Semiconductor device

Abstract

To provide a semiconductor device comprising a constant voltage circuit with a relatively small circuit scale, which does not need an external power source.SOLUTION: A semiconductor device comprises a first output terminal, a second output terminal, an input terminal, a voltage dividing circuit, and a depletion type NMOSFET element. A drain of the depletion type NMOSFET element is connected to the input terminal. A source of the depletion type NMOSFET element is connected to the first output terminal. The voltage dividing circuit is connected to the first output terminal and the second output terminal, and also connected to a gate of the depletion type NMOSFET element.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a circuit configuration of a semiconductor device, and more particularly to a technique that is effective when applied to a constant voltage circuit. [Background technology]

[0002] Many semiconductor devices are equipped with constant voltage circuits to maintain a constant voltage and prevent overvoltage. A constant voltage circuit is a circuit that can supply a constant voltage even if the temperature or input power supply voltage changes, and is generally composed of a Zener diode, a three-terminal regulator, etc.

[0003] An example of a typical conventional constant voltage circuit using a three-terminal regulator is shown in Fig. 16. The conventional constant voltage circuit has three terminals: output terminals 1 and 2 and an input terminal 3, and mainly comprises a depletion-type NMOSFET element 5, an amplifier 10 connected to a reference voltage 26, and resistor elements 28 and 29.

[0004] Background art in this technical field includes, for example, technology such as Patent Document 1. Patent Document 1 discloses "a temperature compensation circuit for a DC constant voltage circuit that can perform temperature compensation of an output voltage with an extremely simple structure that requires only the addition of a small number of components, and that has the effect of easily adjusting the degree of temperature compensation."

[0005] Furthermore, Patent Document 2 discloses a "power supply circuit that operates stably with a low input-output potential difference." [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Publication number 5-42490 [Patent Document 2] JP 2020-135372 A Summary of the Invention [Problem to be solved by the invention]

[0007] However, a conventional constant voltage circuit as shown in FIG. 16 requires circuits such as an amplifier, which results in problems such as a large circuit size and the need for a separate power supply to drive the amplifier.

[0008] The above-mentioned Patent Documents 1 and 2 do not fully consider the above-mentioned problems, and there is room for improvement.

[0009] SUMMARY OF THE PRESENT EMBODIMENT An object of the present invention is to provide a semiconductor device including a constant voltage circuit which has a relatively small circuit scale and does not require an external power supply. [Means for solving the problem]

[0010] In order to achieve the above object, the present invention provides a power supply comprising a first output terminal, a second output terminal, an input terminal, a voltage divider circuit, and a depletion-type NMOSFET element, wherein a drain of the depletion-type NMOSFET element is connected to the input terminal, a source of the depletion-type NMOSFET element is connected to the first output terminal, and the voltage divider circuit is connected to the first output terminal and the second output terminal, respectively, and is connected to a gate of the depletion-type NMOSFET element. Effect of the Invention

[0011] According to the present invention, it is possible to realize a semiconductor device including a constant voltage circuit that has a relatively small circuit scale and does not require an external power supply.

[0012] This contributes to miniaturization and low power consumption of semiconductor devices.

[0013] Problems, configurations and effects other than those described above will become apparent from the following description of the embodiments. [Brief description of the drawings]

