JP3509167B2 - Current mirror device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a current mirror device for driving at a low voltage and reducing variations in output voltage. 2. Description of the Related Art Conventionally, as shown in FIG.
, A first current mirror circuit 53, a second current mirror circuit 54, a transistor 55, and an amplification circuit 56.
Is known. The first current mirror circuit 53 is a so-called PNP type current mirror circuit. The first current mirror circuit 53 connects the bases of PNP type first and second transistors 58 and 59 to each other, and supplies a direct current through each emitter resistor. Voltage source (Vcc)
And the collector of the first transistor 58 is connected between the connections of the respective bases. The connection between the connection of each base and the collector of the first transistor 58 is an input of the first current mirror circuit 53, and the input is connected to the multiplier 5
0 is connected. The second transistor 5
The collector 9 is the output of the first current mirror circuit 53, and is connected to the base of the transistor 55. The second current mirror circuit 54 is a so-called NPN-type current mirror circuit, which connects the bases of NPN-type first and second transistors 60 and 61 and connects each emitter via a resistor. It is configured by grounding and connecting the connection between the respective bases and the collector of the second transistor 61. The connection between the connection of each base and the collector of the second transistor 61 is:
The input section of the second current mirror circuit 54 is connected to the emitter of the transistor 55. Further, the collector of the first transistor 60 is an output part of the second current mirror circuit 54, and the second transistor 59 of the first current mirror circuit 53 is connected to the base of the transistor 55. Connected to the collector. [0005] The collector of the transistor 55 is connected to the DC voltage source (Vcc) via a resistor 62. The collector of the transistor 55 and the resistor 62
Is connected to the input side of the amplifier circuit 56, and the output side of the amplifier circuit 56 is connected to the output terminal 57. In the conventional current mirror device having such a configuration, the current flowing between the emitter and the collector of the first transistor of the first current mirror circuit 53 in response to the AC signal from the multiplier 50 is the same as that of the current mirror device. A current having a value flows between the emitter and the collector of the second transistor 59. As a result, the current having the same current value also flows between the collector and the emitter of the second transistor 61 of the second current mirror circuit 54. This current is converted into a voltage by the resistor 62 and output as an output voltage via the output terminal 57 via the amplifier circuit 56. Next, a current mirror device as shown in FIG. 5 using a so-called Wilson current mirror circuit together with such a current mirror device is conventionally known. In FIG. 5, the current mirror device is
Multiplier 70 and Wilson current mirror circuit 86
, A current mirror circuit 75, a transistor 76,
An amplifier circuit 77 is provided. The above-mentioned Wilson current mirror circuit 86
Is composed of a first current mirror circuit 73 and a second current mirror circuit 74. The first current mirror circuit 73 connects the bases of the first transistor 79 and the second transistor 80 to each other, and connects each emitter to a DC voltage source (Vcc) via a resistor. It is configured by connecting the base connection and the collector of the second transistor 80. The connection between the connection between the respective bases and the collector of the second transistor 80 is an input of the first current mirror circuit 73. The second current mirror circuit 74 connects the bases of the first transistor 81 and the second transistor 82 to each other and connects the emitter of the first transistor 81 to the first transistor of the first current mirror circuit 73. And the emitter of the second transistor 82 is connected to the input of the first current mirror circuit 73, and the connection between the bases is connected to the collector of the first transistor 81. It is constituted by doing. The connection between the connection between the respective bases and the collector of the first transistor 81 is an input of the second current mirror circuit 74, and is connected to the multiplier 70.
Is connected to The current mirror circuit 75 connects the bases of the first and second transistors 84 and 85 to each other, grounds the emitters of the transistors 84 and 85 via the respective emitter resistors, and connects the base between the bases to each other. It is configured by connecting to the collector of the second transistor 85. A connection between the connection between the bases and the collector of the second transistor 85 is an input of the current mirror circuit 75 and is connected to the collector of the transistor 76. Further, the first transistor 8
4 is connected to the collector of the second transistor 82 of the second current mirror circuit 74 via the base of the transistor 76. The collector of the transistor 76 is connected to the DC voltage source (Vcc) via a resistor 83. The collector of the transistor 76 and the resistor 83
Is connected to the input side of the amplifier circuit 77. In the conventional current mirror device using the Wilson current mirror circuit having such a configuration, the current having a value corresponding to the AC signal from the multiplier 50 is supplied to the first current mirror circuit 74 of the second current mirror circuit 74. Flows between the emitter and collector of the transistor 81 of FIG. Thus, the collector current of the second transistor 80 of the first current mirror circuit 73 and the second transistor 8 are connected between the emitter and the collector of the second transistor 82.
