CN111740709A - High-linearity broadband variable gain amplifier - Google Patents
High-linearity broadband variable gain amplifier Download PDFInfo
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- CN111740709A CN111740709A CN202010576617.3A CN202010576617A CN111740709A CN 111740709 A CN111740709 A CN 111740709A CN 202010576617 A CN202010576617 A CN 202010576617A CN 111740709 A CN111740709 A CN 111740709A
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03F—AMPLIFIERS
- H03F1/00—Details of amplifiers with only discharge tubes, only semiconductor devices or only unspecified devices as amplifying elements
- H03F1/42—Modifications of amplifiers to extend the bandwidth
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- H—ELECTRICITY
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Abstract
The invention belongs to the technical field of integrated circuits, and particularly relates to a high-linearity broadband variable gain amplifier. The variable gain amplifier of the present invention comprises: a first stage fixed gain amplifier with a gain fixed at 21 dB; three switches, two of which are connected in parallel with the first-stage fixed gain amplifier, the third switch is connected between the first-stage fixed gain amplifier and the power supply, the two switches in parallel short-circuit the first-stage fixed gain amplifier in the low gain mode, and are disconnected in the high gain mode, the third switch is disconnected in the low gain mode, and is connected in the high gain mode; and the input end of the second-stage variable gain amplifier is connected with the input signal of the whole link in a low gain mode, and is connected with the output of the first-stage fixed gain amplifier in a high gain mode, and the gain variation range of the second-stage variable gain amplifier is changed from 0 dB to 21 dB. The invention can be used for the sampling front end of a high-precision analog-to-digital converter, has variable gain, and realizes high linearity while maintaining wide bandwidth.
Description
Technical Field
The invention belongs to the technical field of integrated circuits, and particularly relates to a variable gain amplifier.
Background
The analog-to-digital converter with high precision and low power consumption is an important component of a broadband receiver, and the successive approximation type analog-to-digital converter is widely concerned due to the characteristic of low power consumption. At present, many researches are devoted to improving the performance of the core chip of the successive approximation type analog-to-digital converter, but few researches are made on the driving circuit of the analog-to-digital converter. For a successive approximation type analog-to-digital converter, the capacitance value of the sampling capacitor is usually large, and it is very difficult to drive a large capacitor within a relatively short sampling window, which makes the driving circuit a bottleneck for high-speed and high-precision analog-to-digital converter research. Although some studies have proposed adding an input buffer before the analog-to-digital converter, the buffer itself cannot provide gain, which limits its application range. In different application scenarios, an amplifier with variable gain is needed in the front end of the analog-to-digital converter.
A variable gain amplifier applied to the front end of the successive approximation type analog-to-digital converter can adjust different gains to amplify different input signals to full swing. The variable gain amplifier has two types of capacitance feedback and resistance feedback, the amplifier of a capacitance feedback structure is based on a charge redistribution principle, but a sampling switch is required to be added to establish a bias voltage, so a time sequence circuit for controlling the switch is required to be added; the amplifier with the resistance feedback structure belongs to a continuous time domain, has a simple structure, has gain determined by the ratio of the feedback resistance to the forward resistance, and is ideally unrelated to the parameters of the operational amplifier, so the amplifier has higher linearity. The linearity is mainly related to the loop gain, and under the condition of high gain, the resistance value of the feedback resistor is increased, and the loop gain is reduced.
Therefore, it is desirable to improve the linearity of a variable gain amplifier applied to the front end of an analog-to-digital converter while increasing the signal bandwidth.
Disclosure of Invention
In view of the above, the present invention provides a wide-band, high-linearity, low-power consumption variable gain amplifier. The variable gain amplifier can realize a gain range of 0-21 dB and a step length of 3 dB in a low gain mode, and can realize a gain range of 21-42 dB and a step length of 3 dB in a high gain mode. The power consumption of the amplifier in the low gain mode is half that in the high gain mode.
