Inverting operational amplifier circuit for eliminating input offset voltage

Abstract

This application relates to the field of operational amplifier circuit technology, and more particularly to an inverting operational amplifier circuit for eliminating input offset voltage. It includes an input resistor for receiving an input voltage; an operational amplifier for inverting and amplifying the input voltage; an output resistor section connected in series between the output terminal of the operational amplifier and the input resistor, the output resistor section being composed of multiple output resistors connected in series; multiple current sources connected to nodes between the various output resistors of the output resistor section, the current sources being used to compensate for the output offset voltage caused by the input offset voltage of the operational amplifier; and a digital code input section for adjusting the current values ​​of the current sources; wherein the voltage value of the output offset voltage is determined based on the current values ​​of the multiple current sources and the corresponding resistance values ​​of the output resistor section. Using this application is advantageous for canceling the output offset voltage caused by the input offset voltage of the operational amplifier and appearing at the output terminal.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of operational amplifier circuit, and particularly relates to an inverting operational amplifier circuit for eliminating input offset voltage. BACKGROUND

[0002] In recent years, in the field of analog and mixed signal circuits, operational amplifiers (OPAMP) are widely used in key links such as signal amplification, filtering and signal conditioning, especially in high-precision sensor signal processing, ADC input buffering and low-noise preamplification applications, and have become indispensable core components. With the continuous expansion of the application range of operational amplifiers, how to reduce errors and improve linearity to ensure the accuracy of the overall performance of the circuit has become an important technical challenge. Among them, eliminating the output offset caused by the input offset voltage (VOS) is a core problem that must be solved in high-precision analog circuit design.

[0003] In the prior art, in order to compensate for the input offset voltage, methods such as voltage trimming, internal differential input pair symmetry, offset cancellation circuit based on voltage reference, or automatic compensation loop (such as automatic zero and chopping technology) are usually used, for example, Japanese Patent No. JP2000091857A, entitled "Operational amplifier and voltage follower circuit applied thereto", Korean Patent No. KR101304147B1, entitled "Operational amplifier circuit". However, these methods generally have high design complexity, large silicon area occupation, high additional power consumption, dependence on external reference voltage, and may introduce high-frequency noise. Especially in the face of offset voltage dynamically generated due to temperature, process fluctuation, stress and other external environmental changes, traditional methods are difficult to achieve real-time and quantitative accurate compensation, showing obvious limitations.

[0004] In addition, in high-precision analog circuit systems, the offset component in the output voltage will cause system nonlinearity, offset error and distortion and other problems. Therefore, eliminating such offset voltage is no longer just an "auxiliary compensation function", but is considered as a key element that determines the overall performance of the system.

[0005] Therefore, the industry has higher requirements for offset voltage compensation technology: it can achieve real-time and quantitative compensation with a simpler circuit structure, and still maintain robust compensation ability under process deviation and temperature change conditions. Related technical requirements are growing. SUMMARY

[0006] The embodiment of the present application provides an inverting operational amplifier circuit for eliminating input offset voltage, which is beneficial to offset the output offset voltage caused by the input offset voltage of the operational amplifier and appearing at the output end

[0007] The first aspect of the embodiment of the present application provides an inverting type operational amplifier circuit for eliminating input offset voltage, comprising:

[0008] an input resistor for receiving input voltage;

[0009] an operational amplifier for inversely amplifying and outputting the input voltage;

[0010] an output resistor part connected in series between the output terminal of the operational amplifier and the input resistor, the output resistor part being composed of a plurality of output resistors connected in series;

[0011] a plurality of current sources connected to nodes between the respective output resistors of the output resistor part, the current sources being used for compensating output offset voltage caused by input offset voltage of the operational amplifier; and

[0012] a digital code input part for adjusting the current values of the current sources; wherein

[0013] the voltage value of the output offset voltage is determined according to the respective current values of the plurality of current sources and the resistance values corresponding to the output resistor part.

