CN112152569B - Chopper amplification device and method - Google Patents
Chopper amplification device and method Download PDFInfo
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- CN112152569B CN112152569B CN201910571190.5A CN201910571190A CN112152569B CN 112152569 B CN112152569 B CN 112152569B CN 201910571190 A CN201910571190 A CN 201910571190A CN 112152569 B CN112152569 B CN 112152569B
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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
- H03F1/30—Modifications of amplifiers to reduce influence of variations of temperature or supply voltage or other physical parameters
- H03F1/303—Modifications of amplifiers to reduce influence of variations of temperature or supply voltage or other physical parameters using a switching device
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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
- H03F1/26—Modifications of amplifiers to reduce influence of noise generated by amplifying elements
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03F—AMPLIFIERS
- H03F3/00—Amplifiers with only discharge tubes or only semiconductor devices as amplifying elements
- H03F3/45—Differential amplifiers
- H03F3/45071—Differential amplifiers with semiconductor devices only
- H03F3/45076—Differential amplifiers with semiconductor devices only characterised by the way of implementation of the active amplifying circuit in the differential amplifier
- H03F3/45179—Differential amplifiers with semiconductor devices only characterised by the way of implementation of the active amplifying circuit in the differential amplifier using MOSFET transistors as the active amplifying circuit
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03F—AMPLIFIERS
- H03F3/00—Amplifiers with only discharge tubes or only semiconductor devices as amplifying elements
- H03F3/45—Differential amplifiers
- H03F3/45071—Differential amplifiers with semiconductor devices only
- H03F3/45076—Differential amplifiers with semiconductor devices only characterised by the way of implementation of the active amplifying circuit in the differential amplifier
- H03F3/45475—Differential amplifiers with semiconductor devices only characterised by the way of implementation of the active amplifying circuit in the differential amplifier using IC blocks as the active amplifying circuit
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03F—AMPLIFIERS
- H03F3/00—Amplifiers with only discharge tubes or only semiconductor devices as amplifying elements
- H03F3/68—Combinations of amplifiers, e.g. multi-channel amplifiers for stereophonics
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Abstract
The invention discloses a chopping amplification method, which comprises the following steps: the shielding oscillator is used for configuring the operational amplification circuit to be in a normal working state; testing the offset voltage of the operational amplification circuit; adjusting the offset voltage of the first operational amplifier according to the test result; and starting the oscillator, and configuring the operational amplification circuit to be in a chopping working state. The invention also discloses a chopping amplification device. The offset voltage of the operational amplifier can be further reduced, so that the operational amplifier can have lower offset voltage and output noise under low power consumption, and has better amplification performance.
Description
Technical Field
The invention relates to the technical field of microelectronics, in particular to a chopping amplification device and a chopping amplification method.
Background
The precision amplifier integrated circuit has wide application in the fields of current industrial control systems, instruments and meters, medical equipment, security and protection, automobiles, aerospace, consumer electronics and the like. The input offset voltage, the temperature drift (drift) of the offset voltage and the flicker noise (1/f noise) are important technical indexes representing the precision of the amplifier, and the performance of the input offset voltage and the temperature drift (drift) of the offset voltage directly influence the precision indexes of the application equipment and the system.
In the fabrication of integrated circuits using semiconductor processes, a number of factors affect the accuracy of the amplifier, such as device adaptation (mismatch), flicker noise, temperature drift of device parameters, package stress (stress), and the like. The initial input offset voltage of the well-designed general amplifier is several millivolts, the temperature drift of the offset voltage is several microvolts per degree centigrade, the low-frequency flicker noise has the jitter of the actual microvolts of the peak value, and in some precise applications, the performance of the general amplifier can not meet the precision requirement of system design.
In most operational amplifier applications, the input offset voltage of the op-amp limits the performance of many systems. In a data sampling system, such as a pre-amplifier circuit of a signal acquisition system, an offset voltage is acquired in a sampling period and appears on an output even if an input signal does not change, so that an error signal is acquired, and an error result is caused. Existing methods of reducing the input offset voltage of operational amplifiers consist of chopping and self-zeroing techniques, for example. The basic chopping technique introduces high frequency noise characteristics at the input stage, and also shifts the offset voltage and low frequency noise of the input stage to the chopping frequency while exhibiting large ripple on the output.
