JPS6156885B2 - - Google Patents
Info
- Publication number
- JPS6156885B2 JPS6156885B2 JP55032837A JP3283780A JPS6156885B2 JP S6156885 B2 JPS6156885 B2 JP S6156885B2 JP 55032837 A JP55032837 A JP 55032837A JP 3283780 A JP3283780 A JP 3283780A JP S6156885 B2 JPS6156885 B2 JP S6156885B2
- Authority
- JP
- Japan
- Prior art keywords
- circuit
- impedance
- amplifier
- output
- operational amplifier
- 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.)
- Expired
Links
- 230000010355 oscillation Effects 0.000 claims description 18
- 239000003990 capacitor Substances 0.000 description 15
- 238000010586 diagram Methods 0.000 description 3
- 230000003247 decreasing effect Effects 0.000 description 1
- 238000006073 displacement reaction Methods 0.000 description 1
- WABPQHHGFIMREM-UHFFFAOYSA-N lead(0) Chemical compound [Pb] WABPQHHGFIMREM-UHFFFAOYSA-N 0.000 description 1
- 230000000670 limiting effect Effects 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03B—GENERATION OF OSCILLATIONS, DIRECTLY OR BY FREQUENCY-CHANGING, BY CIRCUITS EMPLOYING ACTIVE ELEMENTS WHICH OPERATE IN A NON-SWITCHING MANNER; GENERATION OF NOISE BY SUCH CIRCUITS
- H03B5/00—Generation of oscillations using amplifier with regenerative feedback from output to input
- H03B5/08—Generation of oscillations using amplifier with regenerative feedback from output to input with frequency-determining element comprising lumped inductance and capacitance
Description
【発明の詳細な説明】
この発明は例えば変位などの物理量を容量変化
やインダクタンス変化として検出すると共に、そ
の変化に対応した周波数の発振を発生するように
することができ、特に浮遊容量が影響しないLC
発振回路に関する。[Detailed Description of the Invention] This invention can detect physical quantities such as displacement as changes in capacitance or inductance, and can also generate oscillations at a frequency corresponding to the changes, and is particularly free from stray capacitance. L.C.
Regarding oscillation circuits.
物理量の変化をLCのインピーダンスの変化と
して検出するセンサがあり、そのセンサのインピ
ーダンス変化をLC発振回路の周波数決定部の一
部として利用し、その発振回路の発振周波数を測
定することによりセンサの検出インピーダンスを
知ることができる。このような場合そのセンサと
発振回路の主要部とを比較的大きく離すと、これ
らを接続するリード線の大地浮遊容量が大きくな
り、これにより発振周波数が影響されセンサイン
ピーダンスを正確に検出することはできない。 There is a sensor that detects a change in a physical quantity as a change in the impedance of the LC.The sensor's impedance change is used as part of the frequency determining section of the LC oscillation circuit, and the sensor is detected by measuring the oscillation frequency of the oscillation circuit. You can know the impedance. In such cases, if the sensor and the main part of the oscillation circuit are separated by a relatively large distance, the ground stray capacitance of the lead wire connecting them will increase, which will affect the oscillation frequency and make it difficult to accurately detect the sensor impedance. Can not.
この発明の目的は浮遊容量に影響され難いLC
発振回路を提供することにある。 The purpose of this invention is to provide an LC that is not easily affected by stray capacitance.
The purpose of this invention is to provide an oscillation circuit.
この発明によれば増幅器の入力側及び出力側に
並列共振回路が負帰還回路を構成するように接続
され、また増幅器の出力は位相反転回路を通じて
入力側へ供給される。この増幅器の入力インピー
ダンス及び出力インピーダンスはその増幅器から
上記並列共振回路側を見た浮遊インピーダンスと
比較して十分小さく選定される。 According to this invention, parallel resonant circuits are connected to the input and output sides of the amplifier so as to constitute a negative feedback circuit, and the output of the amplifier is supplied to the input side through the phase inversion circuit. The input impedance and output impedance of this amplifier are selected to be sufficiently small compared to the floating impedance seen from the amplifier toward the parallel resonant circuit side.
