JP5919112B2 - Pulse output circuit, display device, and electronic device - Google Patents

Description

The present invention relates to a pulse output circuit. Furthermore, the present invention relates to a display device. Furthermore, the present invention relates to an electronic device.

In recent years, for the purpose of simplifying the manufacturing process and the like, development of a circuit in which all transistors have the same conductivity type (also referred to as a unipolar circuit) has been advanced.

An example of the unipolar circuit is a pulse output circuit constituting a shift register.

For example, Patent Document 1 discloses a shift register having a plurality of stages of pulse output circuits configured using a bootstrap method. By using the bootstrap method, a decrease in the amplitude of the pulse signal output from each pulse output circuit can be suppressed.

FIG. 8 shows an example of a circuit including only N-channel transistors. FIG. 8A is a diagram illustrating a shift register used in a scanning circuit (a source driver or a gate driver) of a flat panel display. The shift register illustrated in FIG. 8A includes output terminals of a plurality of stages of pulse output circuits (pulse output circuits SR_1 to SR_4) in accordance with control signals such as a clock signal (CLK / CLKB) and a start pulse (SP). Pulse signals are sequentially output via (OUT_1 to OUT_4).

8B and 8C are diagrams illustrating circuit configuration examples of the pulse output circuit SR included in the shift register illustrated in FIG. The pulse output circuit SR illustrated in FIG. 8B includes a transistor 11 and a transistor 12 and a circuit 10 that controls the potential of the gates of the transistor 11 and the transistor 12. Further, the circuit 10 includes transistors 13 to 16 as shown in FIG. In each stage, the pulse signal output from the previous pulse output circuit is used as the set signal (S), and the pulse signal output from the next pulse output circuit is used as the reset signal (R).

In response to the set signal (S), the transistors 13 and 16 are turned on to set the node VS to the high level, the node VR to the low level, the transistor 11 to the ON state, the transistor 12 to the OFF state, and the clock signal to the output terminal (OUT). Pass (CK). After that, the transistors 14 and 15 are turned on by the reset signal (R), the node VS is set to low level, the node VR is set to high level, the transistor 11 is turned off, the transistor 12 is turned on, and the clock signal (CK) is turned on. While stopping the passage, the output terminal (OUT) is fixed to the low level.

FIG. 8D shows a timing chart of each control signal and each node. The above-described operation is shown in the periods 51 to 53.

As shown in FIG. 8, in the conventional shift register, the potential of the output signal is set by passing a clock signal through the output end, and a pulse signal is generated.

JP 2002-335153 A

Attention is paid to the state of the transistor 11 in the operation of the shift register shown in FIG.

The transistor 11 is turned on only when a pulse is output by passing the clock signal (CK) through the output terminal (OUT) due to the nature of the operation of the shift register, and is turned off in most periods. At this time, the voltage between the gate and the source of the transistor 11 (also referred to as a gate-source voltage) is 0 V, and the potential of the drain of the transistor 11 constantly varies depending on the clock signal (CK) that is continuously input. That is, a state in which a voltage is applied between the source and drain of the transistor 11 and a state in which the voltage is 0 V appear repeatedly at regular intervals. However, in any case, since the transistor 11 is in the OFF state, there is almost no charge transfer between the source and the drain of the transistor 11.

As described above, when the transistor is turned off due to the condition of the gate-source voltage, if the operation of changing the potential of the source or the drain is repeated, the stress on the transistor is large and the characteristic may be changed.

In a circuit such as the above-described shift register, the time during which the stress is applied to the transistor is very long, so that the characteristic variation is accelerated.

In view of the above problems, an object of one embodiment of the present invention is to reduce stress associated with potential fluctuation of one of a source and a drain of a transistor.

In the above-described shift register, the amplitude of the signal input to the drain of the transistor 11 is equal to the high level potential of the clock signal (CK), that is, the high level potential of the pulse signal appearing at the output terminal (OUT). In order to reduce the stress accompanying the fluctuation of the potential of the drain of the transistor 11, for example, the high level potential of the clock signal (CK) may be reduced, but naturally the high level of the pulse signal output via the output terminal (OUT) is sufficient. Since the level potential is also small, it is not preferable.

In view of the above, according to one embodiment of the present invention, a high-level potential of a control signal such as a clock signal is reduced, and a booster is separately provided in an output portion of a pulse output circuit. With the above structure, the amplitude of the output signal is compensated while reducing the stress on the transistor. Note that at this time, the potential difference between the low-level potential of the control signal and the power supply potential on the low potential side is set to 0 or within a certain value range so that the transistor can be turned off.

One embodiment of the present invention has a function of generating and outputting a pulse signal in accordance with a set signal, a reset signal, and a clock signal, the potential of the gate is controlled by the set signal and the reset signal, and one of the potential of the source and the drain A first transistor whose first power supply potential is applied to one of the source and drain, a second power supply potential applied to one of the source and the drain, and the other The first power supply potential is applied to one of the source and the drain, and the other of the source and the drain is electrically connected to the other of the source and the drain of the third transistor. The fourth power source is connected to the first power source potential of one of the source and the drain, and the other of the source and the drain A fifth transistor electrically connected to the gate of the third transistor, one of a source and a drain is electrically connected to the other of the source and the drain of the first transistor, and the other of the source and the drain is a third A sixth transistor electrically connected to a gate of the first transistor, the first to sixth transistors having the same conductivity type, and the high-level potential of the clock signal and the first power supply potential Is larger than the threshold voltage of the third transistor, the potential difference between the low level potential of the clock signal and the first power supply potential is less than the threshold voltage of the second transistor, and the high level potential of the clock signal Is a pulse output circuit smaller than the second power supply potential.

One embodiment of the present invention is a display device including a driver circuit including a plurality of stages of the pulse output circuit and a pixel circuit in which writing and holding of a data signal is controlled by the driver circuit.

One embodiment of the present invention is an electronic device including a panel including the display device.

According to one embodiment of the present invention, variation in potential of a drain of a transistor in an OFF state can be reduced, so that deterioration of the transistor can be reduced. Furthermore, by providing a separate boosting unit, it is possible to suppress a decrease in the amplitude of the output pulse signal.

The figure for demonstrating the example of a pulse output circuit. The figure for demonstrating the example of a pulse output circuit. The figure for demonstrating the example of a pulse output circuit. The figure for demonstrating the example of a pulse output circuit. FIG. 14 illustrates an example of a display device. 4A and 4B illustrate a structural example of a transistor. FIG. 10 illustrates an example of an electronic device. The figure for demonstrating the example of the conventional pulse output circuit.

An example of an embodiment according to the present invention will be described. Note that it is easy for those skilled in the art to change the contents of the embodiments without departing from the spirit and scope of the present invention. Therefore, for example, the present invention is not limited to the description of the following embodiments.

Note that the contents of the embodiments can be combined with each other as appropriate. Further, the contents of the embodiments can be appropriately replaced with each other.

