Constant current circuit

Abstract

To provide a constant current circuit that reduces a steady current in a starter circuit part.SOLUTION: A control circuit 31 controls on-off of a transistor M5 for supplying current to parasitic capacitances of transistors M1 and M2. A transistor M6 is current-mirror-connected to a transistor M3 and folds back the current flowing through the transistor M3. A resistor R2 is connected in series with the transistor M6 and conducts current flowing through the transistor M6. A depletion type transistor M7 is negatively biased when current flows through the resistor R2.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a constant current circuit. [Background technology]

[0002] Global warming is believed to be caused by an intensification of the greenhouse effect in the atmosphere due to rising concentrations of greenhouse gases such as CO2, and with the rapid development of a communications and information society, reducing the power consumption of electronic devices has become a major issue. Many semiconductor integrated circuits are used in electronic devices, and the present invention aims to reduce the current consumption of constant current circuits, which are widely used in semiconductor integrated circuits, thereby contributing to the prevention of global warming.

[0003] A circuit as shown in FIG. 6 is known as a constant current circuit used in a semiconductor integrated circuit (see, for example, Patent Documents 1 and 2). The constant current circuit 100 shown in FIG. 6 supplies a constant current I REF and a start-up circuit 102 that starts the constant current generating section 101 when the power is turned on.

[0004] The constant current generating unit 101 has current mirror-connected transistors M1 and M2, current mirror-connected transistors M3 and M4, and a resistor R1.

[0005] The start-up circuit section 102 includes transistors M5, M7, and M8. The transistors M7 and M8 are connected in series between a positive power supply terminal T1 and a negative power supply terminal T2. The transistor M5 is connected in series with the transistor M3 and in parallel with the transistor M2 and a resistor R1. The gate of the transistor M5 is connected to the drains of the transistors M7 and M8.

[0006] Next, the operation of the constant current circuit 100 configured as described above will be described. After power-on, when the potential of junction node A, which serves as the gate potential of transistor M1, is lower than the threshold voltage of transistor M8, transistor M8 is in the off state and transistor M7 is in the on state. Therefore, transistor M5 is in the on state and draws an excitation current from transistor M3. Since transistors M3 and M4 are connected as a current mirror, an excitation current is generated in transistor M4. The excitation current from transistor M4 charges the parasitic capacitance between junction node A and negative power supply terminal T2, causing transistors M1 and M2 to change from the off state to the on state.

[0007] When the potential of junction node A exceeds the threshold voltage of transistor M8, transistor M8 turns on. When transistor M8 turns on, transistor M5 turns off, and the extraction of the excitation current ends. At this point, sufficient current flows through transistors M3 and M4 and transistors M1 and M2, and constant current generating unit 101 transitions to a steady state.

[0008] The gate potential of transistor M7 is driven by the gate-source potential difference of transistor M1, and even when transistor M8 is turned on, transistor M7 does not turn off. Transistor M7 is always on and operates similarly to a resistor. Therefore, even after the constant current generating unit 101 transitions to a steady state, the drain current of transistor M7 continues to flow as a steady current in the starter circuit unit 102.

[0009] When the transistors M1 and M2 operate in the subthreshold region, the drain current changes exponentially with respect to the change in the gate-source potential difference. REF The temperature coefficient TC is expressed by the following formulas 1 and 2.

[0010]

number

[0011]

number

[0012] Here, K is the aspect ratio (= W / L), W is the gate width, L is the gate length, and V T is the thermal voltage (=kT / q), k is the Boltzmann coefficient, T is the absolute temperature, q is the unit charge of an electron, and η is the subthreshold swing coefficient.

[0013] From equation 1, the constant current I REF is independent of fluctuations in the power supply voltage. Also, from equation 2, the thermal voltage V T Since the temperature coefficient is positive, the resistor R1 is configured to have a positive temperature coefficient, so the constant current I REF The amount of change in the value can be reduced.

[0014] The on-resistance of transistor M7 is R M7 The steady-state current I M8 is expressed as Equation 3.