The invention provides a high-linearity broadband variable gain amplifier, which is used for providing different gains to amplify an input signal to a full-swing signal, and the structure of the amplifier comprises the following components: the amplifier comprises a first-stage fixed gain amplifier, a second-stage variable gain amplifier and three switches; wherein:
the input of the first-stage fixed gain amplifier is connected with an input signal of the whole link to provide a constant 21 dB gain, and the output end of the first-stage fixed gain amplifier outputs an amplified signal;
two of the three switches are connected in parallel with the first-stage fixed gain amplifier, the third switch is connected between the first-stage fixed gain amplifier and a power supply, and the two switches connected in parallel short-circuit the first-stage fixed gain amplifier in a low gain mode and are disconnected in a high gain mode; the third switch is open in the low gain mode and closed in the high gain mode;
the input end of the second-stage variable gain amplifier is connected with an input signal of the whole link in a low gain mode, and is connected with the output of the first-stage fixed gain amplifier in a high gain mode, the gain change range of the second-stage variable gain amplifier is changed from 0 dB to 21 dB, and the step length is 3 dB.
Preferably, the first-stage fixed gain amplifier consists of a fully differential operational amplifier and four resistors; two resistors are connected in series between an input signal and the fully differential operational amplifier (for short, the two resistors are connected in series), the other two resistors are symmetrically connected to two ends of the fully differential operational amplifier (for short, the two resistors are symmetrically connected), and the 21 dB gain of the fixed gain amplifier is determined by the ratio of the resistance values of the resistors symmetrically connected to the two ends of the fully differential operational amplifier to the resistance values of the resistors connected in series.
Preferably, in the low gain mode, the two switches connected in parallel are turned on to short-circuit the first-stage fixed gain amplifier, the third switch is turned off, the gain is 0 dB, and the power consumption of the link is reduced by half; in the high gain mode, the two switches connected in parallel are open, and the third switch is closed, so that the gain is 21 dB.
Preferably, the fully differential operational amplifier is a two-stage amplifier; the first stage is a fully differential rail-to-rail input stage, the input of the first stage is connected with the two series-connected resistors, the second stage is an AB output stage, the input of the second stage is an output signal of the first stage, the output of the second stage is connected with the two symmetrical-connected resistors, and a Miller compensation capacitor and a zero setting resistor are symmetrically connected between the differential output and the differential input of the second stage. The differential output of the second stage is also respectively connected with two ends of two serially connected large resistors, and the common end of the two serially connected large resistors is connected with the negative input end of a common mode feedback amplifier; the positive input end of the common mode feedback amplifier is connected with a reference voltage signal, and the output end of the common mode feedback amplifier is connected with a bias of the first stage of the fully differential operational amplifier.
Preferably, the reference signal of the positive input terminal of the common mode feedback amplifier is generated by a reference voltage generating circuit. The reference voltage generating circuit is composed of a band gap reference circuit and an amplifier. The output end of the band-gap reference circuit is connected with the positive input end of the amplifier, the output end of the amplifier is connected with the negative input end and is simultaneously connected with one end of two series resistors, the other end of the two series resistors is grounded, and the common end of the two series resistors is connected with the negative input end of the common-mode feedback amplifier.
Preferably, the second stage variable gain amplifier has a structure similar to that of the first stage fixed gain amplifier, except that, in the second stage variable gain amplifier, the resistors symmetrically connected to the two ends of the fully differential operational amplifier are resistor arrays, the resistance values of which are determined by the 3-8 decoders, and the variable gain of the variable gain amplifier is determined by the ratio of the resistance values of the resistors symmetrically connected to the two ends of the fully differential operational amplifier to the resistance values of the resistors connected in series.
The fully differential operational amplifier used in the first stage fixed gain amplifier and the second stage variable gain amplifier are identical.
Preferably, the resistor array is divided into two symmetrical paths, each path includes 8 branches connected in parallel, and each branch includes a resistor and a switch connected in series.
Preferably, the switch signal of the switch is controlled by a 3-8 decoder, and the resistance value of the connected resistor array is controlled by inputting different control signals to the 3-8 decoder, so as to control the gain of the variable gain amplifier.
The variable gain amplifier can realize a gain change range of 0-42 dB, and the gain is determined by using a resistance feedback structure, so that an output signal has higher linearity. Furthermore, the signal bandwidth of the variable gain amplifier is wide because the fully differential operational amplifier used therein has a very high gain-bandwidth product. Also, since the first stage fixed gain amplifier is turned off in the low gain mode, power consumption in the low gain mode is reduced to half that in the high gain mode. Therefore, the invention provides a broadband, high linearity, low power consumption variable gain amplifier.