[0014] Optionally, the plurality of output resistors are connected in series to form a total output resistor, and the resistance value of the total output resistor and the resistance values of the plurality of output resistors satisfy the following relationship:

[0015]

[0016] wherein, is the resistance value of the total output resistor, is the resistance value of the mth output resistor, m is the index of the output resistor, and the value range of m is , and n is the number of the output resistors.

[0017] Optionally, each current source applies a predetermined current through the connection node thereof, so as to realize the offset of the output offset voltage caused by the input offset voltage of the operational amplifier, is the current value of the preset current applied by the kth current source, k is the index of the current source, and the value range of k is , and n-1 is the number of the current sources.

[0018] Optionally, the digital code input part is used for receiving a plurality of digital control codes, each digital control code being used for setting the current value output by the corresponding current source, and the kth digital control code is used for setting the current value output by the kth current source .

[0019] Optionally, the digital code input unit is equipped with a corresponding switch for each current source. The current flow is controlled by controlling the opening or closing state of the switch through the digital control code. When n-1 switches are in the open state at the same time, the total current used for compensation is the sum of the current values ​​applied by n-1 current sources at the same time.

[0020] Optionally, the voltage value of the output offset voltage is equal to:

[0021]

[0022] in, The voltage value of the output offset voltage.

[0023] Optionally, the input offset voltage is caused by input current imbalance due to process imbalance and / or packaging stress, and the output offset voltage is amplified to the input offset voltage. times, of which, The resistance value of the input resistor.

[0024] Optionally, the output voltage value satisfies the following calculation formula:

[0025]

[0026] Where k represents the index of the current source, and m represents the index of the corresponding output resistor after the current source.

[0027] The inverting operational amplifier circuit provided in this application divides the overall output resistance into multiple output resistors to form an output resistance section, inserts multiple current sources between the output resistors, and controls each current source according to digital control code, thereby accurately canceling the output offset voltage caused by the input offset voltage of the operational amplifier and appearing at the output terminal.

[0028] A second aspect of this application provides another inverting operational amplifier circuit for eliminating input offset voltage, comprising:

[0029] An input resistor used to receive the input voltage;

[0030] An operational amplifier used to invert and amplify the input voltage and output it;

[0031] An output resistor section connected in series between the output terminal of the operational amplifier and the input resistor, wherein the output resistor section is composed of a first output resistor and a second output resistor connected in series;

[0032] a current source connected to a node between the first output resistor and the second output resistor, the current source being configured to apply a current to compensate for an output offset voltage caused by an input offset voltage of the operational amplifier;

[0033] a digital current control unit including a plurality of switches, each of the switches being connected in series with a corresponding current source, the digital current control unit being configured to selectively set states of the plurality of switches according to a digital control code to form a plurality of current loops;

[0034] wherein the digital current control unit is further configured to determine an effective current applied to the current source according to the digital control code, and to compensate for an output offset voltage caused by the input offset voltage at the output of the operational amplifier according to a product of the effective current applied by the current source and a resistance value of the second output resistor.

[0035] Optionally, the digital current control unit is configured to have a plurality of switches connected in parallel in a current path of the current source, each of the switches being controlled to be in an on state or an off state according to a bit value of the digital control code, such that the effective current output by the current source is increased in proportion to a number of the switches in the on state.

[0036] Optionally, the output offset voltage compensated by the current source is wherein N represents a number of the switches set to the on state according to the digital control code, a current applied to the current source, a resistance value of the second output resistor.

[0037] The inverting operational amplifier circuit provided by the embodiments of the present application divides the output resistor into two output resistors, and arranges a single current source at a node between the two output resistors, and precisely adjusts the current compensation amount by means of the digital current control unit having a plurality of parallel switches, thereby providing a circuit structure capable of quantitatively removing the output offset voltage without a complex circuit structure.