[0015]

number

[0016] VDD is a positive power supply voltage supplied to the positive power supply terminal T1, and VSS is a negative power supply voltage supplied to the negative power supply terminal T2. M8 In order to turn on the transistor M5, the steady-state current I of the starter circuit 102 must be set to a value greater than the leakage current when the transistor M8 is in the off state. M8 is affected by fluctuations in the power supply voltage and resistance R M7 It depends heavily on the variation of the resistance R M7 The resistance value of varies due to variations in the manufacturing process and temperature fluctuations. M8 It is necessary to design the current value to be larger than the leakage current of transistor M8 with a certain amount of margin, taking into consideration fluctuations in power supply voltage, temperature, manufacturing variations, and the like. [Prior art documents] [Patent documents]

[0017] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-118532 [Patent Document 2] Patent No. 6329633 Summary of the Invention [Problem to be solved by the invention]

[0018] In the conventional constant current circuit 100, even after the constant current generating unit 101 has transitioned to a steady state, a large steady current I M8 However, there was a problem in that the current consumption increased because the current continued to flow.

[0019] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a constant current circuit that reduces the steady-state current of a starter circuit section. [Means for solving the problem]

[0020] In order to achieve the above-mentioned object, the constant current circuit according to the present invention comprises the following features [1] to [ 10 ] is a feature of the product. [1] a constant current generating unit including a first transistor, a second transistor connected to the first transistor in a current mirror configuration and reflecting a current flowing through the first transistor, a third transistor connected in series to the second transistor, and a fourth transistor connected to the third transistor in a current mirror configuration and reflecting a current flowing through the third transistor and connected in series to the first transistor; When power is turned on, the first transistor and the second transistor Between each gate and source or between the base and emitter a start-up circuit unit having a fifth transistor for supplying a current to the parasitic capacitance and a control circuit for controlling the on / off of the fifth transistor; When the fifth transistor is turned on, a current is supplied to the parasitic capacitance, and as a result, the gate-source potential difference or the base-emitter potential difference of the first transistor and the second transistor exceeds a threshold voltage, and the first transistor and the second transistor are turned on. A constant current circuit, the control circuit includes a sixth transistor connected to the third transistor in a current mirror configuration and mirroring a current flowing through the third transistor; and a resistor connected in series to the sixth transistor and through which a current flowing through the sixth transistor flows. The resistor is connected between the gate and the source, a seventh depletion-mode transistor to which a negative bias is applied when a current flows through the resistor; the fifth transistor is connected in series with the third transistor and in parallel with the second transistor; the control circuit includes an eighth transistor connected between the gate and source or between the base and emitter of the fifth transistor and current-mirror-connected to the first transistor, a ninth transistor connected in series to the seventh transistor, and a tenth transistor current-mirror-connected to the ninth transistor and mirroring back a current flowing through the ninth transistor; the eighth transistor and the tenth transistor are connected in series; It must be a constant current circuit. [2] [ 1 In the constant current circuit according to the control circuit has an eleventh transistor connected in series with the seventh transistor and the ninth transistor, turned off when the constant current generating unit is started up, and turned on after the constant current generating unit is started up. It must be a constant current circuit. [3] [ 2 In the constant current circuit according to The gate or base of the eleventh transistor is connected to the gate or base of the fifth transistor. It must be a constant current circuit. [4] [ 2 In the constant current circuit according to The gate or base of the eleventh transistor is connected to the gate or base of the third transistor. It must be a constant current circuit. [5] [1]~[4] In the constant current circuit according to any one of the above items, the control circuit has a twelfth transistor, the gate or base of which is connected to the gate, drain or base, or collector of the third transistor, and the drain or collector of which is connected to the gate of the tenth transistor; It must be a constant current circuit. [6] [1]~[5]In the constant current circuit according to any one of the above items, a threshold voltage of the eighth transistor is lower than threshold voltages of the first transistor and the second transistor; It must be a constant current circuit. [7] In the constant current circuit according to [1], the fifth transistor is connected in series to the first transistor and in parallel to the fourth transistor; the control circuit includes a thirteenth transistor connected in series with the seventh transistor; the gate or base of the fifth transistor is connected to the drain or collector of the seventh transistor and the thirteenth transistor; It must be a constant current circuit. [8] [ 7 In the constant current circuit according to a threshold voltage of the thirteenth transistor is lower than threshold voltages of the third transistor and the fourth transistor; It must be a constant current circuit. [9] [1]~[8] In the constant current circuit according to any one of the above items, At least one of the transistors is a bipolar transistor. It must be a constant current circuit.