次に図面を参照して説明しよう。第１図はこの
発明の原理を説明するためのものであり、交流信
号源１１の一端はコンデンサ１２の一端に接続さ
れ、コンデンサ１２の他端は電流計１３の一端に
接続される。信号源１１及び電流計１３の各他端
は接地される。コンデンサ１２を含みコンデンサ
１２より信号源１１及び電流計１３への各リード
線はシールド１４により静電シールドされる。 Next, let's explain with reference to the drawings. FIG. 1 is for explaining the principle of the invention. One end of an AC signal source 11 is connected to one end of a capacitor 12, and the other end of the capacitor 12 is connected to one end of an ammeter 13. The other ends of the signal source 11 and ammeter 13 are grounded. Lead wires including the capacitor 12 and leading from the capacitor 12 to the signal source 11 and ammeter 13 are electrostatically shielded by a shield 14 .
シールド１４とコンデンサ１２の信号源１１側
との間に第２図に示すように浮遊容量１５が存在
し、またシールド１４とコンデンサ１２の電流計
１３側との間に浮遊容量１６が存在する。しかし
交流信号源１１の内部インピーダンスが充分小さ
く、その出力によりその交流信号電圧ｅに浮遊容
量１５の両端が保持され、また電流計１３の内部
インピーダンスが充分小さく、ゼロオームならば
浮遊容量１６の両端の電圧はゼロとなる。従つて
浮遊容量１６には電流は流れない。この結果コン
デンサ１２に交流電圧ｅを印加した時にコンデン
サ１２に流れる電流が電流計１３に流れ、つまり
浮遊容量に影響されることなくコンデンサ１２を
流れる電流を電流計１３で測定することができ
る。 As shown in FIG. 2, a stray capacitance 15 exists between the shield 14 and the signal source 11 side of the capacitor 12, and a stray capacitance 16 exists between the shield 14 and the ammeter 13 side of the capacitor 12. However, if the internal impedance of the AC signal source 11 is sufficiently small and its output holds both ends of the stray capacitance 15 at the AC signal voltage e, and if the internal impedance of the ammeter 13 is sufficiently small and zero ohm, then both ends of the stray capacitance 16 will be held at the AC signal voltage e. The voltage becomes zero. Therefore, no current flows through the stray capacitance 16. As a result, when the AC voltage e is applied to the capacitor 12, the current flowing through the capacitor 12 flows to the ammeter 13, that is, the current flowing through the capacitor 12 can be measured by the ammeter 13 without being affected by stray capacitance.
このように電流計１３の内部インピーダンスを
ゼロにするには例えば第３図に示すようにする。
即ち端子１７を抵抗値Ｒsの抵抗器１８を通じて
演算増幅器１９の反転入力端に接続し、この反転
入力端と演算増幅器１９の出力端との間に抵抗器
Ｒfの帰還抵抗器２１を接続し、非反転入力端は
接地する。この増幅器の利得は−Ｒf／Ｒsであ
り、反転入力端の電位は非反転端のそれと同一で
あり、つまり反転入力端及び非反転入力端は等価
的に短絡され、入力インピーダンスがゼロとな
る。よつてこの両入力端が第１図における電流計
１３の両端に用いられればよい。 In order to make the internal impedance of the ammeter 13 zero in this way, for example, as shown in FIG. 3 is used.
That is, the terminal 17 is connected to the inverting input terminal of the operational amplifier 19 through the resistor 18 having the resistance value R s , and the feedback resistor 21 having the resistor R f is connected between this inverting input terminal and the output terminal of the operational amplifier 19 . The non-inverting input terminal is grounded. The gain of this amplifier is -R f /R s , and the potential at the inverting input is the same as that at the non-inverting end, that is, the inverting and non-inverting inputs are equivalently shorted and the input impedance is zero. Become. Therefore, these two input terminals may be used at both ends of the ammeter 13 in FIG.
この発明は第１図に示した原理を利用するもの
であり、その一例を第４図に示す。即ち演算増幅
器２３の反転入力端と出力端との間にコンデンサ
２４及びインダクタンス素子２５の並列共振回路
２６が接続される。この増幅器２３の出力端は位
相反転回路２７抵抗器３２を通じて増幅器２３の
入力側に接続される。位相反転回路２７としては
例えば演算増幅器２８が設けられ、その反転入力
端は抵抗器２９を通じて増幅器２３の出力端に接
続され、非反転入力端は接地され、出力端及び反
転入力端に抵抗器３１が接続され、更にその出力
端は抵抗器３２を通じて増幅器２３の反転入力端
に接続される。 This invention utilizes the principle shown in FIG. 1, and an example thereof is shown in FIG. 4. That is, a parallel resonant circuit 26 including a capacitor 24 and an inductance element 25 is connected between the inverting input terminal and the output terminal of the operational amplifier 23. The output end of this amplifier 23 is connected to the input side of the amplifier 23 through a phase inversion circuit 27 and a resistor 32. As the phase inversion circuit 27, for example, an operational amplifier 28 is provided, its inverting input terminal is connected to the output terminal of the amplifier 23 through a resistor 29, its non-inverting input terminal is grounded, and a resistor 31 is connected to its output terminal and inverting input terminal. is connected, and its output terminal is further connected to the inverting input terminal of the amplifier 23 through a resistor 32.