Therefore, a new solution is urgently needed to solve the above technical problems.
Disclosure of Invention
In order to solve the above technical problems, the present invention provides a chopping amplifying device and method, which can further reduce the offset voltage of an operational amplifier, so that the operational amplifier can have lower offset voltage and output noise under low power consumption, and simultaneously has better amplification performance.
According to the present invention, there is provided a chopper amplifier device comprising: the operational amplifier circuit is used for generating an output signal according to an input signal; the detection circuit is connected with the operational amplification circuit and used for detecting the offset voltage of the operational amplification circuit and outputting a corresponding trimming signal according to a detection result; the trimming circuit is connected with the operational amplification circuit and the detection circuit and used for receiving the trimming signal and adjusting the offset voltage of the operational amplification circuit according to the trimming signal; in the trimming stage, the operational amplification circuit works in a non-chopping state; in the chopping stage, the operational amplification circuit introduces the alternating current component of the input signal according to the control signal and works in a chopping state.
Preferably, the operational amplification circuit includes: and the oscillator is used for generating the control signal when in work so as to enable the operational amplification circuit to work in a chopping state.
Preferably, the operational amplifier circuit further includes: the input end of the first operational amplifier is connected with the input end of the operational amplifier through a first switch; the input end of the second operational amplifier is connected with the output end of the first operational amplifier through a second switch; the input end of the third operational amplifier is connected with the output end of the second operational amplifier, and the output end of the third operational amplifier is connected with the output end of the operational amplification circuit; the input end of the fourth operational amplifier is connected with the input end of the operational amplifier, and the output end of the fourth operational amplifier is connected with the input end of the third operational amplifier; a first capacitor connected between the second switch and the output terminal of the third operational amplifier; and a second capacitor connected between the output terminal of the second operational amplifier and the output terminal of the third operational amplifier.
Preferably, the first operational amplifier is respectively connected with the detection circuit and the trimming circuit.
Preferably, the first switch and the second switch are respectively connected with the oscillator, and receive a corresponding control signal output by the oscillator, so as to connect or disconnect the input end and/or the output end of the first operational amplifier and the operational amplifier circuit.
Preferably, the first operational amplifier includes: a grid electrode of the first switching tube is connected with the non-inverting input end of the first operational amplifier, and a second path end of the first switching tube is grounded through a third current source; a grid electrode of the second switching tube is connected with the inverting input end of the first operational amplifier, and a second path end is grounded through a third current source; and the first input end of the double-end output circuit is connected with the first channel end of the first switching tube, the second input end of the double-end output circuit is connected with the first channel end of the second switching tube, and the output end of the double-end output circuit is connected with the output end of the first operational amplifier.
Preferably, the trimming circuit includes: the first current source and the first resistor are sequentially connected in series between the power supply end and the first path end of the first switching tube; and the second current source and the second resistor are sequentially connected in series between a power supply end and a first path end of the second switching tube, wherein the first current source and/or the second current source are/is used for outputting different current signals according to corresponding trimming signals.
Preferably, the first switch tube and the second switch tube are both PMOS transistors.
The invention provides a chopping amplification method, which is characterized by comprising the following steps: the shielding oscillator is used for configuring the operational amplification circuit to be in a normal working state; testing the offset voltage of the operational amplification circuit; adjusting the offset voltage of the first operational amplifier according to the test result; and starting the oscillator, and configuring the operational amplification circuit to be in a chopping working state.
Preferably, the configuring the operational amplifier circuit to a normal operating state further comprises: and connecting a first operational amplifier into the operational amplification circuit, and configuring the operational amplification circuit into a multi-stage operational amplification mode.
Preferably, adjusting the offset voltage of the first operational amplifier according to the test result comprises: when the offset voltage of the operational amplification circuit is detected to be positive offset, outputting a first trimming signal; when the offset voltage of the operational amplification circuit is detected to be negative offset, outputting a second trimming signal; and adjusting the output current of the first current source and/or the second current source according to the first trimming signal or the second trimming signal, so as to adjust the offset voltage of the first operational amplifier.
