Abstract:
The signal transmission circuit comprises a first switch controls output according to a first control pulse, the first source follower outputting signals to the first output line based on signal input into the gate, a first capacitor connected between the gate and the source of the source follower, the first circuit, based on a level of the input signal, fixing the first output line to reference potential, the second switch controlling output according to a second control pulse, the second source follower, according to signals input into the gate, supplying output signals to the subsequent stage and also to a second output line, a second capacitor connected between the gate and the source of the source follower, and the second circuit, based on a level of input signals from the source, fixing the second output line to reference potential.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to a signal transmission circuit that is favorably used in shift registers that drive solid-state imaging apparatuses, liquid crystal displays, memory devices, and the like.  
         [0003]     Priority is claimed on Japanese Patent Application No. 2004-043565, filed Feb. 19, 2004, the contents of which are incorporated herein by reference.  
         [0004]     2. Description of Related Art  
         [0005]      FIG. 11  shows a portion of a signal transmission circuit that is disclosed in Japanese Patent Application Publication (JP-B) No.3-75960 as an example of a conventional signal transmission circuit that is composed solely of NMOS transistors.  
         [0006]     As is shown in  FIG. 11 , an input line φ ST  is connected to a gate of a MOS transistor M 2  via a MOS transistor M 1 , and to a ground line GND via a MOS transistor M 3 . A bootstrap capacitor C 1  is connected between the gate and source of the MOS transistor M 2 , and the source of the MOS transistor M 2  is connected to a gate of a MOS transistor M 52  via a MOS transistor M 51 .  
         [0007]     The source of the MOS transistor M 2  is connected to the ground line GND via a MOS transistor M 4  and a MOS transistor M 53 . A bootstrap capacitor C 51  is connected between the gate and source of the MOS transistor M 52 . The source of the MOS transistor M 52  is connected to the ground line GND via a MOS transistor M 14 , and the source of the MOS transistor M 52  is connected to the subsequent circuit.  
         [0008]     A clock line φ 1  is connected to the gate of the transistors M 1  and M 4  and to the drain of the transistor M 52 , and a clock line φ 2  is connected to the gate of the transistors M 51  and M 14  and to the drain of the transistor M 2 . Thereafter, these transistor and bootstrap capacitor circuits are repeatedly connected in sequence. In addition, OUT 1 , OUT 2  . . . are output lines, G 2 , G 52  . . . are gate lines of the transistors M 2  and M 52 , Cs 1  is a parasitic capacitor that does not contribute to the bootstrap effect that is applied to G 2 , G 52  . . . , C DG  is a capacitor between a drain and a gate, and C L  is an output capacitor.  
         [0009]      FIG. 12  is a timing chart for schematically describing an operation of the signal transmission circuit shown in  FIG. 11 . The signals shown by φ 1 , φ 2 , and φ ST  in  FIG. 12  are applied respectively to the clock lines φ 1  and φ 2  and to the input line φ ST  in the circuit shown in  FIG. 11 , and, in  FIG. 11 , GND is a ground potential. Here, potentials of high level of the input signal φ ST  and the clock signals φ 1  and φ 2  are defined as V H , and potential of all threshold values of the MOS transistors are defined as V th .  
         [0010]     In  FIG. 12 , firstly, when the input signal φ ST  and the clock signal φ 1  change to a high level, the transistor M 1  is in a conducting state. Consequently, the high level of the input signal φ ST  is sent to the transistor M 1 , and charge is accumulated in the bootstrap capacitor C 1 . As a result, as is shown by V G2  in  FIG. 12 , the potential of the gate line G 2  of the transistor M 2  changes to a high level. At this time, if potential of the gate line G 2  of the transistor M 2  is taken as V H ′, the Formula 1 below applies.
 
 V   H   ′=V   H   −V   th   (Formula 1)
 
         [0011]     When the potential V G2  of the gate line G 2  of the transistor M 2  changes to a high level, the transistor M 2  is in a conducting state. As a result, as is shown by V OUT1  in  FIG. 12 , a low level of the clock signal φ 2  is output to the output line OUT 1 .  
         [0012]     Next, when the clock signal φ 2  changes to a high level, the potential V G2  of the gate line G 2  of the transistor M 2  rises by Formula 2 via the bootstrap capacitor C 1 .  
         [0013]     C S1  is a parasitic capacitor that does not contribute to the bootstrap effect and that is caused by the gate of the transistor M 2 .  
         [0014]     As a result, the potential V G2  of the gate line G 2  of the transistor M 2  changes to Formula 3, and, at this time, if the relationship shown in Formula 4 applies, the high level of the clock signal φ 2  is extracted to the source of the transistor M 2 .
 
 V   A   ={C   1 /( C   1   +C   S1 )} V   H   (Formula 2)
 
 V   G2   =V   H   ′+{C   1 /( C   1   +C   S1 )} V   H   (Formula 3)
 
 V   G2   −V   th   ≧V   H   (Formula 4)
 