Further, the ordinal numbers such as the first and the second are given in order to avoid confusion between the constituent elements, and the number of each constituent element is not limited to the ordinal numbers.

(Embodiment 1)
In this embodiment, an example of a pulse output circuit is described.

FIG. 1 is a diagram for explaining a configuration example of a pulse output circuit according to the present embodiment. As shown in FIG. 1A, the pulse output circuit shown in FIG. 1 is connected via an output terminal (OUT) in accordance with an input set signal (S), reset signal (R), and clock signal (CK). It has a function of outputting a pulse signal. Note that a plurality of clock signals may be input to the pulse output circuit.

Further, the pulse output circuit SR illustrated in FIG. 1A includes the transistors 101 to 106 as illustrated in FIG. Note that elements other than the transistors 101 to 106 may be provided in the pulse output circuit SR illustrated in FIG. The transistors 101 to 106 are of the same conductivity type. In the pulse output circuit SR illustrated in FIG. 1A, a booster is formed using the transistors 101 to 106.

For example, a shift register can be formed as illustrated in FIG. 1C by using a plurality of pulse output circuits SR illustrated in FIG. 1A (pulse output circuits SR_1 to SR_n (n is a natural number of 2 or more)). FIG. 1C shows a case where n is 4 or more as an example. At this time, the start pulse (SP) is input to the pulse output circuit SR_1 as the set signal (S). Further, a pulse signal output from the pulse output circuit SR_k−1 as the set signal (S) is input to the pulse output circuit SR_k (k is a natural number of 2 or more and n or less). Further, a pulse signal output from the pulse output circuit SR_m + 1 as the reset signal (R) is input to the pulse output circuit SR_m (m is a natural number equal to or less than n−1). Further, the clock signal (CLK) is input to the odd-numbered pulse output circuit as the clock signal (CK). Further, the clock signal (CLKB) is input to the even-numbered pulse output circuit as the clock signal (CK). The clock signal (CLKB) is an inverted signal of the clock signal (CLK). In the shift register illustrated in FIG. 1C, pulse signals are output through the output terminals (OUT_1 to OUT_n) of the pulse output circuits SR_1 to SR_n. Note that a dummy pulse output circuit may be provided as the (n + 1) th pulse output circuit SR_n + 1. At this time, the pulse signal output from the pulse output circuit SR_n + 1 is input to the pulse output circuit SR_n as a reset signal (R).

Next, the pulse output circuit illustrated in FIGS. 1A and 1B will be further described with reference to FIG. FIG. 2A illustrates an example in which a circuit 100 that controls the gate potentials of the transistors 101, 102, 104, and 105 is provided in addition to the structure illustrated in FIG. 1B. FIG. 5 illustrates an example in which the circuit 100 is configured using transistors 113 to 116. Each component will be described below.

The potential of the gate of the transistor 101 is controlled by a set signal (S) and a reset signal (R). For example, as illustrated in FIG. 2B, the transistor 113 is turned on in accordance with the set signal (S), whereby the potential of the gate (node α) of the transistor 101 is increased. Further, when the transistor 114 is turned on in accordance with the reset signal (R), the potential of the gate of the transistor 101 changes to a value equivalent to the power supply potential VSS. As described above, controlling the gate potential of the transistor 101 by the set signal (S) and the reset signal (R) includes a case of indirectly controlling, for example, controlling by the transistors 113 and 114.

One potential of the source and the drain of the transistor 101 changes in accordance with the clock signal (CK). For example, the clock signal (CK) is input to one of the source and the drain of the transistor 101. Note that the present invention is not limited to this, and a capacitor in which the clock signal (CK) is input to one of the electrodes and the other is connected to one of the source and the drain of the transistor 101 may be provided.

Further, a capacitor C1 may be formed between the gate of the transistor 101 and the other of the source and the drain. For example, a parasitic capacitance between the gate of the transistor 101 and the other of the source and the drain may be used for the capacitor C1. Further, a capacitor element may be separately provided as the capacitor C1.

One of a source and a drain of the transistor 102 is supplied with a power supply potential VSS, and the other is electrically connected to the other of the source and the drain of the transistor 101. Further, the potential of the gate of the transistor 102 is controlled by, for example, a set signal (S) and a reset signal (R). For example, as illustrated in FIG. 2B, when the transistor 116 is turned on in accordance with the set signal (S), the potential of the gate of the transistor 102 changes to a value equivalent to the power supply potential VSS. Further, when the transistor 115 is turned on in accordance with the reset signal (R), the potential of the gate of the transistor 102 is increased. The present invention is not limited to this, and the gate potential of the transistor 102 may be controlled by another signal. Note that the “equivalent value” includes, for example, a value in which the original potential has changed due to a voltage drop or the like.

When the connection point between the other of the source and the drain of the transistor 102 and the other of the source and the drain of the transistor 101 is a node β, the transistor 101 sets the potential of the node β to a value corresponding to the clock signal (CK). It has a function to control whether to do. Further, the transistor 102 has a function of controlling whether the potential of the node β is set to a value corresponding to the power supply potential VSS. Note that the “value corresponding to the signal or potential” includes not only the same value as the signal or potential but also a value changed from the original potential due to, for example, a voltage drop.

One of a source and a drain of the transistor 103 is supplied with a power supply potential VDD, and the other is a potential of a pulse signal to be output. The transistor 103 has a function of controlling whether the potential of the output terminal (OUT) is set to a value corresponding to the power supply potential VDD.

Further, a capacitor C2 may be formed between the gate of the transistor 103 and the other of the source and the drain. For example, a parasitic capacitance between the gate of the transistor 103 and the other of the source and the drain may be used for the capacitor C2. Further, a capacitor element may be separately provided as the capacitor C2.

One of a source and a drain of the transistor 104 is supplied with the power supply potential VSS, and the other is electrically connected to the other of the source and the drain of the transistor 103. Further, the potential of the gate of the transistor 104 is controlled by, for example, a set signal (S) and a reset signal (R). For example, as illustrated in FIG. 2B, when the transistor 116 is turned on in accordance with the set signal (S), the potential of the gate of the transistor 104 becomes equal to the power supply potential VSS. On the other hand, when the transistor 115 is turned on in accordance with the reset signal (R), the potential of the gate of the transistor 104 is increased. The present invention is not limited to this, and the gate potential of the transistor 104 may be controlled by another signal. The transistor 104 has a function of controlling whether to set the potential of the output terminal (OUT) to a value corresponding to the power supply potential VSS.

One of a source and a drain of the transistor 105 is supplied with the power supply potential VSS, and the other is electrically connected to the gate of the transistor 103. Further, the potential of the gate of the transistor 105 is controlled by a reset signal (R), for example. For example, as illustrated in FIG. 2B, the reset signal (R) is input to the gate of the transistor 105, and the potential of the gate of the transistor 105 in the transistor 105 is increased in accordance with the reset signal (R). The present invention is not limited to this, and the gate potential of the transistor 105 may be controlled by another signal. The transistor 105 has a function of controlling whether the potential of the gate (node γ) of the transistor 103 is set to a value corresponding to the power supply potential VSS.

