JP2020077906A - Output circuit and electronic device - Google Patents

Abstract

To suppress variations in an output current in an output circuit.SOLUTION: An output circuit includes a drive circuit including a first transistor that outputs an output current of a magnitude corresponding to the magnitude of a supplied drive voltage, and a second transistor having the same structure as the first transistor, and outputting a voltage according to a gate threshold voltage of the second transistor as a drive voltage.SELECTED DRAWING: Figure 1

Description

  The present invention relates to output circuits and electronic devices.

  The following is known as a technique relating to an output circuit including an open drain type output transistor that outputs a current.

  For example, in Patent Document 1, a pre-drive circuit that outputs a drive signal and a source-grounded / open-drain type output that inputs a drive signal from the pre-drive circuit to a gate terminal and outputs an external output signal from a drain terminal An output circuit composed of a transistor is described. The pre-drive circuit is an on-operation drive circuit that outputs a drive signal for turning on the output transistor, a current source with a SW function that outputs a drive signal for turning off the output transistor, and an on-signal that is turned on. It is composed of an operation drive circuit and a drive control circuit which outputs a control signal for controlling each of the current sources with the SW function. The current of the current source with the SW function is configured to extract the electric charge from the gate terminal with a constant current value even if the gate voltage of the output transistor varies within the variation range of the threshold voltage.

JP, 2010-258527, A

  An output circuit including an open drain type output transistor and a drive circuit for outputting a drive voltage for driving the output transistor is known. In this output circuit, the drive voltage output from the drive circuit is applied between the gate and the source of the output transistor, and the output transistor outputs an output current having a magnitude corresponding to the magnitude of the drive voltage supplied from the drive circuit. Output.

  In the conventional output circuit, the fluctuation of the driving voltage due to the manufacturing variation occurs independently of the fluctuation of the gate threshold voltage of the output transistor due to the manufacturing variation, so that the fluctuation of the output current output from the output transistor becomes large. , There is a problem. For example, there may occur a combination in which the gate-source voltage of the output transistor whose gate threshold voltage is the upper limit of the tolerance is the lower limit of the tolerance. In this case, the output current increases from the standard value (standard median value). Fall below. In addition, a combination may occur in which the gate-source voltage of the output transistor whose gate threshold voltage is the lower limit of the tolerance is the upper limit of the tolerance.In this case, the magnitude of the output current is ) Greatly exceeds.

  The present invention has been made in view of the above points, and an object thereof is to suppress variations in output current in an output circuit.

  An output circuit according to a first aspect of the present invention includes a first transistor that outputs an output current having a magnitude corresponding to a magnitude of a driving voltage that is supplied, and a first transistor that has the same structure as the first transistor. A driving circuit including two transistors and outputting a voltage according to the gate threshold voltage of the second transistor as the driving voltage.

  According to the output circuit of the first aspect, the drive voltage output from the drive circuit fluctuates in the direction in which the fluctuation of the output current due to the fluctuation of the gate threshold voltage of the first transistor is suppressed. It is possible to suppress variations in current.

  The first transistor and the second transistor are preferably transistors provided on the same semiconductor wafer. Further, it is more preferable that the first transistor and the second transistor are provided on the same semiconductor chip. Most preferably, the first transistor is provided in the first region of the semiconductor chip, and the second transistor is provided in the second region adjacent to the first region. By arranging the first transistor and the second transistor in the vicinity of each other, the matching of the gate threshold voltages of these transistors can be further increased, and the effect of suppressing the variation in the output current is promoted. be able to.

  The drive circuit includes a current source for supplying a constant current to the second transistor, and outputs a voltage according to the gate threshold voltage of the second transistor in the state where the constant current flows as the drive voltage. It may be configured as follows.

  The first transistor may be a p-channel MOSFET having a source connected to a power supply line and a drain connected to an output terminal, and the second transistor may have a source connected to the power supply line and a gate. It may be a p-channel type MOSFET whose drain is connected to one end of the resistance element. The current source may be connected to the other end of the resistance element, and the connection point between the current source and the resistance element may be connected to the gate of the first transistor.