         [0015]     Accordingly, as is shown by the V OUT1  in  FIG. 12 , the high level is extracted to the output line OUT 1 . At this time, simultaneously, in synchronization with the clock signal φ 2 , the transistor M 51  is placed in a conducting state. As a result, because a load is accumulated in the bootstrap capacitor C 51 , the potential of the gate line G 52  of the transistor M 52  changes to a high level, as is shown by the V G52  in  FIG. 12 .  
         [0016]     Next, when the clock signal φ 1  once again changes to a high level, the potential V G52  of the gate line  52  of the transistor M 52  is lifted to a higher voltage than the high level potential V H  of the clock signal φ 1  via the bootstrap capacitor C 51 . As a result, the high level of the clock signal φ 1  is extracted to the source of the transistor M 52 , and the high level is extracted to the output line OUT 2 , as is shown by the V OUT2  in  FIG. 12 .  
         [0017]     In the same way, the potentials of the gate line G 102  and the output line OUT 3 , and the potentials of the gate line  152  and the output line OUT 4  that are shown in  FIG. 11  change respectively in the manners shown by V G102 , V OUT3 , V G152 , and V OUT4  shown in  FIG. 12 . Accordingly, in this circuit, high level of the input signal φ ST  are sequentially transmitted, and the high level is extracted in sequence to the output lines OUT 1 , OUT 2 , OUT 3 , and OUT 4 .  
         [0018]      FIG. 13  is a portion of a signal transmission circuit disclosed in Japanese Patent Application Publication (JP-B) No. 5-84967 as an example of a conventional signal transmission circuit that is composed solely of NMOS transistors.  
         [0019]     An input line φ ST  is connected to a gate of the MOS transistor M 2  and to the gate of the MOS transistor M 12  via the MOS transistor M 1 , and the bootstrap capacitor C 1  is connected between the gate and source of the MOS transistor M 2 .  
         [0020]     The source of the MOS transistor M 2  is connected to the gate of the MOS transistor M 52  and to the gate of a MOS transistor M 62  via a MOS transistor M 51 . The source of the MOS transistor M 2  is also connected to a ground line GND via a MOS transistor M 13 , and the bootstrap capacitor C 51  is connected between the gate and source of the MOS transistor M 52 .  
         [0021]     The source of the MOS transistor M 52  is connected to the ground line GND via a MOS transistor M 63 , and the source of the MOS transistor M 52  is connected to the next circuit. Furthermore, a clock line φ 1  is connected to the gates of the MOS transistors M 1  and M 11 , and to the drain of the MOS transistor M 52 . A clock line φ 2  is connected to the gates of the MOS transistors M 51  and M 61 , and to the drain of the MOS transistor M 2 .  
         [0022]     In addition, the drains of the MOS transistors M 11  and M 61  are connected to a power supply line V DD , and the sources of the MOS transistors M 11  and M 61  are connected respectively to the gates of the transistors M 13  and M 63  and to the drains of the MOS transistors M 12  and M 62 . The sources of the MOS transistors M 12  and M 62  are connected to the ground line GND, and, thereafter, these transistor and bootstrap capacitor circuits are repeatedly connected in sequence. Here, OUT 1 , OUT 2  . . . are output lines, G 2 , G 52  . . . are gate lines of the transistors M 2  and M 52 , Cs 1  is a parasitic capacitor that does not contribute to the bootstrap effect and that is applied to G 2 , G 52  . . . , C S2  is a parasitic capacitor that does not contribute to the bootstrap effect and that is caused by the gates of the transistors M 12  and M 62  . . . , and  10 ,  60 ,  110 , and  160  are output line fixed circuits.  
         [0023]     Next, using timing chart shown in  FIG. 14 , an operation of the signal transmission circuit shown in  FIG. 13  will be schematically described.  
         [0024]     The signals shown by φ 1 , φ 2 , and φ ST  in  FIG. 14  are applied respectively to the clock lines φ 1  and φ 2  and to the input line φ ST  in the circuit shown in  FIG. 13 , and, in  FIG. 13 , GND is a ground potential.  
         [0025]     Here, potentials of high level of the input signal φ ST  and the clock signals φ 1  and φ 2  are defined as V H , and all threshold values of the MOS transistors are defined as V th .  
         [0026]     Firstly, when the input signal φ ST  and the clock signal φ 1  change to a high level, the transistor M 1  changes to a conducting state. Consequently, the high level of the input signal φ ST  is sent to the transistor M 1 , and a charge is accumulated in the bootstrap capacitor C 1 . As a result, as is shown by V G2  in  FIG. 14 , the potential of the gate line G 2  of the transistor M 2  changes to a high level. At this time, if the potential of the gate line G 2  of the transistor M 2  is taken as V H ′, the Formula 5 below applies.
 
 V   H   ′=V   H   −V   th   (Formula 5)
 
         [0027]     When the potential V G2  of the gate line G 2  of the transistor M 2  changes to a high level, the transistor M 2  is placed in a conducting state. As a result, as is shown by V OUT1  in  FIG. 14 , a low level of the clock signal φ 2  is output to the potential V OUT1  of the output line OUT 1 . At this time, because the transistor M 12  is also in a conducting state, as is shown by V G13  in  FIG. 14 , the potential of the gate line G 13  of the transistor M 13  becomes the ground potential, and the transistor M 13  changes to a cutoff state.  
         [0028]     Next, when the clock signal φ 2  changes to a high level, the potential V G2  of the gate line G 2  of the transistor M 2  rises by Formula 6 via the bootstrap capacitor C 1 .  
         [0029]     C S1  and C S2  are parasitic capacitors that do not contribute to the bootstrap effect and that is caused respectively by the gates of the transistors M 2  and M 12 .  
         [0030]     As a result, the potential V G2  of the gate line G 2  of the transistor M 2  changes to Formula 7, and if the relationship shown in Formula 8 applies, the high level of the clock signal φ 2  is extracted to the source of the transistor M 2 . At this time, because the potential V G13  of the gate line G 13  of the transistor M 13  is continuously fixed to the ground potential, the transistor M 13  remains fixed in the cutoff state, and is cut off from the output line OUT  1 . Therefore, there are no harmful effects on the output line OUT  1 . Accordingly, the high level is extracted to the output line OUT 1 , as is shown by V OUT1  in  FIG. 14 .
 
 V   A   ={C   1 /( C   1   +C   S1   +C   S2 )} V   H   (Formula 6)
 
 V   G2   =V   H   ′+{C   1 /( C   1   +C   S1   +C   S2 )} V   H   (Formula 7)
 
 V   G2   −V   th   ≧V   H   (Formula 8)
 
