JP3396524B2 - Voltage-current conversion circuit - 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 which outputs a change in voltage as an input as a change in current, and more specifically, in a semiconductor integrated circuit, a voltage control amplifier circuit (hereinafter referred to as VCA (Voltage). -Controlled Amplifi
er). ) Is connected to the input stage and outputs a current or the like as an input signal thereof.

[0002] In recent years, as the use range of semiconductor devices has been expanding, as a characteristic of a semiconductor circuit that constitutes each semiconductor device, a characteristic of outputting an output signal with little distortion to an input signal with a high voltage amplitude. Is required.

Among such semiconductor circuits, a voltage-current conversion circuit is one of the commonly used basic circuit configurations.

[0004]

2. Description of the Related Art As a conventional voltage-current conversion circuit,
A circuit using semiconductor elements such as transistors as a differential pair is generally used.

FIG. 3 shows a first prior art voltage-current conversion circuit using a transistor differential pair. The voltage-current conversion circuit in FIG. 3 is an npn bipolar transistor 10
1 and 102, a fixed resistor 103 and constant current sources 104 and 105, an input bias voltage 106, and a power supply V _CC , which are applied to the base terminals of the transistors 101 and 102. Output current I _OUT corresponding to the input voltage V _IN
02 collector current.

As a source of distortion in this prior art,
Distortion of the output current I _OUT due to the non-linearity of the base-emitter voltage of the transistors 101 and 102 (hereinafter, the base-emitter voltage is referred to as V _BE ) can be considered. Regarding this, in the range where the input voltage V _IN is small, the distortion component due to the non-linearity of V _BE causes the output current I _OUT.
, The distortion rate as the output current I _OUT becomes small.

However, when the input voltage V _IN is in a large range, the distortion component due to the non-linearity of V _BE becomes large, and this distortion component has a large effect on the output current I _OUT. The saturation of 105 prevents the output current I _OUT from changing even when the input voltage V _IN changes, so that the distortion rate of the output current I _OUT as a whole increases.

Therefore, as a voltage-current conversion circuit for solving the above-mentioned problems, there is a second prior art voltage-current conversion circuit shown in FIG. The voltage-current conversion circuit in FIG.
Pnp type bipolar transistors 201, 202,
211, 212, 221, 222 and constant current source 203,
Two differential pairs 200, 210, 2 by 215, 223
20 are respectively configured to include transistors 201 and 22.
The input voltage V _IN is applied to the respective base terminals of No. 2. The output current I _OUT is obtained as the collector current of the transistor 211.

V _BE of each transistor in the prior art
With respect to the distortion due to the non-linearity of, the circuit uses the base terminals of the transistors 201 and 222 as the non-inverting input terminals,
The base terminals of the transistors 202 and 221 serve as inverting input terminals, and the emitter terminals of the transistors 211 and 212 serve as output terminals.
Since 100% of negative feedback is applied, assuming that the open loop gain of the negative feedback circuit is G _OP , the distortion due to the non-linearity of V _BE is compressed to almost 1 / G _OP , and thus the output current with a low distortion rate is obtained. I _OUT is obtained.

[0010]

However, in the second prior art, since the voltage-current conversion resistors 213 and 214 are inserted in series in the output current path, the effect of loss due to these resistors and the constant current source. There is a problem that the dynamic range of the input voltage V _IN is narrowed due to the influence of the voltage required for the operation of 215.

An object of the present invention is to provide a voltage-current conversion circuit which eliminates the influence of distortion of the V _BE of the transistor on the output current I _OUT due to the non-linearity and does not narrow the dynamic range.

[0012]

In order to solve the above problems, the invention described in claim 1 has an input terminal of a current mirror circuit connected to a high potential side power source, as shown in FIG. 1, for example. between the low potential side power supply, a control terminal connected to an output end of the current mirror circuit Rutotomoni input terminal said
A first semiconductor element connected to the input end, and one end of which is the first semiconductor element
It is connected to the output terminal of the semiconductor element and the other end is
It is connected to the power supply on the potential side and flows to the current mirror circuit.
Constant current source that generates a constant current that is uncorrelated with the current
When, a series circuit consisting of is formed, from said entering-force end
Between the low-potential-side power supply and before Kide force terminal for outputting a current having a substantially equal current value and the current input to the first semiconductor element, first have physical properties similar to the first semiconductor element Two semiconductor elements and a bias voltage with a fixed voltage value
A series circuit including a bias power supply for generating the input voltage is formed between the input terminal to which the input voltage to be converted is input and the output terminal of the first semiconductor element .
An input resistance for converting a change into a change in current is connected to the input resistance.

