JPH0323691Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a voltage-current converter, and particularly to a voltage-current converter that can be used by reversing the polarity of the output current.

(Prior Art) As shown in FIG. 4, a conventional voltage-current converter is composed of an impedance circuit including a resistor, etc., and a predetermined voltage V ₁ is applied to this impedance circuit to convert the voltage V ₁ into Current I determined by impedance Z of the impedance circuit (I=V ₁ /Z)
is being converted to . Therefore, the applied voltage can be proportionally converted into current.

(Problems to be Solved by the Invention) However, simply constructing the voltage-current converter from an impedance circuit only provides an output current I having a polarity in one direction, as shown in FIG. For this reason, conventionally it was necessary to prepare two types of voltage-current converters with different output current polarities, and to configure various circuits by selecting one of the voltage-current converters depending on the usage mode. It was hot.
In addition, in electronic devices that use current with reversed polarity, it is necessary to incorporate two types of voltage-current converters with different polarities and add a polarity switching means, making the circuit configuration of electronic devices complicated. It had the disadvantage of being expensive.

The present invention has been made to solve these problems, and an object of the present invention is to provide a voltage-current converter having a configuration in which the polarity of the output current can be reversed.

(Means for Solving the Problems) FIG. 1 is a block diagram showing the configuration of the present invention, in which first and second voltage-current conversion circuits 2 and 3 are connected in parallel to a variable voltage source 1. has been done. The variable voltage source 1 outputs a reference voltage V ₀ , a set voltage Vh larger than the reference voltage, and a set voltage Vl smaller than the reference voltage.

The first voltage-current conversion circuit 2 outputs an output current _I0 when a reference voltage _V0 is applied, and further outputs an output current Ih which increases proportionally when a set voltage Vh is applied.

The second voltage-current conversion circuit 3 outputs an output current I ₀ at the same level when a reference voltage V ₀ is applied, and an output current Il which increases proportionally when a set voltage Vl is applied.
Output.

The polarity inversion circuit 4 is the first voltage-current conversion circuit 2
The polarities of the output currents I ₀ and Ih are inverted to output polarity-inverted output currents I ₀ ' and Ih'.

From the output terminal 5, the output of the polarity inversion circuit 4 and the second
and the output current of the voltage-current conversion circuit 3 are added together and output.

(Function) When the variable voltage source 1 outputs the reference voltage V ₀ , the first and second voltage-current conversion circuits 2 and 3 output the same level of output current I ₀ . On the other hand, the polarity of the output current _I0 of the first voltage-current conversion circuit 2 is reversed by the polarity reversal circuit 4, resulting in a polarity reversal output current.
It is output as I ₀ ′. Therefore, since the output currents I ₀ and I ₀ ′ of the same level with different polarities are added,
No current is output from the output terminal 5 when the reference voltage V ₀ is applied.

When the variable voltage source 1 outputs the set voltage Vh, the first voltage-current conversion circuit 2 outputs an output current Ih with a large level. And this output current Ih
The polarity of is inverted by the polarity inverting circuit 4 and becomes a polarity inverted output current Ih'. On the other hand, the level of the output current of the second voltage-current conversion circuit 3 decreases when the set voltage Vh is applied. Therefore, since the low-level output current output from the second voltage-current conversion circuit 3 and the high-level polarity inverted output current Ih' are added, a polarity-inverted current Ih is output from the output terminal 5. ' is output.

When the variable voltage source 1 outputs the set voltage Vl, the second voltage-current conversion circuit 3 outputs an output current Il with a large level. On the other hand, the level of the output current of the first voltage-current conversion circuit 2 is reduced by application of the set voltage Vl, and the polarity of this output current is inverted by the polarity inversion circuit 4. Therefore, since this small output current with the reversed polarity level and the large output current Il with the above level are added, the output terminal 5
A current I whose polarity is not reversed is output from the terminal.

In the block diagram of FIG. 1, the polarity inversion circuit 4
may be connected to the second voltage-current conversion circuit 3, and the polarity of its output current may be reversed.