Preferably, adjusting the offset voltage of the first operational amplifier according to the test result comprises: and cutting off the current output path of the first current source and/or the second current source by adopting a laser cutting mode.
Preferably, configuring the operational amplifier circuit to be in a chopping operation state includes: outputting a first control signal by the oscillator, controlling a first switch to carry out off/off operation, and modulating an input signal into a high-frequency signal; outputting a second control signal by the oscillator, controlling a second switch to perform an off/on operation, demodulating a high-frequency input signal, and modulating an offset voltage into a high-frequency signal; and filtering the demodulated input signal and the modulated offset voltage according to a certain filtering frequency to filter the offset voltage.
Preferably, the filtering frequency is the frequency of the offset voltage after modulation.
The beneficial effects of the invention are: the offset voltage expected by the operational amplifier is firstly reduced through the trimming circuit, then the offset voltage of the operational amplifier is further reduced through the chopping technology, and the operational amplifier can have lower offset voltage and output noise under low power consumption and better amplification performance on the basis of not increasing power consumption.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.
Drawings
The above and other objects, features and advantages of the present invention will become more apparent from the following description of the embodiments of the present invention with reference to the accompanying drawings.
Fig. 1 is a schematic diagram showing a structure of a chopper amplification device in the prior art;
fig. 2 is a schematic structural diagram of a chopping amplification device provided by an embodiment of the invention;
FIG. 3 is a schematic diagram of the trimming circuit of FIG. 2;
fig. 4 shows a flowchart of a chopping amplification method provided by an embodiment of the present invention.
Detailed Description
To facilitate an understanding of the invention, the invention will now be described more fully with reference to the accompanying drawings. Preferred embodiments of the present invention are shown in the drawings. The invention may, however, be embodied in different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.
The present invention will be described in detail below with reference to the accompanying drawings.
Fig. 1 shows a schematic structure of a chopper amplifier in the prior art.
As shown in fig. 1, the chopper amplifier 100 of the related art includes a plurality of operational amplifiers gm1 to gm4 coupled to each other, a first capacitor C1, a second capacitor C2, and an oscillator OSC.
The input end of the first operational amplifier gm1 is connected with the signal input end VIN of the operational amplification circuit through a first switch K1, and the output end of the first operational amplifier gm1 is connected with the input end of the second operational amplifier gm2 through a second switch K2; the output terminal of the second operational amplifier gm2 is connected to the input terminal of the third operational amplifier gm3, and the output terminal of the third operational amplifier gm3 serves as the signal output terminal VOUT. The input terminal of the fourth operational amplifier gm4 is connected to the signal input terminal VIN of the operational amplifier circuit, and the output terminal thereof is connected to the input terminal of the third operational amplifier gm 3.
A first capacitor C1 is further connected between the output terminal of the first operational amplifier gm1 and the output terminal of the third operational amplifier gm3 (specifically, the first capacitor C1 is located between the second switch K2 and the output terminal of the third operational amplifier gm 3), a second capacitor C2 is further connected between the output terminal of the second operational amplifier gm2 and/or the output terminal of the fourth operational amplifier gm4 and the output terminal of the third operational amplifier gm3, the first capacitor C1 and the second capacitor C2 are used for compensating the output gain signal of the first operational amplifier gm1, and the second capacitor C2 is used for compensating the output gain signal of the second operational amplifier gm2 and/or the fourth operational amplifier gm4, so as to reduce the temperature drift of the circuit and the loss of the ac signal during transmission.
The first operational amplifier gm1, the second operational amplifier gm2, and the third operational amplifier gm3 constitute a first signal transmission path of the operational amplifier circuit, and each operational amplifier in the first signal transmission path has a high gain and a low bandwidth for transmitting a low frequency signal.
The fourth operational amplifier gm4 and the third operational amplifier gm3 constitute a second signal transmission path of the operational amplification circuit, and each operational amplifier in the second signal transmission path has a low gain and a high bandwidth for transmitting a high frequency signal.
A first output of the oscillator OSC is connected to the first switch K1, and the other output of the oscillator OSC is connected to the second switch K2. The oscillator OSC is configured to output a first control signal (i.e., a first pulse signal) to the first switch K1 and output a second control signal (i.e., a second pulse signal) to the second switch K2 when it is operated, and controls the first switch K1 and the second switch K2 to be turned off/on, respectively.