[0014] [Figure 1] 1 is a diagram showing a circuit configuration of a constant voltage circuit according to a first embodiment of the present invention; [Diagram 2] FIG. 2 is a diagram illustrating an application example of the constant voltage circuit of FIG. [Diagram 3] 2 is a diagram illustrating an example of the configuration of a voltage dividing circuit 4 in FIG. 1; [Figure 4] FIG. 11 is a diagram showing a circuit configuration of a constant voltage circuit according to a second embodiment of the present invention. [Diagram 5] FIG. 5 is a diagram showing an application example of the constant voltage circuit of FIG. [Figure 6] FIG. 11 is a diagram showing a circuit configuration of a constant voltage circuit according to a third embodiment of the present invention. [Figure 7] FIG. 7 is a diagram showing an application example of the circuit configuration of FIG. 6. [Figure 8] FIG. 7 is a diagram showing an application example of the circuit configuration of FIG. 6. [Figure 9] FIG. 7 is a diagram showing an application example of the circuit configuration of FIG. 6. [Figure 10] FIG. 11 is a diagram showing a circuit configuration of a constant voltage circuit according to a fourth embodiment of the present invention. [Figure 11] FIG. 11 is a diagram showing an application example of the circuit configuration of FIG. [Figure 12] FIG. 11 is a diagram showing a circuit configuration of a constant voltage circuit according to a fifth embodiment of the present invention. [Figure 13] FIG. 13 is a diagram showing a circuit configuration of a constant voltage circuit according to a sixth embodiment of the present invention. [Figure 14] FIG. 13 is a diagram showing a circuit configuration of a constant voltage circuit according to a seventh embodiment of the present invention. [Figure 15A] FIG. 5 is a diagram showing output characteristics in the circuit configurations of FIGS. [Figure 15B] FIG. 5 is a diagram showing output characteristics in the circuit configurations of FIGS. [Figure 16] FIG. 1 is a diagram showing a circuit configuration of a conventional constant voltage circuit. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the drawings, the same components are designated by the same reference numerals, and detailed description of overlapping parts will be omitted. EXAMPLES

[0016] First, in order to facilitate understanding of the present invention, the above-mentioned conventional constant voltage circuit will be described with reference to FIG.

[0017] As shown in FIG. 16, the conventional constant voltage circuit has three terminals: output terminals 1 and 2 and an input terminal 3, and is equipped with a depletion-type NMOSFET element 5, an amplifier 10 connected to a reference voltage 26, and resistor elements 28 and 29.

[0018] The depletion-type NMOSFET element 5 has a source connected to the output terminal 1 and a drain connected to the input terminal 3 .

[0019] Two resistor elements 28 and 29 connected in series to each other are connected between the output terminal 1 and the output terminal 2. One end of an amplifier 10 connected to a reference voltage 26 is connected between the resistor elements 28 and 29, and the other end of the amplifier 10 is connected to the gate of a depletion-type NMOSFET element 5.

[0020] As described above, a conventional constant voltage circuit is equipped with an amplifier, and a separate external power supply is required to drive the amplifier.

[0021] Next, a semiconductor device according to a first embodiment of the present invention will be described with reference to FIGS.

[0022] Fig. 1 is a diagram showing a circuit configuration of a constant voltage circuit of this embodiment. Fig. 2 is a diagram showing an application example of the constant voltage circuit of Fig. 1. Fig. 3 is a diagram showing a configuration example of a voltage divider circuit 4 of Fig. 1.

[0023] 1, the constant voltage circuit of this embodiment has three terminals: an output terminal 1 (first output terminal), an output terminal 2 (second output terminal), and an input terminal 3, and mainly comprises one voltage divider circuit 4 and one depletion-type NMOSFET element 5. The depletion-type NMOSFET element operates in such a way that the drain current is reduced by the gate bias.

[0024] The drain of the depletion-type NMOSFET element 5 is connected to the input terminal 3 , and the source of the depletion-type NMOSFET element 5 is connected to the output terminal 1 .

[0025] The voltage divider circuit 4 is disposed between the output terminal 1 and the output terminal 2 and is connected to the output terminal 1 and the output terminal 2, respectively, and is also connected to the gate of the depletion-type NMOSFET element 5.

[0026] The operation of the constant voltage circuit in Figure 1 will be explained. As an example, output terminal 1 is a voltage output, output terminal 2 is grounded, and a high voltage is applied to input terminal 3. NMOSFET element 5 is a depletion type, and has a negative Vth. When the midpoint voltage appearing from output terminal 1 via voltage divider circuit 4 falls below the Vth of NMOSFET element 5, the gate of NMOSFET element 5 turns off, and the voltage at output terminal 1 does not increase any further. The voltage appearing at output terminal 1 can be adjusted by the voltage division ratio of voltage divider circuit 4.