  The first transistor may be an n-channel MOSFET in which the source is connected to the ground line and the drain is connected to the output terminal, and the source of the second transistor is connected to the ground line. The gate and the drain may be n-channel type MOSFETs connected to one end of the resistance element. The current source may be connected to the other end of the resistance element, and the connection point between the current source and the resistance element may be connected to the gate of the first transistor.

  An electronic device according to a second aspect of the present invention includes a first transistor that outputs an output current having a magnitude corresponding to a level of a drive voltage that is supplied, and a second transistor that has the same structure as the first transistor. And a load that is driven by the output current, and a drive circuit that outputs a voltage corresponding to the gate threshold voltage of the second transistor as the drive voltage.

  According to the electronic device of the second aspect of the present invention, the drive voltage output from the drive circuit fluctuates in the direction of suppressing the fluctuation of the output current due to the fluctuation of the gate threshold voltage of the first transistor. Therefore, it is possible to suppress variations in the output current. That is, it is possible to suppress variations in the current supplied to the load.

  The load may be, for example, a light emitting element, or may include a coil.

  According to the present invention, it is possible to suppress variations in output current in the output circuit.

It is a figure which shows an example of a structure of the output circuit which concerns on embodiment of this invention. It is a perspective view showing an example of the structure of p channel type MOSFET which constitutes the 1st transistor and the 2nd transistor concerning an embodiment of the present invention. It is a top view showing a semiconductor wafer concerning an embodiment of the present invention. It is a top view which shows the semiconductor chip which concerns on embodiment of this invention. It is a top view showing an example of arrangement of the 1st field in which the 1st transistor concerning the embodiment of the present invention is provided, and the 2nd field in which the 2nd transistor is provided. FIG. 6 is a diagram showing a relationship between variations in the gate threshold voltage of the first transistor T1 and variations in the drive voltage in the output circuit according to the embodiment of the present invention. It is a figure which shows an example of a structure of the output circuit which concerns on a comparative example. FIG. 11 is a diagram showing a relationship between variations in the gate threshold voltage of the first transistor and variations in the drive voltage in the output circuit according to the comparative example. It is a figure which shows an example of a structure of the output circuit which concerns on embodiment of this invention. It is a figure which shows an example of a structure of the electronic device which concerns on embodiment of this invention. It is a figure which shows an example of a structure of the electronic device which concerns on embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the drawings, substantially the same or equivalent constituent elements or parts are designated by the same reference numerals.

[First Embodiment]
FIG. 1 is a diagram showing an example of the configuration of an output circuit 1 according to the first embodiment of the present invention. The output circuit 1 is configured to include a first transistor T1 as an open drain type output transistor that outputs a current, and a drive circuit 10 that outputs a drive voltage Vd that drives the first transistor T1.

  The first transistor T1 is composed of a p-channel MOSFET (metal-oxide-semiconductor field-effect transistor), has a source connected to a power supply line Lp supplied with a power supply voltage VBB, and a drain connected to the output circuit 1. Of the driving circuit 10 is connected to the output terminal 13 of the driving circuit 10. The first transistor T1 outputs an output current Iout having a magnitude corresponding to the magnitude of the driving voltage Vd supplied from the driving circuit 10. A load (not shown) driven by the output current Iout output from the first transistor T1 may be connected to the output terminal 13 of the output circuit 1.

  The drive circuit 10 includes a second transistor, resistance elements R1 and R2, and a current source 11. The second transistor T2 is composed of a p-channel type MOSFET having the same structure as the first transistor T1.

  The second transistor T2 has a source connected to the power supply line Lp and a drain and a gate connected to one end of the resistance element R1. The other end of the resistance element R1 is connected to one end of the current source 11, and the other end of the current source 11 is connected to the ground line. The current source 11 has a function of causing a constant current Id to flow in a series circuit including the second transistor T2, the resistance element R1, and the current source 11. The current source 11 may have a function of turning on / off the current Id flowing in the series circuit according to a control signal supplied from the outside. One end of the resistance element R2 is connected to a connection point between the resistance element R1 and the current source 11. The other end of the resistance element R2 is the output end 12 of the drive circuit 10 and is connected to the gate of the first transistor T1. The resistance element R2 functions as a surge protection element that suppresses a surge current applied to the gate of the first transistor T1.