According to a second aspect of the invention, for example, as shown in FIG. 1, the base terminal is between the input terminal of the current mirror circuit connected to the high potential side power source and the low potential side power source. It is connected to the output terminal of the circuit Rutotomoni collection
Current amplifying transistor whose data terminal is connected to the input end, and one end of which is the emitter end of the current amplifying transistor.
And the other end is connected to the low potential side power source.
And is uncorrelated with the current flowing through the current mirror circuit
A constant current source for generating a constant current, the series circuit consisting of is formed of, said current amplifying transistor from the entering force end
Wherein the front Kide force terminal for outputting a current having a substantially equal current value and the current input to the motor between a low-potential-side power supply, the base of the current amplifying transistor - the same voltage characteristics and emitter voltage characteristic With a semiconductor element having a fixed voltage
A bias power source for generating a bias voltage, the series circuit formed consisting of the input voltage to be converted is input
Emitter of said current amplifier transistor and the input terminal being
The input voltage change to a current change between the input and output terminals.
It is characterized in that an input resistance to be exchanged is connected.

[0014]

According to the invention described in claim 1, for example, as shown in FIG. 1, the input resistance converts a change in the input voltage into a change in the current flowing through the input resistance.

The constant current source keeps the current value of the input current of the first semiconductor element and the current flowing through the input resistance constant. As a result, the input current of the first semiconductor element changes corresponding to the change of the current flowing through the input resistance, and the output current of the first semiconductor element also changes corresponding to the change of the current flowing through the input resistance.

The bias power source provides a bias voltage for fixing the potential of the control terminal of the first semiconductor element. The current mirror circuit supplies a current having a magnitude substantially equal to the output current of the first semiconductor element to the second semiconductor element in order to operate the first semiconductor element and the second semiconductor element under the same condition.

Since the second semiconductor element is manufactured so as to have the same physical characteristics as the first semiconductor element, the second semiconductor element compensates the distortion in current amplification due to the non-linear characteristic of the first semiconductor element. .

Therefore, the distortion during voltage amplification in the first semiconductor element is compensated by the second semiconductor element, and
The input resistance that converts the input voltage to the current and the constant current source
By arranging in the input stage where the voltage is input, there is no voltage loss due to the voltage drop in the resistance of the output stage, so that it is possible to perform voltage-current conversion with less distortion and without narrowing the dynamic range.

According to the second aspect of the present invention, for example, as shown in FIG. 1, the input resistance converts a change in input voltage into a change in current flowing through the input resistance. The constant current source keeps the current value of the emitter current of the current amplification transistor and the current flowing through the input resistance constant.

As a result, the emitter current of the current amplifying transistor changes in accordance with the change in the current flowing through the input resistance, and the collector current of the current amplifying transistor also changes in accordance with the change in the current flowing through the input resistance. .

The bias power source provides a bias voltage for fixing the potential of the base terminal of the current amplifying transistor. The current mirror circuit supplies a current having a magnitude substantially equal to the collector current of the current amplification transistor to the semiconductor element in order to operate the current amplification transistor and the semiconductor element under the same conditions.

The semiconductor element is V of the current amplification transistor.
It is manufactured to have the same voltage characteristics as the _BE characteristics.
As a result, in the expression expressing the collector current (output current) of the current amplification transistor (for example, refer to expression (3) described later), the term indicating the nonlinearity of V _BE of the current amplification transistor is the voltage of the semiconductor element. Since it is canceled by the term indicating the nonlinearity of the characteristic, the distortion at the time of current amplification due to the nonlinearity of V _BE of the current amplification transistor is compensated by the nonlinearity of the voltage characteristic of the semiconductor element. .

Therefore, the input resistance and the constant current source for compensating the distortion at the time of current amplification in the current amplification transistor by the semiconductor element and for converting the input voltage into the current.
By arranging in the input stage where the input voltage is input, there is no voltage loss due to the voltage drop in the resistance of the output stage, so that it is possible to perform voltage-current conversion with less distortion and without narrowing the dynamic range.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, preferred embodiments for explaining the present invention will be described with reference to the drawings. (I) First Embodiment FIG. 1 shows a first embodiment of the present invention.