[0027] An application example of the constant voltage circuit of Fig. 1 will be described with reference to Fig. 2. Fig. 2 shows an example in which the constant voltage circuit of this embodiment is used to charge an internal power supply capacitor 12 of an autonomous synchronous rectifier circuit. Note that Fig. 2 shows a configuration example in which the voltage divider circuit 4 includes two resistance elements 13 and 14 connected in series with each other.

[0028] An autonomous synchronous rectifier circuit is a circuit that can replace a diode. For example, it is used to reduce loss in automotive alternators. The required conditions for this are that it is large enough to replace a diode, and that it is a two-terminal element.

[0029] In order to satisfy the above, it is extremely important that (1) the circuit scale is small, and (2) the circuit is capable of generating the necessary internal power supply in a self-contained manner.

[0030] By adopting a constant voltage circuit including the present invention in an autonomous synchronous rectifier circuit as shown in FIG. 2, it becomes possible to generate an internal voltage self-containedly between two terminals (high voltage (VH) input terminal 6 and low voltage (VL) input terminal 7) with a small circuit scale, and thus it is possible to simultaneously satisfy the above (1) and (2).

[0031] In addition to the configuration shown in FIG. 2, the voltage dividing circuit 4 may be configured to include two depletion-type NMOSFET elements 15 and 16 connected in series to each other, as shown in FIG.

[0032] In the constant voltage circuit of this embodiment, the relationship between the gate-source voltage and the threshold voltage Vth of the depletion-type NMOSFET element 5 is utilized to step down the voltage to a constant voltage without using an amplifier. This makes it possible to realize a constant voltage circuit with a small circuit scale and no external power supply. EXAMPLES

[0033] Second Embodiment A semiconductor device according to a second embodiment of the present invention will be described with reference to FIGS. 4, 5, 15A, and 15B.

[0034] Fig. 4 is a diagram showing a circuit configuration of the constant voltage circuit of this embodiment. Fig. 5 is a diagram showing an application example of the constant voltage circuit of Fig. 4. Figs. 15A and 15B are diagrams showing output characteristics by the circuit configurations of Example 1 (Fig. 1) and Example 2 (Fig. 4).

[0035] 4, the constant voltage circuit of this embodiment differs from that of embodiment 1 (FIG. 1) in that, in addition to the configuration of embodiment 1 (FIG. 1), it further includes one NMOSFET element 17 (first NMOSFET element) different from the depletion type NMOSFET element 5. The NMOSFET element 17 may be either a depletion type or an enhancement type.

[0036] The source of the depletion-type NMOSFET element 5 is connected to the gate of the NMOSFET element 17 and is also connected to the output terminal 1 via the NMOSFET element 17 .

[0037] The voltage divider circuit 4 is connected to the output terminal 1 via an NMOSFET element 17 .

[0038] The drain of NMOSFET element 17 is connected to input terminal 3, the source of NMOSFET element 17 is connected to output terminal 1, and the gate of NMOSFET element 17 is connected to the source of depletion-type NMOSFET element 5 and voltage divider circuit 4.

[0039] The operation of the constant voltage circuit in Fig. 4 will be described below. The same components as those in Fig. 1 operate in the same manner as described in the first embodiment.

[0040] In the constant voltage circuit of Example 1 (FIG. 1), the drain current must be sufficiently large when the gate-source voltage Vgs of the depletion-type NMOSFET element 5 is 0V or less. This is because a constant voltage cannot be maintained if the current consumption between the voltage divider circuit 4 and the output terminals 1 and 2 becomes equal to or greater than the drain current of the depletion-type NMOSFET element 5. The constant voltage circuit of this embodiment (FIG. 4) is an improvement mainly in this respect.

[0041] In the constant voltage circuit of this embodiment (FIG. 4), it is sufficient that the depletion-type NMOSFET element 5 can pass a drain current sufficient only for the current consumption in the voltage divider circuit 4. On the other hand, since the gate voltage of the NMOSFET element 17 is kept at a positive constant voltage based on the relationship between the depletion-type NMOSFET element 5 and the voltage divider circuit 4, a large increase in the drain current can be expected, making it easier to maintain the output terminal 1 at a constant voltage.