One of a source and a drain of the transistor 106 is electrically connected to the other of the source and the drain of the transistor 101, and the other is electrically connected to the gate of the transistor 103. Further, the transistor 106 is diode-connected by electrically connecting the gate of the transistor 106 to one of a source and a drain of the transistor 106, for example, as illustrated in FIG. Note that the present invention is not limited to this, and a signal may be separately input to the gate of the transistor 106. At this time, when the potential of the gate of the transistor 103 is increased, the gate of the transistor 103 needs to be in a floating state in the middle. The transistor 106 has a function of controlling electrical continuity between the other of the source and the drain of the transistor 101 and the gate of the transistor 103.

Further, as the transistors 101 to 106, transistors with low off-state current can be used.

As the transistor with low off-state current, for example, a transistor including a channel formation region that includes an oxide semiconductor having a wider band gap than silicon, and the channel formation region is substantially i-type can be used. At this time, the carrier density of the oxide semiconductor is preferably less than 1 × 10 ¹⁴ / cm ³ , preferably less than 1 × 10 ¹² / cm ³ , and more preferably less than 1 × 10 ¹¹ / cm ³ . For example, a transistor including the above oxide semiconductor can be manufactured by removing impurities such as hydrogen or water as much as possible and supplying oxygen to reduce oxygen vacancies as much as possible. At this time, in the channel formation region, the amount of hydrogen referred to as a donor impurity is preferably reduced to 1 × 10 ¹⁹ / cm ³ or less, preferably 1 × 10 ¹⁸ / cm ³ or less.

As the oxide semiconductor, for example, an In-based metal oxide, a Zn-based metal oxide, an In—Zn-based metal oxide, an In—Ga—Zn-based metal oxide, or the like can be used. Alternatively, a metal oxide containing another metal element instead of part or all of Ga contained in the In—Ga—Zn-based metal oxide may be used.

One of a source and a drain of the transistor 113 is supplied with the power supply potential VDD, and the other is electrically connected to the gate of the transistor 101. Further, the set signal (S) is input to the gate of the transistor 113.

One of a source and a drain of the transistor 114 is supplied with the power supply potential VSS, and the other is electrically connected to the other of the source and the drain of the transistor 113 and the gate of the transistor 101. Further, a reset signal (R) is input to the gate of the transistor 114.

One of a source and a drain of the transistor 115 is supplied with the power supply potential VDD, and the other is electrically connected to the gate of the transistor 104. Further, a reset signal (R) is input to the gate of the transistor 115.

One of a source and a drain of the transistor 116 is supplied with the power supply potential VSS, and the other is electrically connected to the other of the source and the drain of the transistor 115, the gate of the transistor 102, and the gate of the transistor 104. Further, the set signal (S) is input to the gate of the transistor 116.

Further, the potential difference between the high-level potential of the clock signal (CK) and the power supply potential VSS is preferably larger than the threshold voltage of the transistor 103, for example. In addition, the potential difference between the low-level potential of the clock signal (CK) and the power supply potential VSS is preferably less than the threshold voltage of the transistor 102, for example. Further, the high level potential of the clock signal (CK) is smaller than the power supply potential VDD. Thus, stress on the transistor 101 can be reduced.

Further, consider the lower limit of the high level of the clock signal (CK). When the bootstrap method is used, the amount of potential fluctuation required for the output pulse signal is the sum of the amount of fluctuation due to the signal and the amount of fluctuation due to capacitive coupling with the source (corresponding to VDD-VSS). At this time, it is ideal that the amount of variation due to the signal is the same value as the amount of variation due to capacitive coupling with the source, so the lower limit value of the amplitude of the clock signal (CK) is about (VDD−VSS) / 2. The high-level potential of the clock signal (CK) is preferably about (VDD + VSS) / 2 or more. However, since the actual potential of the output terminal (OUT) drops by the threshold voltage of the transistor 103 and the transistor 106, when the threshold voltages of the transistors 101 to 106 are VthN, the lower limit of the amplitude of the clock signal (CK) The value is about (VDD−VSS) / 2 + 2VthN, and the lower limit value of the high level potential of the clock signal (CK) is about (VDD + VSS) / 2 + 2VthN. Therefore, the high-level potential of the clock signal (CK) is preferably about (VDD + VSS) / 2 + 2VthN or more and less than VDD. Note that in the case of using the bootstrap method, assuming that the voltage drop due to the transistor 101 can be ignored, the high-level potential of the clock signal (CK) may be about (VDD + VSS) / 2 + VthN or more and less than VDD. Further, in FIG. 1B, assuming that the potential of the gate of the transistor 106 is controlled to such an extent that a voltage drop due to the transistor 106 can be ignored, the high-level potential of the clock signal (CK) is (VDD + VSS) / 2. It may be less than VDD above.

In the case where the shift register shown in FIG. 1C is configured by using a plurality of pulse output circuits shown in FIG. 2B, the high-level potential of the clock signal (CLK / CLKB) and the start pulse (SP) and the power source The potential difference from the potential VSS is preferably larger than the threshold voltage of the transistor 101, for example. The potential difference between the low-level potential of the clock signal (CLK / CLKB) and the start pulse (SP) and the power supply potential VSS is preferably less than the threshold voltage of the transistor 104, for example. The high level potential of the clock signal (CLK / CLKB) and the start pulse (SP) is preferably smaller than the power supply potential VDD, and the high level of the clock signal (CLK / CLKB) and the start pulse (SP) Is preferably about (VDD + VSS) / 2 + 2VthN or more and less than VDD. Note that the high-level potential of the start pulse (SP) is not necessarily smaller than the power supply potential VDD. Note that in the case of using the bootstrap method, assuming that the voltage drop due to the transistor 101 can be ignored, the high level potential of the clock signal (CLK / CLKB) and the start pulse (SP) is about (VDD + VSS) / 2 + VthN or more and less than VDD. It may be. Further, in FIG. 1B, assuming that the gate potential of the transistor 106 is controlled to such an extent that a voltage drop due to the transistor 106 can be ignored, the high level of the clock signal (CLK / CLKB) and the start pulse (SP) The potential may be about (VDD + VSS) / 2 or more and less than VDD.

Next, as an example of a method for driving the pulse output circuit according to this embodiment, an example of a method for driving the pulse output circuit illustrated in FIG. 2B will be described with reference to a timing chart in FIG. Here, as an example, the power supply potential VDD is a positive power supply potential, the power supply potential VSS is a negative power supply potential, and the transistors 101 to 106 are N-channel transistors. The threshold voltage of the transistors 101 to 106 is VthN.