(Embodiments of the invention) Hereinafter, embodiments of the invention will be described in detail with reference to the drawings.

The voltage-current converter according to the present invention includes a variable voltage source 10, as shown in FIG. This variable voltage source 10 has a power supply 10a and a variable resistor 10b, and a pnp transistor constituting the first power supply-current conversion circuit 11 is connected to the connection terminal 10c.
The base of Q ₅ is connected. Transistor Q ₅
has an emitter follower configuration in which the emitter is connected to the power supply terminal 15 via a resistor _R5 , and the base of an npn transistor _Q6 is connected to this emitter. The emitter of transistor Q ₆ is resistor R ₆
is grounded through.

The collector and base of a pnp transistor Q ₇ forming the polarity inversion circuit 13 are connected to the collector of the transistor Q ₆ . The emitter of this transistor _Q7 is connected to the power supply terminal 15 through the resistor _R7 .
connected to another pnp transistor at its base
Q ₈ base is connected. The emitter of this transistor _Q8 is connected to the power supply terminal 15 through a resistor _R8 .
, and its collector is connected to the output terminal 14. These transistors Q ₇ and Q ₈ have the same characteristics and constitute a current mirror circuit together with resistors R ₇ and R ₈ .

Further, the connection terminal 10c of the variable voltage source 10 is connected to an NPN that constitutes the second voltage-current conversion circuit 12.
The base of transistor Q ₁ is connected. This transistor _Q1 has an emitter follower configuration in which the emitter is grounded via a resistor _R1 . The base of a pnp transistor _Q2 is connected to the emitter of this transistor _Q1 , and the collector and base of an npn transistor _Q3 are connected to the collector of this transistor _Q2 . The base of this transistor _Q3 is connected to the base of an npn transistor _Q4 . The emitters of transistors Q ₃ and Q ₄ are grounded via resistors R ₂ and R ₃ . These transistors Q ₃ and Q ₄ have the same characteristics and constitute a current mirror circuit together with resistors R ₂ and R ₃ . The collector of the transistor Q ₄ is connected to the transistor Q ₈ which constitutes the polarity inversion circuit 13.
It is connected to the connection point between the collector of the output terminal 14 and the output terminal 14 .

Note that the collector of transistor Q ₁ is current terminal 1.
5, and the emitter of transistor Q ₂ is connected to power supply terminal 15 via resistor R ₄ .

Next, the operation of the voltage-current converter of the present invention will be explained.

When the variable resistor 10b of the variable voltage source 10 is operated to output an arbitrary voltage Vin, this voltage Vin is applied to the base of the transistor _Q1 in the second voltage-current conversion circuit 12. ₁ operates and its emitter current controls the base current of transistor _Q2 . Therefore, a current I ₁ expressed by the following equation flows through the collector of this transistor Q ₂ .

I ₁ = (Vcc - Vin) / R ₄ ...... (1) (However, Vcc is the power supply voltage applied to the power supply terminal 15.) This current I ₁ is supplied to the transistor Q ₃ , so this transistor Q A current _{I 2} having the same level as the current I ₁ flows through the collector of the transistor Q ₄ which together with Q ₃ forms a current mirror circuit. Therefore, the output current of the second voltage-current conversion circuit 12 is
I ₂ , and this output current I ₂ can be expressed by the following equation.

_I2 = _I1 =(Vcc-Vin)/ _R4 ...(2) On the other hand, the voltage Vin of the variable voltage source 10 is also applied to the base of the transistor _Q5 of the first voltage-current conversion circuit 11. Therefore, transistor Q ₅
Since the base current of transistor Q ₆ is controlled by the operation of , current I ₃ flows through the collector of transistor Q ₆ . This current _I3 becomes the output current of the first voltage-current conversion circuit 11, and can be expressed by the following equation.