When the oscillator OSC is started, the operational amplifier circuit may be operated in a chopping state, for example, the first switch K1 is controlled to perform a switching operation to modulate a normal input signal of the circuit into a high frequency signal, the second switch K2 is controlled to perform a switching operation to demodulate a high frequency input signal, and the input offset voltage VOS is modulated into a high frequency signal (the frequency of the high frequency signal is the chopping frequency of the circuit), and the high frequency offset voltage VOS may be filtered by filtering.
When the offset voltage VOS is adjusted by the oscillator OSC, the chopper amplifier introduces a characteristic of high-frequency noise into the input stage of the circuit, and when the offset voltage VOS and low-frequency noise in the input stage are shifted to the chopping frequency, a large ripple appears on the output of the circuit.
Fig. 2 shows a schematic structural diagram of a chopping and amplifying device according to an embodiment of the present invention, and fig. 3 shows a schematic structural diagram of a trimming circuit in fig. 2.
As shown in fig. 2, in the present embodiment, the chopper amplifier 200 includes an operational amplifier circuit 210, a detection circuit 220, and a trimming circuit 230.
The operational amplifier circuit 210 is configured to gain-amplify an input signal and generate an output signal according to the input signal, and includes: a plurality of operational amplifiers gm1 to gm4 coupled to each other, a first capacitor C1, a second capacitor C2, and an oscillator OSC.
Further, in the trimming stage, the operational amplifier circuit 210 works in a non-chopping state; in the chopping phase, the operational amplifier circuit 210 introduces an ac component of the input signal according to the control signal and operates in a chopping state.
The input terminal of the first operational amplifier gm1 is connected to the signal input terminal VIN of the operational amplifier circuit 210 through the first switch K1, the output terminal thereof is connected to the input terminal of the second operational amplifier gm2 through the second switch K2, the output terminal of the second operational amplifier gm2 is connected to the input terminal of the third operational amplifier gm3, and the output terminal of the third operational amplifier gm3 is used as the signal output terminal VOUT. The input terminal of the fourth operational amplifier gm4 is connected to the signal input terminal VIN of the operational amplifier circuit, and the output terminal thereof is connected to the input terminal of the third operational amplifier gm 3.
Preferably, a first capacitor C1 is further connected between the output terminal of the first operational amplifier gm1 and the output terminal of the third operational amplifier gm3 (specifically, the first capacitor C1 is located between the second switch K2 and the output terminal of the third operational amplifier gm 3), and a second capacitor C2 is further connected between the output terminal of the second operational amplifier gm2 and/or the output terminal of the fourth operational amplifier gm4 and the output terminal of the third operational amplifier gm 3. The first capacitor C1 and the second capacitor C2 are used for compensating the output gain signal of the first operational amplifier gm1, and the second capacitor C2 is used for compensating the output gain signal of the second operational amplifier gm2 and/or the fourth operational amplifier gm4, so as to reduce the temperature drift of the circuit and the loss of the alternating current signal in the transmission process.
Further, the first operational amplifier gm1, the second operational amplifier gm2 and the third operational amplifier gm3 constitute a first signal transmission path of the operational amplification circuit, and each operational amplifier in the first signal transmission path has a high gain and a low bandwidth for transmitting a low frequency signal.
The fourth operational amplifier gm4 and the third operational amplifier gm3 constitute a second signal transmission path of the operational amplification circuit, and each operational amplifier in the second signal transmission path has a low gain and a high bandwidth for transmitting a high frequency signal.
Preferably, in the present embodiment, the first operational amplifier gm1, the second operational amplifier gm2, the third operational amplifier gm3 and the fourth operational amplifier gm4 are all differential amplifiers.
The oscillator OSC is configured to output a control signal when operating, so that the operational amplifier circuit 210 operates in a chopping state.
