CN109375699B - Voltage-current conversion circuit with high linearity - Google Patents
Voltage-current conversion circuit with high linearity Download PDFInfo
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- CN109375699B CN109375699B CN201811345542.7A CN201811345542A CN109375699B CN 109375699 B CN109375699 B CN 109375699B CN 201811345542 A CN201811345542 A CN 201811345542A CN 109375699 B CN109375699 B CN 109375699B
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- 238000006243 chemical reaction Methods 0.000 title claims abstract description 33
- 230000005669 field effect Effects 0.000 claims abstract description 100
- 238000010586 diagram Methods 0.000 description 6
- 230000003321 amplification Effects 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000003199 nucleic acid amplification method Methods 0.000 description 2
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- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05F—SYSTEMS FOR REGULATING ELECTRIC OR MAGNETIC VARIABLES
- G05F3/00—Non-retroactive systems for regulating electric variables by using an uncontrolled element, or an uncontrolled combination of elements, such element or such combination having self-regulating properties
- G05F3/02—Regulating voltage or current
- G05F3/08—Regulating voltage or current wherein the variable is DC
- G05F3/10—Regulating voltage or current wherein the variable is DC using uncontrolled devices with non-linear characteristics
- G05F3/16—Regulating voltage or current wherein the variable is DC using uncontrolled devices with non-linear characteristics being semiconductor devices
- G05F3/20—Regulating voltage or current wherein the variable is DC using uncontrolled devices with non-linear characteristics being semiconductor devices using diode- transistor combinations
- G05F3/26—Current mirrors
- G05F3/262—Current mirrors using field-effect transistors only
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Abstract
The invention discloses a voltage-current conversion circuit with high linearity, which comprises an input resistor, a transconductance amplifier, a first field effect transistor, a second field effect transistor and an amplifier output level generating device. One end of the input resistor is connected with the input voltage, the other end of the input resistor is connected with the inverting input end of the transconductance amplifier, the drain electrode and the grid electrode of the first field effect tube, the positive input end of the transconductance amplifier is grounded, the grid electrode of the first field effect tube is also directly connected with the grid electrode of the second field effect tube, the source electrode of the first field effect tube is connected with the output end of the transconductance amplifier, the output end of the transconductance amplifier is also directly connected with the source electrode of the second field effect tube, the source electrode of the second field effect tube is also directly connected with the amplifier output level generating device, and the drain electrode of the second field effect tube is used for. The invention adopts the negative feedback circuit and the linear element to carry out voltage and current conversion, eliminates the nonlinear influence of field effect transistor conversion and greatly improves the linearity of the voltage and current conversion circuit.
Description
Technical Field
The present invention relates to a voltage-current conversion circuit, and more particularly to a voltage-current conversion circuit with high linearity.
Background
In many integrated circuit applications, voltage-linearized to current conversion is required, including csi (current to Time converter) -based vtc (voltage to Time converter) and current-based adc (analog to Digital converter) applications.
At present, the most common voltage-to-current mode is to convert the current-to-voltage characteristic of a field effect transistor working in a saturation region, the linearity of the current-to-voltage characteristic depends heavily on the characteristic of the field effect transistor, the nonlinearity is very serious, and the application of the current-to-voltage characteristic to a circuit with higher linearity requirement is greatly limited.
Disclosure of Invention
In view of the problems in the prior art, the present invention provides a voltage-current conversion circuit with high linearity.
The invention provides a voltage-current conversion circuit with high linearity, which is used for converting input voltage into output current, and comprises an input resistor, a transconductance amplifier, a first field effect tube, a second field effect tube and an amplifier output level generating device, wherein one end of the input resistor is connected with the input voltage, the other end of the input resistor is connected with the inverting input end of the transconductance amplifier, the input resistor is also directly connected with the drain electrode and the grid electrode of the first field effect tube, the positive input end of the transconductance amplifier is grounded, the grid electrode of the first field effect tube is also directly connected with the grid electrode of the second field effect tube, the source electrode of the first field effect tube is connected with the output end of the transconductance amplifier, the output end of the transconductance amplifier is also directly connected with the source electrode of the second field effect tube, and the source electrode of the second field effect tube is also directly connected with the amplifier output level generating, and the drain electrode of the second field effect transistor is used for outputting current.
Further, the amplifier output level generating device is an output resistor, and the source of the second field effect transistor is grounded through the output resistor.
Further, the amplifier output level generating device is a third field effect transistor, a source electrode of the third field effect transistor is grounded, a drain electrode of the third field effect transistor is connected with a source electrode of the second field effect transistor, and a grid electrode of the third field effect transistor is connected with the bias voltage of the amplifier output stage.
Furthermore, the conversion circuit further comprises a fourth field effect transistor, and the fourth field effect transistor is cascaded to the drain electrode of the second field effect transistor.
Further, the drain of the fourth field effect transistor is used for outputting current, the source of the fourth field effect transistor is connected with the drain of the second field effect transistor, and the grid of the fourth field effect transistor is connected with the bias voltage of the output stage of the amplifier.
