Reference current generating circuit

Abstract

The present application includes: a third current mirror that flows a current obtained by adding a first reference current copied by a first current mirror and a second reference current copied by a second current mirror; a first type reference resistor that flows a first reference current obtained by subtracting the second reference current copied by the first current mirror from an output of the third current mirror; and a second type reference resistor that flows a second reference current obtained by subtracting the first reference current copied by the first current mirror from another output of the third current mirror; and the second reference current is set to be inversely proportional to a resistance value of the second type reference resistor by the third current mirror so that voltage drops in the first type reference resistor and the second type reference resistor are the same.

Description

TECHNICAL FIELD

[0001] The present application relates to a reference current generating circuit which generates a reference current based on a second reference resistance of a different type from a first type of resistance. BACKGROUND

[0002] In the past, in analog semiconductor integrated circuits, there are a plurality of circuit blocks. In these circuit blocks, sometimes it is desired to operate based on the same reference current. Therefore, a copy of the reference current generated using one reference resistance is generated, and this is used as the reference current for each circuit block.

[0003] Here, due to differences in the types of resistances in the circuit blocks, and the like, it is sometimes desired to use a reference current using a reference resistance of different characteristics (for example, temperature characteristics).

[0004] In such a case, as long as a circuit which generates a reference current based on a reference resistance of different characteristics is provided, a separate reference current generating circuit is required. SUMMARY

[0005] The reference current generating circuit of the present application includes:

[0006] a first current mirror which copies a first reference current;

[0007] a second current mirror which copies a second reference current;

[0008] a third current mirror which flows a current obtained by adding the first reference current copied by the first current mirror to the second reference current copied by the second current mirror;

[0009] a first type of reference resistance which flows the first reference current obtained by subtracting the second reference current copied by the first current mirror from one output of the third current mirror; and

[0010] a second type of reference resistance which flows the second reference current obtained by subtracting the first reference current copied by the first current mirror from the other output of the third current mirror; and

[0011] the second reference current is set to be inversely proportional to the resistance value of the second type of reference resistance by the third current mirror, such that the voltage drops under the first type of reference resistance and the second type of reference resistance are the same.

[0012] According to the present application, without providing a separate reference current generating circuit, the first reference current using the first type of reference resistance can be used to generate the second reference current using the second type of reference resistance. BRIEF DESCRIPTION OF DRAWINGS

[0013] Figure 1is a view showing the configuration of a reference voltage generation circuit according to an embodiment.

[0014] Figure 2 is a view showing the configuration of a variation of the reference voltage generation circuit according to an embodiment. DETAILED DESCRIPTION

[0015] Embodiments of the present application will be described below with reference to the drawings. Note that the following embodiments are not limiting of the present application, and configurations in which a plurality of examples are selectively combined are also included in the present application.

[0016] "Circuit Configuration"

[0017] Figure 1 is a view showing the configuration of a reference voltage generation circuit according to an embodiment. Note that the reference voltage generation circuit uses a MOSFET (Metal-Oxide-Semiconductor Field Effect Transistor) as a transistor.

[0018] One end of a current source CS1 is connected to a power supply line, and a current Iin generated by another reference current generation circuit flows therethrough. Note that the current source CS1 can also be a reference current generation circuit. The current Iin is referred to as a first reference current.

[0019] The current Iin is supplied to a transistor Ml that is an input side of a current mirror CMl. The transistor Ml is N-type, and the gate and the drain are short-circuited (= diode-connected), so that the current Iin directly flows therethrough. The source of the transistor Ml is connected to a ground (or a low-voltage power supply). Note that the current mirror CMl is referred to as a first current mirror.

[0020] The gates of two N-type transistors M2 and M3 are commonly connected to the gate of the transistor Ml. The sources of the transistors M2 and M3 are connected to the same ground as the source of the transistor Ml. Thus, the transistor Ml and the transistors M2 and M3 form the current mirror CMl. Thus, the transistors M2 and M3 replicate the current of the transistor Ml, and the current Iin flows therethrough.