I ₃ = Vin/R ₆ ......(3) Since this output current I ₃ is output via the transistor Q ₇ of the polarity inverting circuit 13, other current mirror circuits are configured together with this transistor Q ₇ . In the collector of transistor Q ₈ there is an output current I ₃
A polarity reversal current I ₄ of the same level flows. Therefore, this polarity reversal current I ₄ can be expressed by the following equation.

I ₄ = I ₃ = Vin/R ₆ ......(4) Therefore, the output current I ₂ and the polarity reversal current I ₄ are added and output from the output terminal 14, so the output current I ₅ is as follows. It becomes like the formula.

I ₅ = I ₄ − I ₂ = Vin / R ₆ − (Vcc − Vin) / R ₄ = (R ₄ + R ₆ ) / R ₄ R ₆ {Vin − R ₆ / (R ₄ + R ₆ )
×Vcc}...(5) From the above, in order for the output current _I5 to become zero, it is sufficient to set Vin=Vcc× _R6 /( _R4 + _R6 ). In other words, the resistance values of resistors R ₄ and R ₆ and the power supply voltage
By setting Vcc, the output current I ₅ of the voltage-to-current converter becomes zero by setting the variable voltage V ₀ (see Figure 3).
can be set arbitrarily.

Then, when a set voltage with a level higher than the reference voltage V ₀ is applied from the reference voltage source 10 in this way,
The output current _I3 of the first voltage-current conversion circuit 11 increases and its polarity is reversed to become the output current _I4 , and the output current _I2 of the second voltage-current conversion circuit 12 decreases, so that the output The current I ₅ becomes I ₅ >0. Furthermore, when a set voltage with a level smaller than the reference voltage V ₀ is applied, the output current of the first voltage-current conversion circuit 11 increases.
Since I ₃ decreases and its polarity is reversed, and the output current I ₂ of the second voltage-current conversion circuit 12 increases, the output current I ₅ becomes 0<I ₅ . Therefore, variable voltage source 1
By changing the set voltage of 0 around the reference voltage V ₀ , a bipolar output current I ₅ is obtained.

(Effect of the invention) According to the invention, the output current of the first voltage-current conversion circuit is increased by applying a set voltage with a level higher than the reference voltage using a variable voltage source, or the output current of the first voltage-current conversion circuit is increased, or the setting voltage with a level lower than the reference voltage is applied. By applying a voltage, the output current of the second voltage-current conversion circuit is increased, and the other output current whose polarity has been reversed by the polarity inverting circuit is added to one output current and outputted. , output currents with different polarities can be obtained with a simple circuit configuration. Therefore, it can be used by incorporating it into various circuits as it is by adapting it to the polarity of the current, and even if it is an electronic device that uses the polarity of the current inverted, it can be incorporated without complicating the circuit configuration. I can do it. Furthermore, since it has a circuit configuration suitable for integration, it has the advantage of being able to miniaturize electronic devices and the like.

[Brief explanation of the drawing]

Figure 1 is a block diagram showing the configuration of the present invention;
The figure is a circuit diagram of a voltage-current converter according to an embodiment of the present invention, FIG. 3 is a diagram showing the output characteristics of the voltage-current converter of FIG. 2, and FIGS. FIG. 1 is a schematic diagram of a voltage-current converter and a diagram showing its output characteristics. 10... Variable voltage source, 11, 12... First and second voltage-current conversion circuits, 13... Polarity inversion circuit, 14... Output terminal.

Claims (1)

[Scope of utility model registration request] a variable voltage source, and a first voltage that outputs a current at a predetermined level when a reference voltage is applied from the variable voltage source and proportionally increases the output current when a set voltage higher than the reference voltage is applied. a current conversion circuit; and a second voltage-current conversion circuit that outputs the current at the predetermined level when the reference voltage is applied and proportionally increases the output current when a set voltage that is lower than the reference voltage is applied. and a polarity inversion circuit that inverts the polarity of the output current of either one of the first and second voltage-current conversion circuits, and the output currents having different polarities are added and output. Voltage-to-current converter.