In the example of the method for driving the pulse output circuit illustrated in FIG. 2B, a pulse of the set signal (S) is input in the first period. Note that the reset signal (R) and the clock signal (CK) are at a low level.

At this time, the transistors 113 and 116 are turned on, and the node α is charged through the transistor 113. Note that the transistors 102, 104, 105, 106, 114, and 115 are in an OFF state. When the transistor 113 is turned on, the node α is charged to a value lower than the power supply potential VDD by the threshold voltage VthN of the transistor 113. When the node α is charged to the above value, the gate-source voltage of the transistor 113 falls below the threshold voltage VthN, and the transistor 113 is turned off. At this time, the node α is in a floating state, and the potential of the node α is held. As a result, the pulse output circuit is set. At this time, since the clock signal (CK) is at the low level, the output terminal (OUT) is at the low level, and the pulse signal output via the output terminal (OUT) is at the low level.

For example, in the case of the shift register illustrated in FIG. 1C, when a start pulse (SP) is input as illustrated in a period 151 in FIG. 2C, the node of the first-stage pulse output circuit SR_1 is input. α is charged and then floats.

In the second period, the clock signal (CK) is at a high level. At this time, the set signal (S) and the reset signal (R) are at a low level.

When the clock signal (CK) is at a high level, the node α is charged in the first period, and the transistor 101 is on, so the node β is charged. Note that the transistors 102, 104, 105, 113, 114, 115, and 116 are in an OFF state.

Further, as the potential of the node β increases, the potential of the node α in a floating state increases due to the bootstrap effect. Since the potential of the node α is higher than the high level potential of the clock signal (CK) by at least the threshold voltage VthN, the node β is charged to a potential equal to the high level of the clock signal (CK). Further, as the potential of the node β increases, the transistor 106 is turned on and the node γ is charged. At this time, the node γ is charged to a potential lower than the potential of the node β by the threshold voltage VthN, the gate-source voltage of the transistor 106 falls below the threshold voltage VthN, and the transistor 106 is turned off. At this time, the node γ is in a floating state, and the potential of the node γ is held.

When the potential of the node γ increases, the transistor 103 is turned on, and the output terminal (OUT) is charged and the potential starts to increase. In this state, the potential of the output terminal (OUT) can only rise to a potential lower than the potential of the node γ by the threshold voltage VthN. However, the output terminal (OUT) of the node γ also has a bootstrap effect. As the potential increases, the potential of the node γ in a floating state further increases. Since the potential of the node γ is higher than the power supply potential VDD by at least the threshold voltage VthN, the output terminal (OUT) is charged to VDD and the pulse signal becomes high level.

For example, in the case of the shift register illustrated in FIG. 1C, when the clock signal (CLK) is at a high level as illustrated in a period 152 in FIG. The potential of the node α of SR_1 rises, and the node β of the first-stage pulse output circuit SR_1 is charged to a potential equal to the high level of the clock signal (CLK). Furthermore, the potential of the node γ of the first-stage pulse output circuit SR_1 rises and then enters a floating state. At this time, as the potential of the output terminal (OUT) increases, the potential of the node γ of the first-stage pulse output circuit SR_1 increases due to the bootstrap effect, and the node γ of the first-stage pulse output circuit SR_1 becomes the power source. The battery is charged to a potential higher than the potential VDD, and the output terminal (OUT) is charged to a potential equal to the power supply potential VDD. Therefore, the pulse of the pulse signal of the first-stage pulse output circuit SR_1 is output.

The pulse of the pulse signal output from the first-stage pulse output circuit SR_1 becomes the pulse of the set signal (S) of the second-stage pulse output circuit SR_2. As described above, the pulse output circuits in the second and subsequent stages sequentially output the pulses of the pulse signals in the same manner as the pulse output circuit SR_1 in the first stage according to the pulse of the pulse signal input from the preceding pulse output circuit.

In the third period, a pulse of the reset signal (R) is input. At this time, the set signal (S) and the clock signal (CK) are at a low level.

When a pulse of the reset signal (R) is input, the transistors 105, 114, and 115 are turned on, and the transistors 102 and 104 are turned on. Note that the transistors 113 and 116 are in an OFF state.

At this time, the potentials of the nodes α, β, γ, and the output terminal (OUT) are at a low level, so that the transistors 101 and 103 are turned off. Therefore, the pulse output circuit is in a reset state.

In the case of the shift register illustrated in FIG. 1C, as illustrated in a period 153 in FIG. 2C, the pulse of the pulse signal of the second-stage pulse output circuit SR_2 is reset to the first-stage pulse output circuit SR_1. Input as (R). At this time, the potentials of the nodes α, β, γ, and the output terminal (OUT) of the first-stage pulse output circuit SR_1 are at a low level.

Similarly, the pulse of the pulse signal output from the third-stage pulse output circuit SR_3 becomes the pulse of the reset signal (R) of the second-stage pulse output circuit. As described above, the pulse output circuits in the second and subsequent stages are reset in the same manner as the pulse output circuit SR_1 in the first stage according to the pulse signal input from the pulse output circuit in the next stage.

The above is the description of the example of the method for driving the pulse output circuit illustrated in FIG.

Note that the structure of the pulse output circuit according to this embodiment is not limited to the above structure.

For example, as shown in FIG. 3A-1, in addition to the pulse output circuit shown in FIG. 1A, a second pulse signal may be output. At this time, the high-level potential of the second pulse signal is smaller than the power supply potential VDD.

In the pulse output circuit illustrated in FIG. 3A-1, as illustrated in FIG. 3A-2, in addition to the structure illustrated in FIG. The pulse signal is output via the output terminal (SROUT). Accordingly, a pulse signal having a high level potential lower than the power supply potential VDD can be generated and output. Therefore, the high-level potential of only the pulse signal as required can be increased, so that power consumption can be reduced.

Further, the shift register illustrated in FIG. 3B can be formed using a plurality of pulse output circuits (pulse output circuits SR_1 to SR_n) illustrated in FIG. FIG. 3B shows a case where n is 4 or more as an example. At this time, the start pulse (SP) is input to the pulse output circuit SR_1 as the set signal (S). Further, the second pulse signal output from the output terminal (SROUT) of the pulse output circuit SR_k−1 is input as the set signal (S) to the pulse output circuit SR_k (k is a natural number of 2 or more). Further, the second pulse signal output from the output terminal (SROUT) of the pulse output circuit SR_k is input to the pulse output circuit SR_k−1 as the reset signal (R). Further, the clock signal (CLK) is input to the odd-numbered pulse output circuit as the clock signal (CK). Further, the clock signal (CLKB) is input to the even-numbered pulse output circuit as the clock signal (CK). In the shift register illustrated in FIG. 3B, pulse signals are output through the output terminals (OUT_1 to OUT_n) of the pulse output circuits SR_1 to SR_n.