[10] [1]~[9] In the constant current circuit according to any one of the above items, At least one of the transistors is a field effect transistor. It must be a constant current circuit. [Effects of the Invention]

[0021] According to the present invention, it is possible to provide a constant current circuit that reduces the steady-state current of the starter circuit section.

[0022] The present invention has been briefly described above. The details of the present invention will become clearer by reading the following detailed description of the invention (hereinafter referred to as "embodiments") with reference to the accompanying drawings. [Brief explanation of the drawings]

[0023] [Figure 1] FIG. 1 is a circuit diagram showing a constant current circuit according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a circuit diagram showing a constant current circuit according to a second embodiment of the present invention. [Figure 3] FIG. 3 is a circuit diagram showing a constant current circuit according to a third embodiment of the present invention. [Figure 4] FIG. 4 is a circuit diagram showing a constant current circuit according to the fourth embodiment of the present invention. [Figure 5] FIG. 5 is a circuit diagram showing a constant current circuit according to a fifth embodiment of the present invention. [Figure 6] FIG. 6 is a circuit diagram showing an example of a conventional constant current circuit. DETAILED DESCRIPTION OF THE INVENTION

[0024] Specific embodiments of the present invention will be described below with reference to the accompanying drawings.

[0025] (First embodiment) First, a constant current circuit 1 according to the first embodiment will be described with reference to Fig. 1. As shown in Fig. 1, the constant current circuit 1 outputs a constant current I REF and a start-up circuit section 3 that starts the constant current generating section 2 when the power is turned on.

[0026] The constant current generating unit 2 includes transistors M1 to M4 and a resistor R1. The transistors M1 and M2 are configured as N-channel field effect transistors. The transistors M3 and M4 are configured as P-channel field effect transistors.

[0027] The source of transistor M1 (=first transistor) is connected to negative power supply terminal T2. A negative power supply voltage VSS is supplied to negative power supply terminal T2. The source of transistor M2 (=second transistor) is connected to negative power supply terminal T2 via resistor R1, and the gate is connected to the gate and drain of transistor M1. In other words, transistors M1 and M2 are connected as a current mirror, and the drain current flowing through transistor M1 is copied and reflected as the drain current of transistor M2.

[0028] The source of the transistor M3 (=third transistor) is connected to the positive power supply terminal T1. The positive power supply terminal T1 is supplied with a positive power supply voltage VDD. The drain and gate of the transistor M3 are connected to the drain of the transistor M2. That is, the transistors M2 and M3 are connected in series. The source of the transistor M4 (=fourth transistor) is connected to the positive power supply terminal T1.

[0029] The gate of transistor M4 is connected to the gate and drain of transistor M3, and the drain is connected to the drain of transistor M1. That is, transistors M3 and M4 are connected as a current mirror, and the drain current flowing through transistor M3 is copied and reflected as the drain current of transistor M4. Furthermore, transistors M1 and M4 are connected in series.

[0030] The startup circuit unit 3 includes a transistor M5 (=fifth transistor) that supplies current to the parasitic capacitances of the transistors M1 and M2 when power is turned on to turn on the transistors M1 and M2, and a control circuit 31 that controls the on / off of the transistor M5. The transistor M5 is configured as an N-channel field-effect transistor. The source of the transistor M5 is connected to the negative power supply terminal T2, and the drain of the transistor M5 is connected to the drains of the transistors M2 and M3. The transistor M5 is connected in series with the transistor M3, and in parallel with the transistor M2 and the resistor R1.

