Abstract:
An oscillator includes: a piezoelectric material to vibrate; a first inverting amplifier; a second inverting amplifier; a first output electrode to apply an output signal of the first inverting amplifier to the piezoelectric material; a second output electrode to apply an output signal of the second inverting amplifier to the piezoelectric material; a first input electrode to receive a voltage signal generated by the piezoelectric material and output the voltage signal to the first inverting amplifier; and a second input electrode to receive the voltage signal and output the voltage signal to the second inverting amplifier, wherein the first and second output electrodes are coupled to the piezoelectric material so that faces of the piezoelectric material move in opposite directions, and the first and second input electrodes are coupled to the piezoelectric material so that the voltage signals are input to the first and second input electrodes.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application is based upon and claims the benefit of priority of the prior Japanese Patent Application No. 2013-102148, filed on May 14, 2013, the entire contents of which are incorporated herein by reference. 
       FIELD 
       [0002]    The embodiments discussed herein are related to an oscillator. 
       BACKGROUND 
       [0003]    A oscillator such as a differential-output-type oscillator transmits a signal such as a clock or data signal. 
         [0004]    A related technique is disclosed in Japanese Laid-open Patent Publication No. 2007-37061. 
       SUMMARY 
       [0005]    According to an aspect of the embodiment, an oscillator includes: a piezoelectric material configured to vibrate in a mode; a first inverting amplifier; a second inverting amplifier; a first output electrode configured to apply an output signal of the first inverting amplifier to the piezoelectric material; a second output electrode configured to apply an output signal of the second inverting amplifier to the piezoelectric material; a first input electrode configured to receive a voltage signal generated by the piezoelectric material and output the voltage signal to the first inverting amplifier; and a second input electrode configured to receive the voltage signal and output the voltage signal to the second inverting amplifier, wherein the first output electrode and the second output electrode are coupled to the piezoelectric material so that faces of the piezoelectric material move in opposite directions, and the first input electrode and the second input electrode are coupled to the piezoelectric material so that the voltage signals which are generated by the piezoelectric material and have opposite phases are input to the first input electrode and the second input electrode. 
         [0006]    The object and advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the claims. 
         [0007]    It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are not restrictive of the invention, as claimed. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0008]      FIG. 1  illustrates an example of a differential-output-type oscillator; 
           [0009]      FIG. 2  illustrates an example of a differential-output-type oscillator; 
           [0010]      FIG. 3  illustrates an example of a differential-output-type oscillator; 
           [0011]      FIG. 4  illustrates an example of a differential-output-type oscillator; 
           [0012]      FIG. 5  illustrates an example of a differential-output-type oscillator; and 
           [0013]      FIG. 6  illustrates an example of a differential-output-type oscillator. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0014]    As the operating speed of a circuit is increased or the operating voltage of the circuit becomes low, misoperation of the circuit may occur due to noise that affects a signal such as a clock or data signal. 
         [0015]    In order to improve the noise immunity of the signal that is transmitted, such as a clock or data signal, differential-type signals may be used. 
         [0016]    A differential-output-type oscillator generates differential-type signals as two synchronous signals having different polarities. The differential-type signals that have been transmitted are received by a receiving circuit. The receiving circuit generates a difference signal based on the difference between the two synchronous signals having different polarities. 
         [0017]      FIG. 1  illustrates an example of a differential-output-type oscillator. 
         [0018]    An oscillator  110  includes a crystal unit  111  that vibrates in a thickness shear mode, an inverter  112 , an output electrode  114 , an input electrode  115 , and a differential-output-type buffer  118 . 
         [0019]    The output electrode  114  applies the output signal of the inverter  112  to the crystal unit  111 . The input electrode  115  receives a voltage signal generated by the crystal unit  111 , and outputs the voltage signal to the inverter  112 . The inverter  112  receives the voltage signal generated by the crystal unit  111 . The inverter  112  inverts and amplifies the voltage signal, and outputs the inverted and amplified voltage signal. 