For example, as shown in FIG. 4, the gate of the transistor 114 of the pulse output circuit shown in FIG. 2B is connected to the source and drain of the transistor 115 instead of inputting the reset signal (R). You may electrically connect to the other. Thus, the potential of the gate of the transistor 114 can be held.

The above is the description of the example of the pulse output circuit according to this embodiment.

As described with reference to FIGS. 1 to 4, in the example of the pulse output circuit according to this embodiment, the amplitude of the clock signal is reduced by making at least the high-level potential of the clock signal smaller than the high power supply potential. Make it smaller. Accordingly, variation in potential of one of the source and the drain when the transistor 101 is in an OFF state, which has been a cause of transistor deterioration, can be reduced.

Furthermore, in the example of the pulse output circuit according to this embodiment, a pulse signal having a high level potential equal to the power supply potential VDD can be generated by providing the boosting unit. Accordingly, it is possible to suppress a decrease in high-level potential of the pulse signal to be output.

(Embodiment 2)
In this embodiment, an example of a display device using the pulse output circuit according to Embodiment 1 is described.

FIG. 5A illustrates a configuration example of the pixel portion 201 and the driver circuit portion 202.

As shown in FIG. 5A, the pixel unit 201 includes a plurality of pixel circuits 211 arranged in X rows (X is a natural number of 2 or more) and Y columns (Y is a natural number of 2 or more). 202 includes a gate driver 221 and a source driver 223.

The gate driver 221 includes a shift register (eg, a shift register illustrated in FIG. 1C) including a plurality of stages of pulse output circuits described in Embodiment 1. For example, the gate driver 221 has a function of controlling the potentials of the scan lines GL_1 to GL_X by a pulse signal output from the shift register. Note that a plurality of gate drivers 221 may be provided, and the scanning lines GL_1 to GL_X may be divided and controlled by the plurality of gate drivers 221.

An image signal is input to the source driver 223. The source driver 223 has a function of generating a data signal to be written in the pixel circuit 211 based on the image signal. For example, the source driver 223 has a function of controlling the potentials of the data lines DL_1 to DL_Y.

The source driver 223 is configured using, for example, a plurality of analog switches. With the plurality of analog switches, the source driver 223 can output a signal obtained by time-sharing the image signal as a data signal. Further, the source driver 223 may be configured using a shift register or the like. At this time, as the shift register, a shift register including a plurality of stages of pulse output circuits described in Embodiment 1 (for example, a shift register illustrated in FIG. 1C) can be used.

Each of the plurality of pixel circuits 211 receives a pulse signal through one of the plurality of scanning lines GL and receives a data signal through one of the plurality of data lines DL. In each of the plurality of pixel circuits 211, writing and holding of data of the data signal is controlled by the gate driver 221. For example, the pixel circuit 211 in the M-th row and the N-th column receives a pulse signal from the gate driver 221 via the scanning line GL_M (M is a natural number equal to or less than X), and the data line DL_N (N is Y A data signal is input from the source driver 223 via the following natural number).

Each of the plurality of pixel circuits 211 includes, for example, a liquid crystal element or a light emitting element, and a transistor that controls input of a data signal for setting a voltage of a pair of electrodes of the liquid crystal element and the light emitting element. .

For example, each of the plurality of pixel circuits 211 includes a liquid crystal element 230, a transistor 231, and a capacitor 233 as illustrated in FIG.

One potential of the pair of electrodes of the liquid crystal element 230 is appropriately set according to the specification of the pixel circuit 211. The alignment state of the liquid crystal element 230 is set according to written data.

For example, as a display method of a display device including a liquid crystal element, a TN (Twisted Nematic) mode, an IPS (In Plane Switching) mode, an STN (Super Twisted Nematic) mode, a VA (Vertical Alignment Alignment mode), and an ASM (Axially Asymmetrical Axially Aligned Alignment). -Cell) mode, OCB (Optically Compensated Birefringence) mode, FLC (Ferroelectric Liquid Crystal) mode, AFLC (Anti-Ferroelectric Liquid Crystal) mode, MVA (Multi-Dominant Binary Mode) mode PVA (Patterned Vertical Alignment) mode, ASV (Advanced Super View) mode, FFS (Fringe Field Switching) mode, TBA (Transverse Bend Alignment) mode, etc. may be used.

Further, a liquid crystal element may be formed using a liquid crystal composition including a liquid crystal exhibiting a blue phase and a chiral agent. A liquid crystal exhibiting a blue phase has a response speed as short as 1 msec or less and is optically isotropic. Therefore, alignment treatment is unnecessary and viewing angle dependency is small.

In the pixel circuit 211 in the Mth row and the Nth column, one of a source and a drain of the transistor 231 is electrically connected to the data line DL_N, and the other is electrically connected to the other of the pair of electrodes of the liquid crystal element 230. The gate of the transistor 231 is electrically connected to the scan line GL_M.

The transistor 231 has a function of controlling data writing of the data signal by being turned on or off.

One of the pair of electrodes of the capacitor 233 is electrically connected to the potential supply line VL, and the other is electrically connected to the other of the pair of electrodes of the liquid crystal element 230. Note that the value of the potential of the potential supply line VL is appropriately set according to the specification of the pixel circuit 211.

The capacitor 233 functions as a storage capacitor that holds written data.

In the display device including the pixel circuit 211 in FIG. 5B, the gate driver 221 sequentially selects the pixel circuits 211 in each row, turns on the transistors 231, and writes data signal data.

The pixel circuit 211 in which the data is written enters a holding state when the transistor 231 is turned off. By sequentially performing this for each row, an image can be displayed.

The above is the description of the example of the display device according to this embodiment.

As described with reference to FIG. 5, in the example of the display device according to this embodiment, a driver circuit is formed using the pulse output circuit described in Embodiment 1. In the above driver circuit, since the stress on the transistor is small, the reliability of the display device can be improved.

(Embodiment 3)
In this embodiment, structural examples of transistors that can be applied to the pulse output circuit of Embodiment 1 and the display device of Embodiment 2 are described with reference to a schematic cross-sectional view of FIG. In addition, each component shown in FIG. 6 may differ from an actual dimension.

The transistor illustrated in FIG. 6A includes a conductive layer 401_1, an insulating layer 402_1, a semiconductor layer 403_1, conductive layers 405a_1 and 405b_1, and an insulating layer 406.

The conductive layer 401_1 is provided over the element formation layer 400_1. Note that the conductive layer 401_1 may be provided over the element formation layer 400_1 with the insulating layer interposed therebetween.

The insulating layer 402_1 is provided over the conductive layer 401_1.

The semiconductor layer 403_1 overlaps with the conductive layer 401_1 with the insulating layer 402_1 interposed therebetween. Note that the entire semiconductor layer 403_1 is not necessarily overlapped with the conductive layer 401_1 with the insulating layer 402_1 interposed therebetween.

The conductive layer 405a_1 and the conductive layer 405b_1 are electrically connected to the semiconductor layer 403_1.

