment of the present invention. 4th order LPF with zero input resistance and negative phase SC integrator 600.800
and positive phase SC integrators 700 and 900 are alternately connected in cascade. Output voltage vl of each operational amplifier, V2. v3. v
Letting it be t, it can be expressed as. Here, Ll, C2, L3. C
4 indicates a constant of the LC ladder type LPF.

第２図において、各演算増幅器の出力レベルがほぼ同一
になるように設定された４次バターワースフィルタ（Ｌ
ＰＦ）を考える。このときに各演算増幅器Ｅｌｆ、　Ｅ
ｌ□、　Ｅ　１３＊　Ｅ　１４に入力オフセットｖ。ｓ
＋＋Ｖｏｓ□ｒ　Ｖ　Ｏ３３ｒ　Ｖ　Ｏ８４が生じたと
すると出力電圧Ｖ。ＵＴ”Ｖ１４との関係は、シミュレ
ーションによれば Ｉ　２Ｖｏｕｔ／　２Ｖｏｓ＋＋　Ｉ　＃２．２５　　
　　　　”・・”＠Ｉ　２　ＶｏｕＴ／　２　Ｖｏｓｕ
　ｌ　＃　Ｏ・”・・４１２Ｖｏｕ？／　２Ｖｏｓ＋ｓ
　Ｉ　＃２．２５　　　　　　・・・・・・０１２　Ｖ
ｏｕｔ／　２　Ｖｏｓ　ｌ　４１　”；　Ｏ”””＠と
近似できる。In Figure 2, a fourth-order Butterworth filter (L
PF). At this time, each operational amplifier Elf, E
l□, E 13 * Input offset v to E 14. s
If ++Vos□r V O33r V O84 occurs, the output voltage V. According to the simulation, the relationship with UT”V14 is I 2Vout/ 2Vos++ I #2.25
”...”@I 2 VouT/ 2 Vosu
l # O・”...412Vou?/2Vos+s
I #2.25 ...012 V
It can be approximated as out/ 2 Vos l 41 ”; O”””@.

従って各演算増幅器Ｅ１−　Ｅ２．Ｅ３．Ｅ４を正相Ｓ
Ｃ積分器で縦続接続した場合は、ＳＣＦ出力のオフセッ
ト感度Ｓ。５ＯＵＴは ５Ｏ５ＯＵＴ”Σ（２ＶｏｕＴ／　２　Ｖｏｓυ＃２，
２５十〇＋２．２５＋０＝４．５　　　・・・・・・＠
となる。一方、第２図においては ５ｏｓｏｕｔ＝Σ（２ＶｏｕＴ／　２　ｏｓ　＋　）：
２．２５＋０−２．２５−０＝Ｏ・・・・・・＠となり
、各演算増幅器の入力オフセットはＳＣＦ出力ではそれ
ぞれ相殺されて低減されると期待される。Therefore, each operational amplifier E1-E2. E3. E4 in positive phase S
When connected in cascade with C integrators, the offset sensitivity S of the SCF output. 5OUT is 5O5OUT”Σ(2VouT/2 Vosυ#2,
2510 + 2.25 + 0 = 4.5 ・・・・・・＠
becomes. On the other hand, in FIG. 2, 5osout=Σ(2Vout/2os+):
2.25+0-2.25-0=O...@, and it is expected that the input offsets of each operational amplifier are canceled out and reduced at the SCF output.

〔発明の効果〕〔Effect of the invention〕

以上説明したように、本発明は複数個のＳＣ積分器を有
するＳＣＦ型ＬＰＦにおいて縦続接続されるＳＣ積分器
のうち少なくとも１個以上の逆相ＳＣ積分器を入れるこ
とによりオペアンプの入力オフセットに対するＳＣＦの
出力感度を低減出来る効果がある。As explained above, the present invention provides an SCF for the input offset of an operational amplifier by inserting at least one anti-phase SC integrator among the SC integrators connected in cascade in an SCF type LPF having a plurality of SC integrators. This has the effect of reducing the output sensitivity of.