Drawings
Fig. 1 is a schematic diagram of the overall structure of the variable gain amplifier of the present invention.
Fig. 2 is a schematic diagram of a first stage fixed gain amplifier according to the present invention.
Fig. 3 is a schematic structural diagram of a second stage variable gain amplifier according to the present invention.
FIG. 4 is a schematic diagram of a fully differential operational amplifier circuit in a variable gain amplifier according to the present invention.
FIG. 5 is a schematic diagram of a common mode feedback circuit in the fully differential operational amplifier according to the present invention.
Detailed Description
The invention will be described in more detail below with reference to the accompanying drawings. Like elements in the various figures are denoted by like reference numerals. For purposes of clarity, the various features in the drawings are not necessarily drawn to scale. Moreover, certain well-known elements may not be shown in the figures.
In the following description, numerous specific details of the invention, such as structure, materials, dimensions, processing techniques and techniques of the devices are described in order to provide a more thorough understanding of the invention. However, as will be understood by those skilled in the art, the present invention may be practiced without these specific details.
Fig. 1 is a schematic diagram of the overall structure of the variable gain amplifier of the present invention.
As shown in fig. 1, the entire link contains a first stage of fixed gain amplifiers providing a constant 21 dB gain and a second stage of variable gain amplifiers providing 0-21 dB gain in steps of 3 dB. Three switches, two of the switches S1, S2 are connected in parallel with the first stage fixed gain amplifier, a third switch S3 is connected between the first stage fixed gain amplifier and the power supply, switches S1 and S2 short circuit the first stage fixed gain amplifier in low gain mode, open in high gain mode, and a third switch S3 open in low gain mode and closed in high gain mode. By using the characteristic, the power consumption in the low gain mode can be reduced to a half of that in the high gain mode.
Fig. 2 is a schematic diagram of a first stage fixed gain amplifier according to the present invention.
As shown in fig. 2, the gain of the first stage fixed gain amplifier is determined by the ratio of the feedback resistance Rf to the forward resistance Rs, which is 21 dB.
Fig. 3 is a schematic structural diagram of a second stage variable gain amplifier according to the present invention.
As shown in fig. 3, the gain of the second stage variable gain amplifier is determined by the ratio of the feedback resistance to the forward resistance, the feedback resistance is a resistor array and comprises 8 branches connected in parallel, and each branch comprises a resistor and a switch connected in series.
As shown in fig. 3, the resistance of the feedback resistor of the access circuit is determined by the 3-8 decoder.
FIG. 4 is a schematic diagram of a fully differential operational amplifier circuit in a variable gain amplifier according to the present invention.
As shown in FIG. 4, transistors M1-M4 form the rail-to-rail input stage of the fully differential operational amplifier. The transistors M5-M8 form a cascode load of the fully differential operational amplifier, and 4 transistors M5 are respectively a transistor M5a, a transistor M5b, a transistor M5c and a transistor M5 d; the gate bias voltage Vcmfb of transistor M5c (M5cd) is determined by the output of the common mode feedback circuit.
As shown in fig. 4, transistors M17 and M18 form a class AB output stage of the fully differential operational amplifier, transistors M9, M14, M15 and M16, and transistors M10, M11, M12 and M13 form transconductance linear loops, respectively. In the transconductance linear loop, the transistor M9 and the transistor M10 are used to set the quiescent current of the class AB output stage, which presents an infinite impedance to the ac signal and does not affect the gain-bandwidth product of the fully differential operational amplifier. Miller capacitance CCAnd a zero setting resistor Rz is connected between the drain and the gate of the class AB output stage for compensating the phase. The fully differential operational amplifier has a very wide gain-bandwidth product, so that the output signal can be ensured to have good linearity when the fully differential operational amplifier is used in a variable gain amplifier.
FIG. 5 is a schematic diagram of a common mode feedback circuit in the fully differential operational amplifier according to the present invention.