         [0031]     At this time, simultaneously, in synchronization with the clock signal φ 2 , the transistor M 51  is placed in a conducting state. As a result, because a load is accumulated in the bootstrap capacitor C 51 , the potential of the gate line G 52  of the transistor M 52  changes to a high level, as is shown by the V G52  in  FIG. 14 .  
         [0032]     Next, when the clock signal φ 1  once again changes to a high level, the potential V G52  of the gate line  52  of the transistor M 52  is lifted to a higher potential than the high level potential V H  of the clock signal φ 1  via the bootstrap capacitor C 51 . As a result, the high level of the clock signal φ 1  is extracted to the source of the transistor M 52 . Accordingly, the high level is extracted to the potential of the output line OUT 2 , as is shown by the V OUT2  in  FIG. 14 .  
         [0033]     Note that, at this time, because the input signal φ ST  is at a low level, the potential V G2  of the gate line G 2  of the transistor M 2  changes to a low level, and the transistor M 12  changes to a cutoff state. In contrast, because the transistor M 11  is in a conducting state, the potential V G13  of the gate line G 13  of the transistor M 13  changes to a high level. As a result, because the transistor M 13  is in a conducting state, the potential V OUT1  of the output line OUT 1  is fixed to the ground potential.  
         [0034]     In the same way, the potentials of the gate line G 102  of the transistor M 102 , the gate line G 113 , the output line OUT 3 , the gate line  152 , the gate line  163  of the transistor M 163 , and the output line OUT  4  as are shown in  FIG. 13 , change respectively in the manners shown by V G102 , V G113 , V OUT3 , V G152 , V G163 , and V OUT4  shown in  FIG. 14 .  
         [0035]     Accordingly, in this circuit, the high level of the input signal φ ST  are sequentially transmitted, and the high level are extracted in sequence to the output lines OUT 1 , OUT 2 , OUT 3 , and OUT 4 .  
       SUMMARY OF THE INVENTION  
       [0036]     The first aspect of the present invention is a signal transmission circuit comprising: a first switch element connecting an input terminal which a start signal or an output signal from a prior stage is input as an input signal to an output terminal outputting a signal depending on a first control pulse; a first source follower comprising: a gate connected to the output terminal of the first switch element; and a drain to which a second control pulse with a different phase to the first control pulse is supplied; wherein the first source follower outputs a signal to a first output line based on a signal input to the gate; a first capacitor component connected between the gate and the source of the first source follower; a first reference potential fixing circuit comprising; an input terminal to which the input signals are supplied; and an output terminal connected to a source of the first source follower; wherein the first reference potential fixing circuit fixes a potential of its own output terminal to the reference potential depending on a level of the input signal; a second switch element which connects an input terminal connected the source of the first source follower to an output terminal outputting a signal referring to the second control pulse; a second source follower comprising: a gate connected to the output terminal of the second switch element; a drain to which the first control pulse is supplied; and a source supplying an output signal to a subsequent stage and also outputting a signal to a second output line; a second capacitor component connected between the gate and the source of the second source follower; and a second reference potential fixing circuit comprising: an input terminal connected to the source of the first source follower; and an output terminal connected to the source of the second source follower, wherein the second reference potential fixing circuit fixes a potential of the output terminal to the reference potential depending on a level of the input signal from the source of the first source follower.  
         [0037]     The second aspect of the present invention is the signal transmission circuit according to the first aspect, further comprising: a first sample hold circuit, comprising an input terminal to which the input signal is supplied and an output terminal connected to the input terminal of the first reference potential fixing circuit, for holding the input signal for a predetermined period; and a second sample hold circuit, comprising an input terminal connected to the source of the first source follower and an output terminal connected to the input terminal of the second reference potential fixing circuit, for holding the signal from the first source follower for a predetermined period.  
         [0038]     The third aspect of the present invention is the signal transmission circuit according to the first aspect, further comprising: a first sample hold circuit, comprising an input terminal connected to the source of the first source follower and an output terminal connected to both the input terminal of the second reference potential fixing circuit and the input terminal of the second switch element, for holding the signal supplied from the source of the first source follower for a predetermined period; and a second sample hold circuit, comprising an input terminal connected to the source of the second source follower and an output terminal connected to both the input terminal of the first reference potential fixing circuit and the input terminal of the first switch element in a next stage, for holding the signal supplied from the source of the second source follower for a predetermined period.  
         [0039]     The fourth aspect of the present invention is the signal transmission circuit according the first aspect, wherein the first reference potential fixing circuit comprises: a first transistor comprising: a gate as the input terminal; and a source fixed to a predetermined potential; a third switch element connected between a power supply line and a drain of the first transistor, wherein the third switch element is controlled by the first control pulse; and a second transistor comprising: a gate connected to the drain of the first transistor, and a source fixed to a predetermined potential, and a drain as the output terminal.  
         [0040]     The fifth aspect of the present invention is the signal transmission circuit according to the first aspect, wherein the second reference potential fixing circuit comprises: a third transistor comprising: a gate as the input terminal; and a source fixed to a predetermined potential; a fourth switch element connected between a power supply line and a drain of the third transistor, wherein the fourth switch element is controlled by the second control pulse; and a fourth transistor comprising: a gate connected to the drain of the third transistor; a source fixed to a predetermined potential; and a drain as the output terminal.  
         [0041]     The sixth aspect of the present invention is the signal transmission circuit according the first aspect, wherein the first reference potential fixing circuit comprises: a first transistor comprising; a gate as the input terminal; and a source fixed to a predetermined potential; a third switch element comprising; a source connected to the drain of the first transistor; a drain, wherein the first control pulse is supplied to; and a gate wherein the drain and the gate are connected; and a second transistor comprising; a gate connected to the drain of the first transistor; a source fixed to a predetermined potential; and a drain as the output terminal.  
         [0042]     The seventh aspect of the present invention is the signal transmission circuit according to the first aspect, wherein the second reference potential fixing circuit comprises: a third transistor comprising; a gate as the input terminal; and a source fixed to a predetermined potential; a fourth switch element comprising; a source connected to the drain of the third transistor, and a drain, wherein the second control pulse is supplied; and a gate, wherein the drain and the gate are connected; and a fourth transistor comprising; a gate connected to the drain of the third transistor; a source fixed to a predetermined potential; and a drain as the output terminal.  
         [0043]     The eighth aspect of the present invention is the signal transmission circuit according to the first aspect, further comprising: a first sample hold circuit, comprising an input terminal to which the input signal is supplied and an output terminal connected to the input terminal of the first reference potential fixing circuit, for holding the input signal for a predetermined period; and a second sample hold circuit, comprising an input terminal connected to the source of the first source follower and an output terminal connected to the input terminal of the second reference potential fixing circuit, for holding the signal for a predetermined period; wherein the first and the second reference potential fixing circuits comprising: a first transistor comprising; a gate as the input terminal of the reference potential fixing circuit; and a source fixed to a predetermined potential; a depression transistor comprising; a drain to which a power supply voltage is supplied; a gate; and a source, wherein the gate and the source are connected to a drain of the first transistor; and a second transistor comprising; a gate connected to the drain of the first transistor; and a source fixed to a predetermined potential; and a drain as the output terminal of the reference potential fixing circuit.  
         [0044]     The ninth aspect of the present invention is the signal transmission circuit according to the first aspect, further comprising: a first sample hold circuit, comprising an input terminal to which the input signal is supplied and an output terminal connected to the input terminal of the first reference potential fixing circuit, for holding the input signal for a predetermined period; and a second sample hold circuit, comprising an input terminal connected to the source of the first source follower and an output terminal connected to the input terminal of the second reference potential fixing circuit, for holding the signal for a predetermined period; wherein, the first sample hold circuit is a transistor comprising; a gate which the first control pulse is supplied to; a drain; and a source, wherein one of the drain and the source is the input terminal of the first sample hold circuit while the other of the drain and the source is the output terminal of the first sample hold circuit; and the second sample hold circuit is a transistor comprising; a gate which the second control pulse is supplied to; a drain; and a source, wherein one of the drain and the source is the input terminal of the second sample hold circuit while the other of the drain and the source is the output terminal of the second sample hold circuit.  
         [0045]     The tenth aspect of the present invention is the signal transmission circuit according to the first aspect, further comprising: a first sample hold circuit, comprising an input terminal to which the input signal is supplied and an output terminal connected to the input terminal of the first reference potential fixing circuit, for holding the input signal for a predetermined period; and a second sample hold circuit, comprising an input terminal connected to the source of the first source follower and an output terminal connected to the input terminal of the second reference potential fixing circuit, for holding the signal for a predetermined period; wherein, the first and the second sample hold circuits comprising: a transistor comprising; a drain as the input terminal of the sample hold circuit; a gate connected to the drain; and a source as the output terminal of the sample hold circuit; and a switch element, wherein a potential of the source of the transistor is controlled and fixed to the reference potential, referring to an input signal from the corresponding first and second sample hold circuits of a subsequent stage. 
     