[0021] The drain of the transistor M2 is connected to a power supply via a transistor M6. The transistor M6 is P-type, and the drain and the gate are short-circuited, and the source is connected to the power supply. Thus, the transistor M6 also flows the current Iin. The gates of transistors M7 and M8, which are also P-type and whose sources are connected to the power supply, are connected to the gate of the transistor M6. The transistor M6 and the transistors M7 and M8 form a current mirror CM4. Thus, the transistors M7 and M8 replicate the current of the transistor M6 and flow the current Iin. Note that the current mirror CM4 is referred to as a fourth current mirror.

[0022] The drain of the transistor M7 is connected to the drain of the N-type transistor M4. The drain and the gate of the transistor M4 are short-circuited. Further, the source of the transistor M4 is connected to the ground via the first type reference resistor Rtype 1.

[0023] The drain of the transistor M8 is connected to the drain of the N-type transistor M5. The gate of the transistor M5 is connected to the gate of the transistor M4. Further, the source of the transistor M5 is connected to the ground via the second type reference resistor Rtype 2.

[0024] Therefore, the transistors M4, M5, the reference resistors Rtype 1, Rtype 2 constitute a current mirror CM3. Therefore, the transistor M5 replicates the current of the transistor M4. Further, the current mirror CM3 is referred to as a third current mirror.

[0025] In addition, the source of the P-type transistor M9 is connected to the power supply, and the gate and the drain are short-circuited, and is connected to the drain of the transistor M8. The gate of the transistor M9 is connected to the gate of the same P-type transistor M10. The source of the transistor M10 is connected to the power supply, and the drain is connected to the drain of the transistor M8. The gate of the transistor M9 is also connected to the gates of the same P-type transistors M11, M12. The transistors M11, M12 are also the sources connected to the power supply. Therefore, the transistor M9 and the transistors M10, M11, M12 constitute a current mirror CM2. The transistors M10, M11, M13 replicate the current of the transistor M9. If the current flowing in the transistor M9 is set to a current Iout, then the current Iout also flows in the transistors M110, M11, M12. Further, the current mirror CM2 is referred to as a second current mirror, and the current Iout is referred to as a second reference current.

[0026] The drain of the transistor M11 is connected to the drain of the N-type transistor M14. The drain and the gate of the transistor M14 are short-circuited, and the source is connected to the ground. The gate of the transistor M14 is connected to the gate of the transistor M13. The source of the transistor M13 is connected to the ground, and the transistor M11 and the transistor M13 constitute a current mirror CM5. Therefore, the transistor M13 replicates the current of the transistor M14, and the current Iout flows in the transistor M13. Further, the current mirror CM5 is referred to as a fifth current mirror.

[0027] The drain of the transistor M13 is connected to the connection point of the source of the transistor M4 and the reference resistor Rtype 1. In addition, the drain of the transistor M3 is connected to the connection point of the source of the transistor M5 and the reference resistor Rtype 2.

[0028] Since the current Iin flows in the transistors M7, M8, the current Iout flows in the transistors M10, M9, and therefore, the current Iin + Iout flows in the transistors M4, M5. Also, since the current Iin + Iout flowing in the transistor M4 is subtracted by the current Iout flowing in the transistor M13, the current Iin flows in the reference resistor Rtype 1.

[0029] On the other hand, since the current Iin + Iout flowing in the transistor M5 is subtracted by the current Iin flowing in the transistor M3, the current Iout flows in the reference resistor Rtype 2.

[0030] Here, the transistors M4 and M5 have their gates commonly connected, and have the same source voltage. Therefore, the voltage drop Iin * Rtype 1 in the reference resistor Rtype 1 and the voltage drop Iout * Rtype 2 in the reference resistor Rtype 2 become the same reference voltage Vref.

[0031] That is, Iin = Vref / Rtype 1

[0032] Iin = Vref / Rtype 1

[0033] Iout = Vref / Rtype 2

[0034] Iout = Iin * Rtype 1 / Rtype 2

[0035] The gate of the transistor M9 is connected to the gate of the P-type transistor 12, and the source of the transistor M12 is connected to the power supply. Therefore, the current Iout flows from the drain of the transistor M12, and is used as a reference current based on the reference resistor Rtype 2 in a prescribed circuit block.

