JP5803465B2 - Oscillator - Google Patents

Oscillator Download PDF

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JP5803465B2
JP5803465B2 JP2011200255A JP2011200255A JP5803465B2 JP 5803465 B2 JP5803465 B2 JP 5803465B2 JP 2011200255 A JP2011200255 A JP 2011200255A JP 2011200255 A JP2011200255 A JP 2011200255A JP 5803465 B2 JP5803465 B2 JP 5803465B2
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amplifier
oscillator
low
stage
pass filter
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JP2013062704A (en
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徹 渡邉
徹 渡邉
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Seiko Epson Corp
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Description

本発明は、異常発振を抑制する発振器に関する。   The present invention relates to an oscillator that suppresses abnormal oscillation.

発振器には発振回路が備えられ、発振回路は発振信号の起動と維持を行う増幅部と、発振周波数を決定する共振部とで構成されるのが一般的である。また、この発振回路を外部回路へ接続する際には、外部回路との一定の絶縁性を確保する事を目的に、緩衝回路を介して接続される。
特許文献１の水晶発振器では、増幅部にインバーター回路と帰還抵抗を、共振部に水晶振動子と容量を、緩衝回路にインバーター回路を用いた事例である。 In general, an oscillator includes an oscillation circuit, and the oscillation circuit generally includes an amplification unit that starts and maintains an oscillation signal and a resonance unit that determines an oscillation frequency. Further, when this oscillation circuit is connected to an external circuit, it is connected via a buffer circuit for the purpose of ensuring a certain insulation from the external circuit.
In the crystal oscillator disclosed in Patent Document 1, an inverter circuit and a feedback resistor are used as an amplification unit, a crystal resonator and a capacitor are used as a resonance unit, and an inverter circuit is used as a buffer circuit.

増幅部で必要となる利得は共振部の損失分により主に決定され、共振部の損失が小さい場合は特許文献１に示す様に１段の増幅器でも必要な利得を実現出来る。
一方で、共振部の損失が大きい場合、１段の増幅器で必要な利得を実現出来ない場合がある。この様な場合は、増幅部の増幅器の段数を増やして必要利得を確保するのが一般的である。 The gain required in the amplifying unit is mainly determined by the loss of the resonance unit. When the loss of the resonance unit is small, the required gain can be realized even with a single-stage amplifier as shown in Patent Document 1.
On the other hand, when the loss of the resonance part is large, a necessary gain may not be realized with a single-stage amplifier. In such a case, the necessary gain is generally secured by increasing the number of amplifiers in the amplifier.

特開２００８−１６７２３６号公報JP 2008-167236 A

しかしながら、増幅部の段数が増加すると利得は増加するが、増幅段全体での位相変動量も増加する。この結果、増幅段の入力信号と出力信号の位相差がゼロとなる周波数ｆ１が共振部の共振周波数ｆ０以下となる現象が発生する。   However, when the number of amplification units increases, the gain increases, but the amount of phase fluctuation in the entire amplification unit also increases. As a result, a phenomenon occurs in which the frequency f1 at which the phase difference between the input signal and the output signal of the amplification stage becomes zero is equal to or lower than the resonance frequency f0 of the resonance unit.

共振部の損失が大きい場合、増幅段の入力信号と出力信号の位相差がゼロとなる周波数ｆ１での発振回路内の閉ループの利得が、共振部の共振周波数ｆ０での閉ループの利得よりも大きくなり、本来望まない発振が生ずる現象、即ち異常発振が発生する。
一般的に増幅器はその性質上、低周波帯域での利得が大きくなる傾向があり、回路内の寄生容量や寄生抵抗が大きい場合、増幅段の入力信号と出力信号の位相差がゼロとなる周波数ｆ１は低周波帯域で生じ、異常発振が発生しやすくなるという課題があった。 When the loss of the resonance unit is large, the gain of the closed loop in the oscillation circuit at the frequency f1 at which the phase difference between the input signal and the output signal of the amplification stage becomes zero is larger than the gain of the closed loop at the resonance frequency f0 of the resonance unit. Thus, a phenomenon in which oscillation that is not desired originally occurs, that is, abnormal oscillation occurs.
In general, amplifiers tend to have higher gain in the low frequency band due to their nature, and when the parasitic capacitance or resistance in the circuit is large, the frequency at which the phase difference between the input signal and output signal of the amplification stage becomes zero. f1 occurs in a low frequency band, and there is a problem that abnormal oscillation is likely to occur.