[0038] The embodiments of the present application can bring the following technical effects: 1. The output voltage compensation can be achieved in fine units by subdividing the overall output resistor into a plurality of output resistors and configuring a current source between the output resistors. 2. Real-time compensation can be achieved by using only a digital code without relying on an external reference voltage or a complex calibration circuit, thereby simplifying the circuit design. 3. The linearity and conversion accuracy of the overall analog circuit can be improved by eliminating the output offset voltage. 4. Since the compensation circuit of the inverting operational amplifier circuit can be designed in a low-area structure, it can be effectively integrated into a high-integration circuit (IC). 5. The input offset voltage caused by environmental changes (such as process, temperature, and power supply fluctuations) can be effectively compensated, ensuring the stability of the output characteristics. BRIEF DESCRIPTION OF DRAWINGS

[0039] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the accompanying drawings needed to be used in the description of the embodiments or the prior art will be briefly introduced. Obviously, the accompanying drawings in the following description only represent some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative effort.

[0040] Figure 1 A structural schematic diagram of a conventional inverting type operational amplifier circuit containing input offset voltage of the operational amplifier is shown;

[0041] Figure 2 A structural schematic diagram of an inverting type operational amplifier circuit for eliminating input offset voltage is shown;

[0042] Figure 3 A structural schematic diagram of an inverting type operational amplifier circuit for eliminating input offset voltage is shown;

[0043] Figure 4 A structural schematic diagram of an inverting type operational amplifier circuit for eliminating input offset voltage is shown;

[0044] Figure 5 A structural schematic diagram of an inverting type operational amplifier circuit for eliminating input offset voltage is shown;

[0045] Figure 6 A structural schematic diagram of an inverting type operational amplifier circuit for eliminating input offset voltage is shown. DETAILED DESCRIPTION

[0046] In the description of the embodiments of the present application, the description of specific structures or functions is only for example, and is not intended to limit the present application. The embodiments can be implemented in various forms, and are not limited to the specific modes listed herein.

[0047] The present application is shown by the accompanying drawings and detailed description, and the purpose is not to limit the present application to the disclosed specific forms, on the contrary, to cover all modifications, equivalents and alternatives within the scope and spirit of the present application.

[0048] The terms such as "first", "second" and the like are only used to distinguish different components, and do not imply any order or importance. Without departing from the scope of the present application, the first component can also be called the second component, and vice versa.

[0049] When a component is said to "connect" or "contact" another component, it may be directly connected or in contact, or there may be an intermediate component. If "directly connected" or "directly in contact" is used, it means there is no intermediate component. Other expressions describing component relationships (such as "between" and "directly between," "adjacent" and "directly adjacent," etc.) should be interpreted similarly.

[0050] Unless otherwise expressly stated, the terms used herein (including technical and scientific terms) shall have the meanings commonly understood by one of ordinary skill in the art to which this application pertains. Where a term is defined in a general dictionary, its meaning shall be understood in the context of the art, and it shall not be interpreted in an overly idealized or rigid manner unless explicitly defined herein.

[0051] The embodiments will be described in detail below with reference to the accompanying drawings. It should be noted that these embodiments are for illustrative purposes only and are not intended to limit the scope of the patent claims. The same reference numerals in different drawings denote the same or similar parts.

[0052] Please refer to Figure 1 This illustration shows a schematic diagram of a conventional inverting operational amplifier circuit including an operational amplifier input offset voltage according to an embodiment of this application. The operational amplifier circuit 100 is a typical inverting amplifier structure used to amplify the input voltage in reverse and output it. Its main components include: an input voltage source for simulating the input voltage (…). ), offset voltage source for simulating offset voltage ( ), input resistance ( ), output resistance ( ), operational amplifier (OPAMP) and output voltage .

[0053] Input voltage source ( The voltage value of the input voltage source is measured relative to a ground reference point. ) through input resistor ( The input voltage is applied by connecting the offset voltage source to the inverting input (-) of the operational amplifier (OPAMP). The input offset voltage () is used to represent the input offset voltage that naturally occurs in an actual operational amplifier (OPAMP) circuit due to input current imbalance and / or manufacturing process deviation. It is connected to the non-inverting input (+) of the operational amplifier.