[0036] Thus, according to the reference current generating circuit of the present embodiment, it is possible to generate a reference current Iout based on a reference resistor Rtype 2 of different characteristics using a reference current Iin based on a reference resistor Rtype 1, and it is possible to generate a reference current based on a reference resistor Rtype 2 using a relatively simple circuit.

[0037] By using the current mirror CM3, it is possible to make the voltage drops in the first-type reference resistor Rtype 1 and the second-type reference resistor Rtype 2 the same, and to set the second reference current to be inversely proportional to the resistance value of the second-type reference resistor Rtype 2.

[0038] "Variation Example Configuration"

[0039] Figure 2is a view showing a modification of the reference voltage generation circuit according to the embodiment. In this modification, the transistors constituting the current mirror are replaced with transistors of the common-emitter-common-base type.

[0040] That is, with respect to the current mirror CM1 including the N-type transistors Ml, M2, M3, N-type transistors Mlc, M2c, M3c are added on the upstream side thereof. The drain of the input-side transistor Mlc is short-circuited to the gate of the transistor Ml, and the gates of the transistors Mlc, M2c, M3c are supplied with a voltage vcn2, so that the transistors Mlc, M2c, M3c are turned on. Thus, the drain voltages of the transistors Ml, M2, M3 are set to the same voltage, and the accuracy of the current mirror can be improved.

[0041] With respect to the current mirror CM4 including the P-type transistors M6, M7, the current mirror CM3 including the N-type transistors M4, M5, the current mirror CM2 including the P-type transistors M9, M10, Ml l, M12, and the current mirror CM5 including the N-type transistors M14, M13, the transistors M6c, M7c, M4c, M5c, M9c, M10c, Ml lc, M12c, M14c, M13c are also added to make them of the common-emitter-common-base type.

[0042] In this way, by making the current mirror of the common-emitter-common-base type, the gate-source voltage of the transistors constituting the current mirror can be made the same on the input side and the output side, and the accuracy thereof can be improved.

[0043] "Other configurations"

[0044] Further, even if the P-type and N-type of the transistors in the embodiment of Figure 1 , 2 are exchanged, and the directions of the currents Iin, Iout are reversed, the current iout can be obtained as well. The currents Iin, Iout added on the upstream side of the current mirror CM3 and the currents Iin, Iout subtracted on the downstream side can be supplied from the current mirror constituted by the transistors of the opposite type.

[0045] In addition, the current mirror makes the sizes of the transistors on the input side and the output side the same, and the same current flows on the input side and the output side. However, the sizes of the transistors on the input side and the output side can also be made different. In this case, however, it is necessary to make the currents flowing in the reference resistors Rtypei, Rtype2 only Iin, Iout.

Claims

1. A reference current generating circuit, comprising: The first current mirror replicates the first reference current; The second current mirror replicates the second reference current; The third current mirror carries the current obtained by adding the first reference current copied by the first current mirror and the second reference current copied by the second current mirror; The first type of reference resistor flows through an output of the third current mirror minus the second reference current replicated by the second current mirror to obtain the first reference current; as well as The second type of reference resistor carries a second reference current obtained by subtracting the first reference current replicated by the first current mirror from the other output of the third current mirror; and Using a third current mirror, the voltage drop is made the same under the first type of reference resistor and the second type of reference resistor, and the second reference current is set to be inversely proportional to the resistance value of the second type of reference resistor.

2. The reference current generating circuit according to claim 1, wherein... After the first reference current, which was replicated using the first current mirror, is replicated using the fourth current mirror, the current is added upstream of the third current mirror. The first reference current, replicated using the first current mirror, is subtracted from the upstream of the second type of reference resistor.

3. The reference current generating circuit according to claim 1, wherein... The second reference current, replicated using the second current mirror, is added upstream of the third current mirror. After the first reference current, which is replicated using the second current mirror, is replicated using the fifth current mirror, it is subtracted from the upstream of the first type of reference resistor.

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