FIG. 2 is a perspective view showing an example of the structure of a p-channel MOSFET 20 that constitutes the first transistor T1 and the second transistor T2. The p-channel MOSFET 20 that constitutes the first transistor T1 and the second transistor T2 includes a body region 21 made of an n-type semiconductor, and a source 22 and a drain made of a p-type semiconductor provided in a surface layer portion of the body region 21. 23 and. The MOSFET 20 is composed of a gate oxide film 24 formed on the surface of the body region 21 between the source 22 and the drain 23 and made of an insulator such as SiO _2, and polysilicon laminated on the gate oxide film 24. And a gate electrode 25. The body region 21 may be composed of, for example, an n-type well region formed on a silicon substrate. The p-type semiconductor forming the source 22 and the drain 23 is formed, for example, by implanting a p-type impurity such as boron into the body region 21 by a known ion implantation method. The gate oxide film 24 is formed by, for example, a known thermal oxidation method. The gate electrode 25 is formed, for example, by forming a polysilicon film on the gate oxide film 24 by a CVD method (chemical vapor deposition) and then patterning the polysilicon film using a known photolithography technique.

  The same structure of the first transistor T1 and the second transistor T2 means that the film thickness d, the gate length L, and the gate width W of the gate oxide film 24 are the same within a range in which manufacturing variations are allowed. Means By making the first transistor T1 and the second transistor T2 have the same structure, the gate threshold voltage Vth1 of the first transistor T1 and the gate threshold voltage Vth2 of the second transistor T2 can be substantially matched. You can Further, the fluctuation tendencies of the gate threshold voltages Vth1 and Vth2 due to manufacturing variations can be matched with each other. For example, when the gate threshold voltage Vth1 of the first transistor T1 changes in the direction of becoming larger than the standard value (standard median value) due to manufacturing variations, the gate threshold voltage Vth2 of the second transistor T2 also becomes It fluctuates in the direction of becoming larger than the standard value (standard median value).

  Each of the first transistor T1 and the second transistor T2 may be configured by connecting a plurality of structural units (unit cells) shown in FIG. 2 in parallel. The first transistor T1 may include more structural units (unit cells) than the second transistor T2. That is, the first transistor T1 may have a larger area than the second transistor T2. As a result, the current capacity of the first transistor T1 can be made larger than that of the second transistor T2.

  The first transistor T1 and the second transistor T2 are preferably provided on the same semiconductor wafer. For example, as shown in FIG. 3, the first transistor T1 is provided in the semiconductor chip 31A provided in the semiconductor wafer 30, and the second transistor T2 is provided in the semiconductor chip 31A provided in the semiconductor wafer 30. May be provided in different semiconductor chips 31B. By providing the first transistor T1 and the second transistor T2 on the same semiconductor wafer, the matching of the gate threshold voltages of these transistors can be further increased, and the effect of suppressing the variation in the output current can be obtained. Can be promoted.

  It is more preferable that the first transistor T1 and the second transistor T2 are provided on the same semiconductor chip. For example, as shown in FIG. 4, the first transistor T1 is provided in the first region 32A in the semiconductor chip 31, and the second transistor T2 is different from the first region 32A in the semiconductor chip 31. It may be provided in the second region 32B. Since the first transistor T1 and the second transistor T2 are provided in the same semiconductor chip 31, the matching of the gate threshold voltages of these transistors can be further increased, and the variations in the output current can be improved. The suppressing effect can be further promoted.