本発明は、上述の課題を解決するためになされたものであり、以下の形態または適用例として実現することが可能である。   The present invention has been made to solve the above-described problems, and can be realized as the following forms or application examples.

［適用例１］本適用例に係る発振器は、発振信号を起動および増幅する増幅部と、所望の発振周波数を決定する共振部と、を備えた発振回路と、前記発振回路の出力端子に緩衝回路が接続された発振器であって、前記増幅部は入出力用の２端子を有する低域濾波器と、３段の増幅回路とを有し、前記増幅回路の１段目と２段目とが不平衡型増幅器で、前記増幅回路の３段目がオペアンプであり、前記２段目の前記不平衡型増幅器の出力端子が、前記低域濾波器の入力端子と前記オペアンプの反転入力端子に接続され、前記低域濾波器の出力端子が、前記オペアンプの非反転入力端子に接続されていることを特徴とする。   Application Example 1 An oscillator according to this application example includes an oscillation circuit including an amplification unit that starts and amplifies an oscillation signal, a resonance unit that determines a desired oscillation frequency, and a buffer at an output terminal of the oscillation circuit. An oscillator to which a circuit is connected, wherein the amplifying unit includes a low-pass filter having two terminals for input and output, and a three-stage amplifier circuit, and the first and second stages of the amplifier circuit, Is an unbalanced amplifier, the third stage of the amplifier circuit is an operational amplifier, and the output terminal of the second stage of the unbalanced amplifier is connected to the input terminal of the low-pass filter and the inverting input terminal of the operational amplifier. The output terminal of the low-pass filter is connected to the non-inverting input terminal of the operational amplifier.

本適用例によれば、増幅回路の３段目のオペアンプの非反転入力端子に低域濾波器を接続することにより、低域周波数での利得を抑圧することが出来る。この結果、低域周波数での発振回路の閉ループの利得を抑える事が出来、発振器の異常発振を抑圧する事が出来る。   According to this application example, by connecting the low-pass filter to the non-inverting input terminal of the third stage operational amplifier of the amplifier circuit, the gain at the low-frequency can be suppressed. As a result, the closed-loop gain of the oscillation circuit at a low frequency can be suppressed, and abnormal oscillation of the oscillator can be suppressed.

本適用例における具体的な数値としては、例えば共振部の共振周波数が１０ＭＨｚであり、増幅段の入力信号と出力信号の位相差がゼロとなる周波数ｆ１が１００ｋＨｚである場合、低域濾波器のカットオフ周波数ｆｃを１ＭＨｚに設定することで実用上十分な効果を得る事が出来る。   As specific numerical values in this application example, for example, when the resonance frequency of the resonance unit is 10 MHz and the frequency f1 at which the phase difference between the input signal and the output signal of the amplification stage is zero is 100 kHz, the low-pass filter A practically sufficient effect can be obtained by setting the cut-off frequency fc to 1 MHz.

［適用例２］上記適用例における発振器において、前記共振部に水晶振動子を備えたことが望ましい。
本適用例によれば、共振部に周波数精度の高い水晶振動子を用いることから、異常発振を抑制した高精度の発振器を提供することができる。 Application Example 2 In the oscillator according to the application example described above, it is preferable that the resonance unit includes a crystal resonator.
According to this application example, since the crystal unit with high frequency accuracy is used for the resonance unit, it is possible to provide a high-accuracy oscillator that suppresses abnormal oscillation.