Further, the first field effect transistor and the second field effect transistor are the same in device type and gate-source voltage difference, and are in proportional relation in size.
The invention utilizes the 'virtual short' and 'virtual break' working characteristics of a negative feedback operational amplification circuit to convert input voltage into input current and feedback current, and then utilizes the current mirror principle of a field effect tube to form a current mirror circuit by a first field effect tube and a second field effect tube, so that the output current mirrors the feedback current, and finally the input voltage is linearly converted into the output current. The linearity of the output current of the structure is basically limited by the linearity of the input resistor, and compared with the traditional VTC based on the voltage and current special effect of the saturation region of the field effect transistor, the linearity of the voltage and current conversion is greatly improved.
Drawings
FIG. 1 is a circuit diagram of a voltage-to-current conversion circuit with high linearity according to a first preferred embodiment of the present invention.
FIG. 2 is a circuit diagram of a voltage-to-current conversion circuit with high linearity according to a second preferred embodiment of the present invention.
FIG. 3 is a circuit diagram of a voltage-to-current conversion circuit with high linearity according to a third preferred embodiment of the present invention.
Detailed Description
In order to make the technical means, the creation characteristics, the achievement purposes and the effects of the invention easy to understand, the invention is further explained below by combining the specific drawings.
In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.
Fig. 1 is a circuit diagram of a voltage-current conversion circuit with high linearity according to a first preferred embodiment of the present invention. The preferred embodiment of the voltage-current conversion circuit with high linearity comprises an input resistor RinTransconductance amplifier AMP and field effect transistor MfbAnd MoutOutput resistor Rout. The input resistor RinAnd an input voltage VinConnected to the inverting input of the transconductance amplifier AMP at the other end and directly connected to the field effect transistor MfbThe drain and the gate of the transistor are connected. The positive input end of the transconductance amplifier AMP is grounded. The field effect transistor MfbThe grid electrode ofAnd field effect transistor MoutIs connected with the grid of the field effect transistor MfbIs connected to the output of the transconductance amplifier AMP.
The output end of the transconductance amplifier AMP is also directly connected with the field effect transistor MoutIs connected with the source electrode of the field effect transistor MoutAlso directly through the output resistor RoutAnd then grounded. The field effect transistor MoutFor outputting a current Iout。
In this embodiment, the input resistor RinFor converting an input voltage VinIs converted into an input current IinThe transconductance amplifier AMP and the input resistor RinAnd field effect transistor MfbForming a negative feedback operational amplifier circuit, the field effect transistor MfbFor generating a feedback current IfbThe feedback current I is based on the characteristics of 'virtual short' and 'virtual break' at the input end of the negative feedback operational amplifier circuitfbAnd an input current IinAre equal, i.e. Ifb＝IinAnd the feedback current IfbAs a current mirror, a field effect transistor MoutThe gate and the source of the field effect transistor M provide a voltage differenceoutFor generating a feedback current IfbAnd provides an output current I of a desired proportionoutSaid output resistance RoutFor generating the output level of the transconductance amplifier AMP.
Specifically, the conversion circuit utilizes the working characteristics of 'virtual short' and 'virtual break' of a negative feedback operational amplification circuit to convert the input voltage VinConversion to input current IinAnd a feedback current IfbThen the current mirror principle of the field effect transistor is utilized to convert the field effect transistor M into the voltage-controlled rectifierfbAnd field effect transistor MoutForming a current mirror circuit to output a current IoutMirror feedback current IfbFinally, the input voltage V isinLinear conversion to output current Iout。
According to the 'virtual short' characteristic of negative feedback operational amplifier circuit, input resistor RinThe voltages at both ends are respectively input voltage VinAnd ground level "0" flowing through the input resistor RinThe current of (a) is then: i isin＝Vin/Rin. According to the 'virtual break' characteristic of negative feedback operational amplifier circuit, flows through input resistor RinWill all flow through the field effect transistor MfbI.e. negative feedback current IfbIs equal to the input current Iin。
According to the working characteristics of the field effect transistor, the current flowing through the field effect transistor completely depends on the voltage difference between the grid electrode and the source electrode, and the specific relationship is as follows:
In the present invention, the field effect transistor MoutAnd field effect transistor MfbThe device types and the gate-source voltage differences are the same, and the sizes are in proportional relation:
where N represents a natural number, W represents a fet channel width, and L represents a fet channel length.
Therefore, in the present invention, the current flows through the field effect transistor MoutOutput current I ofoutFor flowing through field effect transistor MfbIs fed back with a feedback current IfbN times, i.e.:
Therefore, the invention realizes the design goal of converting the input voltage into the output current in a linear way.
Please refer to fig. 2, which illustrates the voltage-current conversion with high linearity according to the present inventionCircuit diagram of a second preferred embodiment of the circuit. The second preferred embodiment of the voltage-current conversion circuit with high linearity of the present invention is different from the first preferred embodiment in that: will output resistance RoutReplacement is by field effect transistor MaoWherein the field effect transistor MaoThe source electrode of the transistor is grounded, the drain electrode of the transistor is grounded, and the field effect transistor MoutIs connected with the source electrode of the field effect transistor MaoGate and amplifier output stage bias voltage VbampAre connected.