[0042] When the voltage at output terminal 1 rises above the value obtained by subtracting the Vth from the gate voltage of NMOSFET element 17, the gate of NMOSFET element 17 turns off, so there is no change in the constant voltage operation between output terminal 1 and output terminal 2. The voltage that appears at output terminal 1 can be adjusted by the voltage division ratio of voltage divider circuit 4.

[0043] Figures 15A and 15B show a comparison of output characteristics between the circuit configurations of Figure 1 (single stage configuration) and Figure 4 (two stage configuration). The figures show examples of output current when the total width (W) size of each resistor element and NMOSFET element is the same.

[0044] Comparing the gate-source voltage Vgs of the single-stage configuration with that of the two-stage configuration, when the output voltage is low, the voltage Vgs of the two-stage configuration is above 0 V. This also significantly improves the charging current Iout.

[0045] FIG. 5 shows an example in which the constant voltage circuit of this embodiment is used to charge the internal power supply capacitor 12 of an autonomous synchronous rectifier circuit.

[0046] As in the first embodiment (FIG. 2), by employing a constant voltage circuit including the present invention in an autonomous synchronous rectifier circuit as shown in FIG. 5, it becomes possible to generate an internal voltage in a self-contained manner between two terminals (high voltage (VH) input terminal 6 and low voltage (VL) input terminal 7) with a small circuit scale. EXAMPLES

[0047] Third Embodiment A semiconductor device according to a third embodiment of the present invention will be described with reference to FIGS.

[0048] Fig. 6 is a diagram showing the circuit configuration of the constant voltage circuit of this embodiment. Fig. 7 to Fig. 9 are diagrams showing application examples of the circuit configuration of Fig. 6.

[0049] As shown in Fig. 6, the constant voltage circuit of this embodiment differs from that of embodiment 2 (Fig. 4) in that the voltage divider circuit 4 includes an NMOSFET element 20 (second NMOSFET element) and a Zener diode 18 (first Zener diode) connected in series to the NMOSFET element 20. In Fig. 6, the output terminal 2 is shown on the right side of the page.

[0050] As shown in FIG. 6, in the constant voltage circuit of this embodiment, the voltage divider circuit 4 includes an NMOSFET element 20 and a Zener diode 18 connected in series to the NMOSFET element 20.

[0051] The gate of the depletion-type NMOSFET element 5 is connected between the NMOSFET element 20 and one end of the Zener diode 18 , and the gate and source of the NMOSFET element 20 are connected to the gate of the depletion-type NMOSFET element 5 .

[0052] The source of the depletion-type NMOSFET element 5 and the gate of the NMOSFET element 17 are connected to the drain of the NMOSFET element 20, and the other end of the Zener diode 18 is connected to the output terminal 2. The Zener diode 18 has a cathode connected to the gate of the depletion-type NMOSFET element 5 and an anode connected to the output terminal 2, respectively.

[0053] The operation of the constant voltage circuit in Fig. 6 will be described. When the source and gate of a depletion-type NMOSFET element are connected, a constant current flows into the drain, so that the NMOSFET element 20 operates at a constant current. At this time, the breakdown of the Zener diode 18 changes the voltage division ratio.

[0054] When the Zener diode 18 is not in breakdown, the gate and source of the depletion-type NMOSFET element 5 are at the same potential, so that a voltage is applied to the gate of the NMOSFET element 17 in the operation when Vgs=0V.

[0055] On the other hand, when the Zener diode 18 is in breakdown, the Zener diode 18 behaves as a low resistance and the NMOSFET element 20 behaves as a high resistance, so that a large voltage is applied between the gate and source of the depletion-type NMOSFET element 5, and the gate of the depletion-type NMOSFET element 5 is turned off.