［適用例３］上記適用例における発振器において、前記共振部にＭＥＭＳ振動子を備えたことが望ましい。
本適用例によれば、共振部にＭＥＭＳ（Micro Electro Mechanical Systems）技術を利用したＭＥＭＳ振動子を用いることから、異常発振を抑制した小型化された発振器を提供することができる。 Application Example 3 In the oscillator according to the application example described above, it is preferable that the resonance unit includes a MEMS vibrator.
According to this application example, since the MEMS vibrator using MEMS (Micro Electro Mechanical Systems) technology is used for the resonance part, it is possible to provide a downsized oscillator that suppresses abnormal oscillation.

［適用例４］本発明に係る別の適用例の発振器は、発振信号を起動および増幅する増幅部と、所望の発振周波数を決定する共振部と、を備えた発振回路と、前記発振回路の出力端子に緩衝回路が接続された発振器であって、前記増幅部は入出力用の２端子を有する低域濾波器と、３段の増幅回路とを有し、前記増幅回路の１段目と３段目とが不平衡型増幅器で、前記増幅回路の２段目がオぺアンプであり、前記１段目の前記不平衡型増幅器の出力端子が、前記低域濾波器の入力端子と前記オペアンプの反転入力端子に接続され、前記低域濾波器の出力端子が、前記オペアンプの非反転入力端子に接続されていることを特徴とする。   Application Example 4 An oscillator according to another application example of the present invention includes an oscillation circuit including an amplification unit that activates and amplifies an oscillation signal, and a resonance unit that determines a desired oscillation frequency. An oscillator having a buffer circuit connected to an output terminal, wherein the amplifying unit includes a low-pass filter having two terminals for input and output, a three-stage amplifier circuit, and the first stage of the amplifier circuit; The third stage is an unbalanced amplifier, the second stage of the amplifier circuit is an operational amplifier, and the output terminal of the first stage unbalanced amplifier is connected to the input terminal of the low-pass filter and the An operational amplifier is connected to an inverting input terminal, and an output terminal of the low-pass filter is connected to a non-inverting input terminal of the operational amplifier.

本適用例によれば、増幅回路の２段目のオペアンプの非反転入力端子に低域濾波器を接続することにより、低域周波数での利得を抑圧することが出来る。この結果、低域周波数での発振回路の閉ループの利得を抑える事が出来、発振器の異常発振を抑圧する事が出来る。   According to this application example, by connecting the low-pass filter to the non-inverting input terminal of the second operational amplifier of the amplifier circuit, the gain at the low-frequency can be suppressed. As a result, the closed-loop gain of the oscillation circuit at a low frequency can be suppressed, and abnormal oscillation of the oscillator can be suppressed.

［適用例５］上記適用例における発振器において、前記共振部に水晶振動子を備えたことが望ましい。
本適用例によれば、共振部に周波数精度の高い水晶振動子を用いることから、異常発振を抑制した高精度の発振器を提供することができる。 Application Example 5 In the oscillator according to the application example described above, it is preferable that the resonance unit includes a crystal resonator.
According to this application example, since the crystal unit with high frequency accuracy is used for the resonance unit, it is possible to provide a high-accuracy oscillator that suppresses abnormal oscillation.

［適用例６］上記適用例における発振器において、前記共振部にＭＥＭＳ振動子を備えたことが望ましい。
本適用例によれば、共振部にＭＥＭＳ（Micro Electro Mechanical Systems）技術を利用したＭＥＭＳ振動子を用いることから、異常発振を抑制した小型化された発振器を提供することができる。 Application Example 6 In the oscillator according to the application example described above, it is preferable that the resonance unit includes a MEMS vibrator.
According to this application example, since the MEMS vibrator using MEMS (Micro Electro Mechanical Systems) technology is used for the resonance part, it is possible to provide a downsized oscillator that suppresses abnormal oscillation.

第一の実施形態に係る発振器の回路構成図。The circuit block diagram of the oscillator which concerns on 1st embodiment. 第一の実施形態に係る発振器に用いた低域濾波器の周波数通過特性図。The frequency pass characteristic figure of the low-pass filter used for the oscillator concerning a first embodiment. 第一の実施形態に係る低域濾波器の構成例。The structural example of the low-pass filter which concerns on 1st embodiment. 第一の実施形態に係る発振器における増幅部の開ループ利得の周波数特性図。The frequency characteristic figure of the open loop gain of the amplifier in the oscillator which concerns on 1st embodiment. 第二の実施形態に係る発振器の回路構成図。The circuit block diagram of the oscillator which concerns on 2nd embodiment.