In this embodiment, the field effect transistor MaoAs well as for generating the output level of the transconductance amplifier AMP. Other amplifier output level generating devices may be used in other embodiments, as long as they are capable of generating an output level for the transconductance amplifier.
Please refer to fig. 3, which is a circuit diagram of a voltage-to-current conversion circuit with high linearity according to a third preferred embodiment of the present invention. The second preferred embodiment of the voltage-current converting circuit with high linearity of the present invention is different from the first preferred embodiment in that the field effect transistor MoutThe drain electrode of the transistor is cascaded with a field effect transistor McascodeThe field effect transistor McascodeThe method is used for improving the output impedance and reducing the influence of the output voltage on the output current. In particular, the field effect transistor McascodeFor outputting a current IoutSource and field effect transistor MoutIs connected to the drain electrode of the field effect transistor McascodeGate and amplifier output stage bias voltage VbiasAre connected.
The above description is only an embodiment of the present invention, and not intended to limit the scope of the present invention, and all equivalent structures made by using the contents of the present specification and the drawings can be directly or indirectly applied to other related technical fields, and are within the scope of the present invention.
Claims (6)
1. A voltage-to-current conversion circuit having high linearity for converting an input voltage to an output current, said conversion circuit comprising a transconductance amplifier, a first field effect transistor and a second field effect transistor, wherein: the conversion circuit further comprises an input resistor and an amplifier output level generating device, wherein one end of the input resistor is connected with an input voltage, the other end of the input resistor is connected with the inverting input end of the transconductance amplifier, the input resistor is also directly connected with the drain electrode and the grid electrode of the first field effect transistor, the positive input end of the transconductance amplifier is grounded, the grid electrode of the first field effect transistor is also directly connected with the grid electrode of the second field effect transistor, the source electrode of the first field effect transistor is connected with the output end of the transconductance amplifier, the output end of the transconductance amplifier is also directly connected with the source electrode of the second field effect transistor, the source electrode of the second field effect transistor is also directly connected with the amplifier output level generating device, and the drain electrode of the second field effect transistor is used.
2. The voltage-to-current conversion circuit with high linearity of claim 1, wherein: the amplifier output level generating device is an output resistor, and the source electrode of the second field effect transistor is grounded through the output resistor.
3. The voltage-to-current conversion circuit with high linearity of claim 1, wherein: the amplifier output level generating device is a third field effect tube, the source electrode of the third field effect tube is grounded, the drain electrode of the third field effect tube is connected with the source electrode of the second field effect tube, and the grid electrode of the third field effect tube is connected with the bias voltage of the amplifier output stage.
4. The voltage-to-current conversion circuit with high linearity of claim 1, wherein: the conversion circuit further comprises a fourth field effect transistor, and the fourth field effect transistor is cascaded to the drain electrode of the second field effect transistor.
5. The voltage-to-current conversion circuit with high linearity of claim 4, wherein: the drain electrode of the fourth field effect tube is used for outputting current, the source electrode of the fourth field effect tube is connected with the drain electrode of the second field effect tube, and the grid electrode of the fourth field effect tube is connected with the bias voltage of the output stage of the amplifier.
6. The voltage-to-current conversion circuit with high linearity of claim 1, wherein: the first field effect transistor and the second field effect transistor are the same in device type and grid-source voltage difference, and are in proportional relation in size.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201811345542.7A CN109375699B (en) | 2018-11-13 | 2018-11-13 | Voltage-current conversion circuit with high linearity |
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| Application Number | Priority Date | Filing Date | Title |
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| CN201811345542.7A CN109375699B (en) | 2018-11-13 | 2018-11-13 | Voltage-current conversion circuit with high linearity |
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| CN109375699A CN109375699A (en) | 2019-02-22 |
| CN109375699B true CN109375699B (en) | 2020-04-21 |
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| CN112904931B (en) * | 2021-01-15 | 2022-07-01 | 北京智芯微电子科技有限公司 | Voltage current conversion circuit and integrated circuit chip |
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| JP3225887B2 (en) * | 1997-05-16 | 2001-11-05 | 日本電気株式会社 | Semiconductor integrated circuit device |
| JP2000182241A (en) * | 1998-12-16 | 2000-06-30 | Hitachi Ltd | Head amplifier and optical disk device using the same |
| CN103324230B (en) * | 2012-03-21 | 2015-01-21 | 华润矽威科技（上海）有限公司 | Voltage-current convertor |
| CN206413094U (en) * | 2016-11-04 | 2017-08-15 | 刘强 | A kind of row level adc circuit for cmos image sensor |
| CN107478890A (en) * | 2017-08-24 | 2017-12-15 | 郑州云海信息技术有限公司 | A kind of current sensing means for integrated circuit |
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