         [0020]    The oscillator  110  has a loop circuit that is formed by the crystal unit  111  and the inverter  112 . The crystal unit  111  receives, from the inverter  112 , feedback of the inverted and amplified signal, thereby vibrating at a resonant frequency to generate a voltage signal. The voltage signal that has been generated at the resonant frequency by the crystal unit  111  is input from the crystal unit  111  to the first inverter  12 . The inverter  112  inverts and amplifies the voltage signal, and outputs the inverted and amplified signal to the output electrode  114  and the buffer  118 . 
         [0021]    The buffer  118  amplifies the output signal of the inverter  112 , and outputs differential-type signals C 1  and C 2  to signal lines  121   a  and  121   b.    
         [0022]    The signal C 1  is transmitted on the signal line  121   a , terminated by a matching circuit  119 , and received by a receiving circuit  120 . The signal C 2  is transmitted on the signal line  121   b , terminated by the matching circuit  119 , and received by the receiving circuit  120 . 
         [0023]    The receiving circuit  120  generates a signal C from the difference between the differential-type signals C 1  and C 2 . 
         [0024]    Noise from the outside may affect the signals C 1  and C 2  that are transmitted on the signal lines  121   a  and  121   b , respectively. For example, noise N 1  affects the signal C 1 , and noise N 2  affects the signal C 2 . The noise N 1  and the noise N 2  simultaneously affect the signals C 1  and C 2 . Thus, the noise N 1  and the noise N 2  may be in synchronization with each other, the size of the noise N 1  and the size of the noise N 2  may be the same, and the noise N 1  and the noise N 2  may have the same polarity. 
         [0025]    In the receiving circuit  120 , when the difference between the signal C 1  and the signal C 2  is obtained, the noise N 1  and the noise N 2  cancel each other out. Thus, the signal C from which the influence of noise has been removed is generated. 
         [0026]    As described above, when the differential-type signals C 1  and C 2  are transmitted on the signal lines  121   a  and  121   b , respectively, the signals C 1  and C 2  may be affected by noise. 
         [0027]      FIG. 2  illustrates an example of a differential-output-type oscillator. 
         [0028]    For example, noise from the outside may affect a signal flowing through the loop circuit that has the inverter  112  and the crystal unit  111  which are included in the oscillator  110 . The buffer  118  receives a signal having noise is output from the inverter  112 , and outputs the differential-type signals C 1  and C 2  that have been amplified. 
         [0029]    For example, the signal C 1  has the noise N 1 , and the signal C 2  has the noise N 2 . The noise N 1  and the noise N 2  are in synchronization with each other, and the size of the noise N 1  and the size of the noise N 2  are substantially the same. However, the noise N 1  and the noise N 2  have opposite polarities. 
         [0030]    When the difference between the signal C 1  and the signal C 2  is obtained in the receiving circuit  120 , noise may not be not removed because the noise N 1  and the noise N 2  have opposite polarities. Thus, noise N that includes the amplified noise N 1  and the amplified noise N 2  may remain in the generated signal C. 
         [0031]      FIG. 3  illustrates an example of a differential-output-type oscillator. 
         [0032]    An oscillator  10  illustrated in  FIG. 3  outputs differential-type signals C 1  and C 2 . The signals C 1  and C 2  may be synchronous signals, may have substantially the same amplitude, and may have opposite polarities. 
         [0033]    The oscillator  10  includes a crystal unit  11  that functions as a piezoelectric material which vibrates in the thickness shear mode, a first inverter  12 , a second inverter  13 , a first output electrode  14 , a first input electrode  15 , a second output electrode  16 , a second input electrode  17 , and a buffer  18 . 
         [0034]    The crystal unit  11  is cut so as to have a plate shape, and has a first face  11   a  and a second face  11   b  which vibrate in such a manner that the positions of the first face  11   a  and the second face  11   b  change in opposite directions. As the crystal unit  11  that vibrates in the thickness shear mode, for example, AT-cut or BT-cut crystal may be used. The crystal unit  11  may be a dielectric material, and may be an electrical insulator. 
         [0035]    In the crystal unit  11 , voltages having opposite polarities are applied to the first face  11   a  and the second face  11   b , whereby the first face  11   a  and the second face  11   b  are driven so as to change the positions thereof in directions opposite to each other. Because the positions of the first face  11   a  and the second face  11   b  change in directions opposite to each other, voltages having opposite polarities may be generated from the first face  11   a  and the second face  11   b.    
