JP2665840B2 - Voltage-current converter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a voltage-current conversion circuit for converting a voltage into a current.

[0002]

2. Description of the Related Art FIG. 2 is a circuit diagram of a conventional voltage-current conversion circuit of this kind. The voltage V _I to be converted to a current is input to the positive input terminal + of the operational amplifier 5, and the output is input to the base of the transistor 1. The emitter of the transistor 1 is grounded via the resistor 4, and the voltage V
₂ is input to the negative input terminal-of the operational amplifier 5.

The collector of the transistor 1 is connected to the collector and the base of the transistor 2, and the transistor 2
Are connected to a constant voltage power supply V _CC . Base and emitter of the transistor 3 is connected to the base and emitter of the transistor 2, from its collector, and outputs a current I ₀ obtained by converting the voltage into a current.

Next, the operation of the voltage-current conversion circuit will be described. Here, the current flowing through the resistor 4 and I _1, and the resistance value of the resistor 4 and R _1, since the input terminal of the operational amplifier 5 is the imaginary short, the voltage V _I and V ₂
Is as follows: V _I = V ₂ (1)

The current I ₁ flowing through the resistor 4 is
Is R ₁ , then I ₁ = V ₂ / R ₁ = V _I / R ₁ (2).

Since the transistors 2 and 3 are current mirror connected, the relationship between the currents I ₀ and I ₁ is I ₁ = I ₀ (3).

When the current I ₀ is represented by the voltage V _I , I ₀ = V _I / R ₁ (4) In this manner, it converts the voltage V _I given to the positive input terminal of the operational amplifier 5 + current I _0.

[0008]

The conventional voltage-current conversion circuit uses an operational amplifier having a complicated circuit configuration.
There is a problem that the circuit is complicated and the response is poor due to the need for phase compensation. The present invention has been made in view of the above problems, and has as its object to provide a voltage-current conversion circuit that does not need to perform phase compensation and has good responsiveness.

[0009]

The collector of the first transistor and the emitters of the fifth, sixth, seventh and eighth transistors are connected to a constant voltage power supply. The emitter of the first transistor is grounded via the tenth and eleventh transistors connected in parallel. The collector of the fifth transistor is connected to the base of the fourth transistor and the collectors of the tenth and eleventh transistors via the second and third transistors connected in series.

The collector of the sixth transistor is grounded via the fourth transistor connected in series and a resistor. The collector of the seventh transistor is connected to the base of the ninth transistor, and is grounded via the ninth transistor. Fifth, sixth, seventh, and eighth transistors are current mirror connected,
The ninth, tenth, and eleventh transistors are connected in a current mirror, a voltage to be converted to a current is input to the base of the first transistor, and a current obtained by converting the voltage to a current is output from the collector of the eighth transistor. I do.

[0011]

Since the fifth, sixth, seventh, and eighth transistors are current mirror connected, the current of the fifth transistor is I ₃ , the current of the sixth transistor is I ₁ , and the current of the seventh transistor is I ₃ Assuming that I ₂ , the current I ₀ flowing through the eighth transistor is I ₀ = I ₁ = I ₂ = I ₃ (5).

Since the ninth, tenth, and eleventh transistors are current mirror connected, the sum of the currents flowing through the tenth and eleventh transistors, I _4, is I ₄ = 2 × I ₂ = 2 × I ₀ … (6)

The current I ₄ is the current I ₄ of the first transistor.
₅ and the current I ₃ of the second transistor, the result is I ₄ = I ₅ + I ₃ = I ₅ + I ₀ (7).

From equations (6) and (7), I ₅ = I ₄ −I ₀ = 2 × I ₀ −I ₀ = I ₀ (8), and I ₀ = I ₁ = I ₂ = I ₃ = I ₅ (9)

Since the first, second, third and fourth transistors are biased by the same current, the respective base-emitter voltages are equal. If this voltage is V _F , the respective emitter voltages are V ₃ , V ₄ , V ₅ , and V _6, and the voltage to be converted to a current is V _I , V ₃ = V _I −V _F (10) V ₄ = V ₃ + V _F (11) V ₅ = V ₄ + V _F (12) V ₆ = V ₅ −V _F (13)

According to equations (10) to (13), the emitter voltage V ₆ of the fourth transistor becomes V ₆ = V _I (14), and the voltage applied to the resistor 4 and the voltage applied to the first transistor 6 The voltage V _I becomes equal, and the current I ₁ of the fourth transistor becomes I ₁ = V _I / R ₁ (15) where R ₁ is the resistance value of the resistor 4.