    
     BRIEF DESCRIPTION THE DRAWINGS  
       [0046]      FIG. 1  is a view showing a circuit structure according to a first embodiment.  
         [0047]      FIG. 2  is a view showing a timing chart of the circuit according to the first embodiment.  
         [0048]      FIG. 3  is a view showing another circuit structure of an output line fixed section.  
         [0049]      FIG. 4  is a view showing a circuit structure according to a second embodiment.  
         [0050]      FIG. 5  is a view showing a timing chart of the circuit according to the second embodiment.  
         [0051]      FIG. 6  is a view showing another circuit structure of an output line fixed section.  
         [0052]      FIG. 7  is a view showing a circuit structure according to a variant example of the second embodiment.  
         [0053]      FIG. 8  is a view showing a circuit structure according to a third embodiment.  
         [0054]      FIG. 9  is a view showing a timing chart of the circuit according to the third embodiment.  
         [0055]      FIG. 10  is a view showing a circuit structure according to a variant example of the third embodiment.  
         [0056]      FIG. 11  is a view showing a conventional circuit structure.  
         [0057]      FIG. 12  is a view showing a timing chart of a conventional circuit.  
         [0058]      FIG. 13  is a view showing another conventional circuit structure.  
         [0059]      FIG. 14  is a view showing a timing chart of another conventional circuit. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0060]     While preferred embodiments of the invention have been described and illustrated above, it should be understood that these are exemplary of the invention and are not to be considered as limiting. Additions, omissions, substitutions, and other modifications can be made without departing from the spirit or scope of the present invention. Accordingly, the invention is not to be considered as limited by the foregoing description and is only limited by the scope of the appended claims.  
         [0061]     The signal transmission circuit according to the present invention will now be described in detail with reference made to  FIGS. 1 through 10 .  
         [0000]     (First Embodiment)  
         [0062]      FIG. 1  is a circuit diagram showing a first embodiment of the signal transmission circuit of the present invention.  
         [0063]     Note that component elements that correspond to those in the conventional example shown in  FIG. 13  are given the same symbols.  
         [0064]     An input line φ ST  is connected to a gate of a MOS transistor M 2  via a MOS transistor M 1 , and the input line φ ST  is connected to a gate of a MOS transistor M 12 . In addition, a bootstrap capacitor C 1  is connected between the gate and source of the MOS transistor M 2 , and the source of the MOS transistor M 2  is connected to a gate of a MOS transistor M 52  via a MOS transistor M 51  and to the ground line GND via a MOS transistor M 13 .  
         [0065]     The source of the MOS transistor M 2  is connected to the gate of a MOS transistor M 62 , and a bootstrap capacitor C 51  is connected between the gate and source of the MOS transistor M 52 . The source of the MOS transistor M 52  is connected to the ground line GND via a MOS transistor M 63 . Furthermore, the source of the MOS transistor M 52  is connected to the next circuit.  
         [0066]     A clock line φ 1  is connected to the gate of the MOS transistors M 1  and M 11  and to the drain of the MOS transistor M 52 , and a clock line φ 2  is connected to the gate of the MOS transistors M 51  and M 61  and to the drain of the MOS transistor M 2 . The power supply line V DD  is connected to the drains of the MOS transistors M 11  and M 61 .  
         [0067]     The sources of the MOS transistors M 11  and M 61  are connected respectively to the gates of the transistors M 13  and M 63 , and to the drains of the MOS transistors M 12  and M 62 . The sources of the MOS transistors M 12  and M 62  are connected to the ground line GND. Thereafter, these transistor and bootstrap capacitor circuits are repeatedly connected in sequence. Note that OUT 1 , OUT 2  . . . are output lines, G 2 , G 52  . . . are gate lines of the transistors M 2  and M 52 , G 13  and G 63  are gate lines of transistors M 13  and M 63  . . . , Cs 1  is a parasitic capacitor that does not contribute to the bootstrap effect that is applied to G 2 , G 52  . . . , and  10 ,  60 ,  110 , and  160  are output line fixed circuit.  
         [0068]     Next, an operation of the signal transmission circuit shown in  FIG. 1  will be described schematically using the timing chart shown in  FIG. 2 .  
         [0069]     Note that, in the circuit shown in  FIG. 1 , the signals shown by φ 1 , φ 2 , and φ ST  in  FIG. 2  are applied respectively to the clock lines φ 1  and φ 2  and to the input line φ ST  in the circuit shown in  FIG. 1 , and, in  FIG. 1 , VDD is a power supply potential and GND is a ground potential. In addition, high level potentials of the input signal φ ST  and the clock signals φ 1  and φ 2  are defined as V H , and all threshold values of the MOS transistors are defined as V th .  
         [0070]     Firstly, when the clock signal φ 1  and the input signal φ ST  change to a high level, the transistor M 1  is placed in a conducting state. Consequently, a high level of the input signal φ ST  is sent to the transistor M 1 , and, as is shown in  FIG. 2 , the potential V G2  of the gate line G 2  of the transistor M 2  changes to a high level. Here, if the high level potential of the gate line G 2  of the transistor M 2  is taken as V H ′, then Formula 10 below applies to V H ′.
 