The insulating layer 406 is provided over the semiconductor layer 403_1, the conductive layer 405a_1, and the conductive layer 405b_1 and is in contact with the insulating layer 402_1. By using the insulating layers 406 and 402_1 to cover the semiconductor layer 403_1, the conductive layer 405a_1, and the conductive layer 405b_1, entry of impurities from the outside can be suppressed.

A transistor illustrated in FIG. 6B includes a conductive layer 401_2, an insulating layer 402_2, a semiconductor layer 403_2, conductive layers 405a_2 and 405b_2, conductive layers 407a to 407c, an insulator 409, and an insulating layer. 410.

The conductive layers 407a to 407c are provided over the element formation layer 400_2. Note that the conductive layers 407a to 407c may be provided over the element formation layer 400_2 with the insulating layer interposed therebetween.

The insulator 409 is embedded between each of the conductive layers 407a to 407c.

The insulating layer 410 is provided over the conductive layer 407a.

The semiconductor layer 403_2 overlaps with the conductive layer 407a with the insulating layer 410 interposed therebetween.

The conductive layer 405a_2 is electrically connected to the semiconductor layer 403_2 and the conductive layer 407b.

The conductive layer 405b_2 is electrically connected to the semiconductor layer 403_2 and the conductive layer 407c.

Note that the interval between the conductive layer 405a_2 and the conductive layer 405b_2 may be, for example, less than 50 nm, preferably 30 nm or less.

The insulating layer 402_2 is provided over the semiconductor layer 403_2, the conductive layer 405a_2, and the conductive layer 405b_2.

The conductive layer 401_2 overlaps with the semiconductor layer 403_2 with the insulating layer 402_2 interposed therebetween.

Further, each component will be described below. Each component is not necessarily limited to a single layer, and may be a stacked layer.

As the element formation layer 400 </ b> _K (K is a natural number of 2 or less), a substrate such as a glass substrate, an insulating layer, or the like can be used.

The conductive layer 401_K functions as a gate of the transistor. As the conductive layer 401_K, for example, a layer containing a metal material such as molybdenum, titanium, chromium, tantalum, magnesium, silver, tungsten, aluminum, copper, neodymium, scandium, or ruthenium can be used.

The insulating layer 402_K functions as a gate insulating layer of the transistor. As the insulating layer 402_K, for example, a layer containing a material such as silicon oxide, silicon nitride, silicon oxynitride, silicon nitride oxide, aluminum oxide, aluminum nitride, aluminum oxynitride, aluminum nitride oxide, or hafnium oxide can be used. For example, a stack of a silicon nitride layer and a silicon oxynitride layer can be used as the insulating layer 402_1. At this time, the silicon nitride layer may be a stack of a plurality of silicon nitride layers having different compositions. Alternatively, an oxide layer may be used as the insulating layer 402_K. As the oxide layer, for example, an oxide layer having an atomic ratio of In: Ga: Zn = 1: 3: 2 can be used.

The semiconductor layer 403_K functions as a layer in which a channel of the transistor is formed (also referred to as a channel formation layer).

For example, an oxide semiconductor layer can be used as the semiconductor layer 403 </ b> _K.

As the oxide semiconductor, for example, an In-based metal oxide, a Zn-based metal oxide, an In—Zn-based metal oxide, an In—Ga—Zn-based metal oxide, or the like can be used. Alternatively, a metal oxide containing another metal element instead of part or all of Ga contained in the In—Ga—Zn-based metal oxide may be used.

As the other metal element, for example, a metal element capable of bonding with more oxygen atoms than gallium may be used. For example, one or more elements of titanium, zirconium, hafnium, germanium, and tin are used. That's fine. As the other metal element, any one or more of lanthanum, cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium may be used. Good. These metal elements have a function as a stabilizer. Note that the added amount of these metal elements is an amount by which the metal oxide can function as a semiconductor. By using a metal element capable of bonding with more oxygen atoms than gallium, and further supplying oxygen into the metal oxide, oxygen defects in the metal oxide can be reduced.

A first oxide semiconductor layer having an atomic ratio of In: Ga: Zn = 1: 1: 1; a second oxide semiconductor layer having an atomic ratio of In: Ga: Zn = 3: 1: 2; Alternatively, the semiconductor layer 403 </ b> _K may be formed using a stack of third oxide semiconductor layers with an atomic ratio of In: Ga: Zn = 1: 1: 1. When the semiconductor layer 403 </ b> _K is formed using the above stack, for example, the field-effect mobility of the transistor can be increased.

The oxide semiconductor may be a C Axis Aligned Crystal Oxide Semiconductor (also referred to as a CAAC-OS).

The CAAC-OS refers to an oxide semiconductor with a crystal-amorphous mixed phase structure where a crystal part is included in an amorphous phase and is not completely single crystal nor completely amorphous. Further, in the crystal part included in the CAAC-OS, the c-axis is aligned in a direction parallel to the normal vector of the formation surface of the oxide semiconductor layer or the normal vector of the surface, and viewed from a direction perpendicular to the ab plane. It has a triangular or hexagonal atomic arrangement, and metal atoms or metal atoms and oxygen atoms are arranged in layers as viewed from the direction perpendicular to the c-axis. Note that in this specification, the term “perpendicular” includes a range of 85 ° to 95 °. In addition, a simple term “parallel” includes a range from −5 ° to 5 °.

For example, the CAAC-OS can be formed by a sputtering method using a polycrystalline oxide semiconductor sputtering target. When ions collide with the sputtering target, the crystal region included in the sputtering target may be cleaved from the ab plane, and may be separated as flat or pellet-like sputtering particles having a plane parallel to the ab plane. . In this case, when the flat sputtered particles reach the substrate while maintaining the crystalline state, the crystalline state of the sputtering target is transferred to the substrate. Thereby, the CAAC-OS is formed.

In order to form a CAAC-OS, it is preferable to apply the following conditions.

For example, when the CAAC-OS is formed with a reduced impurity concentration, collapse of the oxide semiconductor crystal state due to the impurities can be suppressed. For example, it is preferable to reduce impurities (such as hydrogen, water, carbon dioxide, and nitrogen) present in the deposition chamber. Further, it is preferable to reduce impurities in the deposition gas. For example, a film forming gas having a dew point of −80 ° C. or lower, preferably −100 ° C. or lower is preferably used as the film forming gas.

Further, by increasing the substrate heating temperature during film formation, migration of the sputtered particles occurs after the substrate adheres. Specifically, the film is formed at a substrate heating temperature of 100 ° C. to 740 ° C., preferably 200 ° C. to 500 ° C. By increasing the substrate heating temperature during film formation, when the flat sputtered particles reach the substrate, they migrate on the substrate and adhere to the substrate with the flat surface facing.

In addition, it is preferable to reduce the plasma damage during the film formation by increasing the oxygen ratio in the film formation gas and optimizing the electric power. The oxygen ratio in the deposition gas is 30% by volume or more, preferably 100% by volume.