つまりこの例では位相反転回路２７として反転
増幅器が用いられた場合である。またこの例では
抵抗器３１の両端にダイオード３３，３４が逆極
性で並列に接続されたリミツタが抵抗器３５を通
じて接続されて振幅制限も行われるようにされて
いる。この振幅制限作用により発振を安定化させ
ることができる。 That is, in this example, an inverting amplifier is used as the phase inverting circuit 27. Further, in this example, a limiter in which diodes 33 and 34 are connected in parallel with opposite polarities to both ends of the resistor 31 is connected through a resistor 35, so that amplitude limitation is also performed. This amplitude limiting action can stabilize oscillation.
増幅器２３の入力インピーダンス及び出力イン
ピーダンスを増幅器２３の入力端及び出力端より
それぞれ並列共振回路２６側を見た時の各浮遊イ
ンピーダンスと比較して充分小さくなるようにす
る。一般に演算増幅器２３はそれ自体に負帰還回
路が組込まれて出力インピーダンスが小さくされ
ている。その出力インピーダンスが充分小さくな
ければ増幅器２３の外部に負帰還回路を接続して
出力インピーダンスを充分小さくすればよい。増
幅器２３の反転入力端の入力インピーダンスは第
３図について説明した理由により充分小さいもの
になる。 The input impedance and output impedance of the amplifier 23 are made to be sufficiently small compared to each floating impedance when looking at the parallel resonant circuit 26 side from the input terminal and output terminal of the amplifier 23, respectively. Generally, the operational amplifier 23 has a negative feedback circuit incorporated therein to reduce its output impedance. If the output impedance is not sufficiently small, a negative feedback circuit may be connected outside the amplifier 23 to make the output impedance sufficiently small. The input impedance at the inverting input of amplifier 23 is sufficiently small for the reasons explained in connection with FIG.
この第４図に示したLC発振回路によれば共振
回路２６の共振周波数においては共振回路２６の
インピーダンスが充分大きくなるため増幅器２３
に対する共振回路２６を通じる負帰還量が充分小
さくなり、増幅器２３、共振回路２６及び抵抗器
３２の部分の利得が充分大きくなり、かつその出
力は位相反転回路２７を通じて増幅器２３に正帰
還され発振が生じる。 According to the LC oscillation circuit shown in FIG. 4, the impedance of the resonant circuit 26 becomes sufficiently large at the resonant frequency of the resonant circuit 26, so the amplifier 23
The amount of negative feedback through the resonant circuit 26 becomes sufficiently small, the gain of the amplifier 23, the resonant circuit 26, and the resistor 32 becomes sufficiently large, and the output is positively fed back to the amplifier 23 through the phase inverting circuit 27 to prevent oscillation. arise.
この場合共振回路２６について見れば、増幅器
２３の出力側が第１図における交流信号源１１と
対応し増幅器２３の入力側が電流計１３と対応す
る。従つて増幅器２３より共振回路２６側を第１
図に示した場合と同様にシールドすると、増幅器
２３の入出力インピーダンスは充分小さくされて
いるため共振回路２６側の浮遊容量は共振回路２
６に影響を与えない。つまり共振回路２６を増幅
器２３から離して設けても共振回路２６によつて
決る周波数でこの発振回路は発振する。このため
例えばコンデンサ２４又はインダクタンス素子２
５をインピーダンスセンサとして用いると、その
インピーダンスセンサの検出インピーダンスと正
確に対応した発振周波数の発振が得られる。 In this case, regarding the resonant circuit 26, the output side of the amplifier 23 corresponds to the AC signal source 11 in FIG. 1, and the input side of the amplifier 23 corresponds to the ammeter 13. Therefore, the side of the resonant circuit 26 from the amplifier 23 is the first one.
When shielded as in the case shown in the figure, the input/output impedance of the amplifier 23 is sufficiently small, so the stray capacitance on the resonance circuit 26 side is
Does not affect 6. That is, even if the resonant circuit 26 is provided apart from the amplifier 23, this oscillation circuit oscillates at a frequency determined by the resonant circuit 26. For this purpose, for example, the capacitor 24 or the inductance element 2
5 as an impedance sensor, oscillation at an oscillation frequency that accurately corresponds to the impedance detected by the impedance sensor can be obtained.