A current of a value obtained by adding the base current of 0 flows. The current flowing through the second transistor 82 is output as the output current of the second current mirror circuit 74. In this Wilson current mirror circuit, the output of the first current mirror circuit 73 can be fed back as the input of the second current mirror circuit 74.
Since the output of the second current mirror circuit 74 can be fed back as the input of the first current mirror circuit 73, the output current from the second current mirror circuit 74 can be stabilized. The output current from the second current mirror circuit 74 thus stabilized is fed back to the input section of the first current mirror circuit 73, and the output current of the transistor 76 and the current mirror circuit 75 This is supplied to one transistor 84. Thereby, the collector of the first transistor 84 of the current mirror circuit 75 is
A current having the same value as the current flowing between the emitters flows through the second transistor 85. This current is converted to a voltage by the resistor 83 and output as an output voltage via the output terminal 78 via the amplifier circuit 77. Here, the amplification factor of the conventional current mirror device shown in FIG. 4 is obtained by converting the resistance value R _IN of the resistor 63 of the multiplier 50 and the current into a voltage. It is determined by the resistance value R _OUT of the resistor 62 to be taken out. That is, the first current mirror circuit 53
, The amplification factor is h _FE , the collector currents of the first and second transistors 58 and 59 are Ic, and each transistor 5
Assuming that the base current of 8,59 is IB, the multiplier 5
The AC signal Iin supplied from 0 is as follows: Iin = Ic + 2IB = Ic + 2Ic / h _FE = Ic (1 + 2 / h _FE ) The first current mirror circuit 53
Output current Iout is expressed as follows: Iout = Ic = Iin / (1 + 2 / h _FE ) This indicates that when the amplification factor (h _FE ) is small, the influence of the temperature characteristic of the amplification factor appears. For this reason, the conventional current mirror device is Ii
There has been a problem that the way of changing Iout with respect to n changes depending on the temperature, and the output varies. Further, in the conventional current mirror device using the Wilson current mirror circuit shown in FIG. 5, the amplification factor is h _FE and the collector current of the first current mirror circuit 73 is the same as that of the Wilson current mirror circuit 86. Ic, assuming that the base current of the first current mirror circuit 73 is 2 IB, the AC signal Iin supplied from the multiplier 70 is Iin = Ic + [(Ic + 2IB) / (1 + h _FE )] = Ic [(1 + h _FE) ) +1] +2 IB × 1 / (1 + h _FE ) = h _FE IB [(1 + h _FE ) +1] +2 IB × 1 / (1 + h _FE ) = IB (h _FE ² + 2h _FE +2) / (1 + h _FE ). The output current Iout of the Wilson current mirror circuit 86 is as follows: Iout = h _FE (Ic + 2IB) / (1 + h _FE ) = h _FE (h _FE IB + 2 IB) / (1 + h _FE ) = IB (h _FE ² + 2h _{FE) ) / (1 + h FE)} = the ^{_{Iin (h FE 2 + 2h FE}} ) / (h FE 2 + 2h FE +2) = Iin / ^{_{[1 + 2 / (h FE 2}} + 2h FE) ]. This indicates that even if the amplification factor slightly changes, the output is not affected, indicating that a stable output can be obtained with little influence of the temperature characteristics. However, the conventional current mirror device using this Wilson current mirror circuit required a voltage of 2 V _BE to drive the Wilson current mirror circuit 86 as shown in FIG. For this reason, the transistors 71 and 72 of the multiplier 70 are saturated, and it is difficult to provide the low-voltage driven electronic device. The current mirror device shown in FIG. 4 uses 1 V to drive the first current mirror circuit 53.