（第一の実施形態）
以下、本発明の第一の実施形態について、図面を参照して説明する。
図１は第一の実施形態に係る発振器の回路構成である。
発振器１００は、発振信号を起動および増幅する増幅部１２０と、所望の発振周波数を決定する共振部１３０と、で構成された発振回路１１０と、発振回路１１０の出力端子に接続された緩衝回路１６０と、を有している。
増幅部１２０は、１段目増幅器１２１と２段目増幅器１２２と、３段目増幅器１２３と、低域濾波器１４０とを有している。
１段目増幅器１２１と２段目増幅器１２２は不平衡型の増幅器であり、３段目増幅器１２３はオペアンプにて構成されている。
低域濾波器１４０は入力端子１４１と出力端子１４２を備え、入力端子１４１は、２段目増幅器１２２の出力端子と３段目増幅器１２３の反転入力端子１２３Ａとに接続されており、低域濾波器１４０の出力端子１４２は、３段目増幅器１２３の非反転入力端子１２３Ｂに接続されている。
また、共振部１３０は水晶振動子、またはＭＥＭＳ振動子などで構成される。
なお、ＭＥＭＳ振動子とは、半導体プロセスを使用して半導体基板上に形成された、固有振動周波数での機械的振動を有する微小構造体であり、振動を電気特性に変換する仕組みを持った素子である。 (First embodiment)
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings.
FIG. 1 shows a circuit configuration of an oscillator according to the first embodiment.
The oscillator 100 includes an oscillation circuit 110 that includes an amplification unit 120 that starts and amplifies an oscillation signal, a resonance unit 130 that determines a desired oscillation frequency, and a buffer circuit 160 that is connected to an output terminal of the oscillation circuit 110. And have.
The amplifying unit 120 includes a first stage amplifier 121, a second stage amplifier 122, a third stage amplifier 123, and a low-pass filter 140.
The first stage amplifier 121 and the second stage amplifier 122 are unbalanced amplifiers, and the third stage amplifier 123 is composed of an operational amplifier.
The low-pass filter 140 includes an input terminal 141 and an output terminal 142. The input terminal 141 is connected to the output terminal of the second-stage amplifier 122 and the inverting input terminal 123A of the third-stage amplifier 123. The output terminal 142 of the device 140 is connected to the non-inverting input terminal 123B of the third stage amplifier 123.
Further, the resonating unit 130 is configured by a crystal resonator, a MEMS resonator, or the like.
A MEMS vibrator is a micro structure having mechanical vibration at a natural vibration frequency formed on a semiconductor substrate using a semiconductor process and having a mechanism for converting vibration into electrical characteristics. It is.

ここで、低域濾波器１４０の周波数通過特性を図２に示す。横軸に周波数、縦軸に濾波器の通過量を示す。
図２の通り、低域濾波器１４０は直流から一定のカットオフ周波数ｆｃ以下では通過量の減衰がほぼゼロであるが、カットオフ周波数ｆｃ以上では減衰量が斬増し、通過量が減少する特性を有する。 Here, the frequency pass characteristic of the low-pass filter 140 is shown in FIG. The horizontal axis shows the frequency, and the vertical axis shows the amount of passage through the filter.
As shown in FIG. 2, the low-pass filter 140 has a characteristic that the attenuation of the passing amount is almost zero at a certain cutoff frequency fc or less from DC, but the attenuation amount increases sharply and the passing amount decreases above the cutoff frequency fc. Have

この低域濾波器１４０の特性によれば、増幅部１２０での低周波帯域（例えば周波数ｆ２の信号）の利得は、３段目増幅器（オペアンプ）１２３では反転入力端子１２３Ａと非反転入力端子１２３Ｂには同じ振幅の交流信号（交流電圧）が注入されるため、信号は増幅されず、増幅部１２０全体での利得は１段目増幅器１２１及び２段目増幅器１２２での利得で決定される。   According to the characteristics of the low-pass filter 140, the gain of the low frequency band (for example, the signal of the frequency f2) in the amplification unit 120 is the inverting input terminal 123A and the non-inverting input terminal 123B in the third stage amplifier (operational amplifier) 123. Since an AC signal (AC voltage) having the same amplitude is injected into, the signal is not amplified, and the gain of the entire amplifying unit 120 is determined by the gains of the first stage amplifier 121 and the second stage amplifier 122.