[0054] The operational amplifier amplifies the voltage difference between the inverting input (-) and the non-inverting input (+) and outputs it through the output terminal. Simultaneously, the inverting input (-) is connected to the input resistor (...). ) receives the input voltage and passes it through the output resistor ( receiving an output voltage from the output terminal , thereby forming a closed feedback loop.

[0055] In an ideal case, the voltage difference between the two input terminals of the operational amplifier circuit should tend to zero, thereby realizing an accurate inverting amplification function. However, in an actual circuit, due to the existence of offset voltage, an unintended deviation will be introduced into the output voltage. Therefore, the actual output voltage can be represented by the following formula:

[0056]

[0057] As shown in the above formula, the offset voltage existing in the input terminal will be amplified by the gain coefficient (A) of the operational amplifier and output, and therefore, even a tiny offset voltage can cause a larger voltage distortion in the output voltage.

[0058] Therefore, Figure 1 The structure shown in the above formula is a general inverting amplifier structure formed by using an operational amplifier OPAMP, but due to the manufacturing process and physical stress, etc., an offset voltage will inevitably be generated, thereby including an error component in the output signal, which has certain limitations.

[0059] Please refer to Figure 2 , which shows a structure diagram of an inverting operational amplifier circuit for eliminating input offset voltage provided by an embodiment of the present application. The inverting operational amplifier circuit (200) comprises: an input resistor (210) for receiving an input voltage; an operational amplifier (220) for inverting and amplifying the input voltage and outputting; an output resistor part (230) connected in series between the output terminal of the operational amplifier and the input resistor, the output resistor part (230) being formed by a plurality of output resistors connected in series; a plurality of current sources (240) connected to the nodes between the respective output resistors of the output resistor part (230), the current sources (240) being used for compensating the output offset voltage caused by the input offset voltage of the operational amplifier (220); and a digital code input part (250) for adjusting the current value of the current sources (240).

[0060] One end of the input resistor (210) is connected to an input voltage source, and the other end is electrically connected to the inverting input terminal (—) of the operational amplifier (220). The input resistor (210) is used for receiving an input voltage (Vin) applied from outside and transmitting it to the inverting input terminal (—) of the operational amplifier (220).

[0061] ​​The operational amplifier (220) is a device that amplifies the potential difference between the inverting input terminal (-) and the non-inverting input terminal (+) and outputs it. In the present embodiment, the non-inverting input terminal is set to a ground (GND) state. The operational amplifier (220) realizes an inverting amplification function with a gain (Gain) set to by adjusting the sum of the voltage input to the inverting input terminal (-) and the voltage fed back from the output terminal to tend to zero.

[0062] The output resistance section (230) is connected in series between the output terminal of the operational amplifier (220) and the input resistance (210) and is composed of a plurality of output resistances connected in series to constitute a total output resistance. The output resistances are connected in series and are set to total resistance values that satisfy the following relationship:

[0063] The resistance values of the total output resistance and the plurality of output resistances satisfy the following relationship:

[0064]

[0065] wherein is the resistance value of the total output resistance, is the resistance value of the mth output resistance, m is the index of the output resistance, and m takes a value in the range of , and n is the number of output resistances.

[0066] The plurality of current sources (240) are respectively connected to the nodes between the output resistances of the output resistance section (230), that is, the current source is connected to the node between and , the current source is connected to the node between and , and the current source is connected to the node between and .

[0067] Each of the current sources (240) applies a predetermined current through its connection node to thereby realize cancellation of the output offset voltage caused by the input offset voltage of the operational amplifier (220), is the current value of the preset current applied by the kth current source, k is the index of the current source, and k takes a value in the range of , and n-1 is the number of current sources.

[0068] The digital code input section (250) is configured to receive a plurality of digital control codes , , , each digital control code is used to set the current value of the corresponding current source output, the kth digital control code is used to set the current value of the kth current source output .