[0031] The control circuit 31 includes a transistor M6, a resistor R2, and transistors M7 to M11. The transistors M6, M9, M10, and M11 are P-channel field-effect transistors. The transistors M7 and M8 are N-channel field-effect transistors.

[0032] The source of transistor M6 (=sixth transistor) is connected to the positive power supply terminal T1, and the gate is connected to the gate of transistor M3. Transistor M6 is connected to transistor M3 as a current mirror, and reflects the current flowing through transistor M3. One end of resistor R2 is connected to the drain of transistor M6, and the other end is connected to the negative power supply terminal T2. The current reflected by transistor M6 flows through resistor R2.

[0033] The gate of the transistor M7 (=seventh transistor) is connected to the negative power supply terminal T2, and the source is connected to the negative power supply terminal T2 via the resistor R2. The transistor M7 is a depletion-type transistor, and a negative bias is applied to the transistor M7 when the current folded back by the transistor M6 flows through the resistor R2.

[0034] The transistor M8 (=eighth transistor) has a drain connected to the gate of the transistor M5, a source connected to the source of the transistor M5, and a gate connected to the gate of the transistor M1. The transistor M8 is current-mirror connected to the transistor M1 and mirrors the current flowing through the transistor M1.

[0035] The drain of the transistor M9 (=ninth transistor) is connected to its own gate and the drain of the transistor M7, and the source is connected to the positive power supply terminal T1 via the transistor M11 (described later). That is, the transistors M7 and M9 are connected in series.

[0036] The transistor M10 (=tenth transistor) has a source connected to the positive power supply terminal T1, a drain connected to the drain of the transistor M8, and a gate connected to the gate of the transistor M9. The transistor M10 is current-mirror connected to the transistor M9 and mirrors the current flowing through the transistor M9. The transistors M8 and M10 are connected in series, and a junction node C, which is the connection point between their drains, is connected to the gate of the above-mentioned transistor M5.

[0037] The drain of the transistor M11 (=the eleventh transistor) is connected to the source of the transistor M9, and the source is connected to the positive power supply terminal T1. The transistor M11 is connected in series with the transistors M7 and M9. The gate of the transistor M11 is connected to the junction node C.

[0038] Next, the operation of the constant current circuit 1 configured as described above will be described. First, the operation will be described when, after power-on, the potential of junction node A, which serves as the gate potential of transistor M1, is lower than the threshold voltages of transistors M1, M2, and M8. In this case, transistors M1, M2, and M8 are in the off state. Furthermore, depletion-mode transistor M7 is in the on state, and the drain potential of transistor M7 drops, so transistor M10 is in the on state.

[0039] When transistor M8 is off and transistor M10 is on, the potential of junction node C is high, transistor M5 is on, and transistor M11 is off. When transistor M5 is on, it draws the excitation current from transistor M3. Because transistors M3 and M4 are connected as a current mirror, this excitation current is copied to the drain current of transistor M4. This excitation current from transistor M4 charges the parasitic capacitance between junction node A and the negative power supply terminal T2. When the gate-source potential difference of transistors M1 and M2 exceeds the threshold voltage as a result of charging the parasitic capacitance, transistors M1 and M2 change from the off state to the on state.

[0040] Furthermore, when the gate-source potential difference of transistor M8 exceeds the threshold voltage as a result of charging the parasitic capacitance, transistor M8 changes from the off state to the on state. When transistor M8 turns on, the potential of junction node C changes from high to low, transistor M5 turns off, and extraction of the excitation current ends. At this point, sufficient current flows through transistors M3, M4 and transistors M1, M2, and constant current generating unit 2 transitions to a steady state.

[0041] On the other hand, in the starter circuit 3, when the potential of the junction node C changes from a high state to a low state (i.e., when the constant current generating unit 2 transitions to a steady state), the transistor M11 is turned on, and a current flows through the transistors M7 and M9. At this time, the drain current I M6 flows into the negative power supply terminal T2 via resistor R2. This applies a negative bias to transistor M7, reducing the current flowing through depletion-mode transistor M7. The same current as that of transistor M7 flows through transistors M9 and M11. Because transistors M9 and M10 are connected in a current mirror configuration, the drain current of transistor M10 is a copy of the current proportional to the current flowing through transistor M9.