_Since only the voltage of _BE is required, the transistors 51 and 52 of the multiplier 50 do not saturate and can be provided in a low-voltage driven electronic device, but the output varies as described above. The present invention has been made in view of the above problems, and has as its object to provide a current mirror device capable of stabilizing the output and enabling low-voltage driving. I do. According to the present invention, there is provided a current mirror device, wherein a first current mirror circuit and an output transistor of the first current mirror circuit are connected to an input transistor. A second current mirror circuit in which an output transistor is connected to an input transistor of the first current mirror circuit. Further, the semiconductor device has an AC signal input terminal connected to a connection point between the transistor on the output side of the first current mirror circuit and the transistor on the input side of the second current mirror circuit. The current mirror device according to the present invention has a direct current source connected to the input side of the second current mirror circuit. In the current mirror device according to the present invention, the transistor on the input side of the second current mirror circuit is connected to the transistor on the output side of the first current mirror circuit. The transistor on the output side of the second current mirror circuit is connected to the transistor on the input side. An AC signal input terminal is provided at a connection point between the output transistor of the first current mirror circuit and the input transistor of the second current mirror circuit. In the current mirror device according to the present invention, a DC current source is connected to the input side of the second current mirror circuit. The current from the DC current source is I, the current supplied through the AC signal input terminal is ΔIin, the amplification factor is h _FE , the collector current of each transistor of the first current mirror circuit is Ic, The base current of each transistor is 2 IB, and the current Δ supplied from the DC current source I through the AC signal input terminal is Δ
Considering that the current has increased by ΔIc by subtracting Iin, Ic ^, which is the collector current of the first transistor ^, is expressed as Ic ^, = Ic − [(ΔIc + 2ΔIB) / (1+
h _FE )]. Further, DerutaIin a current supplied through the AC signal input terminals, ΔIin = Ic + ΔIc-Ic , = Ic + ΔIc- [Ic- (ΔIc + 2ΔIB) / ( 1 + h FE) ] = ΔIc + [(ΔIc + 2ΔIB) / (1 + h _FE )] = ΔIB (h _FE ² +2 h _FE +2) / (1 + h _FE ). The output current of the current mirror device, ΔIout, is as follows: ΔIout = h _FE (ΔIc + 2ΔIB) / (1 + h _FE ) = h _FE (h _FE ΔIB + 2ΔIB) / (1 + h _FE ) = ΔIB (h _FE ² + 2h _{FE) ) / (1 + h FE)} = a ^{_{(h FE 2 + 2h FE)}} / (h FE 2 + 2h FE +2) = ΔIin / ^{_{[1 + 2 / (h FE 2}} + 2h FE) ]. This indicates that even if the amplification factor slightly changes, the output is not affected. For this reason, a stable output can be obtained with less influence of the temperature characteristic as in the so-called Wilson current mirror circuit. Further, since the AC signal input terminal is connected between the connection between the output section of the first current mirror circuit and the input section of the second current mirror circuit, focusing on the AC signal alone, Set the first current mirror circuit to 1
It can be driven at V _BE , can be driven at low voltage, and is connected to the AC signal input terminal.
For example, it is possible to prevent such a problem that a transistor of another circuit such as a multiplier is saturated. In a low voltage driven integrated circuit, a stable output can be obtained similarly to the Wilson current mirror circuit even if the Wilson current mirror circuit cannot be used due to the potential. Because it is possible, it can contribute to the design of the integrated circuit. Preferred embodiments of the current mirror device according to the present invention will be described below in detail with reference to the drawings. First, the current mirror device according to the first embodiment of the present invention is a PNP type current mirror device as shown in FIG.
, A current mirror circuit 2, a DC current source 3 and an AC signal input terminal 10. The first current mirror circuit 1 has a first
The bases of the transistors 4 and 5 are connected to each other, the emitters of the transistors 4 and 5 are connected to a DC voltage source (Vcc) via resistors 6 and 7, and the bases of the transistors 4 and 5 are connected to each other. Is connected to the collector of the second transistor 5 to form an input section of the first current mirror circuit 1. The second current mirror circuit 2 has a first
The bases of the first transistor 8 and the second transistor 9 are connected to each other, and the emitter of the first transistor 8 is connected to the first transistor 4 of the first current mirror circuit 1.
, And the emitter of the second transistor 9 is connected to the input of the first current mirror circuit 1. In addition, the collector of the second transistor 9 is connected to the output terminal 11 and the connection point of each of the transistors 8 and 9 is connected to the collector of the first transistor 8. 2 input sections are formed. The input of the second current mirror circuit 2 is connected to the other end of the DC current source 3 whose one end is grounded. An AC signal is connected to a connection point between the collector (output unit) of the first transistor 4 of the first current mirror circuit 1 and the emitter of the first transistor 8 of the second current mirror circuit 2. The input terminal 10 is connected. In such a current mirror device,
The current from the DC current source 3 is I, the current supplied through the AC signal input terminal 10 is ΔIin, and the amplification factor is h.
