CN110032235B - Current conversion voltage buffer with logarithmic operational amplifier - Google Patents
Current conversion voltage buffer with logarithmic operational amplifier Download PDFInfo
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- CN110032235B CN110032235B CN201910269891.3A CN201910269891A CN110032235B CN 110032235 B CN110032235 B CN 110032235B CN 201910269891 A CN201910269891 A CN 201910269891A CN 110032235 B CN110032235 B CN 110032235B
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- operational amplifier
- triodes
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- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05F—SYSTEMS FOR REGULATING ELECTRIC OR MAGNETIC VARIABLES
- G05F1/00—Automatic systems in which deviations of an electric quantity from one or more predetermined values are detected at the output of the system and fed back to a device within the system to restore the detected quantity to its predetermined value or values, i.e. retroactive systems
- G05F1/10—Regulating voltage or current
- G05F1/46—Regulating voltage or current wherein the variable actually regulated by the final control device is dc
- G05F1/56—Regulating voltage or current wherein the variable actually regulated by the final control device is dc using semiconductor devices in series with the load as final control devices
- G05F1/561—Voltage to current converters
Abstract
The invention discloses a current conversion voltage buffer of a logarithmic operational amplifier, wherein the positive input end of the operational amplifier is connected with a fixed bias, the negative input end of the operational amplifier is connected with a dynamically fluctuating input current, and the output end of the operational amplifier outputs voltage. Particularly, a closed loop formed by a group of I-to-V main triodes and a group of offset triodes is connected between the negative input end and the output end of the operational amplifier, wherein the collector electrodes of all the triodes are connected to the negative input end of the operational amplifier, the emitter electrodes of all the triodes are connected to the output end of the operational amplifier, and the base electrode of the main triode is connected to a fixed offset consistent with the connection of the operational amplifier. The buffer designed by applying the technology of the invention has the advantages that the whole circuit is composed of the triode, and the whole framework is simple; the circuit greatly reduces the influence of parasitic capacitance of the BE junction of the triode, obviously improves the step response speed of the input small current and gives consideration to the stability of the circuit.
Description
Technical Field
The present invention relates to a device for converting a current signal into a voltage signal, and more particularly, to a current-to-voltage conversion buffer for performing a transient step response on a current with a very large dynamic range in a logarithmic amplifier.
Background
With the increasing development of electronic application technologies, the technology is developed as a hardware base, and the microelectronics also continuously breaks through and develops in the technical problem. In the microelectronic design of many application systems, especially on the basis of the photoelectric conversion hardware developed in the communication field, the current with very large dynamic range is usually input into the microelectronic system after signal conversion, and the current needs to be converted into a voltage signal for further system operation. In the existing traditional scheme, the I-to-V signal conversion is realized by adopting an architecture of an operational amplifier combined triode. However, the conventional architectures have many disadvantages inevitably in terms of achieving the desired functions and providing certain advantages.
Fig. 1 is a schematic circuit diagram of a conventional structure of this type. As can be seen from the figure, the positive input end of the operational amplifier is connected with a fixed bias, the negative input end of the operational amplifier is connected with a dynamically fluctuating input current, and a biased triode is directly connected between the negative input end and the output end of the operational amplifier, namely, the base electrode and the collector electrode of the triode are in short circuit. Although the circuit operation stability under the structure is reliable, the response of the input current is slow due to the large parasitic capacitance of the input port, and particularly the response speed is difficult to reach the ideal degree when the input current reaches the micro-scale.
Fig. 2 is a schematic circuit diagram of another conventional architecture of this type. The same portions as those of the circuit configuration shown in fig. 1 are omitted from description, except for operational amplificationThe negative electrode input end and the output end of the device are connected with a common triode and an external auxiliary biasing circuit instead of a biasing triode, and the base part of the triode is connected with another fixed bias V with higher control requirementbias_B. Although the parasitic capacitance of the input port is suppressed to be small and the step response speed of the input small current is high under the structure, in order to prevent the situation that the transient response is interrupted due to the excessively small input current, an additional circuit is needed to assist in achieving stability, and the whole circuit is complex.
In summary, it is a problem to be solved by those skilled in the art how to coordinate both the transient step response speed and the circuit stability for an input current with a very large dynamic range, especially for an input current which may be as small as nA, without increasing the circuit complexity.
Disclosure of Invention
The invention aims to provide a current conversion voltage buffer for logarithmic operational amplifiers, which aims to solve the problems that various traditional structures have the defects which cannot be ignored objectively and the performance of the whole circuit is influenced.