[0069] The digital code input unit (250) is provided with a corresponding switch for each current source (240), and the flow of current is controlled by controlling the opening or closing state of the switch through the digital control code. When n-1 switches are simultaneously in the open state, the total current used for compensation is the sum of the current values of n-1 current sources (240) simultaneously applied.

[0070] The voltage value of the output offset voltage is determined according to the current value of each of the plurality of current sources and the resistance value corresponding to the output resistance unit, which satisfies the following relationship:

[0071]

[0072] The input offset voltage is caused by the input current imbalance due to process imbalance or / and package stress, and the output offset voltage is amplified to times of the input offset voltage, wherein, is the resistance value of the input resistance.

[0073] The output voltage ( ) includes a reverse amplification component of the input voltage ( ), an influence component of the input offset voltage ( ), and an output offset voltage component compensated by the current source, which can be represented by the following formula:

[0074]

[0075] Wherein, k represents the index of the current source, and m represents the index of the output resistance after the corresponding current source.

[0076] In summary, Figure 2 The inverting operational amplifier circuit (200) shown can accurately cancel the output offset voltage caused by the input offset voltage of the operational amplifier and appearing at the output end by dividing the overall output resistance into a plurality of output resistances to form an output resistance unit, and inserting a plurality of current sources between the output resistances, and controlling each current source according to a digital control code.

[0077] Please refer to Figure 3Fig. 3 shows a schematic diagram of an inverting operational amplifier circuit for eliminating input offset voltage according to another embodiment of the present application. The inverting operational amplifier circuit (300) comprises: an input resistor (310) for receiving an input voltage (Vin); an operational amplifier (320) for inverting and amplifying the input voltage (Vin) and outputting; an output resistor section (330) connected in series between the output of the operational amplifier (320) and the input resistor (310), the output resistor section (330) comprising a first output resistor (R1) and a second output resistor (R2) connected in series; a current source (340) connected to a node between the first output resistor (R1) and the second output resistor (R2), the current source (340) for applying a current to compensate for an output offset voltage caused by an input offset voltage of the operational amplifier (320); and a digital current control section (350) comprising a plurality of switches, each of the switches being connected in series with a corresponding current source (340), the digital current control section (350) selectively setting states of the plurality of switches according to a digital control code to form a plurality of current loops.

[0078]

[0079] The input resistor (310) is a resistor element for receiving an input voltage (Vin) applied by an external voltage source and transmitting the input voltage (Vin) to the inverting input terminal (—) of the operational amplifier (320). The first end of the input resistor (310) is electrically connected to the input voltage source, and the second end is electrically connected to the inverting input terminal (—) of the operational amplifier (320).

[0080] The operational amplifier (320) is an operational element for generating an output voltage (Vout) at the output terminal by amplifying a potential difference between the inverting input terminal (—) and the non-inverting input terminal (+) to which a reference potential is applied. The input offset voltage (Vos) of the operational amplifier (320) is 0 in an ideal condition, but the input offset voltage (Vos) exists in an actual circuit due to process errors and / or package stress. The operational amplifier (320) amplifies the input offset voltage (Vos) according to the voltage gain (Gain) of the inverting amplifier and outputs the input offset voltage (Vos) at the output terminal, thereby forming an output offset voltage.

[0081] ​​​​​​​​​​The output resistance part (330) is connected in series between the output of the operational amplifier (320) and the input resistance (310), and is composed of a first output resistance (R1) ) and a second output resistance (R2) ). The output resistance part (330) is composed of two series resistances by dividing the total output resistance. The output resistance part (330) is a path through which the output voltage of the operational amplifier (320) is fed back to the input, and plays a core role in realizing the inverting amplification of the operational amplifier.

[0082] The current source (340) is electrically connected to the node between the first output resistance (R1) ) and the second output resistance (R2) ), and functions to compensate for the output offset voltage generated at the output due to the input offset voltage of the operational amplifier (320) by providing a constant current. The single current source (340) can be configured to apply a current with a value of , and the compensation direction is determined according to the polarity of the input offset voltage.