In this embodiment, a first output terminal of the oscillator OSC is connected to the first switch K1, and a second output terminal of the oscillator OSC is connected to the second switch K2. The oscillator OSC is configured to output a first control signal (i.e., a first pulse signal) to the first switch K1 and output a second control signal (i.e., a second pulse signal) to the second switch K2 when the oscillator is operating, so as to control the first switch K1 and the second switch K2 to perform corresponding on/off operations, respectively, and further to connect or disconnect the input terminal and/or the output terminal of the first operational amplifier gm1 from the operational amplifier circuit 210.
Further, the oscillator OSC outputs a first control signal for controlling the first switch K1 to perform an off/off operation, and can modulate a normal input signal of the circuit into a high frequency signal; and outputting a second control signal to control the second switch K2 to be turned off/on, demodulating a high-frequency input signal, modulating the input offset voltage VOS into a high-frequency signal (the frequency of the high-frequency signal is the chopping frequency or the filtering frequency of the circuit), and filtering the high-frequency signal through filtering processing to reduce the offset voltage VOS of the circuit.
The detection circuit 220 is connected to the operational amplifier circuit 210, and is configured to detect an offset voltage of the operational amplifier circuit 210 and output a corresponding trimming signal according to a detection result.
In this embodiment, the input offset voltage VOS of the operational amplifier circuit 210 includes a positive offset (e.g., + 5V) and a negative offset (e.g., -5V), and the detection circuit 220 can detect whether the input offset voltage VOS of the operational amplifier circuit is a positive offset or a negative offset, and output a corresponding trimming signal according to a detection result. Further, the detection circuit 220 is connected to the input terminal of the first operational amplifier gm1 of the operational amplifier circuit 210 to detect the input offset voltage VOS of the first operational amplifier gm 1.
The trimming circuit 230 is connected to the operational amplifier circuit 210 and the detection circuit 220, and is configured to receive the trimming signal output by the detection circuit 220 and adjust the offset voltage of the operational amplifier circuit 210 according to the trimming signal.
As shown in fig. 3, in the present embodiment, the first operational amplifier gm1 is a differential amplifier, and includes: a first switch tube T1, a second switch tube T2, and a third current source I bias3 And a two-terminal output circuit A1. The grid of the first switch tube T1 is connected to the non-inverting input terminal IN + of the first operational amplifier gm1, the first path terminal is connected to the first input terminal of the double-ended output circuit A1, and the second path terminal is connected to the third current source I bias3 Grounding; the grid electrode of the second switch tube T2 is connected with the inverting input end IN-of the first operational amplifier gm1, the first path end is connected with the second input end of the double-end output circuit A1, and the second path end passes through the third current source I bias3 And (4) grounding. The output terminal of the two-terminal output circuit A1 is the output terminal OUT (including the first output terminal OUT +, and the second output terminal OUT-) of the first operational amplifier gm 1.
The trimming circuit 230 is a load circuit of the first operational amplifier gm1, and is connected to the differential input terminal of the first operational amplifier gm1, i.e. the first pass terminals of the two switching transistors T1 and T2, through a chip pad and a metal bonding wire. The method comprises the following steps: a first current source I bias1 A first resistor R1, a second current source I bias2 And a second resistor R2. A first current source I bias1 The first resistor R1 is sequentially connected in series between a power supply end Vdd and a first path end of the first switching tube T1; a second current source I bias2 And the second resistor R2 is sequentially connected in series between the power supply end Vdd and the first path end of the second switch tube T2.
Preferably, the first switch transistor T1 and the second switch transistor T2 are PMOS transistors.
Further, the trimming circuit 230 receives the trimming signal outputted from the detecting circuit 220 and is driven by the first current source I via the corresponding trimming signal bias1 And/or a second current source I bias2 Different current signals are output, and thus the input offset voltage VOS of the first operational amplifier gm1 can be reduced.
It should be noted that, in the present embodiment, an operational amplifier of a CMOS process with a small offset voltage VOS is used, but the scheme of the present invention is also applicable to a conventional differential amplifier composed of transistors.
In this embodiment, the input offset voltage of the operational amplifier circuit can be reduced for multiple times through the trimming circuit and the oscillator, so that the operational amplifier can have lower offset voltage and output noise under low power consumption, and has better amplification performance.
Fig. 4 shows a flowchart of a chopping amplification method provided by an embodiment of the present invention.