一方で低域濾波器１４０のカットオフ周波数ｆｃ以上の周波数帯域（例えば周波数ｆ１の信号）では、３段目増幅器１２３の反転入力端子１２３Ａには一定の交流信号が入力されるのに対し、非反転入力端子１２３Ｂには低域濾波器１４０で阻止された交流信号が入力されないため、オペアンプの増幅能力に準じて信号が増幅される。この結果、増幅部１２０全体での利得は１段目増幅器１２１、２段目増幅器１２２及び３段目増幅器１２３の利得で決定される。   On the other hand, in a frequency band higher than the cut-off frequency fc of the low-pass filter 140 (for example, a signal of frequency f1), a constant AC signal is input to the inverting input terminal 123A of the third stage amplifier 123, whereas Since the AC signal blocked by the low-pass filter 140 is not input to the inverting input terminal 123B, the signal is amplified according to the amplification capability of the operational amplifier. As a result, the gain of the entire amplification unit 120 is determined by the gains of the first stage amplifier 121, the second stage amplifier 122, and the third stage amplifier 123.

この結果、低域濾波器１４０のカットオフ周波数ｆｃ以上の周波数帯域（例えば周波数ｆ２）の増幅段の利得よりも低域濾波器１４０のカットオフ周波数ｆｃ以下の周波数帯域（例えば周波数ｆ１）の増幅段の利得を低く抑える事ができる。これにより、低周波帯域での異常発振の発生を抑える事が出来る。   As a result, the amplification in the frequency band (for example, frequency f1) below the cut-off frequency fc of the low-pass filter 140 than the gain of the amplification stage in the frequency band (for example, frequency f2) above the cut-off frequency fc of the low-pass filter 140. The gain of the stage can be kept low. Thereby, the occurrence of abnormal oscillation in the low frequency band can be suppressed.

図３は低域濾波器１４０の構成例を示した図である。ここでは抵抗Ｒｘと容量Ｃｘそれぞれ１素子による構成例を示しているが、例えばこれを複数段形成した２段以上の低域濾波器で構成されていても良い。   FIG. 3 is a diagram illustrating a configuration example of the low-pass filter 140. Here, a configuration example using one element for each of the resistor Rx and the capacitor Cx is shown. However, for example, the resistor Rx and the capacitor Cx may be composed of two or more low-pass filters in which a plurality of stages are formed.

図４に発振器における増幅部１２０の閉ループを１段目増幅器の入力端子で切断した場合の開ループ利得の周波数特性図を示す。この周波数特性図では横軸に周波数、縦軸に利得を示す。
上記で説明した通り、低周波帯域（例えば周波数ｆ２）での増幅部１２０の利得が抑えられている事がわかる。 FIG. 4 shows a frequency characteristic diagram of the open loop gain when the closed loop of the amplifying unit 120 in the oscillator is disconnected at the input terminal of the first stage amplifier. In this frequency characteristic diagram, the horizontal axis represents frequency and the vertical axis represents gain.
As described above, it can be seen that the gain of the amplification unit 120 in the low frequency band (for example, the frequency f2) is suppressed.

なお、上記において共振部１３０の例として水晶振動子やＭＥＭＳ振動子を示したが、これに限らず、セラミック発振子やその他の振動子及び共振器を用いても良い。   In the above description, a crystal resonator or a MEMS resonator is shown as an example of the resonance unit 130. However, the present invention is not limited to this, and a ceramic resonator, another resonator, and a resonator may be used.