[0042] In addition, since the gate-source potential difference of transistor M7 has a negative temperature coefficient, by configuring resistor R2 to have a positive temperature coefficient, the current I of the constant current source composed of transistor M7 and resistor R2 due to temperature fluctuations can be reduced. M7 The amount of change in the value can be reduced.

[0043] At this time, the steady-state current of the starter circuit 3 is the drain current I of the transistor M7. M7 and the drain current I of transistor M10, which is connected to transistor M9 as a current mirror. M10 and the drain current I of transistor M6 M6 The drain current I of the transistors M7 and M10 M7 , I M10 is the drain current I of transistor M6 M6The drain current I of the transistor M6 is reduced by the action of the depletion-type transistor M7. M6 becomes dominant.

[0044] The drain current I of the transistor M7 in the example of the conventional constant current circuit 100 shown in FIG. M7 , as seen from Equation 3, varies greatly due to the influence of the power supply voltage, temperature, etc. However, the drain current I M6 is the constant current I generated by the constant current generator 2 REF =I M1 =I M2 Since it is proportional to the drain current I of transistor M6, the fluctuation amount due to the power supply voltage and temperature is small compared to Equation 1 and Equation 2. M6 When designing a current larger than the leakage current of the transistor M5, there is no need to provide a margin for fluctuations due to the power supply voltage, temperature, etc., and the steady-state current of the starter circuit unit 3 can be reduced.

[0045] Therefore, the constant current circuit 1 in the first embodiment has a circuit configuration in which the steady-state current of the starter circuit unit 3 is less susceptible to fluctuations in the power supply voltage and temperature fluctuations. As a result, the steady-state current of the starter circuit unit 3 can be designed to be low, which has the effect of making it possible to reduce the current consumption of the entire constant current circuit 1.

[0046] Furthermore, by setting the absolute value of the threshold voltage of transistor M8 lower than that of transistors M1 and M2 that constitute the constant current generating unit 2, the time it takes for transistor M8 to change from an off state to an on state is shortened, and the startup time of the startup circuit unit 3 is improved.

[0047] (Second embodiment) Next, a constant current circuit 1B of a second embodiment will be described with reference to Fig. 2. In Fig. 2, the same components as those in the circuit shown in Fig. 1 are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0048] As shown in the figure, the constant current circuit 1B includes a constant current generating unit 2 and a starter circuit unit 3B, similar to the first embodiment. The constant current generating unit 2 is similar to that of the first embodiment described above, and therefore a detailed description thereof will be omitted here.

[0049] The difference between the starter circuit 3 of the first embodiment and the starter circuit 3B of the second embodiment is the configuration of the control circuit 31B. As in the first embodiment, the control circuit 31B has transistors M6 to M11, a resistor R2, and a transistor M12. The transistor M12 is configured as a P-channel field effect transistor. The source of the transistor M12 (=twelfth transistor) is connected to the positive power supply terminal T1, the drain is connected to the gates of the transistors M9 and M10, and the gate is connected to the gates of the transistors M3 and M4.

[0050] The operation of the constant current circuit 1B having the above-described configuration is basically the same as that of the first embodiment, except for the points described below. That is, in the first embodiment, when the constant current generating unit 2 transitions to the steady state, the drain current I M7 and the drain current I M10 and the drain current I M6 In contrast, in the second embodiment, when the constant current generating unit 2 is in a steady state, the transistor M12 is in an on state and the transistor M10 is in an off state, so that the drain current I M10 Therefore, the steady-state current of the starter circuit 3 is the drain current I M6 and the drain current I M7 This becomes the case.

[0051] Therefore, the steady-state current of the starter circuit unit 3B in the second embodiment is larger than the steady-state current of the starter circuit unit 3 in the first embodiment by a factor of 1. M10 The time is reduced.