As an example of the sputtering target, an In—Ga—Zn—O compound target is described below.

In-Ga-Zn that is polycrystalline by mixing InO _x powder, GaO _y powder, and ZnO _z powder at a predetermined ratio, and after heat treatment at a temperature of 1000 ° C. to 1500 ° C. -O compound target is formed. Note that x, y, and z are arbitrary positive numbers. Here, the predetermined ratio is, for example, 2: 2: 1, 8: 4: 3, 3: 1: 1, 1: 1: 1, 4: InO _x powder, GaO _y powder, and ZnO _z powder. The molar ratio is 2: 3 or 3: 1: 2. Note that the type of powder and the mixing ratio may be changed as appropriate depending on the sputtering target to be manufactured.

A transistor whose channel formation region is the CAAC-OS has high reliability because variation in electrical characteristics due to irradiation with visible light or ultraviolet light is low.

Since the transistor including the oxide semiconductor has a wide band gap, leakage current due to thermal excitation is small. Furthermore, the effective mass of holes is as heavy as 10 or more, and the height of the tunnel barrier is as high as 2.8 eV or more. Thereby, the tunnel current is small. Furthermore, there are very few carriers in the semiconductor layer. Thus, the off-state current can be reduced. For example, the off-state current is 1 × 10 ⁻¹⁹ A (100 zA) or less per channel width of 1 μm at room temperature (25 ° C.). More preferably, it is 1 × 10 ⁻²² A (100 yA) or less. The lower the off-state current of the transistor, the better. However, the lower limit value of the off-state current of the transistor is estimated to be about 1 × 10 ⁻³⁰ A / μm. Note that the semiconductor layer is not limited to the above oxide semiconductor layer, and a semiconductor layer containing silicon may be used as the semiconductor layer 403 </ b> _K.

The conductive layer 405a_K functions as one of a source and a drain of the transistor, and the conductive layer 405b_K functions as the other of the source and the drain of the transistor. As the conductive layer 405a_K and the conductive layer 405b_K, for example, a layer containing a metal material such as molybdenum, titanium, chromium, tantalum, magnesium, silver, tungsten, aluminum, copper, neodymium, scandium, or ruthenium can be used.

The insulating layer 406 functions as a protective layer. As the insulating layer 406, for example, a layer containing a material such as silicon oxide, silicon nitride, silicon oxynitride, silicon nitride oxide, aluminum oxide, aluminum nitride, aluminum oxynitride, aluminum nitride oxide, or hafnium oxide can be used. For example, the insulating layer 406 may be a stacked layer of a first silicon oxynitride layer and a second silicon oxynitride layer. At this time, the hydrogen concentration of the first silicon oxynitride layer is preferably lower than the hydrogen concentration of the second silicon oxynitride layer.

The conductive layer 407a functions as a gate of the transistor. Note that when one of the conductive layers 401_2 and 407a functions as a back gate of the transistor, the threshold voltage of the transistor can be controlled.

The conductive layers 407b and 407c have a function as a wiring layer.

As the conductive layers 407a to 407c, a layer of a material that can be used for the conductive layer 401_K can be used, for example.

The insulator 409 has a function of planarizing unevenness caused by the conductive layers 407a to 407c. For example, an insulating layer of a material that can be used for the insulating layer 402_K is formed over the conductive layers 407a to 407c, and then the insulating layer is polished by a polishing process to expose the upper surfaces of the conductive layers 407a to 407c. An insulator 409 is formed.

The transistors illustrated in FIGS. 6A and 6B include, for example, the transistors 101 to 106 included in the pulse output circuit of Embodiment 1 or the gate driver 221, the source driver 223, and the pixel of the display device of Embodiment 2. The invention can be applied to a transistor included in one or more of the circuits 211. Note that transistors having different structures may be used for the pixel circuit 211 and the gate driver 221 or the source driver 223, for example. For example, the transistor shown in FIG. 6A may be used for the pixel circuit 211, and the transistor shown in FIG. 6B may be used for one or both of the gate driver 221 and the source driver 223.

The above is the description of the structure example of the transistor illustrated in FIGS.

As described with reference to FIGS. 6A and 6B, in the example of the transistor according to this embodiment, a channel formation region is formed using an oxide semiconductor layer. With the above structure, for example, potential fluctuation due to a leakage current of a transistor can be suppressed.

(Embodiment 4)
In this embodiment, an example of an electronic device including a panel using the display device of Embodiment 2 is described with reference to FIGS.

The electronic device illustrated in FIG. 7A is an example of a portable information terminal.

An electronic device illustrated in FIG. 7A includes a housing 1011, a panel 1012 provided in the housing 1011, buttons 1013, and a speaker 1014.

Note that the housing 1011 may be provided with a connection terminal and an operation button for connecting to an external device.

Further, the panel 1012 may be configured using the display device of Embodiment 2.

Further, the panel 1012 may be configured using a touch panel. Accordingly, touch detection can be performed on the panel 1012.

The button 1013 is provided on the housing 1011. For example, if the button 1013 is a power button, whether or not the electronic device is turned on can be controlled by pressing the button 1013.

The speaker 1014 is provided in the housing 1011. The speaker 1014 outputs sound.

Note that the housing 1011 may be provided with a microphone. By providing the housing 1011 with a microphone, for example, the electronic device illustrated in FIG. 7A can function as a telephone.

The electronic device illustrated in FIG. 7A functions as one or more of a telephone set, an e-book reader, a personal computer, and a game machine, for example.

The electronic device illustrated in FIG. 7B is an example of a folding information terminal.

An electronic device illustrated in FIG. 7B includes a housing 1021a, a housing 1021b, a panel 1022a provided in the housing 1021a, a panel 1022b provided in the housing 1021b, a shaft portion 1023, and a button 1024. A connection terminal 1025, a recording medium insertion portion 1026, and a speaker 1027.

The housing 1021a and the housing 1021b are connected by a shaft portion 1023.

Further, the panels 1022a and 1022b may be formed using the display device of Embodiment 2.

Further, the panels 1022a and 1022b may be configured using a touch panel. Accordingly, touch detection can be performed on the panels 1022a and 1022b.

Since the electronic device illustrated in FIG. 7B includes the shaft portion 1023, the panel 1022a and the panel 1022b can be folded to face each other.

The button 1024 is provided on the housing 1021b. Note that a button 1024 may be provided on the housing 1021a. For example, by providing the button 1024 having a function as a power button, the supply of power voltage to the electronic device can be controlled by pressing the button 1024.

The connection terminal 1025 is provided on the housing 1021a. Note that the connection terminal 1025 may be provided on the housing 1021b. A plurality of connection terminals 1025 may be provided on one or both of the housing 1021a and the housing 1021b. The connection terminal 1025 is a terminal for connecting the electronic device illustrated in FIG. 7B to another device.