Since the sixth transistor and the eighth transistor are current-mirror connected, I ₀ = I ₁ = V _I / R ₁ (16), and the current I ₀ according to the voltage applied to the resistor 4 is obtained. Obtained from the eighth transistor. Thus, the voltage-converted current responds at a high speed to the voltage to be converted to current.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings showing the embodiments. FIG. 1 is a circuit diagram of a voltage-current conversion circuit according to the present invention. The collector of the first transistor T1 to which the voltage to be converted into the current is input to the base is connected to the constant voltage power supply V _CC , the emitter is the emitter of the second transistor T2,
The collector of the tenth transistor T10 and the eleventh transistor T1
Connected to 1 collector.

The collector of the second transistor T2 is connected to its base and the emitter of the third transistor T3. The collector of the third transistor T3 has its base and
It is connected to the base of the fourth transistor T4 and the collector of the fifth transistor T4. The emitter of the fifth transistor T5 is connected to the constant voltage power supply V _CC . The emitter of the fourth transistor T4 is grounded via the resistor 4,
The collector is connected to the collector and the base of the sixth transistor T6, and the emitter of the sixth transistor T6 is connected to the constant voltage power supply V _CC .

The emitter of the seventh transistor T7 is connected to the constant-voltage power supply V _CC, its collector ninth transistor T9
Connected to the base and collector. The emitter of the eighth transistor T8 is connected to the constant-voltage power supply V _CC, the current I ₀ is made to flow out converted from its collector voltage V _I to the current.

Fifth, sixth, seventh and eighth transistors TT, T
The bases of 6, T7 and T8 are commonly connected. The emitter of the ninth transistor T9 is grounded, and its base is commonly connected to the bases of the tenth and eleventh transistors T10 and T11. The first, second, third, and fourth transistors T1, T2, T3, T4 are all formed in the same shape.

Fifth, sixth, seventh and eighth transistors
T5, T6, T7 , and T8 are all formed in the same shape. Further, the ninth, tenth, and eleventh transistors T9, T10, T11 are all formed in the same shape. The fifth, sixth, seventh, eighth
The transistors T5, T6, T7, T8 are in a current mirror connection, and the ninth, tenth, and eleventh transistors T9, T10, T11 are in a current mirror connection.

Next, the operation of the voltage-current conversion circuit thus configured will be described. Here, the current flowing through the collector of the ninth transistor T9 is I ₂ , the current flowing through the collector of the fifth transistor T5 is I ₃ , and the tenth and eleventh transistors T10 and T11
I ₄ , the sum of the currents of the collectors of the first and second transistors
The current flowing through the emitter of T1 is I ₅ , and the first transistor T1
The emitter voltage V _3, the emitter voltage of the third transistor T3 V _4, V ₅ the base voltage of the fourth transistor T4,
The emitter voltage of the fourth transistor T4 and V _6.

Fifth transistor T5 and sixth transistor
Since the transistor T6, the seventh transistor T7, and the eighth transistor T8 have the same shape and are current mirror connected,
The current I ₀ flowing through the collector of the transistor T8 is I ₀ = I ₁ = I ₂ = I ₃ (17)

Since the ninth transistor T9, the tenth transistor T10, and the eleventh transistor T11 have the same shape and are current mirror connected, the tenth transistor T10,
The current I ₄ of the sum of the currents of the collectors of the eleventh transistor T11
Is I ₄ = 2 × I ₂ = 2 × I ₀ (18)

Since the current I ₄ is the sum of the current I _{5 at} the emitter of the first transistor T 1 and the current I _{3 at} the collector of the fifth transistor T 5, I ₄ = I ₅ + I ₃ = I ₅ + I ₀ . 19)