         [0036]    As a piezoelectric material that vibrates in the thickness shear mode, in addition to a crystal unit, for example, lithium tantalate, lithium niobate, or the like that is cut so as to vibrate in the thickness shear mode may be used. 
         [0037]    The first output electrode  14  is disposed on the first face  11   a  of the crystal unit  11 . The first output electrode  14  applies a first output signal B 1  of the first inverter  12  to the crystal unit  11 . The first inverter  12  and the first output electrode  14  is coupled to each other by the signal line. 
         [0038]    The first input electrode  15  is disposed on the second face  11   b  of the crystal unit  11 . The first input electrode  15  receives a first voltage signal A 1  generated by the crystal unit  11 , and outputs the first voltage signal A 1  to the first inverter  12 . The first inverter  12  and the first input electrode  15  are coupled to each other by the signal line. 
         [0039]    The first voltage signal A 1  that has been generated by the crystal unit  11  is input to the first inverter  12 . The first inverter  12  inverts and amplifies the first voltage signal A 1  to obtain the first output signal B 1 , and outputs the first output signal B 1 . The first output signal B 1  of the first inverter  12  is output to the first output electrode  14  and a first input part of the buffer  18 . 
         [0040]    A first loop circuit R 1  having a loop in which a signal flows is formed by the crystal unit  11 , the first inverter  12 , the first output electrode  14 , and the first input electrode  15 . 
         [0041]    In the first loop circuit R 1 , in order to set a resonant frequency, a capacitor may be disposed. The first loop circuit R 1  may have a resistor element. 
         [0042]    The second output electrode  16  is disposed on the second face  11   b  of the crystal unit  11  so as to be separated from the first input electrode  15 . The second output electrode  16  may not be electrically coupled to the first input electrode  15 . The second output electrode  16  applies a second output signal B 2  of the second inverter  13  to the crystal unit  11 . The second inverter  13  and the second output electrode  16  are coupled to each other by a signal line. 
         [0043]    The second input electrode  17  is disposed on the first face  11   a  of the crystal unit  11  so as to be separated from the first output electrode  14 . The second input electrode  17  may not be electrically coupled to the first output electrode  14 . A second voltage signal A 2  that has been generated by the crystal unit  11  is input to the second input electrode  17 , and the second input electrode  17  outputs the second voltage signal A 2  to the second inverter  13 . The second inverter  13  and the second input electrode  17  are coupled to each other by a signal line. 
         [0044]    The second inverter  13  receives the second voltage signal A 2  generated by the crystal unit  11 , inverts and amplifies the second voltage signal A 2  to obtain the second output signal B 2 , and outputs the second output signal B 2 . The second output signal B 2  of the second inverter  13  is output to the second output electrode  16  and a second input part of the buffer  18 . 
         [0045]    A second loop circuit R 2  having a loop in which a signal flows is formed by the crystal unit  11 , the second inverter  13 , the second output electrode  16 , and the second input electrode  17 . The second loop circuit R 2  may not be electrically coupled to the first loop circuit R 1 . The first loop circuit R 1  and the second loop circuit R 2  may be acoustically unified by vibration of the crystal unit  11 . 
         [0046]    In the second loop circuit R 2 , in order to set a resonant frequency, a capacitor may be disposed. The second loop circuit R 2  may have a resistor element. 
         [0047]    The capacitances of the capacitors are set so that the resonant frequency of the first loop circuit R 1  and the resonant frequency of the second loop circuit R 2  are substantially the same. 
         [0048]    In the oscillator  10 , the first output electrode  14  and the second output electrode  16  may be coupled to the crystal unit  11  so that the crystal unit  11  vibrates in the thickness shear mode in such a manner that the positions of the first face  11   a  and the second face  11   b  of the crystal unit  11  are changed in opposite directions. The first input electrode  15  and the second input electrode  17  may be coupled to the crystal unit  11  so that voltage signals having opposite phases, which are generated by vibration of the crystal unit  11  in the thickness shear mode, are input to the first input electrode  15  and the second input electrode  17 . 