なお、図１では３段目増幅器（オペアンプ）１２３の出力端子からの出力信号が発振回路出力として緩衝回路１６０へ接続されているが、接続方法はこれに限らず、例えば２段目増幅器１２２の出力端子、若しくは１段目増幅器１２１の出力端子が緩衝回路１６０に接続されていても良い。即ち、発振回路１１０の出力信号が効率良く緩衝回路１６０に注入される接続形態であれば良い。   In FIG. 1, the output signal from the output terminal of the third-stage amplifier (op-amp) 123 is connected to the buffer circuit 160 as an oscillation circuit output. However, the connection method is not limited to this, and for example, the second-stage amplifier 122 The output terminal or the output terminal of the first stage amplifier 121 may be connected to the buffer circuit 160. That is, any connection configuration in which the output signal of the oscillation circuit 110 is efficiently injected into the buffer circuit 160 may be used.

（第二の実施形態）
図５は第二の実施形態に係る発振器の回路構成である。
発振器２００は、発振信号を起動および増幅する増幅部２２０と、所望の発振周波数を決定する共振部２３０と、で構成された発振回路２１０と、発振回路２１０の出力端子に接続された緩衝回路２６０と、を有している。
増幅部２２０は、１段目増幅器２２１と、２段目増幅器２２２と、３段目増幅器２２３と、低域濾波器２４０と、を有している。
１段目増幅器２２１と３段目増幅器２２３は不平衡型の増幅器であり、２段目増幅器２２２はオペアンプにて構成されている。
前記低域濾波器２４０は入力端子２４１と出力端子２４２を備え、１段目増幅器２２１の出力端子と２段目増幅器２２２の反転入力端子２２２Ａとに接続されており、低域濾波器２４０の出力端子２４２は、２段目増幅器２２２の非反転入力端子２２２Ｂに接続されている。
また、共振部２３０は水晶振動子、またはＭＥＭＳ振動子などで構成される。 (Second embodiment)
FIG. 5 shows a circuit configuration of an oscillator according to the second embodiment.
The oscillator 200 includes an oscillation circuit 210 including an amplification unit 220 that starts and amplifies an oscillation signal, a resonance unit 230 that determines a desired oscillation frequency, and a buffer circuit 260 connected to an output terminal of the oscillation circuit 210. And have.
The amplifying unit 220 includes a first stage amplifier 221, a second stage amplifier 222, a third stage amplifier 223, and a low-pass filter 240.
The first stage amplifier 221 and the third stage amplifier 223 are unbalanced amplifiers, and the second stage amplifier 222 is configured by an operational amplifier.
The low-pass filter 240 has an input terminal 241 and an output terminal 242, and is connected to the output terminal of the first-stage amplifier 221 and the inverting input terminal 222A of the second-stage amplifier 222. The terminal 242 is connected to the non-inverting input terminal 222B of the second stage amplifier 222.
In addition, the resonating unit 230 is configured by a crystal resonator or a MEMS resonator.

低域濾波器２４０の通過特性は第一の実施形態と同様に、直流から一定のカットオフ周波数ｆｃ以下の周波数帯域（例えば周波数ｆ２の信号）では減衰量がほぼゼロであるが、カットオフ周波数ｆｃ以上の周波数帯域（例えば周波数ｆ１の信号）では減衰量が斬増する特性を有する。   As in the first embodiment, the low-pass filter 240 has a substantially zero attenuation in a frequency band (for example, a signal of the frequency f2) from DC to a certain cutoff frequency fc or less, but the cutoff frequency. In a frequency band equal to or higher than fc (for example, a signal of frequency f1), there is a characteristic that the amount of attenuation sharply increases.

これによれば、増幅部２２０での低周波帯域（例えば周波数ｆ２の信号）の利得は、２段目増幅器（オペアンプ）２２２では反転入力端子２２２Ａと非反転入力端子２２２Ｂには同じ振幅の交流信号（交流電圧）が注入されるため、信号は増幅されず、増幅部２２０全体での利得は１段目増幅器２２１及び３段目増幅器２２３での利得で決定される。   According to this, the gain of the low frequency band (for example, the signal of frequency f2) in the amplification unit 220 is the AC signal having the same amplitude in the inverting input terminal 222A and the non-inverting input terminal 222B in the second stage amplifier (operational amplifier) 222. Since (alternating voltage) is injected, the signal is not amplified, and the gain of the entire amplification unit 220 is determined by the gains of the first stage amplifier 221 and the third stage amplifier 223.