In this embodiment, the current mirror circuit 6 connected to the power source V _CC , the collector terminal is connected to the input terminal of the current mirror circuit 6, the base terminal is connected to the output terminal of the current mirror circuit 6, and the emitter is connected. The first transistor 1 whose terminal is grounded via the constant current source 5 for flowing the constant current I _C , and the base terminal and the collector terminal are commonly connected, and the output terminal of the current mirror circuit 6 and the base of the first transistor 1 A second transistor 2 connected to a connection point of the terminals and having an emitter terminal grounded via a fixed bias power supply V _B for fixing the base potential of the first transistor 1.
And an input resistor 3 connected between a connection point between the emitter terminal of the first transistor 1 and the constant current source 5 and the input terminal IN.

[0026] The current flowing through the input terminal of the current mirror circuit 6 is also output current I _{OU T} of this embodiment, and is also intended as a reference current of the current mirror circuit 6. The current mirror circuit 6 is a three-transistor type current mirror circuit including three pnp type bipolar transistors 61, 62 and 63, and has a fixed resistor 64 and a fixed resistor 64 for reducing the influence of the Early effect of each transistor on the output current I _OUT . 65 is connected between the respective emitter terminals of the transistors 61 and 62 and the power supply V _CC .

The current mirror circuit 6 includes a transistor 62.
An output current having the same magnitude as the reference current flowing as the collector current of the transistor 61 flows as the collector current of the transistor 61.

The first transistor 1 and the second transistor 2 are composed of npn-type bipolar transistors manufactured such that the temperature characteristics and the physical characteristics such as the non-linearity of V _BE are the same.

In the voltage-current conversion circuit of this embodiment, the input voltage V _IN is applied to the first transistor 1 via the input resistor 3.
Input to the emitter terminal of. At this time, input voltage V _IN
An emitter input bias voltage V _E1 for fixing the operating point of the first transistor 1 is superposed on.

Next, the operation will be described. The change of the input voltage V _IN input together with the emitter input bias voltage V _E1 is
The input resistance 3 converts it into a change in the current I _R flowing through the input resistance 3.

Here, the current I_RAnd the first transistor 1
Emitter current I_E1The value of the combined current is the constant current source 5
Therefore, a constant value (I_C) Is kept. Therefore,
Flow I _RChanges the current I_E1Is transformed into a change of.

Since the base current of the first transistor 1 is set to be almost zero, the change in the current I _E1 is directly amplified and directly changes into the collector current of the first transistor 1. The current becomes the output current I _OUT .

By the above operation, the change of the input voltage V _IN is converted into the change of the output current I _OUT , and the circuit of this embodiment operates as a voltage-current conversion circuit. Next, the current mirror circuit 6 is connected to the collector terminal of the first transistor 1 and the second
A substantially equal current is supplied to the collector terminal of the transistor 2.

Further, when the present embodiment is manufactured as a semiconductor integrated circuit, the first transistor 1 and the second transistor 2 are manufactured through a common process and are manufactured close to each other. The dependence and the non-linearity of V _BE will have the same characteristics.

Therefore, in the above voltage-current conversion process, the V _BE of the first transistor 1 having the nonlinearity that affects the output current I _OUT is canceled by the V _{BE of} the second transistor, and the first _BE for the output current I _OUT is canceled. Transistor 1
The effect of V _BE non-linearity is eliminated.

[0036] Detailed description will next be made with respect to the first transistor 1 of the V _BE is offset by V _BE of the second transistor. Now, the first transistor 1 of the V _BE V _BE1, the V _BE of the second transistor V _BE2, the resistance R _IN of the input resistor 3, the common base current amplification factor of the first transistor 1 h
Let _FB be the emitter input bias voltage V in FIG.
_E1 , input voltage V _IN , input resistance 3, first transistor 1,
In a closed circuit composed of the second transistor 2 and the fixed bias power supply V _B , the following equation (1) is established with the potential at the connection point between the emitter terminal of the first transistor 1 and the input resistor 3 as the center.