_FE , the collector current of each of the transistors 4 and 5 of the first current mirror circuit 1 is Ic, and the base current of each of the transistors is IB, and I is the current of the DC current source 3.
If the current is increased by ΔIc by subtracting ΔIin, which is the current supplied through the AC signal input terminal 10 from the above, I _{C ′} which is the collector current of the first transistor 4 becomes ] It becomes. The current ΔIin supplied through the AC signal input terminal 10 is as follows: ΔIin = Ic + ΔIc−Ic ^, = Ic + ΔIc− [Ic− (ΔIc + 2ΔIB) / (1 + h _FE )] = ΔIc + [(ΔIc + 2ΔIB) / (1 + h _FE )] = ΔIB (h _FE ² +2 h _FE +2) / (1 + h _FE ) (2) The output current ΔIout of the current mirror device is ΔIout = h _FE (ΔIc + 2ΔIB) / (1 + h _FE ) = h _FE (h _FE ΔIB + 2ΔIB) / (1 + h _FE ) = ΔIB (h _FE ² +2 h _FE) ) / become _{(1 + h FE) = (} h FE 2 + 2h FE) / (h FE 2 + 2h FE +2) = ΔIin / ^{_{[1 + 2 / (h FE 2}} + 2h FE) ] (3 equation). From equations (1) to (3), it can be seen that focusing only on the AC signal, even if the amplification factor slightly changes, the output is not affected. For this reason, the current mirror device according to the present embodiment can obtain a stable output with little influence of the temperature characteristic as in the so-called Wilson current mirror circuit. Since the AC signal input terminal is connected between the output of the first current mirror circuit 1 and the input of the second current mirror circuit 2, the DC voltage source (Vcc) to the input section (ΔIin) of the second current mirror circuit 2 can be driven with at least 1 V _BE . Accordingly, low-voltage driving can be performed, and inconvenience such as saturating a transistor of another circuit such as a multiplier connected to the AC signal input terminal 10 can be prevented. In a low-voltage driven integrated circuit, even if a Wilson current mirror circuit cannot be used due to the potential, by providing the current mirror device, a stable output can be obtained similarly to the Wilson current mirror circuit. In addition, low-voltage driving can be performed, which can contribute to the design of the integrated circuit. Next, the current mirror device according to the second embodiment of the present invention is an NPN type current mirror device as shown in FIG.
A second current mirror circuit 22, a DC current source 23,
An AC signal input terminal 30 is provided. The first current mirror circuit 21 connects the bases of the first and second transistors 28 and 29 to each other, and connects the connection point between the bases and the second transistor 2.
9 to form an input section of the first current mirror circuit 21 and to connect the emitters of the transistors 28 and 29 to ground via resistors 26 and 27, respectively. . The second current mirror circuit 22 connects the bases of the first and second transistors 24 and 25 to each other, and connects the connection point between the bases and the first transistor 2.
4 to form an input section of the second current mirror circuit 22. The input section (collector) of the second current mirror circuit 22 is connected to one end of a DC current source 23, and the other end of the DC current source 23 is connected to a DC voltage source (Vcc).
Is connected to The collector of the second transistor 25, which is the output of the second current mirror circuit 22, is connected to the output terminal 31. Further, the emitter of the first transistor 24 is connected to the collector (output unit) of the first transistor 28 of the first current mirror circuit 21, and the emitter of the second transistor 25 is connected to the second transistor 25. 1 current mirror circuit 2
It is connected to the collector (input section) of one second transistor 29. The AC signal input terminal 30 is connected to the first transistor 28 of the first current mirror circuit 21.