一方で低域濾波器２４０のカットオフ周波数ｆｃ以上の周波数帯域（例えば周波数ｆ１の信号）では、２段目増幅器（オペアンプ）２２２の反転入力端子２２２Ａには一定の交流信号が入力されるのに対し、非反転入力端子２２２Ｂには前記低域濾波器２４０で阻止された交流信号が入力されないため、２段目増幅器（オペアンプ）２２２の増幅能力に準じて信号が増幅される。この結果、増幅部２２０全体での利得は１段目増幅器２２１、３段目増幅器２２３及び２段目増幅器（オペアンプ）２２２の利得で決定される。   On the other hand, in a frequency band higher than the cutoff frequency fc of the low-pass filter 240 (for example, a signal of frequency f1), a constant AC signal is input to the inverting input terminal 222A of the second stage amplifier (op amp) 222. On the other hand, since the AC signal blocked by the low-pass filter 240 is not input to the non-inverting input terminal 222B, the signal is amplified according to the amplification capability of the second-stage amplifier (op-amp) 222. As a result, the gain of the entire amplification unit 220 is determined by the gains of the first-stage amplifier 221, the third-stage amplifier 223, and the second-stage amplifier (operational amplifier) 222.

この結果、低域濾波器２４０のカットオフ周波数ｆｃ以上の周波数帯域（例えば周波数ｆ２の信号）の増幅段の利得よりも前記低域濾波器２４０のカットオフ周波数ｆｃ以下の周波数帯域（例えば周波数ｆ１の信号）での増幅器の利得を低く抑える事ができる。これにより、低周波帯域での異常発振の発生を抑える事が出来る。   As a result, the frequency band (for example, frequency f1) below the cut-off frequency fc of the low-pass filter 240 is higher than the gain of the amplification stage in the frequency band (for example, the signal of frequency f2) higher than the cut-off frequency fc of the low-pass filter 240. The gain of the amplifier at the same time can be kept low. Thereby, the occurrence of abnormal oscillation in the low frequency band can be suppressed.

なお、上記において共振部２３０の実例として水晶振動子やＭＥＭＳ振動子を示したが、第一の実施形態と同様に、セラミック発振子やその他の振動子及び共振器を用いても良い。   In the above description, a crystal resonator or a MEMS resonator is shown as an example of the resonance unit 230. However, a ceramic resonator, other resonators, and a resonator may be used as in the first embodiment.

なお、図５では３段目増幅器２２３の出力端子からの出力信号が発振回路出力として緩衝回路２６０へ接続されているが、接続方法はこれに限らず、例えば２段目増幅器（オペアンプ）２２２の出力端子、若しくは１段目増幅器２２１の出力端子が緩衝回路２６０に接続されていても良い。即ち、発振回路２１０の出力信号が効率良く緩衝回路２６０に注入される接続形態であれば良い。   In FIG. 5, the output signal from the output terminal of the third-stage amplifier 223 is connected to the buffer circuit 260 as the oscillation circuit output. However, the connection method is not limited to this, and for example, the second-stage amplifier (op-amp) 222 The output terminal or the output terminal of the first-stage amplifier 221 may be connected to the buffer circuit 260. That is, any connection configuration in which the output signal of the oscillation circuit 210 is efficiently injected into the buffer circuit 260 may be used.