[0056] The voltage between output terminal 1 and output terminal 2 is set by the breakdown voltage of Zener diode 18. The gate voltage of NMOSFET element 17 is the point at which Zener diode 18 breaks down and balances with the current of NMOSFET element 20.

[0057] The constant voltage circuit in FIG. 6 has the advantage that the charging voltage is determined by the breakdown voltage of the Zener diode 18 and is not easily affected by Vth variations in the MOSFET elements, and therefore has good controllability and accuracy of the output voltage.

[0058] Furthermore, when the NMOSFET element 20 behaves as a high resistor, the resistance becomes higher than a simple resistor, and the NMOSFET element 20 operates at a constant current, so that the current consumption is small.

[0059] An application example of the constant voltage circuit of FIG. 6 will be described with reference to FIG.

[0060] The constant voltage circuit in FIG. 7 further includes a Zener diode 19 (second Zener diode), an NMOSFET element 21 (third NMOSFET element), and an NMOSFET element 22 (fourth NMOSFET element) in addition to the configuration in FIG.

[0061] The drain of the NMOSFET element 21 is connected to the source and gate of the NMOSFET element 20, the source of the NMOSFET element 21 is connected to the anode of the Zener diode 18 and the output terminal 2, and the gate of the NMOSFET element 21 is connected to the output terminal 1 via the Zener diode 19 and is also connected to the drain of the NMOSFET element 22.

[0062] The drain of NMOSFET element 22 is connected to output terminal 1 via Zener diode 19 and is also connected to the gate of NMOSFET element 21, and the source and gate of NMOSFET element 22 are connected to output terminal 2 and the anode of Zener diode 18.

[0063] The operation of the constant voltage circuit in Fig. 7 will now be described. The same components as those in Fig. 6 operate in the same manner as described in Fig. 6.

[0064] Depending on whether the Zener diode 19 breaks down or not, the gates of the depletion-type NMOSFET element 5 and the NMOSFET element 17 are turned on / off more clearly.

[0065] When Zener diode 19 does not break down, NMOSFET element 22 operates in constant current mode, so that NMOSFET element 21 is gate-off. If Zener diode 18 does not break down either, NMOSFET element 20 is constant current=high resistance, but no connection is made between the gate and source of depletion-type NMOSFET element 5 except for the path via NMOSFET element 20. Therefore, depletion-type NMOSFET element 5 operates with gate-source voltage Vgs=0V, and a voltage is applied to the gate of NMOSFET element 17.

[0066] On the other hand, when the Zener diode 19 breaks down, and if a Zener diode 19 that breaks down at the desired voltage between output terminal 1 and output terminal 2 is selected, the gate of the NMOSFET element 21 turns on at the moment when the Zener diode 19 breaks down. The NMOSFET element 21 has a gate-on state=low resistance, but the NMOSFET element 20 has a constant current state=high resistance, so a large potential difference is generated between the gate and source of the depletion-type NMOSFET element 5, and the depletion-type NMOSFET element 5 turns off. Subsequently, the gate voltage of the NMOSFET element 17 also drops, and the gate turns off. The Zener diode 18 here serves as a safety measure when the gate voltage of the depletion-type NMOSFET element 5 unintentionally rises too high.

[0067] The constant voltage circuit of FIG. 7 has the advantage that the charging voltage is approximately equal to the breakdown voltage of the Zener diode 19 and is hardly affected by the Vth variations of the MOSFET elements, and therefore has better controllability and accuracy of the output voltage.

[0068] Furthermore, since NMOSFET element 20 and NMOSFET element 22 operate under constant current, they have a higher resistance than simple resistors and consume less current.

[0069] Another application example of the constant voltage circuit of Fig. 6 will be described with reference to Fig. 8. In addition to the configuration of Fig. 7, the constant voltage circuit of Fig. 8 further includes diodes 23 and 24 between NMOSFET element 17 and output terminal 1, and between Zener diode 18, NMOSFET element 21, and NMOSFET element 22 and output terminal 2, respectively.