 V   H   ′=V   H   −V   th   (Formula 10)
 
         [0071]     When the potential V G2  of the gate line G 2  of the transistor M 2  changes to a high level, the transistor M 2  is in a conducting state, and a low level from the clock line φ 2  is output to the potential V OUT1  of the output line OUT 1 .  
         [0072]     In contrast, in the output line fixed circuit shown by  10  in  FIG. 1 , when the input signal φ ST  changes to a high level, the transistor M 12  is placed in a conducting state, and the potential of the gate line G 13  of the transistor M 13  changes to the ground potential, as is shown by V G13  in  FIG. 2 . Accordingly, the transistor M 13  changes to a cutoff state, and, because it is cut off from the output line OUT  1 , there are no harmful effects on the output line OUT  1 .  
         [0073]     Next, when the clock signal φ 2  changes to a high level, the potential V G2  of the gate line G 2  of the transistor M 2  rises by the amount shown in Formula 11 via the bootstrap capacitor C 1 .  
         [0074]     C S1  is a parasitic capacitor that does not contribute to the bootstrap effect and that is caused by the gate of the transistor M 2 .
 
 V   A   ={C   1 /( C   1   +C   S1 )} V   H   (Formula 11)
 
         [0075]     As a result, the potential V G2  of the gate line G 2  of the transistor M 2  changes as is shown in Formula 12.  
         [0076]     At this time, if the relationship shown in Formula 13 applies, the high level of the clock signal φ 2  is extracted to the source of the transistor M 2 . Accordingly, the high level is extracted to the output line OUT 1  as is shown by the V OUT1  in  FIG. 2 . Simultaneously with this, because the transistor M 51  changes to a conducting state in synchronization with the clock signal φ 2 , the potential of the gate line G 52  of the transistor M 52  changes to a high level, as is shown by the V G52  in  FIG. 2 .
 
 V   G2   =V   H   ′+{C   1 /( C   1   +C   S1 )} V   H   (Formula 12)
 
 V   G2   −V   th   ≧V   H   (Formula 13)
 