The recording medium insertion portion 1026 is provided in the housing 1021a. A recording medium insertion portion 1026 may be provided in the housing 1021b. Further, a plurality of recording medium insertion portions 1026 may be provided in one or both of the housing 1021a and the housing 1021b. For example, by inserting a card-type recording medium into the recording medium insertion unit, data on the card-type recording medium can be read out to the electronic device, or data in the electronic device can be written into the card-type recording medium.

The speaker 1027 is provided in the housing 1021b. The speaker 1027 outputs sound. Note that the speaker 1027 may be provided in the housing 1021a.

Note that a microphone may be provided in the housing 1021a or the housing 1021b. With the microphone provided in the housing 1021a or the housing 1021b, the electronic device illustrated in FIG. 7B can function as a telephone, for example.

The electronic device illustrated in FIG. 7B functions as one or more of a telephone set, an e-book reader, a personal computer, and a game machine, for example.

The electronic device illustrated in FIG. 7C is an example of a stationary information terminal. An electronic device illustrated in FIG. 7C includes a housing 1031, a panel 1032 provided in the housing 1031, buttons 1033, and a speaker 1034.

Further, the panel 1032 may be formed using the display device of Embodiment 2.

Further, the panel 1032 may be configured using a touch panel. Accordingly, touch detection can be performed on the panel 1032.

Note that a panel similar to the panel 1032 may be provided on the deck portion 1035 of the housing 1031.

Furthermore, you may provide the ticket output part which outputs a ticket etc. to the housing | casing 1031, a coin insertion part, a banknote insertion part, etc.

The button 1033 is provided on the housing 1031. For example, if the button 1033 is a power button, supply of the power voltage to the electronic device can be controlled by pressing the button 1033.

The speaker 1034 is provided in the housing 1031. The speaker 1034 outputs sound.

The electronic device illustrated in FIG. 7C has a function as, for example, an automatic teller machine, an information communication terminal (also referred to as a multimedia station) for ordering a ticket, or a gaming machine.

FIG. 7D illustrates an example of a stationary information terminal. An electronic device illustrated in FIG. 7D includes a housing 1041, a panel 1042 provided in the housing 1041, a support base 1043 that supports the housing 1041, a button 1044, a connection terminal 1045, a speaker 1046, and the like. .

Note that a connection terminal for connecting the housing 1041 to an external device may be provided.

Further, the panel 1042 may be formed using the display device of Embodiment 2.

Further, the panel 1042 may be configured using a touch panel. Thus, touch detection can be performed on the panel 1042.

The button 1044 is provided on the housing 1041. For example, if the button 1044 is a power button, the supply of power voltage to the electronic device can be controlled by pressing the button 1044.

The connection terminal 1045 is provided on the housing 1041. The connection terminal 1045 is a terminal for connecting the electronic device illustrated in FIG. 7D to another device. For example, when the electronic device illustrated in FIG. 7D is connected to the personal computer through the connection terminal 1045, an image corresponding to a data signal input from the personal computer can be displayed on the panel 1042. For example, if the panel 1042 of the electronic device illustrated in FIG. 7D is larger than the panel of another electronic device to which the electronic device panel 1042 is connected, a display image of the other electronic device can be enlarged, and a plurality of people can easily view the image simultaneously. Become.

The speaker 1046 is provided in the housing 1041. The speaker 1046 outputs sound.

The electronic device illustrated in FIG. 7D functions as one or more of an output monitor, a personal computer, and a television device, for example.

The above is the description of the example of the electronic device illustrated in FIG.

As described with reference to FIG. 7, in the electronic device according to the present embodiment, a highly reliable electronic device can be provided by providing the panel using the display device of Embodiment 2.

10 circuit 11 transistor 12 transistor 13 transistor 14 transistor 15 transistor 16 transistor 100 circuit 101 transistor 102 transistor 103 transistor 104 transistor 105 transistor 106 transistor 113 transistor 114 transistor 115 transistor 116 transistor 201 pixel portion 202 drive circuit portion 211 pixel circuit 221 gate driver 223 Source driver 230 Liquid crystal element 231 Transistor 233 Capacitor element 400_K Element formation layer 401_K Conductive layer 402_K Insulating layer 403_K Semiconductor layer 405a_K Conductive layer 405b_K Conductive layer 406 Insulating layer 407a Conductive layer 407b Conductive layer 407c Conductive layer 409 Insulator 410 Insulating layer 1011 Body 1012 Panel 101 3 Button 1014 Speaker 1021a Case 1021b Case 1022a Panel 1022b Panel 1023 Shaft 1024 Button 1025 Connection terminal 1026 Recording medium insertion portion 1027 Speaker 1031 Case 1032 Panel 1033 Button 1034 Speaker 1035 Deck 1041 Case 1042 Panel 1043 Support base 1044 Button 1045 Connection terminal 1046 Speaker

Claims (4)

Has a function to generate and output a pulse signal according to the set signal, reset signal and clock signal,
The potential of the gate is controlled by the set signal and the reset signal, a first transistor potential of one of the source or drain is changed according to said clock signal,
One first power supply potential is applied to the source or drain, a second transistor and the other of the source and the drain is electrically connected to the other of the source and the drain of said first transistor,
One second power supply potential is applied to the source or drain, a third transistor other potential of the source or drain is the potential of the pulse signal,
While the first power supply potential is applied to the source or drain, a fourth transistor and the other of the source and the drain is electrically connected to the other of the source and the drain of the third transistor,
While the first power supply potential is applied to the source or drain, and a fifth transistor having the other of the source and the drain is electrically connected to a gate of said third transistor,
One of a source and a drain is electrically connected to the other of the source and the drain of said first transistor, a sixth transistor having the other of the source and the drain is electrically connected to a gate of said third transistor, Have
The first to sixth transistors are of the same conductivity type,
The potential difference between the high level potential of the clock signal and the first power supply potential is larger than the threshold voltage of the third transistor,
The potential difference between the low level potential of the clock signal and the first power supply potential is less than the threshold voltage of the second transistor,
A pulse output circuit in which a high level potential of the clock signal is smaller than the second power supply potential. The first to sixth transistors include an oxide semiconductor layer in which a channel is formed,
The oxide semiconductor layer is
An atomic arrangement in which the band gap is wider than that of silicon, the c-axis is aligned in a direction parallel to the normal vector of the surface to be formed or the normal vector of the surface, and triangular or hexagonal when viewed from the direction perpendicular to the ab plane 2. The pulse output circuit according to claim 1, further comprising: a phase in which the metal atoms are arranged in layers or the metal atoms and oxygen atoms are arranged in layers as viewed from a direction perpendicular to the c-axis. A drive circuit comprising a shift register, wherein the shift register has a plurality of stages of pulse output circuits according to claim 1 or 2;
A pixel circuit in which writing and holding of data of a data signal is controlled by the driving circuit.   An electronic device comprising a panel using the display device according to claim 3.

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