[0070] In the configuration of FIG. 7, the source of NMOSFET element 17 and output terminal 1 are directly connected, whereas in the configuration of FIG. 8, the anode of diode 23 is connected to the source of NMOSFET element 17 and the cathode of diode 23 is connected to output terminal 1.

[0071] In addition, in the configuration of FIG. 7, the anode of the Zener diode 18 and the output terminal 2 are directly connected, whereas in the configuration of FIG. 8, the output terminal 2 is connected to the cathode of the diode 24, and the anode of the Zener diode 18 is connected to the anode of the diode 24.

[0072] Another application example of the constant voltage circuit of Fig. 6 will be described with reference to Fig. 9. Fig. 9 shows an example in which the constant voltage circuit of this embodiment is used to charge the internal power supply capacitor 12 of an autonomous synchronous rectifier circuit.

[0073] As in the first embodiment (FIG. 2) and the second embodiment (FIG. 5), by employing a constant voltage circuit including the present invention in an autonomous synchronous rectifier circuit as shown in FIG. 9, it becomes possible to generate an internal voltage in a self-contained manner between two terminals (high voltage (VH) input terminal 6 and low voltage (VL) input terminal 7) with a small circuit scale. EXAMPLES

[0074] Fourth Embodiment A semiconductor device according to a fourth embodiment of the present invention will be described with reference to FIGS.

[0075] Fig. 10 is a diagram showing a circuit configuration of the constant voltage circuit of this embodiment, and Fig. 11 is a diagram showing an application example of the circuit configuration of Fig. 10.

[0076] As shown in Fig. 10, the constant voltage circuit of this embodiment differs from that of embodiment 1 (Fig. 1) in that the voltage divider circuit 4 includes an NMOSFET element 20 (second NMOSFET element) and a Zener diode 18 (first Zener diode) connected in series to the NMOSFET element 20. In Fig. 10, the output terminal 2 is shown on the right side of the page.

[0077] As shown in FIG. 10, in the constant voltage circuit of this embodiment, the voltage divider circuit 4 includes an NMOSFET element 20 and a Zener diode 18 connected in series to the NMOSFET element 20.

[0078] The gate of the depletion-type NMOSFET element 5 is connected between the NMOSFET element 20 and the Zener diode 18 , and is also connected to the gate and source of the NMOSFET element 20 and the cathode of the Zener diode 18 .

[0079] The source of the depletion-type NMOSFET element 5 and the drain of the NMOSFET element 20 are connected to the output terminal 1 .

[0080] The anode of the Zener diode 18 is connected to the output terminal 2 .

[0081] An application example of the constant voltage circuit of FIG. 10 will be described with reference to FIG.

[0082] The constant voltage circuit of FIG. 11 further includes a Zener diode 19 (second Zener diode), an NMOSFET element 21 (third NMOSFET element), and an NMOSFET element 22 (fourth NMOSFET element) in addition to the configuration of FIG.

[0083] The drain of the NMOSFET element 21 is connected to the source and gate of the NMOSFET element 20, the source of the NMOSFET element 21 is connected to the anode of the Zener diode 18 and the output terminal 2, and the gate of the NMOSFET element 21 is connected to the output terminal 1 via the Zener diode 19 and is also connected to the drain of the NMOSFET element 22.

[0084] The drain of NMOSFET element 22 is connected to output terminal 1 via Zener diode 19 and is also connected to the gate of NMOSFET element 21, and the source and gate of NMOSFET element 22 are connected to output terminal 2 and the anode of Zener diode 18. EXAMPLES

[0085] Fifth embodiment A semiconductor device according to a fifth embodiment of the present invention will be described with reference to FIG.

[0086] FIG. 12 is a diagram showing a circuit configuration of a constant voltage circuit of this embodiment, which corresponds to a modification of the second embodiment (FIG. 4).

[0087] As shown in FIG. 12, the constant voltage circuit of this embodiment is configured by connecting a plurality of constant voltage circuits, each of which is formed by a combination of a depletion-type NMOSFET element 5 (5a, 5b), an NMOSFET element 17 (17a, 17b), and a voltage divider circuit 4 (4a, 4b), in parallel between the output terminal 1 and the output terminal 2.