         [0077]     Moreover, at this time, because a high level of the output signal V OUT1  of the previous stage is input into the output line fixed circuit shown by  60  in  FIG. 1 , the transistor M 62  is placed in a conducting state, and the potential of the gate line G 63  of the transistor M 63  changes to the ground potential, as is shown by the V G63  in  FIG. 2 . Accordingly, the transistor M 63  changes to a cutoff state, and, because it is cut off from the output line OUT  2 , there are no harmful effects on the output line OUT  2 .  
         [0078]     Next, when the clock signal φ 1  once again changes to a high level, the potential V G52  of the gate line  52  of the transistor M 52  is lifted to a higher potential than the high level potential V H  of the clock signal φ 1  via the bootstrap capacitor C 51 . As a result, the high level of the clock signal φ 1  is extracted to the source of the transistor M 52 . Accordingly, the high level is extracted to the potential of the output line OUT 2 , as is shown by the V OUT2  in  FIG. 2 .  
         [0079]     At this time, in the output line fixed circuit shown by  10  in  FIG. 1 , because a low level of the input signal φ ST  is input, the transistor M 12  is placed in a cutoff state. Moreover, because a high level of the clock signal φ 1  is input into the transistor M 11 , it changes to a conducting state. Furthermore, because the transistor M 11  is in a conducting state, the potential V G13  of the gate line G 13  of the transistor M 13  changes to a high level. Accordingly, the transistor M 13  changes to a conducting state, and the potential V OUT1  of the output line OUT 1  is fixed to the ground potential.  
         [0080]     In the same way, the potentials of the gate line G 102  of the transistor M 102 , of the gate line G 113  of the transistor M 113 , of the output line OUT 3 , of the gate line  152  of the transistor M 152 , of the gate line G 163  of the transistor M 163 , and of the output line OUT  4  that are shown in  FIG. 1  change respectively in the manners shown by V G102 , V G113 , V OUT3 , V G152 , V G163 , and V OUT4  shown in  FIG. 2 . Accordingly, in this circuit, transmission of high level signals of the input signal φ ST  is performed.  
         [0081]     In this manner, according to the circuit shown in  FIG. 1 , because output lines that are not selected are fixed to the ground potential by the output line fixing circuits  10 ,  60  . . . , it is possible to suppress output noise that is synchronous with changes in the clock signal φ 1  or φ 2 .  
         [0082]     In addition, because control of the output line fixed circuits  10 ,  60  . . . is performed by an input signal or by the output signal, no excess parasitic capacitors are added to the gate lines G 2 , G 52  . . . of the transistors M 2 , M 52  . . . . Accordingly, there is no need to increase the bootstrap capacitors, and any increase in the surface area of the chip can be suppressed.  
         [0083]     Next,  FIG. 3  shows the output line fixed circuits  10 ,  60  . . . of  FIG. 1  in a separate structural example.  
         [0084]     Namely, the MOS transistors M 11 , M 61  . . . of  FIG. 1  are altered like the MOS transistors M 14 , M 64  . . . of  FIG. 3 . In the MOS transistors M 14 , M 64  . . . shown in  FIG. 3 , the gates and drains are altered so as to be connected to clock lines. The remainder of the structure is the same as that shown in  FIG. 1  and the timing chart thereof is the same as that shown in  FIG. 2 .  
         [0085]     A description will now be given using the circuit shown in  FIG. 3  of the operation of the output line fixed circuit.  
         [0086]     Firstly, when the input signal φ ST  and the clock signal φ 1  change to a high level, in the output line fixed circuit  10 , the transistors M 12  and M 14  are placed in a conducting state. As a result, the potential of the gate line G 13  of the transistor M 13  changes to the ground potential, as is shown by V G13  in  FIG. 2 . As a result, because the transistor M 13  is placed in a cutoff state, it is cut off from the output line OUT 1 .  
         [0087]     Next, when the clock signal φ 2  changes to a high level, the high level is extracted to the potential of the output line OUT  1 , as is shown by the V OUT1  in  FIG. 2 . At this time, because the high level of the V OUT1  is input into the output line fixed circuit  60 , the transistor M 62  is placed in a conducting state. As a result, the potential of the gate line G 63  of the transistor M 63  changes to the ground potential, as is shown by V G63  in  FIG. 2 . Consequently, because the transistor M 63  is placed in a cutoff state, it is cut off from the output line OUT 2 .  
         [0088]     Next, when the clock signal φ 1  once again changes to a high level, because a low level of the input signal φ ST  is input into the output line fixed circuit  10 , the transistor M 12  changes to a cutoff state. In contrast, because the transistor M 14  is placed in a conducting state, the potential V G13  of the gate line G 13  of the transistor M 13  changes to a high level. As a result, the transistor M 13  changes to a conducting state, and the potential V OUT1  of the output line OUT 1  is fixed to the ground potential. The same operation is subsequently repeated. In this manner, by constructing the output line fixed circuits  10 ,  60  . . . shown in  FIG. 1  in the manner shown in  FIG. 3 , it is possible to fix the non-selected output line to the ground potential without using the power supply line V DD .  
         [0000]     (Second Embodiment)  
         [0089]      FIG. 4  is a circuit diagram showing the second embodiment relating to the signal transmission circuit of the present invention.  
         [0090]     In contrast to the circuit shown in  FIG. 1 , this circuit is additionally provided with sample hold circuits (referred to below as SH circuits)  20 ,  70 ,  120 , and  170  shown in  FIG. 4 . The SH circuits  20 ,  70  . . . are formed respectively by the MOS transistors M 21 , M 71  . . . . The gates of the MOS transistors M 21 , M 71  . . . are connected to the clock line φ 1  or the clock line φ 2 , the drains thereof are connected to the input line φ ST  or to the previous output terminal, and the sources thereof are connected to gates of the transistors M 12 , M 62  . . . that form the output line fixed circuits  10 ,  60  . . . . Note that component elements that correspond to those in the first embodiment have been given the same descriptive symbols.  
         [0091]     Next, an operation of the signal transmission circuit shown in  FIG. 4  will be described schematically using the timing chart shown in  FIG. 5 .  
         [0092]     Firstly, when the clock signal φ 1  and the input signal φ ST  change to a high level, in the SH circuit  20 , the transistor M 21  is placed in a conducting state. Consequently, a high level of the input signal φ ST  is sent to the transistor M 21 , and the potential V G12  of the gate line G 12  of the transistor M 12  changes to a high level. As a result, in the output line fixed circuit  10 , the transistor M 12  is placed in a conducting state, and the potential V G13  of the gate line G 13  of the transistor M 13  is fixed to the ground potential.  
         [0093]     In addition, the transistor M 13  is placed in a cutoff state, and is cut off from the output line OUT 1 .  
         [0094]     Here, even if the clock signal φ 1  changes to a low level, the potential V G12  of the gate line G 12  of the transistor M 12  holds its high level. Therefore, the transistor M 13  reliably continues its cutoff state, and there are no harmful effects on the output line OUT 1 .  
         [0095]     Next, when the clock signal φ 2  changes to a high level, a high level of the clock signal φ 2  is extracted to the potential V OUT1  of the output line OUT 1 . Moreover, in the SH circuit  70 , because the transistor M 71  is placed in a conducting state, an output signal V OUT1  is sent to the transistor M 71 , and the potential V G62  of the gate line G 62  of the transistor M 62  changes to a high level. As a result, in the output line fixed circuit  60 , the transistor M 62  changes to a conducting state, and the potential V G63  of the gate line G 63  of the transistor M 63  is fixed to the ground potential.  