As shown in fig. 4, the chopping and amplifying method provided in this embodiment includes steps S01 to S04 performed on the chopping and amplifying device 200, and specifically includes:
in step S01, the oscillator is shielded, and the operational amplifier circuit is configured to be in a normal operating state.
Referring to fig. 2, a first output terminal of the oscillator OSC is connected to the first switch K1, and the other output terminal of the oscillator OSC is connected to the second switch K2. The oscillator OSC is configured to output a first control signal (i.e., a first pulse signal) to the first switch K1 and output a second control signal (i.e., a second pulse signal) to the second switch K2 when the oscillator is in operation, and respectively control the first switch K1 and the second switch K2 to perform corresponding on/off operations, thereby connecting or disconnecting the input terminal and/or the output terminal of the first operational amplifier gm1 and the operational amplifier circuit 210.
In this embodiment, the operational amplifier circuit 210 can be configured to normally operate in the multi-stage operational amplifier mode by shielding the oscillator OSC, closing the first switch K1 and the second switch K2, and connecting the first operational amplifier gm1 to the operational amplifier circuit 210.
Further, when the operational amplifier circuit 210 is in normal operation, the first operational amplifier gm1, the second operational amplifier gm2 and the third operational amplifier gm3 form a first signal transmission path of the operational amplifier circuit, and each operational amplifier in the first signal transmission path has a high gain and a low bandwidth, and is used for transmitting low-frequency signals. The fourth operational amplifier gm4 and the third operational amplifier gm3 constitute a second signal transmission path of the operational amplification circuit, and each operational amplifier in the second signal transmission path has a low gain and a high bandwidth for transmitting a high frequency signal.
In one embodiment of the present invention, the oscillator OSC is shielded by disconnecting the oscillator OSC from the operational amplifier 210 during the trimming phase.
In another embodiment of the invention, the oscillator OSC is shielded by turning off the oscillator OSC during the trimming phase.
In step S02, the offset voltage of the operational amplifier circuit is tested.
In this embodiment, when the operational amplifier circuit 210 operates in the multi-stage operational amplifier mode, the detection circuit 220 can test the offset voltage in the operational amplifier circuit 210 at this time, and transmit different trimming signals to the trimming circuit 230 according to the corresponding test result.
Further, in the embodiment, the input offset voltage VOS of the operational amplifier circuit 210 includes a positive offset (e.g., an offset voltage of + 5V) and a negative offset (e.g., an offset voltage of-5V).
In step S03, the offset voltage of the first operational amplifier is adjusted according to the test result.
In this embodiment, when it is detected that the offset voltage VOS of the operational amplifier circuit 210 is a positive offset, the detection circuit 220 outputs a first trimming signal; when the offset voltage VOS of the operational amplifier circuit 210 is detected as negative offset, the detection circuit 220 outputs a second trimming signal.
Referring to the chopper amplification apparatus described in fig. 2, since the input offset voltage of the fourth operational amplifier gm4 is divided by the product of the gains of the first operational amplifier gm1 and the second operational amplifier gm2 when the input to the circuit is calculated, the ratio of the offset voltage of the first operational amplifier gm1 to the gain of the second operational amplifier gm2 is the largest in the entire operational amplification circuit, and therefore, the offset voltage of the first operational amplifier gm1 needs to be modified by the modifying circuit 230 to obtain the extremely small offset voltage.
Further, in a preferred embodiment of the present invention, the trimming circuit 230 is connected to the packaged operational amplifier chip, and receives the first trimming signal or the second trimming signal output by the detecting circuit 220, and adjusts the first current source I according to the corresponding trimming signal bias1 And/or a second current source I bias2 The purpose of adjusting the offset voltage of the first operational amplifier gm1 is further achieved. Since the offset voltage of the first operational amplifier gm1 is adjusted to be as small as possible, the ripple of the output signal thereof can be reduced.
In another embodiment of the present invention, before the operational amplifier chip is integrated, the current output path of the first current source and/or the second current source is cut off by laser cutting for the chip structure located on the wafer (i.e. the metal wire connecting the first path end of the first switching tube T1 and/or the second switching tube T2 in the first operational amplifier gm1 to the corresponding current source is cut off), so that the supply current of the current source is deflected, and the offset voltage of the first operational amplifier gm1 is adjusted.