[0088] The source of the depletion-mode NMOSFET element 5 is connected to the output terminal 1 via one or more NMOSFET elements 17 .

[0089] The voltage divider circuit 4 is connected to the output terminal 1 via one or more NMOSFET elements 17 .

[0090] The drain of NMOSFET element 17 is connected to input terminal 3 directly or through one or more NMOSFET elements 17, and the source of NMOSFET element 17 is connected to output terminal 1 directly or through one or more NMOSFET elements 17. EXAMPLES

[0091] Sixth Embodiment With reference to FIG. 13, a semiconductor device according to a sixth embodiment of the present invention will be described.

[0092] FIG. 13 is a diagram showing a circuit configuration of a constant voltage circuit of this embodiment, which corresponds to a modification of the first embodiment (FIG. 1).

[0093] As shown in FIG. 13, the constant voltage circuit of this embodiment further includes an amplifier 25 connected to a reference potential 27 in addition to the configuration of the first embodiment (FIG. 1).

[0094] The voltage dividing circuit 4 is connected to the output terminal 1 and the output terminal 2 , and is also connected to the gate of the depletion-type NMOSFET element 5 via an amplifier 25 .

[0095] Even if the constant voltage circuit includes an amplifier as in this embodiment, if a power supply with a constant output can be secured within the circuit in which the constant voltage circuit is mounted, the effect of the present invention can be obtained by setting the reference potential 27 to the power supply within that circuit rather than an external power supply. In other words, the present invention does not exclude constant voltage circuits that include an amplifier as a component. EXAMPLES

[0096] Seventh Embodiment With reference to FIG. 14, a semiconductor device according to a seventh embodiment of the present invention will be described.

[0097] FIG. 14 is a diagram showing a circuit configuration of a constant voltage circuit of this embodiment, which corresponds to another modified example of the first embodiment (FIG. 1).

[0098] 14, the constant voltage circuit of this embodiment further includes a resistive element 27 (first resistive element) connected between the output terminal 1 and the source of the depletion-type NMOSFET element 5, in addition to the configuration of the first embodiment (FIG. 1). The voltage divider circuit 4 includes a resistive element 28 (second resistive element) and a resistive element 29 (third resistive element) connected in series to the resistive element 28.

[0099] The source of the depletion-type NMOSFET element 5 is connected to the output terminal 1 via a resistance element 27 , and the gate of the depletion-type NMOSFET element 5 is connected between a resistance element 28 and a resistance element 29 .

[0100] According to this embodiment, the constant voltage circuit can be configured using relatively simple components.

[0101] The present invention is not limited to the above-described embodiments, and includes various modified examples. For example, the above-described embodiments have been described in detail to clearly explain the present invention, and the present invention is not necessarily limited to those including all of the configurations described. It is also possible to replace a part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. It is also possible to add, delete, or replace a part of the configuration of each embodiment with another configuration. [Explanation of symbols]

[0102] 1,2...Output terminals 3...Input terminal 4, 4a, 4b...Voltage divider circuit 5, 5a, 5b, 15, 16... Depletion-type NMOSFET elements 6...High voltage (VH) input terminal 7...Low voltage (VL) input terminal 8...NMOSFET element 9,23,24...Diodes 10,11,25…Amplifier 12…Capacitor 13, 14, 27, 28, 29...Resistance elements 17, 17a, 17b...NMOSFET elements 18,19...Zener diode 20, 21, 22...NMOSFET elements 26…Reference voltage 27...Reference potential.

Claims

1. A first output terminal; A second output terminal; and An input terminal; A voltage divider circuit; a depletion-type NMOSFET element; a drain of the depletion-mode NMOSFET device connected to the input terminal; a source of the depletion mode NMOSFET device connected to the first output terminal; the voltage divider circuit is connected to the first output terminal and the second output terminal, respectively, and is also connected to the gate of the depletion-type NMOSFET element.