         [0096]     Accordingly, the transistor M 63  is placed in a cutoff state, and is cut off from the output line OUT 2 . Here, in the same way, even if the clock signal φ 2  changes to a low level, because the potential V G62  of the gate line G 62  of the transistor M 62  maintains a high level, the transistor M 63  reliably continues its cutoff state, and there are no harmful effects on the output line OUT 2 .  
         [0097]     Next, when the clock signal φ 1  once again changes to a high level, a high level of the clock signal φ 1  is extracted to the potential V OUT2  of the output line OUT 2 . Moreover, in the SH circuit  20 , because the transistor M 21  is placed in a conducting state and a low level of the input signal φ ST  is input, the potential V G12  of the gate line G 12  of the transistor M 12  changes to a low level.  
         [0098]     As a result, in the output line fixed circuit  10 , because the transistor M 12  changes to a cutoff state, the transistor M 11  changes to a conducting state, and the power supply voltage V DD  is sent to the gate line G 13  of the transistor M 13 , the potential V G13  of the gate line G 13  of the transistor M 13  changes to a high level. Accordingly, the transistor M 13  is placed in a conducting state, and the potential V OUT1  of the output line OUT 1  is fixed to the ground potential. Thereafter, the same operation is repeated.  
         [0099]     Accordingly, in the case of the structure shown in  FIG. 4  as well, in the same way as in the first embodiment, because a non-selected output line is fixed to a reference potential, output noise can be controlled. In addition, no excess parasitic capacitors are added to the gate lines G 2 , G 52  . . . of the transistors M 2 , M 52  . . . , and any increase in the surface area of the chip can be suppressed.  
         [0100]     Furthermore, according to the structure shown in  FIG. 4 , because the output line fixed circuit is controlled via the SH circuit, even after the previous output has been reversed, because the gate line G 13  of the transistor M 13  of the output line fixed circuit is fixed to the ground potential when selected, it is possible to reliably operate the output line fixed circuit.  
         [0101]     Next,  FIG. 6  shows another structural example of the output line fixed circuits  10 ,  60  . . . that are shown in  FIG. 4 .  
         [0102]     Namely, the MOS transistors M 11 , M 61  . . . of  FIG. 4  are altered like the depression MOS transistors M 15 , M 65  . . . of  FIG. 6 . In the depression MOS transistors M 15 , M 65  . . . of  FIG. 6 , the gates and sources are altered so as to be connected to the gates of the MOS transistors M 13 , M 63  . . . . The remainder of the structure is the same as that shown in  FIG. 4 , and the timing chart thereof is the same as that shown in  FIG. 5 . Here, by connecting the gates and sources, the depression MOS transistors M 15 , M 65  . . . operate as constant current sources whose current value is fixed depending on the configuration. Hereinafter, only the operation of this output line fixed circuit is described.  
         [0103]     Firstly, when the clock signal φ 1  and the input signal φ ST  change to a high level, the output portion of the SH circuit  20  changes to a high level. Accordingly, in the output line fixed circuit  10 , the transistor M 12  is placed in a conducting state. As a result of this, the current capability of the transistor M 12  is made larger than the current capability of the transistor M 15 . Consequently, because the potential V G13  of the gate line G 13  of the transistor M 13  is fixed to the ground potential, it is cut off from the output line OUT 1 . Here, even if the clock signal φ 1  changes to a low level, the potential of the gate line G 12  of the transistor M 12  holds its high level. Therefore, the transistor M 13  reliably continues its cutoff state, and there are no harmful effects on the output line OUT 1 .  
         [0104]     Next, when the clock signal φ 2  changes to a high level, the output portion of the SH circuit  70  changes to a high level. Accordingly, in the output line fixed circuit  60 , because the transistor M 62  changes to a conducting state, and the potential V G63  of the gate line G 63  of the transistor M 63  is fixed to the ground potential, it is cut off from the output line OUT 2 . Here, even if the clock signal φ 2  changes to a low level, the potential V G62  of the gate line G 62  of the transistor M 62  holds its high level. Therefore, the transistor M 63  reliably continues its cutoff state, and there are no harmful effects on the output line OUT 2 .  
         [0105]     Next, when the clock signal φ 1  once again changes to a high level, the output portion of the SH circuit  20  changes to a low level. Accordingly, in the output line fixed circuit  10 , because the transistor M 12  changes to a cutoff state, and because the transistor M 15  is supplying current, the potential V G13  of the gate line  13  of the transistor M 13  rises to the power supply potential V DD . As a result, the transistor M 13  is placed in a conducting state, and the potential V OUT1  of the output line OUT 1  is fixed to the ground potential. Thereafter, the same operation is repeated.  
         [0106]     In this manner, in  FIG. 4 , even if the output line fixed circuits  10 ,  60  . . . are constructed in the manner shown in  FIG. 6 , the output line can be fixed to the ground potential when not selected. In addition, according to the structure shown in  FIG. 6 , when the transistor M 12  is in a cutoff state, it is possible to lift the potential V G13  of the gate line G 13  of the transistor M 13  to the power supply potential V DD , and it is possible to lower the ON resistance of the transistor M 13 . Moreover, in  FIG. 4 , by constructing the output line fixed circuits  10 ,  60  . . . in the manner shown in  FIG. 3 , the output line that is not selected can be fixed to the ground potential without using the power supply line V DD .  
         [0107]     Next,  FIG. 7  shows a variation of the structure of the SH circuits  20 ,  70  . . . shown in  FIG. 4 .  
         [0108]     The SH circuits  20 ,  70  . . . are formed by the MOS transistors M 22 , M 72  . . . and the MOS transistors M 23 , M 73  . . . . The gates and drains of the MOS transistors M 22 , M 72  . . . are connected to an input terminal or to the previous output terminal, while the sources thereof are connected to the gates of the transistors M 12 , M 62  . . . that make up the output line fixed circuits  10 ,  60  . . . , and to the drains of the transistors M 23 , M 73  . . . . Moreover, the sources of the transistors M 23  and M 73  are connected to ground lines, and the gates are connected to the next output terminal. The remainder of the structure is the same as that shown in  FIG. 4  and the timing chart thereof is the same as that shown in  FIG. 5 .  
         [0109]     A description will now be given of the operation of this structure that is different from that of the structure shown in  FIG. 4 .  
         [0110]     Firstly, when the clock signal φ 1  and the input signal φ ST  change to a high level, in the SH circuit  20 , the transistor M 22  is placed in a conducting state and the transistor M 23  is placed in a cutoff state. Because of this, a high level of the input signal φ ST  is sent to the transistor M 22 , and the potential V G12  of the gate line G 12  of the transistor M 12  changes to a high level. As a result of this, the output line fixed circuit  10  is cutoff from the output line OUT 1 . Here, even if the clock signal φ 1  changes to a low level, the potential V G12  of the gate line G 12  of the transistor M 12  holds its high level. Therefore, the transistor M 13  reliably continues its cutoff state, and there are no harmful effects on the output line OUT 1 .  
         [0111]     Next, when the clock signal φ 2  changes to a high level, the high level of the clock signal φ 2  is extracted to the output line OUT 1  and, in the SH circuit  70 , the transistor M 72  changes to a conducting state and the transistor M 73  changes to a cutoff state. Because of this, the potential V OUT1  of the previous output line OUT 1  is sent to the transistor M 72 , and the potential V G62  of the gate line G 62  of the transistor M 62  changes to a high level. As a result of this, the output line fixed circuit  60  is cutoff from the output line OUT 2 . Here, even if the clock signal φ 2  changes to a low level, the potential V G62  of the gate line G 62  of the transistor M 62  holds its high level. Therefore, the transistor M 63  reliably continues its cutoff state, and there are no harmful effects on the output line OUT 2 .  