[0027] Then the equation (18) and (19), the current I ₅ of the emitter of the first transistor _{T1 I 5 = I 4 -I 0} = 2 × I 0 -I 0 = I 0 ... (20) becomes From these equations, the current I _{0 at} the emitter of the eighth transistor T8 is expressed as follows: I ₀ = I ₁ = I ₂ = I ₃ = I ₅ (21)

First transistor T1, second transistor T
Since the second transistor T3 and the fourth transistor T4 have the same shape, they are respectively biased by the same current, so that the base-emitter voltages of the transistors T1, T2, T3 and T4 are equal. Therefore, the base, the emitter voltage and V _F, the emitter voltage V of the first transistor T1
₃ , the emitter voltage V ₄ of the third transistor T3, the collector voltage V ₅ of the fifth transistor T5, and the emitter voltage V ₆ of the fourth transistor T4

V ₃ = V _I -V _F (22) V ₄ = V ₃ + V _F (23) V ₅ = V ₄ + V _F (24) V ₆ = V ₅ -V _F (25) Become.

From the equations (22) to (25), V ₆ = V _I (26) is obtained, and the voltage applied to the resistor 4 and the voltage V to be converted into the current input to the base of the first transistor T1 are obtained. _I becomes equal, and the current I ₁ flowing through the resistor 4 becomes I ₁ = V _I / R ₁ (27).

Sixth transistor T6 and eighth transistor
T8 is the same shape, since the current mirror connection, the voltage V _I to be input to the base of the first transistor T1 as the following equation is converted into a current I ₀ flowing through the collector of the eighth transistor T8. I ₀ = I ₁ = V _I / R ₁ (28)

The voltage-current conversion circuit configured as described above
Since all transistors are used and no operational amplifier is used, the circuit is simplified, and there is no need to perform phase compensation by negative feedback, so that the converted current responds quickly to the voltage converted to current. Become.

[0033]

As described in detail above, the voltage-current conversion circuit of the present invention makes the voltage applied to the resistor provided for converting a voltage to a current equal to the voltage to be converted to a current, Since a voltage-converted current is obtained from a transistor biased with a current equal to the current flowing through the resistor, an operational amplifier is not required and the circuit is simplified. Also, since there is no need to perform phase compensation, it is possible to respond to a high speed. Therefore, according to the present invention, there is an excellent effect that a voltage-current conversion circuit having extremely good responsiveness can be provided.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a voltage-current conversion circuit according to the present invention.

FIG. 2 is a circuit diagram of a conventional voltage-current conversion circuit.

[Explanation of symbols]

4 resistor T1 first transistor T2 second transistor T3 third transistor T4 fourth transistor T5 fifth transistor T6 sixth transistor T7 seventh transistor T8 eighth transistor T9 ninth transistor T10 tenth transistor T11 eleventh transistor T12 twelfth transistor V _CC constant voltage power supply

Claims (1)

(57) [Claims] 1. A voltage-current conversion circuit for converting a voltage to a current, wherein a voltage to be converted to a current is input to a base, a first transistor having a collector connected to a constant voltage power supply, and an emitter connected to the first transistor. A second transistor connected to the emitter of the transistor;
Third connected to the base and collector of the transistor
A transistor, a fourth transistor having a base connected to a base and a collector of the third transistor,
A fifth transistor having a collector connected to the base of the fourth transistor and an emitter connected to the constant voltage power supply; a base and a collector connected to the base of the fifth transistor and a collector of the fourth transistor; Are connected to the constant voltage power supply, the base is connected to the base of the sixth transistor, the emitter is connected to the constant voltage power supply, the base is connected to the base of the seventh transistor, and the emitter is connected to the base of the seventh transistor. An eighth transistor connected to the constant voltage power supply and outputting a current obtained by converting the voltage from a collector; a resistor interposed between an emitter of the fourth transistor and a predetermined potential; Connect to the collector of the transistor,
A ninth transistor having an emitter connected to a predetermined potential, a tenth transistor having a base connected to the base of the ninth transistor, an emitter connected to a predetermined potential, and a collector connected to the emitters of the first and second transistors; And a base connected to the bases of the tenth and ninth transistors, and an eleventh transistor connected in parallel with the tenth transistor.