V _E1 + V _IN + R · I _R = V _B + V _BE2 −V _BE1 (1) Further, the following formula (2) is established for the output current I _OUT . I _OUT = h _FB · IE ₁ = h _FB (I _C −I _R ) ... (2) Therefore, from the formulas (1) and (2), I _OUT = h _FB {I _C − (V _B + V _BE2 − V _BE1 −V _E1 −V _IN ) / R} (3) where the first transistor 1 and the second transistor 2 are V
_{The BE} is manufactured so that the physical characteristics such as non-linearity and temperature dependence are substantially equal to each other, and in this embodiment, the current mirror circuit 6 allows the first transistor 1 and the second transistor
Since the collector terminal of the transistor 2 is supplied with a current having a substantially equal value, the first transistor 1 and the second transistor 1
Since the transistor 2 operates under the same condition, the following equation (4)
Is established.

V _BE2 = V _BE1 (4) Therefore, from the formulas (3) and (4), I _OUT = h _FB {I _C − (V _B −V _E1 −V _IN ) / R} (5) ), And the value of I _OUT is irrelevant to V _BE2 or V _BE1 from the equation (5).

Therefore, the first with respect to the output current I _OUT
The influence of the non-linearity of V _BE of the transistor 1 is eliminated. Further, according to the present embodiment, there is no voltage loss due to the voltage drop in the resistance of the output stage, so that the dynamic range of the input voltage V _IN is not narrowed. (II) Second Embodiment FIG. 2 shows a second embodiment of the present invention.

In this embodiment, the same parts as those in the first embodiment are designated by the same reference numerals, and detailed description thereof will be omitted. The present embodiment is an example in which the output current I _OUT of the voltage-current conversion circuit of the present invention is utilized as the input current of the VCA circuit.

In this embodiment, in addition to the voltage-current conversion circuit shown in the first embodiment in which the compensation transistor 4 is added, a mirror image current I _C1 of the constant current I _C output from the constant current source 5 is generated to generate the mirror image current I _C1 . A current mirror circuit 8 for maintaining a constant current value (I _C1 ) of the combined current of the emitter current I _E1 of one transistor 1 and the current I _R flowing through the input resistor 3, and the input current of the VCA circuit 10. Mirror current I _OUT2 of output current I _OUT
And an output circuit 7 for generating I _OUT3 , and a VCA circuit 10.

The output circuit 7 constitutes another current mirror circuit together with the transistor 62 of the current mirror circuit 6 and outputs the mirror image current I _OUT2 of the output current I _OUT , and the transistor 62 of the current mirror circuit 6.
Together with another current mirror circuit to form an output current I
It is composed of a transistor 72 that outputs a mirror image current I _{OUT3 of OUT} . Here, the output current I _OUT and the output current I
_{Between the OUT} mirror image currents I _OUT2 and I _OUT3 , I _OUT2 = I
The relation of _OUT3 = I _OUT is established.

The VCA circuit 10 constitutes another current mirror circuit together with the output transistors 11, 12, 13 and 14 forming the _two differential pairs S ₁ and S ₂ and the transistor 81 of the current mirror circuit 8. A transistor 66 for generating a mirror image current I _C2 having a current value twice that of the constant current source I _C , and a transistor 72 in the output circuit 7.
Current mirror circuit 9 for generating a mirror image current of the output current I _OUT3 of the above and making it the input signal current I _{S2-IN of the} differential pair S _2.
It consists of and.

In the VCA circuit 10 of this embodiment, the current I _S1-IN flowing through the emitter terminals of the output transistors 11 and 12 and the current I _S2-IN flowing through the emitter terminals of the output transistors 13 and 14 are used as input signal currents. The base-base voltages V _CTL1 and V _CTL2 of the output transistors of the differential pairs S ₁ and S ₂ are used as control signals output from a control circuit (not shown), and the amplification factors of the output transistors 11, 12, 13 and 14 are set. Is controlled to change two output currents OUTPUT having a reverse phase relationship (relationship between a normal rotation signal and a reverse rotation signal).

Here, in order to obtain two outputs having opposite phases to each other, a current I _S1-IN and a current I _S which are input signal currents are obtained.
Also regarding _S2-IN , it is necessary to input so as to have an opposite phase relation to each other.

Next, the operation will be described. In the circuit shown in this embodiment, in addition to the operation of the circuit shown in the first embodiment, the compensating transistor 4 includes a current mirror circuit 6 to a first circuit.
The currents supplied to the collector terminals of the transistor 1 and the second transistor 2 are made equal.