         [0112]     Next, when the clock signal φ 1  once again changes to a high level, the high level of the clock signal φ 1  is extracted to the potential V OUT2  of the output line OUT 2  and, at the same time, is input into the gate of the transistor M 23  of the SH circuit  20 . Because of this, in the SH circuit  20 , the transistor M 23  is placed in a conducting state and the potential V G12  of the gate line G 12  of the transistor M 12  changes to a low level. Accordingly, the potential V OUT1  of the output line OUT 1  is fixed to the ground potential via the output line fixed circuit  10 .  
         [0113]     In this manner, even when the structures of the SH circuits  20 ,  70  . . . that are shown in  FIG. 4  are formed in the manner shown in  FIG. 7 , it is possible to control the output line fixed circuits  10 ,  60  . . . using the SH circuits  20 ,  70 . . . . In addition, according to the structure shown in  FIG. 7 , because the SH circuits  20 ,  70  . . . are not connected to the clock lines, an increase in the operation speed, and a reduction in the drive capability of an external circuit supplying the clock signal to the signal transmission circuit can be obtained. Moreover, it is also possible in the structure shown in  FIG. 7  to form the output line fixed circuits  10 ,  60  . . . in the manners shown in  FIG. 3  and  FIG. 6 .  
         [0000]     (Third Embodiment)  
         [0114]      FIG. 8  is a circuit diagram showing the third embodiment relating to the signal transmission circuit of the present invention.  
         [0115]     In contrast to the first embodiment shown in  FIG. 1 , this circuit is altered so as to be connected to the next stage via the SH circuits  20 ,  70  . . . . The remainder of the structure is the same. Note that component elements that correspond to those in the first embodiment have been given the same descriptive symbols. Only operations that are different from those of the first embodiment are described below.  
         [0116]     An operation of the signal transmission circuit shown in  FIG. 8  will be described schematically using the timing chart shown in  FIG. 9 .  
         [0117]     Firstly, when the input signal φ ST  and the clock signal φ 1  change to a high level, the output line fixed circuit  10  is cutoff from the output line OUT 1 . Next, when the clock signal φ 2  changes to a high level, the high level of the clock signal φ 2  is extracted to the potential V OUT1  of the output line OUT 1 .  
         [0118]     In addition, because the transistor M 21  of the SH circuit  20  is in a conducting state, the potential V D51  of the drain D 51  of the transistor M 51  changes to a high level. Accordingly, the output line fixed circuit  60  is cutoff from the output line OUT 2 . Here, even if the clock signal φ 2  changes to a low level, the potential V D51  of the drain D 51  of the transistor M 51  holds its high level. Therefore, the transistor M 63  reliably continues its cutoff state, and there are no harmful effects on the output line OUT 2 .  
         [0119]     Next, when the clock signal φ 1  once again changes to a high level, the high level of the clock signal φ 1  is extracted to the potential V OUT2  of the output line OUT 2 , and a potential V D101  of the drain D 101  of the transistor M 101  changes to a high level. Moreover, the potential V OUT1  of the output line OUT 1  is fixed to the ground potential by the output line fixed circuit  10 .  
         [0120]     Next, when the clock signal φ 2  once again changes to a high level, in the SH circuit  20 , because the transistor M 21  changes to a conducting state and a low level of the previous output V OUT1  is input, the potential V D51  of the drain D 51  of the transistor M 51  changes to a low level. Accordingly, the potential V OUT2  of the output line OUT 2  is fixed to the ground potential by the output line fixed circuit  60 . The same operation is subsequently repeated.  
         [0121]     Accordingly, as is shown in  FIG. 8 , even if a connection is made with a subsequent stage via the SH circuits  20 ,  70  . . . , in the same way as in the first embodiment, because a non-selected output line is fixed to a reference potential, output noise can be controlled. In addition, no excess parasitic capacitors are added to the gate lines G 2 , G 52  . . . of the transistors M 2 , M 52  . . . , and any increase in the surface area of the chip can be suppressed. Furthermore, according to the structure shown in  FIG. 8 , because the output line fixed circuit is controlled via the SH circuit, even after the previous output has been reversed, because the gate line G 63  of the transistor M 63  of the output line fixed circuit is fixed to the ground potential when selected, it is possible to reliably operate the output line fixed circuit.  
         [0122]     Next,  FIG. 10  shows a variation of the structure of the SH circuits  20 ,  70  . . . shown in  FIG. 8 , while the remainder of the structure is the same as that shown in  FIG. 8 . The timing chart thereof is the same as that shown in  FIG. 9 . Even when the SH circuits  20 ,  70  . . . are constructed in the manner shown in  FIG. 10 , the output line fixed circuits can be controlled using the SH circuits  20 ,  70  . . . . In addition, because the SH circuits  20 ,  70  . . . are not connected to the clock lines, an increase in the operation speed, and a reduction in the drive capability of an external circuit supplying the clock signal to the signal transmission circuit can be obtained.  
         [0123]     Moreover, in  FIG. 8  and  FIG. 10 , by constructing the output line fixed circuits  10 ,  60  . . . in the manner shown in  FIG. 3 , the output line when not selected can be fixed to the ground potential without using the power supply line V DD . Furthermore, in  FIG. 8  and  FIG. 10 , even if the output line fixed circuits  10 ,  60  . . . are constructed in the manner shown in  FIG. 6 , the output line can be fixed to the ground potential when not selected. In addition, when the transistor M 12  is in a cutoff state, it is possible to lift the potential V G13  of the gate line G 13  of the transistor M 13  to the power supply potential V DD , and it is possible to lower the ON resistance of the transistor M 13 .  
         [0124]     Embodiments of the present invention have been described in detail above with reference made to the drawings, however, the specific structure thereof is not limited to these embodiments, and various design modifications and the like may be made insofar as they do not depart from the scope of the present invention.  
         [0125]     According to the present invention, because the output line that is not selected is fixed to a reference potential, the effect is obtained that it is possible to control output noise. In addition, there is no need to increase the bootstrap capacity, and any increase in the surface area of the chip can be controlled.  
         [0126]     In addition, by providing a sample hold circuit, an output line can be reliably fixed to the reference potential even after an output signal from the previous stage has been reversed.  
         [0127]     Moreover, according to the present invention, it is possible to form a reference potential fixing circuit simply, and an output line that is not selected can be fixed to the reference potential. In addition, in the reference potential fixing circuit, the ON resistance can be reduced when the output line is fixed to the reference potential.  
         [0128]     In addition, according to the present invention, the sample hold circuit can be formed simply by one transistor, so that an output line can be reliably fixed to the reference potential even after an output signal from the previous stage has been reversed.  
         [0129]     Furthermore, according to the present invention, the sample hold circuit can be formed by two transistors, so that an output line can be reliably fixed to the reference potential even after an output signal from the previous stage has been reversed. In addition, because no control pulse is supplied to the sample hold circuit, it is possible to reduce the load on the line that is used to supply the control pulse. As a result, an improvement in the operating speed and a reduction in the drive capability of an external circuit supplying the clock signal to the signal transmission circuit become possible.