  Further, as shown in FIG. 5, the first transistor T1 is provided in the first region 32A of the semiconductor chip, and the second transistor T2 is provided in the second region adjacent to the first region 32A of the semiconductor chip. Most preferably, it is provided in the region 32B. Since the first transistor T1 and the second transistor T2 are provided in regions adjacent to each other in the same semiconductor chip, the matching of the gate threshold voltages of these transistors can be further enhanced, and the output The effect of suppressing variations in current can be further promoted. Further, the first transistor T1 may be configured to include a plurality of unit cells 33 provided in the first region 32A and connected in parallel to each other, and the second transistor T2 may be configured to include the second region T2. It may be configured to include a plurality of unit cells 33 provided in 32B and connected in parallel with each other. Each of the unit cells 33 may have the structure shown in FIG. 2, for example.

The operation of the output circuit 1 according to the embodiment of the present invention will be described below. When the power supply voltage VBB applied to the power supply line Lp is higher than the gate threshold voltage Vth2 of the second transistor T2, the second transistor T2 is turned on, and the second transistor T2, the resistance element R1, and the current A constant current Id flows through the series circuit including the source 11. At this time, the drive voltage Vd output from the output terminal 12 of the drive circuit 10 is represented by the following equation (1).
Vd = VBB- (Vth2 + Id × R1) (1)

  As shown in the equation (1), a voltage that is a level dropped from the level of the power supply voltage VBB and that corresponds to the gate threshold voltage Vth2 of the second transistor T2 is output as the drive voltage Vd. .. Of the factors causing the above voltage drop, the gate threshold voltage Vth2 of the second transistor T2 occupies most. That is, Vth2 >> (Id × R1).

The gate-source voltage Vgs1 of the first transistor T1 when the drive voltage Vd represented by the equation (1) is output from the drive circuit 10 is represented by the following equation (2). When the gate-source voltage Vgs1 represented by the equation (2) exceeds the gate threshold voltage Vth1 of the first transistor T1, the first transistor T1 is turned on and the output current Iout is output from the output terminal 13. Is output.
Vgs1 = Vth2 + Id × R1 (2)

  FIG. 6 is a diagram showing a relationship between variations in the gate threshold voltage Vth1 of the first transistor T1 and variations in the driving voltage Vd in the output circuit 1. As shown in FIG. 6, the first transistor T1 outputs an output current Iout having a magnitude corresponding to the magnitude of the gate-source voltage Vgs1. That is, when the gate-source voltage Vgs1 applied to the first transistor T1 by the drive voltage Vd exceeds the gate threshold voltage Vth1 of the first transistor T1, the output current Iout flows. The magnitude of the output current Iout increases as the gate-source voltage Vgs1 increases.

  FIG. 6 shows the relationship between the gate-source voltage Vgs1 and the output current Iout when the gate threshold voltage Vth1 of the first transistor T1 is small, medium, and large. Further, FIG. 6 shows variations in the drive voltage Vd output from the drive circuit 10. The variations in the gate threshold voltage Vth1 and the driving voltage Vd are caused by manufacturing variations.

  According to the output circuit 1 of the embodiment of the present invention, the first transistor T1 and the second transistor T2 have the same structure. Specifically, the film thickness d, the gate length L, and the gate width W of the gate oxide film 24 are the same within the range in which manufacturing variations are allowed. As a result, the tendency of fluctuations in the gate threshold voltages of the first transistor T1 and the second transistor T2 due to manufacturing variations can be matched with each other.

  For example, when the gate threshold voltage Vth1 of the first transistor T1 changes in the direction of becoming larger than the standard value (standard median value) due to manufacturing variations, the gate threshold voltage Vth2 of the second transistor T2 also becomes It fluctuates in the direction of becoming larger than the standard value (standard median value). Therefore, when the gate threshold voltage Vth1 of the first transistor T1 becomes relatively large, the magnitude of the driving voltage Vd seen from the ground line becomes relatively small, and as a result, the gate of the first transistor T1 becomes The source-source voltage Vgs1 becomes relatively large. In this case, the first transistor T1 operates at the operating point A shown in FIG.