[0052] Therefore, in the constant current circuit 1B of this second embodiment, the circuit configuration is such that the steady-state current of the start-up circuit section 3B is less susceptible to the effects of fluctuations in power supply voltage and temperature fluctuations, thereby reducing the steady-state current of the start-up circuit section 3B and achieving the effect of reducing the current consumption of the entire constant current circuit 1B.

[0053] (Third embodiment) Next, a constant current circuit 1C of a third embodiment will be described with reference to Fig. 3. In Fig. 3, the same components as those in the circuit shown in Fig. 1 are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0054] As shown in the figure, the constant current circuit 1C includes a constant current generating unit 2 and a start-up circuit unit 3C, similar to the first embodiment. The constant current generating unit 2 is similar to that of the first embodiment described above, and therefore a detailed description thereof will be omitted here.

[0055] The difference between the starter circuit 3 of the first embodiment and the starter circuit 3C of the third embodiment is the connection destination of the gate of the transistor M11 that constitutes the control circuit 31C. The gate of the transistor M11 of the third embodiment is connected to the gates of the transistors M3 and M4.

[0056] The operation of the constant current circuit 1C configured as described above is basically the same as that of the first embodiment, except for the points described below. That is, when the power is turned on and the constant current generating unit 2 transitions to a steady state, in the first embodiment, the potential of the junction node C is low, so that the transistor M11 is turned on, and the transistors M9 and M10 operate as a current mirror connection. In contrast, in the third embodiment, sufficient current flows through the transistor M4, so that the transistor M11 is turned on, and the transistors M9 and M10 operate as a current mirror connection. Therefore, although the connection of the gate of the transistor M11 in the third embodiment is different from that in the first embodiment, the circuit operation is the same.

[0057] Therefore, in the constant current circuit 1C of this third embodiment, the steady-state current of the start-up circuit section 3C is configured to be less susceptible to the effects of power supply voltage fluctuations and temperature fluctuations, and the steady-state current of the start-up circuit section 3C can be designed to be low, thereby achieving the effect of reducing the current consumption of the entire constant current circuit 1C.

[0058] (Fourth embodiment) Next, a constant current circuit 1D of a fourth embodiment will be described with reference to Fig. 4. In Fig. 4, the same components as those in the circuit shown in Fig. 2 are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0059] As shown in the figure, the constant current circuit 1D includes a constant current generating unit 2 and a starter circuit unit 3D, similar to the second embodiment. The constant current generating unit 2 is similar to that of the first embodiment described above, and therefore a detailed description thereof will be omitted here.

[0060] The difference between the starter circuit 3B of the second embodiment and the starter circuit 3D of the fourth embodiment is the connection destination of the gate of the transistor M11 constituting the control circuit 31D. The gate of the transistor M11 of the fourth embodiment is connected to the gates of the transistors M3 and M4.

[0061] The operation of the constant current circuit 1D configured as described above is basically the same as that of the second embodiment, except for the points described below. That is, when the constant current generating unit 2 transitions to a steady state, in the second embodiment, the potential of the junction node C is low, so that the transistor M11 is turned on, and the transistors M9 and M10 operate as a current mirror connection. In contrast, in the fourth embodiment, sufficient current flows through the transistor M4, so that the transistor M11 is turned on, and the transistors M9 and M10 operate as a current mirror connection. Therefore, although the connection of the gate of the transistor M11 in the fourth embodiment is different from that in the second embodiment, the circuit operation is the same.

[0062] Therefore, in the constant current circuit 1D of this fourth embodiment, the circuit configuration is such that the steady-state current of the start-up circuit section 3D is less susceptible to the effects of power supply voltage fluctuations and temperature fluctuations, and the steady-state current of the start-up circuit section 3D can be designed to be low, thereby achieving the effect of reducing the current consumption of the entire constant current circuit 1D.