The technical solution of the present invention for achieving the above object is a current-to-voltage conversion buffer for a logarithmic operational amplifier, wherein a positive input terminal of an operational amplifier is connected to a fixed bias, a negative input terminal of the operational amplifier is connected to a dynamically fluctuating input current, and an output terminal of the operational amplifier outputs a voltage, characterized in that: and a closed loop formed by a group of I-to-V main triodes and a group of bias triodes is connected between the negative input end and the output end of the operational amplifier, wherein the collector electrodes of all the triodes are connected to the negative input end of the operational amplifier, the emitter electrodes of all the triodes are connected to the output end of the operational amplifier, and the base electrode of the main triode is connected to a fixed bias consistent with the input of the operational amplifier.
Preferably, the bias triode is a device with a base electrode thereof short-circuited with a collector electrode.
Preferably, the sum of the number of the main triode and the bias triode is set in proportion to the range of the input current.
Further preferably, the ratio of the number of main transistors is greater than the ratio of the number of bias transistors.
Preferably, the input current is as small as on the order of nA.
The improved design of the circuit structure has the prominent substantive characteristics and remarkable progress: the whole circuit of the buffer is composed of triodes, and the whole framework is simple; the circuit greatly reduces the influence of parasitic capacitance of the BE junction of the triode, obviously improves the step response speed of the input small current and gives consideration to the stability of the circuit.
Drawings
Fig. 1 is a schematic diagram of a conventional circuit of a current-converting voltage buffer.
Fig. 2 is a schematic diagram of another conventional circuit of a current-converting voltage buffer.
Fig. 3 is a schematic diagram of a circuit structure of an innovative design of the current conversion voltage buffer of the present invention.
Detailed Description
The following detailed description of the embodiments of the present invention is provided in connection with the accompanying drawings for the purpose of understanding and controlling the technical solutions of the present invention, so as to define the protection scope of the present invention more clearly.
Aiming at the defects of the traditional structure of the current conversion voltage buffer of the operational amplifier in the prior art, the designer of the invention integrates the experience of the industry for many years, aims to seek breakthrough for the omnibearing optimization of the circuit performance and meets the stable conversion of the input current with very large dynamic range and extremely low lower limit.
To be more specific, as shown in FIG. 3, the circuit structure of the current-converting voltage buffer for logarithmic op-amp according to the embodiment of the present invention is shown, in which the positive input terminal of the operational amplifier is connected to the fixed bias VbiasThe negative input end of the operational amplifier is connected with the dynamically fluctuated input current, and the output end of the operational amplifier outputs voltage. The dynamic range of the input current is very large and ranges from nA magnitude to mA magnitude, and the characteristic of a triode is relied on for realizing current conversion voltage. The characteristic circuit structure of the design is that the negative pole input of the operational amplifierA closed loop consisting of a group of main triodes with I-to-V conversion and a group of offset triodes is connected between the terminal and the output terminal, wherein the collector electrodes of all the triodes are connected to the negative input terminal of the operational amplifier, the emitter electrodes of all the triodes are connected to the output terminal of the operational amplifier, and the base electrode of the main triode is connected to the fixed offset V consistent with the input of the operational amplifierbiasThe so-called biased triode is a device with a base electrode thereof short-circuited with a collector electrode.
The base voltage of the main triode is fixedly biased by VbiasThe parasitic capacitance of the closed loop is only present in the biased transistor. Therefore, for the current input end, even if the input current is extremely small, the parasitic capacitor can be rapidly charged and discharged, and the transient step response is rapid.
Here, the sum of the number of the main transistors and the number of the bias transistors is set in proportion to the range of the input current, that is, the larger the dynamic range of the input current is, the more the total number of the transistors is required, and otherwise, the less the total number of the transistors is. Moreover, only a very small proportion of the base electrode and the collector electrode of the triode are in short circuit to serve as a biasing triode, so that the stability of the whole circuit is improved. The base bias voltage of most of the main triodes is consistent with the fixed bias connected to the operational amplifier, and the main triodes are responsible for responding to the input current and converting the input current into voltage. It should be noted that the main transistor and the bias transistor shown in fig. 3 are merely representative, and may actually be a parallel connection of a plurality of transistors.
For example, for the case that the dynamic range of the input current is in the range of μ a to mA, the required performance of the whole circuit can be satisfied by connecting 5 to 10I to V main transistors and 1 offset transistor between the negative input end and the output end of the operational amplifier to form a closed loop, wherein the main transistors are responsible for converting input currents of different sizes into voltage output, and the offset transistors are responsible for maintaining the stability of the circuit, so that the transient response interruption can be avoided even if the input current is in the lower limit of the dynamic range.