  On the other hand, when the gate threshold voltage Vth1 of the first transistor T1 fluctuates in the direction of becoming larger than the standard value (standard median value) due to manufacturing variations, the gate threshold voltage Vth2 of the second transistor T2 also becomes It fluctuates in the direction of becoming larger than the standard value (standard median value). That is, when the gate threshold voltage Vth1 of the first transistor T1 is relatively small, the magnitude of the driving voltage Vd as viewed from the ground line is relatively large, and as a result, the gate of the first transistor T1 is The source-source voltage Vgs1 becomes relatively small. In this case, the first transistor T1 operates at the operating point B shown in FIG.

  As described above, according to the output circuit 1 according to the embodiment of the present invention, the drive circuit 10 includes the second transistor T2 having the same structure as the first transistor T1, and the gate of the second transistor T2. The drive voltage Vd corresponding to the threshold voltage Vth2 is output. As a result, the drive voltage Vd (gate-source voltage Vgs1 of the first transistor T1) varies in association with the variation of the gate threshold voltage Vth1 of the first transistor T1 due to manufacturing variations. Specifically, the drive voltage Vd fluctuates in the direction of suppressing the fluctuation of the output current Iout due to the fluctuation of the gate threshold voltage Vth1 of the first transistor T1. As described above, the fluctuations in the gate threshold voltage Vth1 and the driving voltage Vd are interlocked with each other, so that the fluctuations in the output current Iout can be suppressed as compared with the case where the fluctuations occur independently of each other.

  Here, FIG. 7 is a diagram illustrating an example of the configuration of the output circuit 1X according to the comparative example. The output circuit 1X according to the comparative example does not include the second transistor T2 included in the output circuit 1 (see FIG. 1) according to the embodiment of the present invention.

The drive voltage Vd output from the output terminal 12 of the drive circuit 10X according to the comparative example is expressed by the following equation (3).
Vd = VBB-Id × R1 (3)

The gate-source voltage Vgs1 of the first transistor T1 when the drive voltage Vd represented by the equation (3) is output from the drive circuit 10X is represented by the following equation (4).
Vgs1 = Id × R1 (4)

  FIG. 8 is a diagram showing a relationship between variations in the gate threshold voltage Vth1 of the first transistor T1 and variations in the drive voltage Vd in the output circuit 1X according to the comparative example. FIG. 8 shows the relationship between the gate-source voltage Vgs1 and the output current Iout when the gate threshold voltage Vth1 of the first transistor T1 is small, medium, and large. Further, FIG. 8 shows variations in the drive voltage Vd output from the drive circuit 10X.

  According to the output circuit 1X of the comparative example, the gate threshold voltage Vth1 and the drive voltage Vd of the first transistor T1 change independently of each other. Therefore, there may be a combination in which the gate threshold voltage Vth1 is the upper limit of the tolerance and the gate-source voltage Vgs1 of the first transistor T1 is the lower limit of the tolerance. In this case, the first transistor T1 operates at the operating point C shown in FIG. 8, and the magnitude of the output current Iout may be much lower than the standard value (standard median value). In addition, there may be a combination in which the gate-source voltage Vgs1 of the first transistor T1 whose gate threshold voltage Vth1 is the lower limit of the tolerance is the upper limit of the tolerance. In this case, the first transistor T1 operates at the operating point D shown in FIG. 8, and the magnitude of the output current Iout may be much lower than the standard value (standard median value). Therefore, the output circuit 1X according to the comparative example has a problem that the variation in the output current Iout becomes large. According to the output circuit 1X of the comparative example, it is necessary to take measures such as increasing the size of the first transistor T1 in order to satisfy the standard of the output current Iout even when the output current Iout is minimized. Therefore, the manufacturing cost becomes high.

  On the other hand, according to the output circuit 1 according to the embodiment of the present invention, as described above, the drive voltage Vd suppresses the fluctuation of the output current Iout due to the fluctuation of the gate threshold voltage Vth1 of the first transistor T1. Since it fluctuates in the direction, it is possible to suppress variations in the output current Iout. Therefore, it is not necessary to take measures such as increasing the size of the first transistor T1 in consideration of the excessive variation in the output current Iout, and the manufacturing cost can be suppressed.