[0063] (Fifth embodiment) Next, a constant current circuit 1E of a fifth embodiment will be described with reference to Fig. 5. In Fig. 5, the same components as those in the circuit shown in Fig. 1 are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0064] As shown in the figure, the constant current circuit 1E includes a constant current generating unit 2 and a start-up circuit unit 3E, similar to the first embodiment. The constant current generating unit 2 is similar to that of the first embodiment described above, and therefore a detailed description thereof will be omitted here.

[0065] The starter circuit 3E of the fifth embodiment differs from the starter circuit 3 of the first embodiment in the connection of the transistor M5E and in that a transistor M13 is provided instead of the transistors M8 to M11. The transistors M5E and M13 are configured as P-channel field effect transistors.

[0066] The transistor M5E (=fifth transistor) has a source connected to the positive power supply terminal T1 and a drain connected to the drain of the transistor M1. The transistor M5E is connected in series to the transistor M1 and in parallel to the transistors M3 and M4.

[0067] The source of the transistor M13 (=the thirteenth transistor) is connected to the positive power supply terminal T1, the drain is connected to the drain of the transistor M7, and the gate is connected to the gates of the transistors M3 and M4. The transistors M7 and M13 are connected in series. The gate of the transistor M5E is connected to a junction node D, which is the connection point between the drains of the transistors M7 and M13.

[0068] Next, the operation of the constant current circuit 1E having the above-described configuration will be described. First, after power is turned on, The following describes the operation when the potential of junction node A, which serves as the gate potential of transistor M1, is lower than the threshold voltages of transistors M1 and M2. In this case, depletion-mode transistor M7 is turned on. Meanwhile, since sufficient current does not flow through transistors M3 and M4, transistor M13 is turned off.

[0069] When transistor M7 is on and transistor M13 is off, the potential of junction node D is low, and transistor M5E is on. When transistor M5E is on, current is supplied to the parasitic capacitance between junction node A and negative power supply terminal T2 through transistor M5E, charging the parasitic capacitance. When the gate-source potential difference of transistors M1 and M2 exceeds the threshold voltage as a result of charging the parasitic capacitance, transistors M1 and M2 change from off to on, and constant current generating unit 2 transitions to a steady state.

[0070] On the other hand, in the starter circuit 3E, when the constant current generating unit 2 is in a steady state and a sufficient current flows through the transistors M3 and M4, the transistor M13 is turned on, the transistor M5E is turned off, and the drain current I M7 is playing.

[0071] In the fifth embodiment, the steady-state current of the starter circuit unit 3E is the drain current I M6 and the drain current I M6 The reduced drain current I M7 The steady-state current is the drain current I M6 becomes dominant. Drain current I M6 is the constant current I generated by the constant current generator 2 REF Since it is proportional to the drain current I M6 This eliminates the need to provide a margin for fluctuations due to the power supply voltage, temperature, etc., and allows the steady-state current of the starter circuit section 3E to be designed to be low.

[0072] Therefore, in the constant current circuit 1E of this fifth embodiment, the circuit configuration is such that the steady-state current of the start-up circuit section 3E is less susceptible to the effects of power supply voltage fluctuations and temperature fluctuations, and the steady-state current of the start-up circuit section 3E can be designed to be low, thereby achieving the effect of reducing the current consumption of the entire constant current circuit 1E.

[0073] Furthermore, by setting the absolute value of the threshold voltage of transistor M13 lower than that of transistors M3 and M4 that constitute the constant current generating unit 2, the time it takes for transistor M13 to change from an off state to an on state is shortened, and the startup time of the startup circuit unit 3E is improved.

[0074] The present invention is not limited to the above-described embodiments, and can be appropriately modified, improved, etc. Furthermore, the material, shape, size, number, location, etc. of each component in the above-described embodiments are arbitrary and not limited as long as they can achieve the present invention.