         [0049]    The first output signal B 1  of the first inverter  12  is applied via the first output electrode  14  to the first face  11   a  of the crystal unit  11 . The crystal unit  11  is driven in the thickness shear mode, whereby the positions of the first face  11   a  and the second face  11   b  change in opposite directions. Thus, voltages having opposite polarities are generated from the first face  11   a  and the second face  11   b  by a piezoelectric effect. 
         [0050]    The second inverter  13  receives, via the second input electrode  17 , the second voltage signal A 2  generated by the crystal unit  11 . The second inverter  13  inverts and amplifies the second voltage signal A 2  to obtain the second output signal B 2 , and outputs the second output signal B 2 . The second output signal B 2  of the second inverter  13  is applied via the second output electrode  16  to the second face  11   b  of the crystal unit  11 . The crystal unit  11  is driven in the thickness shear mode, whereby voltages having opposite polarities are generated from the first face  11   a  and the second face  11   b.    
         [0051]    The first inverter  12  receives, via the first input electrode  15 , the first voltage signal A 1  generated by the crystal unit  11 . The first inverter  12  inverts and amplifies the first voltage signal A 1  to obtain the first output signal B 1 , and outputs the first output signal B 1 . 
         [0052]    The first voltage signal A 1  and the second voltage signal A 2  may be synchronous signals, may have substantially the same amplitude, and may have opposite polarities. The first output signal B 1  and the second output signal B 2  may be synchronous signals, may have substantially the same amplitude, and may have opposite polarities. 
         [0053]    In the first loop circuit R 1 , the first inverter  12  receives the first voltage signal A 1  having a phase opposite to the phase of the second voltage signal A 2  generated by the crystal unit  11 . The first inverter  12  outputs the first output signal B 1  to the crystal unit  11  so as to change the position of the crystal unit  11  in a phase direction opposite to the phase of the second output signal B 2 . 
         [0054]    In the second loop circuit R 2 , the second inverter  13  receives the second voltage signal A 2  having a phase opposite to the phase of the first voltage signal A 1  generated by the crystal unit  11 . The second inverter  13  outputs the second output signal B 2  to the crystal unit  11  so as to change the position of the crystal unit  11  in a phase direction opposite to the phase of the first output signal B 1 . 
         [0055]    The first loop circuit R 1  and the second loop circuit R 2  resonate, while being acoustically unified, at substantially the same resonant frequency so as to have opposite phases, thereby generating differential-type signals that are synchronous signals. 
         [0056]    The buffer  18  amplifies the individual output signals of the first inverter  12  and the second inverter  13  to obtain the differential-type signals C 1  and C 2  that are synchronous signals, and outputs the signals C 1  and C 2 . 
         [0057]      FIG. 4  illustrates an example of a differential-output-type oscillator. 
         [0058]    For example, noise from the outside may affect signals flowing through the oscillator  10  that has the first loop circuit R 1  and the second loop circuit R 2 . 
         [0059]    The first loop circuit R 1  and the second loop circuit R 2  are not electrically coupled to each other. Thus, noises that are synchronization with each other and that have the same phase may affect signals flowing through the individual circuits. 
         [0060]    Noises having the same phase affect the signals C 1  and C 2  output from the buffer  18 . The signal C 1  may have noise N 1 , and the signal C 2  may have noise N 2 . The noise N 1  and the noise N 2  may be in synchronization with each other. The size of the noise N 1  and the size of the noise N 2  may be substantially the same, and the noise N 1  and the noise N 2  may have the same polarity. 
         [0061]    In a receiving circuit that has received the signals C 1  and C 2 , when the difference between the signal C 1  and the signal C 2  is received, the noise N 1  and the noise N 2  cancel each other out. Thus, a signal from which the influence of noise has been removed may be generated. 
         [0062]    Even in the case where the signals C 1  and C 2  output from the buffer  18  are affected by noise when the signals C 1  and C 2  are transmitted on line signals, as illustrated in  FIG. 1 , a signal from which the influence of noise has been removed may be generated. 