2. 2. The semiconductor device according to claim 1, a first NMOSFET device different from the depletion mode NMOSFET device; a source of the depletion-mode NMOSFET device is connected to a gate of the first NMOSFET device and is connected to the first output terminal via the first NMOSFET device; the voltage divider circuit is connected to the first output terminal via the first NMOSFET device; a drain of the first NMOSFET device connected to the input terminal; a source of the first NMOSFET device connected to the first output terminal; a gate of said first NMOSFET element is connected to a source of said depletion-type NMOSFET element and to said voltage divider circuit.

3. 3. The semiconductor device according to claim 2, the voltage divider circuit includes a second NMOSFET element and a first Zener diode connected in series to the second NMOSFET element; a gate of the depletion-mode NMOSFET device is connected between the second NMOSFET device and one end of the first Zener diode, and a gate and a source of the second NMOSFET device are connected to the gate of the depletion-mode NMOSFET device; the source of the depletion mode NMOSFET device and the gate of the first NMOSFET device are connected to the drain of the second NMOSFET device; the other end of the first Zener diode is connected to the second output terminal.

4. 4. The semiconductor device according to claim 3, a second Zener diode, a third NMOSFET device, and a fourth NMOSFET device; the drain of the third NMOSFET device is connected to the source and gate of the second NMOSFET device; a source of the third NMOSFET device is connected to the other end of the first Zener diode and to the second output terminal; a gate of the third NMOSFET device is connected to the first output terminal via the second Zener diode and to a drain of the fourth NMOSFET device; a drain of the fourth NMOSFET device is connected to the first output terminal via the second Zener diode and to a gate of the third NMOSFET device; a source and a gate of the fourth NMOSFET element are connected to the second output terminal and the other end of the first Zener diode.

5. 5. The semiconductor device according to claim 4, a diode between the first NMOSFET element and the first output terminal, and between the Zener diode, the third NMOSFET element, and the fourth NMOSFET element and the second output terminal,

6. 2. The semiconductor device according to claim 1, the voltage divider circuit includes a second NMOSFET element and a first Zener diode connected in series to the second NMOSFET element; a gate of the depletion-mode NMOSFET device is connected between the second NMOSFET device and one end of the first Zener diode, and a gate and a source of the second NMOSFET device are connected to one end of the first Zener diode; a source of the depletion mode NMOSFET device and a drain of the second NMOSFET device connected to the first output terminal; the other end of the first Zener diode is connected to the second output terminal.

7. 3. The semiconductor device according to claim 2, a plurality of constant voltage circuits each formed by a combination of the depletion-type NMOSFET element, the first NMOSFET element, and the voltage divider circuit are connected in parallel between the first output terminal and the second output terminal; a source of the depletion-mode NMOSFET device is connected to the first output terminal through one or more first NMOSFET devices; the voltage divider circuit is coupled to the first output terminal through one or more first NMOSFET devices; a drain of the first NMOSFET device is connected to the input terminal, either directly or through one or more first NMOSFET devices; A semiconductor device, characterized in that a source of the first NMOSFET element is connected to the first output terminal directly or via one or more first NMOSFET elements.

8. 2. The semiconductor device according to claim 1, further comprising an amplifier connected to a reference potential; the voltage divider circuit is connected to the first output terminal and the second output terminal, respectively, and is connected to the gate of the depletion-type NMOSFET element via the amplifier.

9. 2. The semiconductor device according to claim 1, a first resistive element connected between the first output terminal and a source of the depletion mode NMOSFET device; a source of the depletion-mode NMOSFET device is connected to the first output terminal via the first resistive element; the voltage dividing circuit includes a second resistive element and a third resistive element connected in series to the second resistive element; a gate of the depletion-type NMOSFET element is connected between the second resistance element and the third resistance element.

10. 2. The semiconductor device according to claim 1, The semiconductor device is characterized in that the voltage divider circuit includes two resistor elements or two depletion-type NMOSFET elements connected in series to each other.

Images