[Second Embodiment]
FIG. 9 is a diagram showing an example of the configuration of the output circuit 1A according to the second embodiment of the present invention. The output circuit 1A is configured to include a first transistor T1 as an open drain type output transistor that outputs a current, and a drive circuit 10A that outputs a drive voltage Vd that drives the first transistor T1.

  The first transistor T1 is composed of an n-channel MOSFET, the source is connected to the ground line, the drain is connected to the output terminal 13 of the output circuit 1, and the gate is connected to the output terminal 12 of the drive circuit 10A. Has been done. The first transistor T1 outputs an output current Iout having a magnitude corresponding to the level of the drive voltage Vd supplied from the drive circuit 10A. A load (not shown) driven by the output current Iout output from the first transistor T1 may be connected to the output terminal 13 of the output circuit 1A.

  The drive circuit 10A includes a second transistor T2, resistance elements R1 and R2, and a current source 11. The second transistor T2 is composed of an n-channel type MOSFET having the same structure as the first transistor T1.

  The second transistor T2 has a source and a gate connected to the ground line, and a drain connected to one end of the resistance element R1. The other end of the resistance element R1 is connected to one end of the current source 11, and the other end of the current source 11 is connected to the power supply line Lp. The current source 11 has a function of causing a constant current Id to flow in a series circuit including the current source 11, the resistance element R1, and the second transistor T2. The current source 11 may have a function of turning on / off the current Id flowing in the series circuit according to a control signal supplied from the outside. One end of the resistance element R2 is connected to a connection point between the resistance element R1 and the current source 11. The other end of the resistance element R2 is the output end 12 of the drive circuit 10A that outputs the drive voltage Vd, and is connected to the gate of the first transistor T1. The resistance element R2 functions as a surge protection element that suppresses a surge current applied to the gate of the first transistor T1.

The operation of the output circuit 1A will be described below. When the power supply voltage VBB applied to the power supply line Lp is higher than the gate threshold voltage Vth2 of the second transistor T2, the second transistor T2 is turned on, and the current source 11, the resistance element R1 and the second transistor T2 are turned on. A constant current Id flows in the series circuit including the transistor T2. At this time, the drive voltage Vd output from the output terminal 12 of the drive circuit 10A is represented by the following equation (5).
Vd = Vth2 + Id × R1 (5)

  As shown in the equation (5), a voltage corresponding to the gate threshold voltage Vth2 of the second transistor T2 is output as the drive voltage Vd. Of the factors causing the above voltage drop, the gate threshold voltage Vth2 of the second transistor T2 occupies most. That is, Vth2 >> (Id × R1). The drive voltage Vd represented by the equation (5) from the drive circuit 10 is supplied to the first transistor T1 as the gate-source voltage Vgs1 of the first transistor T1.

  According to the output circuit 1A according to the second embodiment, the drive circuit 10A includes the second transistor having the same structure as the first transistor T1 as in the output circuit 1 according to the first embodiment. The drive voltage Vd corresponding to the gate threshold voltage Vth2 of the second transistor T2 is output. As a result, the drive voltage Vd (gate-source voltage Vgs of the first transistor T1) varies in association with the variation of the gate threshold voltage Vth1 of the first transistor T1 due to manufacturing variations. Specifically, the drive voltage Vd fluctuates in the direction of suppressing the fluctuation of the output current Iout due to the fluctuation of the gate threshold voltage Vth1 of the first transistor T1. As described above, the fluctuations in the gate threshold voltage Vth1 and the driving voltage Vd are interlocked with each other, so that the fluctuations in the output current Iout can be suppressed as compared with the case where the fluctuations occur independently of each other. Therefore, it is not necessary to take measures such as increasing the size of the first transistor T1 in consideration of the excessive variation in the output current Iout, and the manufacturing cost can be suppressed.

[Third Embodiment]
FIG. 10: is a figure which shows an example of a structure of the electronic device 100 which concerns on the 3rd Embodiment of this invention. The electronic device 100 includes the output circuit 1 according to the first embodiment and the light emitting element 40 as a load driven by the output current Iout output from the output circuit 1.