The current mirror circuit 8 has a mirror image current I _C1 having the same magnitude as the constant current I _C output from the constant current source 5.
Is generated and the value of the current obtained by combining the emitter current I _E1 of the first transistor 1 and the current I _R flowing through the input resistor 3 is maintained at a constant value (I _C1 ). Therefore, as in the first embodiment, the change in the current I _R due to the change in the input voltage V _IN is converted into the change in the current I _E1 .

The transistors 71 and 72 in the output circuit 7 together with the transistor 62 of the current mirror circuit 6 form a separate current mirror circuit, respectively, and are the mirror image current I _{OUT2 of the} output current I _OUT flowing as the collector current of the first transistor 1. And I _OUT3 . Therefore, the output circuit 7 outputs two currents I _OUT2 and I _OUT3 having the same magnitude as the output current I _OUT, which are V
Input signal currents I _S1-IN and I in the CA circuit 10
It is supplied to the VCA circuit 10 to generate _S2-IN .

The current mirror circuit 9 in the VCA circuit 10 outputs the output current I of the transistor 72 of the output circuit 7.
_By further applying the mirror image effect to _OUT3 , the input signal current I _S2-IN of the differential pair S ₂ is generated.

Transistor 66 in VCA circuit 10
Form a transistor 81 of the current mirror circuit 8 and another current mirror circuit. As a result, as the collector current of the transistor 66, a constant current I _C2 having a current value twice that of the constant current I _C output by the constant current source 5 flows. Therefore, the value of the current obtained by combining the output current I _OUT2 output from the transistor 71 of the output circuit 7 and the input signal current I _S1-IN of the differential pair S ₁ is kept at a constant value (I _C2 ). An input signal current I _{S1 -IN} having a reverse phase relationship with the output current I _OUT2 is obtained. Here, the output current I _OUT2 has the same magnitude as the input signal current I _{S2-I N} of the differential pair S ₂ .

Due to the current mirror circuit 9 and the transistor 66 described above, the output current I
Input signal current I _S1-IN and I _{S2 -IN} that varies in response to _OUT change is obtained.

In the VCA circuit 10, the above-mentioned input signal currents I _S1-IN and I _S2-IN are used as input signal currents, and V
Output transistor 1 using _CTL1 and V _CTL2 as control signals
The amplification factor of 1, 12, 13 and 14 is controlled, and the output current O
Change UTPUT.

By the operation of the circuit shown in the second embodiment described above, the VCA which operates by the input current corresponding to the change of the input voltage V _IN is constructed. In the voltage-current conversion circuit in each of the above embodiments, V of the first transistor 1 is
By offset by the _BE second transistor 2 of V _BE, can be eliminated distortion of the output current I _OUT by nonlinearities and temperature dependence possessed by V _BE.

Furthermore, the voltage drop in the resistance of the output stage
There is no voltage loss due to input voltage V _INDynamic
It doesn't narrow down.Variant example In the above two examples, all npn bipo
Place the transistor on the pnn bipolar transistor
Replace all pnp bipolar transistors with n
Replaced with pn type bipolar transistor, current
V_CC, Emitter input bias voltage V_EIAnd fixed bias
Current V_BInvert the positive and negative polarities of and reverse the direction of the constant current source 5.
The same effect can be obtained in the case of the above configuration. This and
Becomes the first transistor 1 and the second transistor 2
The conditions for each pnp-type bipolar transistor are
Temperature dependence of V and V_BEPhysical properties such as nonlinearity of
Must be equal to.

Further, some or all of the transistors in the above two embodiments may be field effect transistors. At this time, the field effect transistors used as the first transistor 1 and the second transistor 2 need to have the same physical characteristics such as temperature dependence.

[0056]

As described above, according to the first aspect of the invention, the currents of substantially the same magnitude are supplied to the first semiconductor element and the second semiconductor element having the same physical characteristics. By doing so, the distortion of the first semiconductor element during current amplification is compensated by the second semiconductor element, and
The input resistance that converts the input voltage to the current and the constant current source
By arranging in the input stage where the voltage is input, there is no voltage loss due to the voltage drop of the resistance of the output stage, so that it is possible to perform voltage-current conversion without distortion and without narrowing the dynamic range.

According to the second aspect of the present invention, the current amplification transistor and the semiconductor element manufactured to have the same voltage characteristic as the base-emitter voltage characteristic of the current amplification transistor have substantially the same size. The non-linearity of V _BE of the current amplifying transistor is canceled by the non-linearity of the voltage characteristic of the semiconductor element by supplying the current.