         [0063]    In the oscillator  10 , the differential-type signals C 1  and C 2  that are synchronous signals are generated by two circuit that are not electrically coupled to each other and that are independent of each other. Thus, even when the oscillator  10  is affected by noise, the noise N 1  and the noise N 2  having the same phase affect the signals C 1  and C 2 , respectively. Therefore, when the difference between the signal C 1  and the signal C 2  is obtained in the receiving circuit, the noise N 1  and the noise N 2  cancel each other out. A signal from which the influence of noise has been removed may be generated. The noise immunity of the signal may be improved. 
         [0064]      FIG. 5  illustrates an example of a differential-output-type oscillator. In  FIG. 5 , components substantially the same as or similar to those illustrated in  FIG. 3  or  4  are denoted by the same reference numerals, and a description thereof may be omitted or reduced. 
         [0065]    In an oscillator  10  illustrated in  FIG. 5 , a crystal unit  20  includes a first crystal unit  21  and a second crystal unit  22 . 
         [0066]    The first crystal unit  21  is cut so as to have a plate shape, and has a first face  21   a  and a second face  21   b  which vibrate in the thickness shear mode in such a manner that the positions of the first face  21   a  and the second face  21   b  change in opposite directions. The second crystal unit  22  is cut so as to have a plate shape, and has a first face  22   a  and a second face  22   b  which vibrate in the thickness shear mode in such a manner that the positions of the first face  22   a  and the second face  22   b  change in opposite directions. 
         [0067]    The first crystal unit  21  and the second crystal unit  22  are cut so as to have the same thickness in the same direction, and may have substantially the same natural frequency. 
         [0068]    A first output electrode  14  and a second input electrode  17  are disposed between the second face  21   b  of the first crystal unit  21  and the first face  22   a  of the second crystal unit  22  so as to be separated from each other. The first output electrode  14  and the second input electrode  17  may not be electrically coupled to each other. 
         [0069]    The first crystal unit  21  and the second crystal unit  22  may be joined together in such a manner that the first output electrode  14  and the second input electrode  17  intervene between the first crystal unit  21  and the second crystal unit  22 . As a method for joining an electrode and a crystal unit, for example, a positive-electrode joining method may be used. 
         [0070]    A first input electrode  15  is disposed on the first face  21   a  of the first crystal unit  21 . A second output electrode  16  is disposed on the second face  22   b  of the second crystal unit  22 . 
         [0071]    A first loop circuit R 1  having a loop in which a signal flows is formed by the first crystal unit  21 , a first inverter  12 , the first output electrode  14 , and the first input electrode  15 . 
         [0072]    A second loop circuit R 2  having a loop in which a signal flows is formed by the second crystal unit  22 , a second inverter  13 , the second output electrode  16 , and the second input electrode  17 . The second loop circuit R 2  may not be electrically coupled to the first loop circuit R 1 . 
         [0073]    In the first loop circuit R 1  and the second loop circuit R 2 , capacitors are disposed so that the resonant frequency of the first loop circuit R 1  and the resonant frequency of the second loop circuit R 2  are substantially the same. 
         [0074]    A first output signal B 1  of the first inverter  12  is applied via the first output electrode  14  to the second face  21   b  of the first crystal unit  21 . The first crystal unit  21  is driven in the thickness shear mode, whereby the positions of the first face  21   a  and the second face  21   b  change in opposite directions. Thus, voltages having opposite polarities are generated from the first face  21   a  and the second face  21   b  by a piezoelectric effect. 
         [0075]    The second inverter  13  receives, via the second input electrode  17 , a second voltage signal A 2  generated by the first crystal unit  21 . The second inverter  13  inverts and amplifies the second voltage signal A 2  to obtain a second output signal B 2 , and outputs the second output signal B 2 . The second output signal B 2  of the second inverter  13  is applied via the second output electrode  16  to the second face  22   b  of the second crystal unit  22 . The second crystal unit  22  is driven in the thickness shear mode, whereby voltages having opposite polarities are generated from the first face  22   a  and the second face  22   b.    