In step S04, the oscillator is turned on, and the operational amplifier circuit is set to a chopper operation state.
In this embodiment, the oscillator OSC is activated, so that the operational amplifier circuit 210 operates in a chopping state. At this time, the oscillator OSC outputs a first control signal to control the first switch K1 to perform an off/on operation, and can modulate a normal input signal of the circuit into a high-frequency signal; and outputting a second control signal, controlling the second switch K2 to carry out on/off operation, demodulating a high-frequency input signal, modulating the input offset voltage VOS into a high-frequency signal, and filtering the high-frequency signal through filtering processing to reduce the offset voltage VOS of the circuit.
Furthermore, the chopping frequency or the filtering frequency of the circuit is the frequency of the modulated offset voltage.
In the chopping amplification method provided by this embodiment, the offset voltage expected by the operational amplifier is first reduced, and then the offset voltage is further reduced by the chopping technique. Therefore, the operational amplifier has lower offset voltage and output noise under low power consumption, and has better amplification performance.
It should be noted that, in this document, the contained 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 phrases "comprising a," "8230," "8230," or "comprising" does not exclude the presence of additional like elements in a process, method, article, or apparatus that comprises the element.
Finally, it should be noted that: it should be understood that the above examples are only for clearly illustrating the present invention and are not intended to limit the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. And obvious variations or modifications of the invention may be made without departing from the scope of the invention.
Claims (14)
1. A chopper amplification apparatus, comprising:
an operational amplifier circuit for generating an output signal from an input signal, the operational amplifier circuit including a plurality of operational amplifiers on a first signal transmission path for transmitting a low frequency signal of the input signal and a second signal transmission path for transmitting a high frequency signal of the input signal;
the detection circuit is connected with the first signal transmission path of the operational amplification circuit and used for detecting the offset voltage of the first signal transmission path of the operational amplification circuit and outputting a corresponding trimming signal according to a detection result; and
the trimming circuit is connected with the first signal transmission path of the operational amplification circuit and the detection circuit and is used for receiving the trimming signal and generating a current signal according to the trimming signal;
during the trimming stage, the operational amplifiers of the operational amplification circuit work in a non-chopping state;
in the chopping phase, a first operational amplifier connected with a signal input end in a first signal transmission path of the operational amplification circuit works in a chopping state according to a control signal, the trimming circuit reduces the offset voltage of the first signal transmission path of the operational amplification circuit by adopting the current signal, and the first operational amplifier modulates the offset voltage into a high-frequency signal, so that the input offset voltage can be further reduced through filtering processing.
2. The chopper amplification device according to claim 1, wherein the operational amplification circuit includes:
and the oscillator is used for generating the control signal when in work so as to enable the operational amplification circuit to work in a chopping state.
3. The chopper amplification device of claim 2,
the first signal transmission path of the operational amplification circuit further includes a second operational amplifier and a third operational amplifier, the second signal transmission path of the operational amplification circuit includes a fourth operational amplifier,
the input end of the first operational amplifier is connected with the input end of the operational amplifier through a first switch;
the input end of the second operational amplifier is connected with the output end of the first operational amplifier through a second switch;
the input end of the third operational amplifier is connected with the output end of the second operational amplifier, and the output end of the third operational amplifier is connected with the output end of the operational amplification circuit; and
the input end of the fourth operational amplifier is connected with the input end of the operational amplifier, the output end of the fourth operational amplifier is connected with the input end of the third operational amplifier,
the operational amplification circuit further includes:
a first capacitor connected between the second switch and the output terminal of the third operational amplifier; and
and the second capacitor is connected between the output end of the second operational amplifier and the output end of the third operational amplifier.
4. The chopper amplification device of claim 3, wherein the first operational amplifier is connected to the detection circuit and the trimming circuit, respectively.
5. The chopper amplification device of claim 3, wherein the first switch and the second switch are each coupled to an oscillator for receiving a respective control signal from the oscillator to electrically connect or disconnect the input and/or output of the first operational amplifier to the operational amplification circuit.