Therefore, V of the current amplifying transistor is
The distortion at the time of current amplification due to the nonlinearity of BE is compensated by the nonlinearity of the voltage of the semiconductor element, and the input voltage is reduced.
Input voltage is input to the input resistance and constant current source
By arranging it in the input stage, there is no voltage loss due to the voltage drop of the resistance of the output stage, so that it is possible to perform voltage-current conversion without distortion and without narrowing the dynamic range.

[Brief description of drawings]

FIG. 1 is a diagram showing a first embodiment of the present invention.

FIG. 2 is a diagram showing a second embodiment of the present invention.

FIG. 3 is a diagram showing a first conventional technique.

FIG. 4 is a diagram showing a second conventional technique.

[Explanation of symbols]

1 ... 1st transistor 2 ... 2nd transistor 3 ... Input resistance 4 ... Compensation transistor 5 ... Constant current source 6, 8, 9 ... Current mirror circuit 7 ... Output circuit 10 ... VCA 11-14 ... Output transistors 61-63, 66, 71, 72, 81, 82 ... Transistors 64, 65 ... Resistors 100 ... Differential pairs 101, 102 ... Npn bipolar transistors 103 ... Fixed resistors 104, 105 ... Constant current source 106 ... Input bias voltages 200, 210, 220 ... differential pair 201,202,211,212,221,222 ... transistors 213 and 214 ... voltage-current conversion resistor 203,215,223 ... constant current source S _1, S ₂ ... differential pair IN ... input terminal V _IN ... input voltage V _CC ... supply V _E1 ... emitter input bias voltage V _B ... fixed bias voltage I _OUT ... output current I _OUT2, I _OUT3 ... output current _OUT mirror image current I _R ... input current I _E1 ... first transistor of emitter current I _C ... constant current I _C1, I _C2 ... constant current I _C of the mirror current I _S1-IN ... differential pair S ₁ of the input signal current I _S2-IN ... Input signal current V _CTL1 , V _{CTL2 of} differential pair S ₂ ... Control signal OUTPUT ... Output current

─────────────────────────────────────────────────── ─── Continuation of front page (56) Reference JP-A-4-316203 (JP, A) JP-A 52-154332 (JP, A) JP-A 2-180414 (JP, A) JP-A 62- 126705 (JP, A) (58) Fields surveyed (Int.Cl. ⁷ , DB name) H03F 1/32 H03F 3/34

Claims (2)

(57) [Claims] To 1. A between the input terminal of the current mirror circuit connected to the high potential power supply and the low potential side power supply, a control terminal connected to an output end of the current mirror circuit Rutotomoni input
A first semiconductor element having a terminal connected to the input end, and one end
Is connected to the output terminal of the first semiconductor element and
The end is connected to the low potential side power source and the current mirror
The current flowing in over circuit and <br/> constant current source for generating constant current uncorrelated, the series circuit is formed consisting of approximately equal to the current input from the entering force end to said first semiconductor element Yes wherein the Kide force end before outputting current having a current value between the low-potential-side power supply, a second semiconductor element having similar physical properties as the first semiconductor element, a fixed voltage value
A bias power source for generating a bias voltage to a series circuit consisting of is formed, the input terminal of the input voltage to be converted is input first
Change of the input voltage between the output terminal of one semiconductor element
A voltage-current conversion circuit, which is connected to an input resistor for converting the current into a change in current. Between the input terminal and the low potential side power supply 2. A current mirror circuit connected to the high potential power supply, Rutotomoni co base terminal is connected to the output terminal of the current mirror circuit
A current amplifying transistor whose collector terminal is connected to the input end and an emitter of the current amplifying transistor at one end.
The other end is connected to the low potential side power source.
And the current flowing through the current mirror circuit is
A constant current source for generating constant current correlation, the series circuit consisting of is formed, entering-force prior to output a current having a substantially equal current value and the current input to the current amplifying transistor from end Kide < A semiconductor element having a voltage characteristic similar to the base-emitter voltage characteristic of the current amplification transistor, and a bias having a fixed voltage value, between the power end and the low-potential-side power supply.
A series circuit composed of a bias power source for generating a voltage is formed, and an input terminal to which an input voltage to be converted is input and the power source are connected.
Between the emitter terminal of a flow amplifying transistor, the entering
A voltage-current conversion circuit, to which an input resistor for converting a change in force voltage into a change in current is connected.