[0083] The digital current control part (350) is a circuit module connected in series in the current application path of the current source (340), and includes a plurality of parallel switches, and sets each switch to an on or off state according to a digital control code (D) ). The digital current control part (350) has a circuit structure in which the switches are connected in parallel, and only when the switch corresponding to the bit value of the digital control code is set to "1", the switch is in an on state, thereby forming a current loop.

[0084] The total current applied to the circuit by the current source (340) can be linearly adjusted according to the number (N) of switches set to the on state. The current applied by the current source (340) flows through the second output resistance (R2) ), and thereby forms a compensation voltage at the output. Therefore, the total output voltage (Vout) ) includes the inverted amplification result of the input voltage (Vin) ), the amplification component of the input offset voltage (Vos) ), and the compensation component introduced by the current source.

[0085] In summary, the inverting operational amplifier circuit (300) divides the output resistance into two output resistances, and arranges a single current source at the node between the divided output resistances, and simultaneously adjusts the current compensation amount accurately through the digital current control part having a plurality of parallel switch structures, thereby providing a circuit structure capable of quantitatively removing the output offset voltage without a complex circuit structure.

[0086] Please refer to Figure 4Fig. 4 shows a schematic diagram of an inverting operational amplifier circuit for eliminating input offset voltage according to another embodiment of the present application. The inverting operational amplifier circuit (400) comprises: an input resistor (Rin) for receiving an input voltage (Vin); ); an operational amplifier (OPAMP) for inverting amplifying the input voltage (Vin) and outputting; an output resistor section connected in series between the output of the operational amplifier (OPAMP) and the input resistor (Rin), the output resistor section being composed of a plurality of output resistors connected in series; ; a plurality of current sources (I1, I2, I3, I4) connected respectively to nodes between the output resistors of the output resistor section, the current sources being used to compensate for output offset voltage caused by input offset voltage of the operational amplifier (OPAMP); and a digital code input section for adjusting current values of the current sources.

[0087] The input resistor (Rin) is a resistor element for receiving an input voltage (Vin) applied from outside and transmitting it to the inverting input terminal (—) of the operational amplifier (OPAMP). One end of the input resistor (Rin) is connected to the input voltage source, and the other end is connected to the inverting input terminal of the operational amplifier (OPAMP). The operational amplifier (OPAMP) amplifies the voltage difference between the inverting input terminal (—) and the non-inverting input terminal (+) and generates an output voltage (Vout) at the output terminal. The non-inverting input terminal is connected to a reference potential (e.g., ground). The operational amplifier (OPAMP) can generate current imbalance at the input terminal due to manufacturing process deviation and / or package stress, thereby generating input offset voltage (Vos). The input offset voltage (Vos) is amplified according to the gain coefficient of the circuit and then output, thereby forming output offset voltage.

[0088] The output resistor section is connected in series between the output of the operational amplifier and the input resistor (Rin) and is composed of a plurality of output resistors (R1, R2, R3, R4) connected in series, thereby constituting total output resistance (Rout). The current sources (I1, I2, I3, I4) are connected respectively to nodes between the output resistors (R1, R2, R3, R4). Each current source applies a current of a specific direction to the output resistor after the node to which it is connected, thereby generating a voltage drop for canceling the output offset voltage. For example, the current source (I1) connected to the node between the input resistor (Rin) and the output resistor (R1) applies a current of a specific direction to the output resistor (R1) after the node to which it is connected, thereby generating a voltage drop for canceling the output offset voltage.

[0089] The output resistor section is connected in series between the output of the operational amplifier and the input resistor (Rin) and is composed of a plurality of output resistors (R1, R2, R3, R4) connected in series, thereby constituting total output resistance (Rout). The current sources (I1, I2, I3, I4) are connected respectively to nodes between the output resistors (R1, R2, R3, R4). Each current source applies a current of a specific direction to the output resistor after the node to which it is connected, thereby generating a voltage drop for canceling the output offset voltage. For example, the current source (I1) connected to the node between the input resistor (Rin) and the output resistor (R1) applies a current of a specific direction to the output resistor (R1) after the node to which it is connected, thereby generating a voltage drop for canceling the output offset voltage.