なお実験によればコンデンサ２４の容量を0.01
μＦ、インダクタンス素子２５のインダクタンス
を1Hとして周波数1545Hzの発振を得た。コンデ
ンサ２４の一端及び又は両端と接地との間に
20pF〜0.1μＦのコンデンサを浮遊容量として接
続した。その付加容量が0.01μＦで1543Hzと１Hz
減少し0.1μＦで1541Hzと４Hz減少したに過ぎな
い。浮遊容量は一般にpF程度のオーダであるか
らこの発明の発振回路は浮遊容量に実質的には全
く影響されないと云える。 According to experiments, the capacitance of capacitor 24 is 0.01
Oscillation at a frequency of 1545 Hz was obtained with μF and the inductance of the inductance element 25 being 1H. between one end and/or both ends of the capacitor 24 and ground.
A capacitor of 20 pF to 0.1 μF was connected as a stray capacitance. The additional capacitance is 0.01μF, 1543Hz and 1Hz
It decreased by 0.1μF to 1541Hz, which was only a 4Hz decrease. Since stray capacitance is generally on the order of pF, it can be said that the oscillation circuit of the present invention is not substantially affected by stray capacitance at all.
第１図はこの発明の原理を説明するためのコン
デンサの電流測定回路を示す図、第２図は第１図
の回路の等価回路図、第３図は入力インピーダン
スが充分小さい回路の例を示す図、第４図はこの
発明によるLC発振回路の一例を示す接続図であ
る。
２３：演算増幅器、２６：並列共振回路、２
７：位相反転回路。
Figure 1 is a diagram showing a capacitor current measurement circuit for explaining the principle of this invention, Figure 2 is an equivalent circuit diagram of the circuit in Figure 1, and Figure 3 is an example of a circuit with sufficiently small input impedance. 4 are connection diagrams showing an example of the LC oscillation circuit according to the present invention. 23: Operational amplifier, 26: Parallel resonant circuit, 2
7: Phase inversion circuit.
Claims (1)
その演算増幅器の反転入力端子及び出力端子間に
負帰還回路を構成するようにそれぞれシールド線
を介して接続された並列共振回路と、上記演算増
幅器の出力を位相反転し、抵抗器を介して上記演
算増幅器の反転入力端子へ供給する位相反転回路
とを具備し、上記負帰還回路が接続された上記演
算増幅器の入力インピーダンス及び出力インピー
ダンスはそれぞれその演算増幅器の入力側及び出
力側から上記並列共振回路側を見た浮遊インピー
ダンスと比較して充分小さく選定されているLC
発振回路。1 an operational amplifier whose non-inverting input terminal is grounded;
A parallel resonant circuit is connected between the inverting input terminal and the output terminal of the operational amplifier through shielded wires to form a negative feedback circuit, and the output of the operational amplifier is phase-inverted and and a phase inversion circuit that supplies an inverting input terminal of the operational amplifier, and the input impedance and output impedance of the operational amplifier to which the negative feedback circuit is connected are connected to the parallel resonant circuit from the input side and the output side of the operational amplifier, respectively. The LC is selected to be sufficiently small compared to the stray impedance when looking at the side.
Oscillation circuit.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP3283780A JPS56129410A (en) | 1980-03-14 | 1980-03-14 | Lc oscillation circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP3283780A JPS56129410A (en) | 1980-03-14 | 1980-03-14 | Lc oscillation circuit |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS56129410A JPS56129410A (en) | 1981-10-09 |
| JPS6156885B2 true JPS6156885B2 (en) | 1986-12-04 |
Family
ID=12369925
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP3283780A Granted JPS56129410A (en) | 1980-03-14 | 1980-03-14 | Lc oscillation circuit |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS56129410A (en) |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5239180A (en) * | 1975-09-23 | 1977-03-26 | Omron Tateisi Electronics Co | Proximity switch circuit |
| JPS5444536U (en) * | 1978-08-08 | 1979-03-27 |
-
1980
- 1980-03-14 JP JP3283780A patent/JPS56129410A/en active Granted
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5239180A (en) * | 1975-09-23 | 1977-03-26 | Omron Tateisi Electronics Co | Proximity switch circuit |
| JPS5444536U (en) * | 1978-08-08 | 1979-03-27 |
Also Published As
| Publication number | Publication date |
|---|---|
| JPS56129410A (en) | 1981-10-09 |
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