As shown in fig. 5, the outputs Vout + and Vout-of the fully differential operational amplifier are connected to the two ends of the large common-mode feedback resistor Rcmfb, respectively, and their average value becomes the negative input terminal of the common-mode feedback amplifier, the output voltage Vcmfb of the common-mode feedback amplifier is the gate bias voltage of the transistor M5c (transistor d) in the fully differential operational amplifier, and the positive input terminal of the common-mode feedback amplifier is from the bandgap voltage generating circuit. The output of the bandgap reference circuit is fed to the positive input of the operational amplifier, the output of the operational amplifier is connected to the negative input and to one end of the series resistors R1 and R2, and the other ends of R1 and R2 are connected to ground, so that the voltage at the common terminal of R1 and R2 is proportional to the output voltage of the bandgap reference circuit, and this ratio is determined by the relative resistance values of R1 and R2.
It is noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.
While embodiments in accordance with the invention have been described above, these embodiments are not intended to be exhaustive or to limit the invention to the precise embodiments described. Obviously, many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the invention and the practical application, to thereby enable others skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated. The invention is limited only by the claims and their full scope and equivalents.
Claims (8)
1. A high linearity, wideband variable gain amplifier for providing differential gain to amplify an input signal to a full-swing signal, the structure comprising: the amplifier comprises a first-stage fixed gain amplifier, a second-stage variable gain amplifier and three switches; wherein:
the input of the first-stage fixed gain amplifier is connected with an input signal of the whole link to provide a constant 21 dB gain, and the output end of the first-stage fixed gain amplifier outputs an amplified signal;
two of the three switches are connected in parallel with the first-stage fixed gain amplifier, the third switch is connected between the first-stage fixed gain amplifier and a power supply, and the two switches connected in parallel short-circuit the first-stage fixed gain amplifier in a low gain mode and are disconnected in a high gain mode; the third switch is open in the low gain mode and closed in the high gain mode;
the input end of the second-stage variable gain amplifier is connected with an input signal of the whole link in a low gain mode, and is connected with the output of the first-stage fixed gain amplifier in a high gain mode, the gain change range of the second-stage variable gain amplifier is changed from 0 dB to 21 dB, and the step length is 3 dB.
2. The wideband variable gain amplifier according to claim 1, wherein the first stage fixed gain amplifier is comprised of a fully differential operational amplifier and four resistors; the two resistors are connected in series between an input signal and the fully differential operational amplifier and are called as series connection resistors, the other two resistors are symmetrically connected to two ends of the fully differential operational amplifier and are called as symmetrical connection resistors; the 21 dB gain of the fixed gain amplifier is determined by the ratio of the resistance values of the symmetrically connected resistors to the resistance values of the serially connected resistors.
3. The wideband variable gain amplifier of claim 1, wherein the three switches, in low gain mode, are closed to short circuit the first stage fixed gain amplifier, and the third switch is open to gain 0 dB while reducing link power consumption by half; in the high gain mode, the two switches connected in parallel are open, and the third switch is closed, so that the gain is 21 dB.
4. The wideband variable gain amplifier according to claim 2, wherein the fully differential operational amplifier is a two-stage amplifier; the first stage is a fully differential rail-to-rail input stage, the input of the first stage is connected with the two series-connected resistors, the second stage is an AB output stage, the input of the second stage is an output signal of the first stage, the output of the second stage is connected with the two symmetrical connected resistors, and a Miller compensation capacitor and a zero setting resistor are symmetrically connected between the differential output and the differential input of the second stage; the differential output of the second stage is also connected to two ends of two series resistors respectively, and the common end of the two series resistors is connected with the negative input end of a common mode feedback amplifier; the positive input end of the common mode feedback amplifier is connected with a reference voltage signal, and the output end of the common mode feedback amplifier is connected with a bias of the first stage of the fully differential operational amplifier.
5. The wide-band variable-gain amplifier according to claim 4, wherein the common-mode feedback amplifier has a reference signal at its positive input terminal generated by a reference voltage generating circuit; the reference voltage generating circuit consists of a band gap reference circuit and an amplifier; the output end of the band-gap reference circuit is connected with the positive input end of the amplifier, the output end of the amplifier is connected with the negative input end and is simultaneously connected with one end of two series resistors, the other end of the two series resistors is grounded, and the common end of the two series resistors is connected with the negative input end of the common-mode feedback amplifier.