And for the condition that the dynamic range of the input current is in the nA magnitude-mA magnitude, 18 main triodes for converting I into V and 2 bias triodes can be connected between the negative input end and the output end of the operational amplifier to form a closed loop, so that the required performance of the whole circuit can be met. In the same way, the current is converted into voltage to be output, and the number of the biased triodes is only slightly increased so as to further compress the parasitic capacitance and meet the requirement of circuit design.
In summary, with reference to the detailed description of the illustrated embodiments, the improved circuit structure design of the present invention has the following substantial features and significant improvements: the whole circuit of the buffer consists of the triode, an additional biasing circuit is not required to be connected, and the whole framework is simple; the circuit greatly reduces the influence of parasitic capacitance of the BE junction of the triode, obviously improves the step response speed of the input small current and gives consideration to the stability of the circuit.
Although the preferred embodiments of the present invention have been described in detail, the present invention is not limited to the specific embodiments, and modifications and equivalents within the scope of the claims may be made by those skilled in the art and are included in the scope of the present invention.
Claims (7)
1. A current conversion voltage buffer for logarithmic operational amplifier is disclosed, wherein the positive input terminal of operational amplifier is connected with fixed bias VbiasThe negative pole input end of the operational amplifier is connected with the dynamically fluctuated input current, and the output end of the operational amplifier outputs voltage, and the operational amplifier is characterized in that: a closed loop consisting of a group of main triodes with I-to-V conversion and a group of bias triodes is connected between the negative input end and the output end of the operational amplifier, wherein the collector electrodes of all the triodes are connected with the negative input end of the operational amplifier, the emitter electrodes of all the triodes are connected with the output end of the operational amplifier, and the base electrode of the main triode is connected with a fixed bias V consistent with the input of the operational amplifierbiasThe bias triode is a device with a base electrode thereof in short circuit with a collector electrode.
2. The logarithmic op-amp current-to-voltage buffer of claim 1, wherein: the sum of the number of the main triodes and the number of the bias triodes is set in direct proportion to the range of the input current.
3. The logarithmic op-amp current-to-voltage buffer of claim 2, wherein: the number proportion of the main triodes is larger than that of the offset triodes.
4. The logarithmic op-amp current-to-voltage buffer of claim 1, wherein: the input current is as small as the order of nA.
5. The logarithmic op-amp current-to-voltage buffer of claim 1, wherein: and 5I-to-V main triodes and 1 bias triode are connected between the negative input end and the output end of the operational amplifier to form a closed loop.
6. The logarithmic op-amp current-to-voltage buffer of claim 1, wherein: and 10 main triodes for converting I into V and 1 bias triode are connected between the negative input end and the output end of the operational amplifier to form a closed loop.
7. The logarithmic op-amp current-to-voltage buffer of claim 1, wherein: and 18 main triodes for converting I into V and 2 bias triodes are connected between the negative input end and the output end of the operational amplifier to form a closed loop.
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Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103095232A (en) * | 2013-01-08 | 2013-05-08 | 上海创远仪器技术股份有限公司 | Dual slope logarithmic amplifier circuit structure |
| CN207851804U (en) * | 2018-02-01 | 2018-09-11 | 湖南省青鸟博宇互联网有限公司 | A kind of computer interactive education system |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20060028260A1 (en) * | 2004-08-04 | 2006-02-09 | Baumgartner Richard A | Logarithmic amplifier with base and emitter in feedback path |
| US7889006B1 (en) * | 2009-09-23 | 2011-02-15 | Maxim Integrated Products, Inc. | dB-linear process-independent variable gain amplifier |
| US8004341B1 (en) * | 2010-04-30 | 2011-08-23 | Analog Devices, Inc. | Logarithmic circuits |
| CN102664594B (en) * | 2012-05-29 | 2014-09-10 | 东南大学 | Log amplifier with temperature compensation function |
| CN103151989B (en) * | 2013-03-05 | 2015-06-17 | 东南大学 | Logarithmic amplifier with low voltage and low temperature coefficient |
| CN208401525U (en) * | 2018-04-27 | 2019-01-18 | 黄河科技学院 | A kind of electronic equipment measuring and controlling protective device |
| CN109327146B (en) * | 2018-12-07 | 2024-03-22 | 中国电子科技集团公司第四十三研究所 | Loop compensation circuit and compensation method of voltage control isolation type DC/DC converter |
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Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103095232A (en) * | 2013-01-08 | 2013-05-08 | 上海创远仪器技术股份有限公司 | Dual slope logarithmic amplifier circuit structure |
| CN207851804U (en) * | 2018-02-01 | 2018-09-11 | 湖南省青鸟博宇互联网有限公司 | A kind of computer interactive education system |
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