[0090]

[0091] ​​​​​​​​​​​​​ between the input voltage and the output voltage, and the output voltage is formed by the input voltage and the output offset voltage caused by the input offset voltage of the operational amplifier. between the input voltage and the output voltage, and the output voltage is formed by the input voltage and the output offset voltage caused by the input offset voltage of the operational amplifier. The current sources apply currents to a range of resistance regions to form a compensation voltage. Each current source can be controlled by a switch or a current DAC.

[0092] The digital code input unit receives a digital control code composed of digital codes of , , …, , and adjusts the on / off state or current value of the corresponding current source according to the bit value of each digital code.

[0093] The output offset voltage is caused by the input offset voltage (Vos_in) and is a voltage formed at the output end of the operational amplifier (OPAMP). The compensation amount of the output offset voltage is composed of the sum of the currents of the current sources and the output resistances at the positions after the current sources, and satisfies the following relationship:

[0094]

[0095] At this point, the overall output voltage (Vout) includes an amplified component of the input voltage (Vin), an amplified component of the input offset voltage (Vos_in), and an output offset voltage component compensated by the current sources, and can be represented by the following formula:

[0096]

[0097] where k represents the index of the current source, and m represents the index of the output resistance after the corresponding current source.

[0098] In summary, Figure 4 , the inverting type operational amplifier circuit (400) includes an output resistance unit composed of a plurality of output resistances, a plurality of current sources connected to the nodes between the output resistances, and a digital code input unit for digitally controlling the current sources, and has a structure that quantitatively eliminates the output offset voltage caused by the input offset voltage of the operational amplifier by a current compensation method.

[0099] Please refer to Figure 5 , which shows the structure of the inverting type operational amplifier circuit for eliminating the input offset voltage provided by another embodiment of the present application. The inverting type operational amplifier circuit (500) includes: an input resistance (Rin) for receiving an input voltage; an operational amplifier (OPAMP) for inversely amplifying and outputting the input voltage; and an output resistance unit connected in series between the output end of the operational amplifier and the input resistance (Rin), the output resistance unit being composed of a first output resistance (R1), a second output resistance (R2), a third output resistance (R3), and a fourth output resistance (R4). ​​​​​​) and the second output resistor ( It is formed by series connection; connected to the first output resistor ( ) and the second output resistor ( The current source at the node between the operational amplifiers is used to apply current to compensate for the output offset voltage caused by the input offset voltage of the operational amplifier; a digital current control unit including multiple switches, each switch being connected in series with its corresponding current source, the digital current control unit selectively setting the state of the multiple switches according to digital control codes to form multiple current loops.

[0100] Input resistance ( () is a resistive element whose function is to receive the input voltage applied by an external voltage source. ), and pass it to the inverting input (—) of the operational amplifier (OPAMP). Input resistance ( The first terminal of the amplifier is electrically connected to the input voltage source, and the second terminal is connected to the inverting input terminal (—) of the operational amplifier (OPAMP).

[0101] An operational amplifier (OPAMP) is a computational element that generates an output voltage by amplifying the potential difference between its inverting input (-) and its non-inverting input (+), to which a reference potential is applied. Operational amplifiers (OPAMPs) may exhibit input offset voltage due to process errors and / or packaging stress. The operational amplifier (OPAMP) adjusts the input offset voltage based on the voltage gain of the inverting amplifier. The voltage is amplified and output at the output terminal, thereby forming the output offset voltage.

[0102] The output resistor is connected in series with the output terminal of the operational amplifier (OPAMP) and the input resistor ( Between ) by the first output resistor ( ) and the second output resistor ( The total output resistance is formed by connecting them in series. ).

[0103] The current source is electrically connected to the output resistor section. and The nodes between them, and using that node as a reference point to... Applying current creates a voltage drop in the resistive section, which in turn counteracts the output offset voltage.