6. A wide-band variable gain amplifier according to any one of claims 1 to 5, wherein the second stage variable gain amplifier is similar in structure to the first stage fixed gain amplifier, except that in the second stage variable gain amplifier, the resistors symmetrically connected to both ends of the fully differential operational amplifier are resistor arrays whose resistance values are determined by the 3-8 decoder, and the variable gain of the variable gain amplifier is determined by the ratio of the resistance values of the resistors symmetrically connected to both ends of the fully differential operational amplifier to the resistance values of the resistors connected in series;
the fully differential operational amplifier used in the first stage fixed gain amplifier and the second stage variable gain amplifier are identical.
7. The wideband variable gain amplifier according to claim 6, wherein the resistor array is divided into two symmetrical paths, each path includes 8 parallel branches, and each branch includes a resistor and a switch connected in series.
8. The wideband variable gain amplifier according to claim 7, wherein the switch signals are controlled by the 3-8 decoder, and the magnitude of the resistance of the resistor array is controlled by inputting different control signals to the 3-8 decoder, so as to control the gain of the variable gain amplifier.
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| CN202010576617.3A CN111740709A (en) | 2020-06-22 | 2020-06-22 | High-linearity broadband variable gain amplifier |
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| CN202010576617.3A CN111740709A (en) | 2020-06-22 | 2020-06-22 | High-linearity broadband variable gain amplifier |
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112165306A (en) * | 2020-12-02 | 2021-01-01 | 深圳市南方硅谷半导体有限公司 | Switching circuit of multiple gain low noise amplifier |
| CN113328711A (en) * | 2021-06-21 | 2021-08-31 | 浙江大学 | Constant cross-rail-to-rail input differential output high-speed programmable gain amplifier |
| CN114640329A (en) * | 2022-05-18 | 2022-06-17 | 深圳市时代速信科技有限公司 | Drive circuit, drive chip and electronic equipment |
| CN115065234A (en) * | 2022-08-15 | 2022-09-16 | 英彼森半导体(珠海)有限公司 | Analog filter framework working at various power supply voltages and filtering method |
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| CN103248330A (en) * | 2013-01-31 | 2013-08-14 | 南京邮电大学 | Programmable gain amplifier with high gain accuracy |
| CN103944523A (en) * | 2014-04-26 | 2014-07-23 | 长沙云腾微电子有限公司 | Programmable gain amplifier |
| CN104639068A (en) * | 2014-12-09 | 2015-05-20 | 中国航空工业集团公司第六三一研究所 | Linear programmable gain amplifier realized by switched capacitor |
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2020
- 2020-06-22 CN CN202010576617.3A patent/CN111740709A/en active Pending
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103248330A (en) * | 2013-01-31 | 2013-08-14 | 南京邮电大学 | Programmable gain amplifier with high gain accuracy |
| CN103944523A (en) * | 2014-04-26 | 2014-07-23 | 长沙云腾微电子有限公司 | Programmable gain amplifier |
| CN104639068A (en) * | 2014-12-09 | 2015-05-20 | 中国航空工业集团公司第六三一研究所 | Linear programmable gain amplifier realized by switched capacitor |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112165306A (en) * | 2020-12-02 | 2021-01-01 | 深圳市南方硅谷半导体有限公司 | Switching circuit of multiple gain low noise amplifier |
| CN113328711A (en) * | 2021-06-21 | 2021-08-31 | 浙江大学 | Constant cross-rail-to-rail input differential output high-speed programmable gain amplifier |
| CN114640329A (en) * | 2022-05-18 | 2022-06-17 | 深圳市时代速信科技有限公司 | Drive circuit, drive chip and electronic equipment |
| CN115065234A (en) * | 2022-08-15 | 2022-09-16 | 英彼森半导体(珠海)有限公司 | Analog filter framework working at various power supply voltages and filtering method |
| CN115065234B (en) * | 2022-08-15 | 2022-11-18 | 英彼森半导体(珠海)有限公司 | Analog filter framework working at various power supply voltages and filtering method |
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