１００…発振器、１１０…発振回路、１２０…増幅部、１２１…１段目増幅器、１２２…２段目増幅器、１２３…３段目増幅器（オペアンプ）、１３０…共振部、１４０…低域濾波器、１６０…緩衝回路、２００…発振器、２１０…発振回路、２２０…増幅部、２２１…１段目増幅器、２２２…２段目増幅器（オペアンプ）、２２３…３段目増幅器、２３０…共振部、２４０…低域濾波器、２６０…緩衝回路。   DESCRIPTION OF SYMBOLS 100 ... Oscillator 110 ... Oscillator circuit 120 ... Amplifier part 121 ... First stage amplifier 122 ... Second stage amplifier 123 ... Third stage amplifier (op amp) 130 ... Resonance part 140 ... Low-pass filter DESCRIPTION OF SYMBOLS 160 ... Buffer circuit, 200 ... Oscillator, 210 ... Oscillator circuit, 220 ... Amplification part, 221 ... First stage amplifier, 222 ... Second stage amplifier (op amp), 223 ... Third stage amplifier, 230 ... Resonance part, 240 ... Low-pass filter, 260 ... buffer circuit.

Claims (6)

発振信号を起動および増幅する増幅部と、
所望の発振周波数を決定する共振部と、を備えている発振器であって、
前記増幅部は入出力用の２端子を有する低域濾波器と、３段の増幅回路とを有し、
前記増幅回路の１段目と２段目とが不平衡型増幅器で、前記増幅回路の３段目がオペア
ンプであり、
前記２段目の前記不平衡型増幅器の出力端子が、前記低域濾波器の入力端子と前記オペ
アンプの反転入力端子に接続され、
前記低域濾波器の出力端子が、前記オペアンプの非反転入力端子に接続されていること
を特徴とする発振器。 An amplifier for starting and amplifying the oscillation signal;
A oscillator and a, a resonance unit for determining a desired oscillation frequency,
The amplifying unit includes a low-pass filter having two terminals for input and output, and a three-stage amplifier circuit,
The first and second stages of the amplifier circuit are unbalanced amplifiers, and the third stage of the amplifier circuit is an operational amplifier.
The output terminal of the unbalanced amplifier at the second stage is connected to the input terminal of the low-pass filter and the inverting input terminal of the operational amplifier.
An oscillator characterized in that an output terminal of the low-pass filter is connected to a non-inverting input terminal of the operational amplifier. 前記共振部に水晶振動子を備えていることを特徴とする請求項１に記載の発振器。 Oscillator of claim 1, characterized in that it comprises a crystal oscillator before Symbol resonance part. 前記共振部にＭＥＭＳ振動子を備えていることを特徴とする請求項１に記載の発振器。 Oscillator of claim 1, characterized in that it comprises a MEMS vibrator before Symbol resonance part. 発振信号を起動および増幅する増幅部と、
所望の発振周波数を決定する共振部と、を備えている発振器であって、
前記増幅部は入出力用の２端子を有する低域濾波器と、３段の増幅回路とを有し、
前記増幅回路の１段目と３段目とが不平衡型増幅器で、前記増幅回路の２段目がオぺア
ンプであり、
前記１段目の前記不平衡型増幅器の出力端子が、前記低域濾波器の入力端子と前記オペ
アンプの反転入力端子に接続され、
前記低域濾波器の出力端子が、前記オペアンプの非反転入力端子に接続されていること
を特徴とする発振器。 An amplifier for starting and amplifying the oscillation signal;
A oscillator and a, a resonance unit for determining a desired oscillation frequency,
The amplifying unit includes a low-pass filter having two terminals for input and output, and a three-stage amplifier circuit,
The first and third stages of the amplifier circuit are unbalanced amplifiers, and the second stage of the amplifier circuit is an operational amplifier.
The output terminal of the unbalanced amplifier at the first stage is connected to the input terminal of the low-pass filter and the inverting input terminal of the operational amplifier.
An oscillator characterized in that an output terminal of the low-pass filter is connected to a non-inverting input terminal of the operational amplifier. 前記共振部に水晶振動子を備えていることを請求項４に記載の特徴とする発振器。 Oscillator characterized according by comprising a crystal oscillator before Symbol resonance unit in claim 4. 前記共振部にＭＥＭＳ振動子を備えていることを特徴とする請求項４に記載の発振器。 Oscillator of claim 4, characterized in that it comprises a MEMS vibrator before Symbol resonance part.
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