Of the second current mirror circuit 22 and the emitter of the first transistor 24 of the second current mirror circuit 22. The NPN-type current mirror device having such a configuration also has a relationship between Iin and Iout as shown in the above-mentioned equations (1) to (3), similarly to the PNP-type current mirror apparatus according to the first embodiment. become. For this reason, the current mirror device can also obtain the same effect as the current mirror device according to the above-described first embodiment. Next, as shown in FIG. 3, the current mirror device according to the third embodiment of the present invention includes a multiplier 41 serving as an AC signal supply source and the current mirror device according to the first embodiment. , A PNP-type current mirror device 40, a current mirror circuit 42, and an amplifying circuit 4
4. Since the current mirror device 40 has the same configuration as the current mirror device according to the above-described first embodiment, the same reference numerals are given to portions exhibiting the same operations, and detailed description thereof will be omitted. That is, in the current mirror device according to the third embodiment, the multiplier 41 is connected to the AC signal input terminal 10 of the current mirror device 40, and the output terminal 1
1, a current mirror circuit 42 is connected. The current mirror circuit 42 includes first to third transistors 49, 47a, 47b. The second and third transistors 47a and 47b are
Each base is connected to each other, and each emitter is connected to a resistor 48
a, 48b are grounded. The connection point between the bases and the collector of the second transistor 47b are connected to form an input portion. The emitter of the first transistor 49 is connected to the input section (collector). The base of the first transistor 49 is connected to the output terminal 11 of the current mirror device 40, and the collector is connected to a DC voltage source (Vcc) via a resistor 43. The input terminal of the amplifier circuit 44 is connected between the connection between the resistor 43 and the collector of the first transistor 49, and the output terminal of the amplifier circuit 44 is connected to the output terminal 45. I have. In the current mirror device according to the third embodiment having such a configuration, the current corresponding to the AC signal from the multiplier 41 flows as if reflected on the output terminal 11 side. The current flowing to the side of the current mirror circuit 42 flows like a mirror image to the first transistor 49 side. This current is converted into a voltage by the resistor 43, amplified with a predetermined gain by an amplifier circuit 44, and output via an output terminal 45. As described above, the current mirror device 4
0 can obtain a stable output as a stable amplification factor without being affected by the temperature characteristics of the amplification factor.
Second current mirror circuit 2 from DC voltage source (Vcc)
Can be driven with a minimum of 1 V _BE up to the input section (ΔIin). Accordingly, low voltage driving can be performed, and inconveniences such as saturating the transistors 46a and 46b of the multiplier 41 connected to the AC signal input terminal 10 can be prevented. In the above description of the third embodiment, the multiplier 41 is provided as an AC signal supply source. However, the multiplier 41 may be anything as long as it can supply an AC signal. The voltage is converted into a voltage by using the resistor 43, and the voltage is taken out. Of course, the voltage may be taken out as a current. The current mirror device according to the present invention comprises a transistor on the output side of the first current mirror circuit and a second current mirror circuit.
Since the AC signal input terminal is provided at the connection point of the current mirror circuit with the transistor on the input side, low-voltage driving with at least 1 V _BE can be performed. Further, it is possible to prevent such a disadvantage that the transistor of another circuit, such as a multiplier, connected to the AC signal input terminal is saturated. As in the case of the so-called Wilson current mirror circuit, the amplification factor is not affected by the temperature characteristics.
A stable output can be obtained. In a low-voltage driven integrated circuit, even if a Wilson current mirror circuit cannot be used because of the potential, a stable output can be obtained similarly to the Wilson current mirror circuit. Because it is possible, it can contribute to the design of the integrated circuit.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a circuit diagram showing a PNP-type current mirror device according to a first embodiment of the present invention. FIG. 2 is a circuit diagram showing an NPN-type current mirror device according to a second embodiment of the present invention. FIG. 3 is a circuit diagram showing a current mirror device according to a third embodiment of the present invention in which a multiplier, an amplifier circuit, and the like are connected to the PNP-type current mirror device. FIG. 4 is a circuit diagram of a conventional current mirror device. FIG. 5 is a circuit diagram of a conventional current mirror device using a Wilson current mirror circuit. [Description of Signs] 1,21 First current mirror circuit 2,22 Second current mirror circuit 3,23 DC current source 4,28 First transistor 5,29 of first current mirror circuit First current Second transistor 6, 7, 26, 27 of mirror circuit Resistance 8, 24 First transistor 9, 25 of second current mirror circuit Second transistor 10, 30 of second current mirror circuit AC signal input terminal 11, 31 Output terminal 41 Multiplier 40 Current mirror device 42 Current mirror circuit 43 Resistance 44 Amplifier circuit 45 Output terminal

Claims (1)

(57) [Claim 1] A first current mirror circuit, and an input transistor is connected to an output transistor of the first current mirror circuit, and the first current mirror circuit is connected to the first current mirror circuit. A second current mirror circuit in which an output transistor is connected to the input transistor of the second current mirror circuit; an output transistor of the first current mirror circuit; and an input transistor of the second current mirror circuit. An AC current signal input terminal connected to the connection point; and an AC current signal input terminal connected to the input side of the second current mirror circuit.
A current mirror device comprising a current source .