6. The chopper amplification device of claim 4, wherein the first operational amplifier includes:
a grid electrode of the first switching tube is connected with a non-inverting input end of the first operational amplifier, and a second path end of the first switching tube is grounded through a third current source;
a grid electrode of the second switching tube is connected with the inverting input end of the first operational amplifier, and a second path end is grounded through a third current source; and
and the first input end of the double-end output circuit is connected with the first channel end of the first switching tube, the second input end of the double-end output circuit is connected with the first channel end of the second switching tube, and the output end of the double-end output circuit is connected with the output end of the first operational amplifier.
7. The chopper amplification device of claim 4, wherein the trimming circuit comprises:
the first current source and the first resistor are sequentially connected in series between the power supply end and the first path end of the first switching tube;
a second current source and a second resistor which are sequentially connected in series between the power supply end and the first path end of the second switch tube,
wherein the first current source and/or the second current source is configured to output different current signals according to corresponding trimming signals.
8. The chopper amplification device of claim 6 or 7, wherein the first and second switching transistors are both PMOS transistors.
9. A chopping amplification method, comprising:
the operational amplifier circuit comprises a plurality of operational amplifiers positioned on a first signal transmission path and a second signal transmission path, wherein the first signal transmission path is used for transmitting a low-frequency signal of an input signal, and the second signal transmission path is used for transmitting a high-frequency signal of the input signal;
testing the offset voltage of a first signal transmission path of the operational amplification circuit, wherein the operational amplifiers of the operational amplification circuit work in a non-chopping state;
adjusting the offset voltage of a first signal transmission path of the operational amplification circuit according to the test result;
starting an oscillator, configuring a first operational amplifier connected with a signal input end in a first signal transmission path of the operational amplification circuit to be in a chopping working state,
the first operational amplifier modulates the offset voltage into a high-frequency signal in a chopping working state, so that the input offset voltage is further reduced through filtering processing.
10. The chopper amplification method of claim 9, wherein configuring the operational amplifier circuit to a normal operating state further comprises:
and connecting a first operational amplifier into the operational amplification circuit, and configuring the operational amplification circuit into a multi-stage operational amplification mode.
11. The chopper amplification method of claim 9, wherein adjusting the offset voltage of the first signal transmission path of the operational amplification circuit according to the test result comprises:
when the offset voltage of the operational amplification circuit is detected to be positive offset, outputting a first trimming signal;
when the offset voltage of the operational amplification circuit is detected to be negative offset, outputting a second trimming signal;
and adjusting the output current of the first current source and/or the second current source according to the first trimming signal or the second trimming signal, so as to adjust the offset voltage of the first operational amplifier.
12. The chopper amplification method of claim 9, wherein adjusting the offset voltage of the first signal transmission path of the operational amplifier circuit based on the test result includes:
and cutting off the current output path of the first current source and/or the second current source by adopting a laser cutting mode.
13. The chopping amplification method of claim 9, wherein configuring the operational amplification circuit in a chopping operational state comprises:
outputting a first control signal by the oscillator, controlling a first switch to carry out off/off operation, and modulating an input signal into a high-frequency signal; and
outputting a second control signal by the oscillator, controlling a second switch to perform an off/off operation, demodulating a high frequency input signal, and modulating an offset voltage into a high frequency signal.
14. The chopper amplification method of claim 13, wherein the filtering frequency of the filtering process is the frequency of the modulated offset voltage.
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| CN108494370A (en) * | 2018-05-31 | 2018-09-04 | 福州大学 | Chopper-stabilized instrumentation amplifier |
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| US7132883B2 (en) * | 2005-02-08 | 2006-11-07 | Maxim Integrated Products, Inc. | Chopper chopper-stabilized instrumentation and operational amplifiers |
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| US6275098B1 (en) * | 1999-10-01 | 2001-08-14 | Lsi Logic Corporation | Digitally calibrated bandgap reference |
| CN106972834A (en) * | 2017-02-24 | 2017-07-21 | 浙江大学 | A kind of ripple cancellation loop for Capacitance Coupled chopper amplifier |
| CN107332521A (en) * | 2017-05-31 | 2017-11-07 | 苏州真感微电子科技有限公司 | High accuracy, low drifting, low imbalance, the chopper amplifier of low noise |
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