  The light emitting device 40 may be an LED (light emitting diode) used in a lighting device such as a head lamp or a tail lamp of an automobile. The light emitting element 40 emits light with a light emission intensity according to the magnitude of the output current Iout output from the output circuit 1.

  According to the electronic device 100 of the present embodiment, it is possible to suppress the variation in the output current Iout, and thus it is possible to suppress the variation in the light emission intensity of the light emitting element 40. The electronic device 100 may include the output circuit 1A according to the second embodiment, instead of the output circuit 1 according to the first embodiment.

[Fourth Embodiment]
FIG. 11: is a figure which shows an example of a structure of 100 A of electronic devices which concern on the 4th Embodiment of this invention. The electronic device 100A includes the output circuit 1 according to the first embodiment and the coil 41 as a load driven by the output current Iout output from the output circuit 1.

  The coil 41 may be, for example, a linear solenoid that directly moves a shift lock pin of an automobile. The coil 41 generates a magnetic field having an intensity according to the magnitude of the output current Iout output from the output circuit 1.

  According to the electronic device 100A of the present embodiment, the variation in the output current Iout can be suppressed, so that the variation in the strength of the magnetic field generated by the coil 41 can be suppressed. The electronic device 100A may include the output circuit 1A according to the second embodiment, instead of the output circuit 1 according to the first embodiment.

  1, 1A ... Output circuit, 10, 10A ... Driving circuit, 11 ... Current source, 13 ... Output terminal, 30 ... Semiconductor wafer, 31, 31A, 31B ... Semiconductor chip, 32A ... 1st area | region, 32B ... 2nd area | region, 40 ... Light emitting element, 41 ... Coil, 100, 100A ... Electronic device, T1 ... 1st transistor, T2 ... Second transistor, R1, R2 ... Resistance element

Claims (10)

A first transistor that outputs an output current having a magnitude corresponding to the magnitude of the driving voltage supplied,
A drive circuit including a second transistor having the same structure as the first transistor, and outputting a voltage according to the gate threshold voltage of the second transistor as the drive voltage;
Output circuit including. The output circuit according to claim 1, wherein the first transistor and the second transistor are transistors provided on the same semiconductor wafer. The output circuit according to claim 1, wherein the first transistor and the second transistor are provided on the same semiconductor chip. The said 1st transistor is provided in the 1st area | region of a semiconductor chip, and the said 2nd transistor is provided in the 2nd area | region adjacent to the said 1st area | region. The output circuit described. The drive circuit includes a current source for supplying a constant current to the second transistor, and outputs a voltage according to the gate threshold voltage of the second transistor in the state where the constant current flows as the drive voltage. The output circuit according to any one of claims 1 to 4. The first transistor is a p-channel type MOSFET whose source is connected to the power supply line and whose drain is connected to the output terminal,
The second transistor is a p-channel MOSFET whose source is connected to the power supply line and whose gate and drain are connected to one end of a resistance element.
The current source is connected to the other end of the resistance element,
The output circuit according to claim 5, wherein a connection point between the current source and the resistance element is connected to a gate of the first transistor. The first transistor is an n-channel MOSFET whose source is connected to the ground line and whose drain is connected to the output terminal,
The second transistor is an n-channel MOSFET whose source is connected to the ground line and whose gate and drain are connected to one end of a resistance element.
The current source is connected to the other end of the resistance element,
The output circuit according to claim 5, wherein a connection point between the current source and the resistance element is connected to a gate of the first transistor. A first transistor that outputs an output current having a magnitude corresponding to the level of the drive voltage supplied,
A drive circuit including a second transistor having the same structure as the first transistor, and outputting a voltage according to the gate threshold voltage of the second transistor as the drive voltage;
A load driven by the output current,
Including an electronic device. The electronic device according to claim 8, wherein the load includes a light emitting element. The electronic device according to claim 8, wherein the load includes a coil.