         [0076]    The first inverter  12  receives, via the first input electrode  15 , a first voltage signal A 1  generated by the first crystal unit  21 . The first inverter  12  inverts and amplifies the first voltage signal A 1  to obtain the first output signal B 1 , and outputs the first output signal B 1 . 
         [0077]    The first voltage signal A 1  and the second voltage signal A 2  may be synchronous signals, may have substantially the same amplitude, and may have opposite polarities. The first output signal B 1  and the second output signal B 2  may be synchronous signals, may have substantially the same amplitude, and may have opposite polarities. 
         [0078]    In the first loop circuit R 1 , the first voltage signal A 1  having a phase opposite to the phase of the second voltage signal A 2  generated by the first crystal unit  21  is input to the first inverter  12 . The first inverter  12  outputs the first output signal B 1 , which has a phase opposite to the phase of the second output signal B 2 , to the first crystal unit  21  so that the position of the first crystal unit  21  is changed in the phase direction opposite to the second output signal B 2 . 
         [0079]    In the second loop circuit R 2 , the second voltage signal A 2  having a phase opposite to the phase of the first voltage signal A 1  generated by the second crystal unit  22  is input to the second inverter  13 . The second inverter  13  outputs the second output signal B 2 , which has a phase opposite to the phase of the first output signal B 1 , to the second crystal unit  22  so that the position of the second crystal unit  22  is changed in the phase direction opposite to the first output signal B 1 . 
         [0080]    In this manner, the first loop circuit R 1  and the second loop circuit R 2  resonate, while being acoustically unified, at substantially the same resonant frequency so as to have opposite phases, thereby generating differential-type signals that are synchronous signals. 
         [0081]    A buffer  18  amplifies the individual output signals of the first inverter  12  and the second inverter  13  to obtain the differential-type signals C 1  and C 2  that are synchronous signals, and outputs the signals C 1  and C 2 . 
         [0082]      FIG. 6  illustrates an example of a differential-output-type oscillator. In  FIG. 6 , components substantially the same as or similar to those illustrated in 
         [0083]      FIG. 3  or  4  are denoted by the same reference numerals, and a description thereof may be omitted or reduced. 
         [0084]    Noise from the outside may affect signals flowing through the oscillator  10  that has the first loop circuit R 1  and the second loop circuit R 2 . 
         [0085]    For example, noises having the same phase may affect the signals C 1  and C 2  output from the buffer  18 . For example, the signal C 1  may have the noise N 1 , and the signal C 2  may have the noise N 2 . The noise N 1  and the noise N 2  may be in synchronization with each other. The size of the noise N 1  and the size of the noise N 2  may be substantially the same, and the noise N 1  and the noise N 2  may have the same polarity. 
         [0086]    In the receiving circuit that has received the signals C 1  and C 2 , when the difference between the signal C 1  and the signal C 2  is obtained, the noise N 1  and the noise N 2  cancel each other out. Thus, a signal from which the influence of noise has been removed may be generated. 
         [0087]    Even in the case where the signals C 1  and C 2  output from the buffer  18  are affected by noise when the signals C 1  and C 2  are transmitted on line signals, as illustrated in  FIG. 1 , a signal from which the influence of noise has been removed may be generated. 
         [0088]    The oscillator  10  illustrated in  FIG. 5  or  6  may have effects substantially the same as or similar to effects that the oscillator  10  illustrated in  FIG. 3  or  4  has. 
         [0089]    For example, the above-described oscillator may have buffers. In the case of outputting generated differential-type signals without amplifying the signals, the oscillator may not have the buffers. 
         [0090]    The above-described oscillator may have inverters as inverting amplifiers. Each of the inverting amplifiers may have a circuit other than an inverter if the inverting amplifier is configured to receive a voltage signal generated by a piezoelectric material, and to invert and amplify the voltage signal. 
         [0091]    All examples and conditional language recited herein are intended for pedagogical purposes to aid the reader in understanding the invention and the concepts contributed by the inventor to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions, nor does the organization of such examples in the specification relate to a showing of the superiority and inferiority of the invention. Although the embodiments of the present invention have been described in detail, it should be understood that the various changes, substitutions, and alterations could be made hereto without departing from the spirit and scope of the invention.