[0075] For example, in the first to fifth embodiments described above, the transistors M1 to M4, M5(E), and M6 to M13 are configured as field-effect transistors, but this is not limited to this. At least one of M1 to M4, M5(E), and M6 to M13 may be configured as a bipolar transistor. In this case, the transistor gate can be described as the base, the source as the emitter, and the drain as the collector. [Explanation of symbols]

[0076] 1, 1B~1E constant current circuit 2 Constant current generator 3, 3B~3E Startup circuit section 31, 31B to 31E control circuit M1 transistor (first transistor) M2 transistor (second transistor) M3 transistor (third transistor) M4 transistor (fourth transistor) M5, M5E transistors (fifth transistor) M6 transistor (sixth transistor) M7 transistor (seventh transistor) M8 transistor (8th transistor) M9 transistor (9th transistor) M10 Transistor (10th transistor) M11 transistor (11th transistor) M12 transistor (12th transistor) M13 transistor (13th transistor) R1, R2 resistor

Claims

1. a constant current generating unit including a first transistor, a second transistor connected to the first transistor in a current mirror configuration and reflecting a current flowing through the first transistor, a third transistor connected in series to the second transistor, and a fourth transistor connected to the third transistor in a current mirror configuration and reflecting a current flowing through the third transistor and connected in series to the first transistor; a startup circuit unit having a fifth transistor for supplying a current to a parasitic capacitance between the gate and source or between the base and emitter of each of the first transistor and the second transistor when power is turned on, and a control circuit for controlling on / off of the fifth transistor, wherein the first transistor and the second transistor are turned on when a gate-source potential difference or a base-emitter potential difference of the first transistor and the second transistor exceeds a threshold voltage as a result of the current being supplied to the parasitic capacitance by turning on the fifth transistor, the control circuit includes a sixth transistor connected to the third transistor in a current mirror configuration and mirroring a current flowing through the third transistor, a resistor connected in series to the sixth transistor and through which a current flowing through the sixth transistor flows, and a depletion-type seventh transistor having the resistor connected between its gate and source and to which a negative bias is applied when a current flows through the resistor; the fifth transistor is connected in series with the third transistor and in parallel with the second transistor; the control circuit includes an eighth transistor connected between the gate and source or between the base and emitter of the fifth transistor and current-mirror-connected to the first transistor, a ninth transistor connected in series to the seventh transistor, and a tenth transistor current-mirror-connected to the ninth transistor and mirror-connected to the ninth transistor, the eighth transistor and the tenth transistor are connected in series; Constant current circuit.

2. 2. The constant current circuit according to claim 1, the control circuit has an eleventh transistor connected in series to the seventh transistor and the ninth transistor, turned off when the constant current generating unit is started up, and turned on after the start-up. Constant current circuit.

3. 3. The constant current circuit according to claim 2, the gate or base of the eleventh transistor is connected to the gate or base of the fifth transistor; Constant current circuit.

4. 3. The constant current circuit according to claim 2, the gate or base of the eleventh transistor is connected to the gate or base of the third transistor; Constant current circuit.

5. The constant current circuit according to any one of claims 1 to 4, the control circuit has a twelfth transistor, the gate or base of which is connected to the gate, drain or base, and collector of the third transistor, and the drain or collector of which is connected to the gate of the tenth transistor; Constant current circuit.

6. The constant current circuit according to any one of claims 1 to 5, a threshold voltage of the eighth transistor is lower than threshold voltages of the first transistor and the second transistor; Constant current circuit.

7. 2. The constant current circuit according to claim 1, the fifth transistor is connected in series to the first transistor and in parallel to the fourth transistor; the control circuit includes a thirteenth transistor connected in series with the seventh transistor; a gate or a base of the fifth transistor is connected to a drain or a collector of the seventh transistor and the thirteenth transistor; Constant current circuit.

8. 8. The constant current circuit according to claim 7, a threshold voltage of the thirteenth transistor is lower than threshold voltages of the third transistor and the fourth transistor; Constant current circuit.

9. The constant current circuit according to any one of claims 1 to 8, At least one of the transistors is a bipolar transistor. Constant current circuit.

10. The constant current circuit according to any one of claims 1 to 9, At least one of the transistors is a field effect transistor. Constant current circuit.

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