【図面の簡単な説明】[Brief explanation of the drawing]

第１図は本発明の一実施例を示す回路図、第２図は本発
明の他の実施例を示す回路図、第３図は第１図の回路と
同一の周波数特性を持つ従来の回路例を示す回路図であ
る。 １００．２００，３００，４００，６００，８００・・
・・・・逆相ＳＣ積分器、５００，７００，９００，１
００’〜５００′・・・・・・正相ＳＣ積分器、Ｅ１〜
Ｅ、、Ｅ、、〜Ｅ１４・・・・・・演算増幅器、Ｃ，・
・・・・・容量素子、ｓｆｉ・・団・スイッチ、φ１．
φ２・・・・・・クロック。 代理人　弁理士　　内　原　　　音Fig. 1 is a circuit diagram showing one embodiment of the present invention, Fig. 2 is a circuit diagram showing another embodiment of the invention, and Fig. 3 is a conventional circuit having the same frequency characteristics as the circuit shown in Fig. 1. FIG. 2 is a circuit diagram showing an example. 100.200,300,400,600,800...
...Reverse phase SC integrator, 500, 700, 900, 1
00'~500'... Positive phase SC integrator, E1~
E, , E, , ~E14... operational amplifier, C, .
... Capacitive element, SFI group switch, φ1.
φ2...Clock. Agent Patent Attorney Oto Uchihara

Claims (1)

【特許請求の範囲】[Claims] 複数個のスイッチドキャパシタ積分器を縦属接続したス
イッチドキャパシタフィルタ回路において、前記複数個
のスイッチドキャパシタ積分器の少なくとも１個以上は
入出力信号が逆相である積分器であることを特徴とする
スイッチドキャパシタフィルタ回路。A switched capacitor filter circuit in which a plurality of switched capacitor integrators are connected in series, characterized in that at least one of the plurality of switched capacitor integrators is an integrator whose input and output signals are in opposite phase. Switched capacitor filter circuit.
JP63135881A 1988-06-01 1988-06-01 Switched capacitor filter circuit Expired - Lifetime JPH0770967B2 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
JP63135881A JPH0770967B2 (en) 1988-06-01 1988-06-01 Switched capacitor filter circuit

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP63135881A JPH0770967B2 (en) 1988-06-01 1988-06-01 Switched capacitor filter circuit

Publications (2)

Publication Number Publication Date
JPH01303913A true JPH01303913A (en) 1989-12-07
JPH0770967B2 JPH0770967B2 (en) 1995-07-31

Family

ID=15161958

Family Applications (1)

Application Number Title Priority Date Filing Date
JP63135881A Expired - Lifetime JPH0770967B2 (en) 1988-06-01 1988-06-01 Switched capacitor filter circuit

Country Status (1)

Country Link
JP (1) JPH0770967B2 (en)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1298352A2 (en) 2001-09-28 2003-04-02 JATCO Ltd Torque converter
JP2011058991A (en) * 2009-09-11 2011-03-24 Seiko Epson Corp Detector, physical quantity measuring instrument, and electronic equipment
JP2011058990A (en) * 2009-09-11 2011-03-24 Seiko Epson Corp Detector, physical quantity measuring instrument, and electronic equipment

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5587030U (en) * 1978-12-13 1980-06-16
JPS5896414A (en) * 1981-12-03 1983-06-08 Nec Corp High order general-purpose switched capacitor filter
JPS59216315A (en) * 1983-05-24 1984-12-06 Nec Corp Programmable switched capacitor filter

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5587030U (en) * 1978-12-13 1980-06-16
JPS5896414A (en) * 1981-12-03 1983-06-08 Nec Corp High order general-purpose switched capacitor filter
JPS59216315A (en) * 1983-05-24 1984-12-06 Nec Corp Programmable switched capacitor filter

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1298352A2 (en) 2001-09-28 2003-04-02 JATCO Ltd Torque converter
JP2011058991A (en) * 2009-09-11 2011-03-24 Seiko Epson Corp Detector, physical quantity measuring instrument, and electronic equipment
JP2011058990A (en) * 2009-09-11 2011-03-24 Seiko Epson Corp Detector, physical quantity measuring instrument, and electronic equipment

Also Published As

Publication number Publication date
JPH0770967B2 (en) 1995-07-31

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