[0104] The digital current control unit is connected in series with the current source. The current application path includes a plurality of parallel switches, each of which is set to an open or closed state according to the bit value of a digital control code. The digital control code can be provided by an external control circuit or an internal sequential controller, and the number of current paths is determined by the different combination states of the switches.

[0105] According to the number N of switches set to the on state, the current source The effective current actually applied to the circuit satisfies the following relationship:

[0106]

[0107] wherein, is the reference current amount applied by the single path, is the number of switches in the open state.

[0108] The current source The applied current flows through the output resistor and forms the following compensation voltage at the output end:

[0109]

[0110] The output voltage is composed of the inverse amplification component of the input voltage , the output offset voltage caused by the input offset voltage, and the current compensation voltage, and can be represented by the following formula.

[0111]

[0112] wherein, is the sum of and , and is the resistance value of the second input resistor.

[0113] In summary, Figure 5 The inverting operational amplifier circuit (500) shown in the figure divides the output resistor into only two output resistors and , and connects a single current source , and the digital current control code is used to quantitatively control the current applied by the current source, thereby providing a circuit structure capable of simply and accurately compensating for the output offset voltage. In addition, the digital current control part can cope with various offset voltage conditions through the hierarchical selection of the current while maintaining a simple hardware structure, thereby improving the compensation accuracy of the output offset voltage caused by process deviation or temperature variation. Therefore, the inverting operational amplifier circuit (500) based on the embodiment can not only maintain the accuracy of the analog circuit, but also effectively reduce the circuit area and power consumption in aspects such as simplifying the output resistor part structure, reducing the number of current sources, and adopting a flexible compensation method based on digital codes, thereby exhibiting the advantages of efficient composition.

[0114] Please refer to Figure 6 , which shows the performance simulation result diagram of the inverting operational amplifier circuit for eliminating input offset voltage provided by an embodiment of the present application. Figure 6 The simulation result shown is used to confirm the quantitative effect of the output offset voltage compensation function by comparing the conventional inverting operational amplifier circuit with the input offset voltage and the inverting operational amplifier circuit for eliminating the input offset voltage in the present application. In this simulation, the gain coefficient is fixed at 1, the input offset voltage is set to 10.2 mV, and a time-based input signal linearly varying from -200 mV to +200 mV is applied. First, the simulation takes the conventional inverting operational amplifier circuit without eliminating the input offset voltage as the reference. The circuit is composed of an input resistor receiving an input voltage, an operational amplifier (OPAMP) inverting and amplifying the input voltage, and an output resistor connected in series between the output end of the OPAMP and the input resistor.

[0115] Figure 6 In the simulation result shown, the output voltage characteristic of the conventional circuit is represented by the red line, which shows a displacement trend of about 20.4 mV in the vertical direction compared to the origin (0, 0). This intuitively shows the phenomenon of output voltage distortion caused by the input offset voltage. Subsequently, the simulation constructs an inverting operational amplifier circuit applying the input offset voltage elimination function of the present application. The circuit includes an input resistor receiving an input voltage, an operational amplifier (OPAMP) inverting and amplifying the input voltage, a first output resistor and a second output resistor connected in series as the output resistor part, a current source connected to the node between and , a digital current control part composed of multiple switches connected in series in the current application path of the current source, and a digital control code controlling the above switches. Wherein, N represents the number of parallel current paths set to the on state according to the digital control code, which is set to 20.4 mV. It can be seen that the output offset voltage component in the output voltage is quantitatively completely eliminated, and the output voltage strictly follows the ideal inverting amplification characteristic curve.

[0116] Figure 6 In the simulation results of the compensation circuit, the output waveform is represented by a blue line, and it can be confirmed that when the input voltage is 0V, the output voltage is also accurately maintained at 0V. As a result, Figure 6 The simulation shows the following numerical comparison results.

[0117] By Figure 6 , it is demonstrated that the output offset voltage compensation method of the present application can accurately predict the influence of the input offset voltage on the output, and can quantitatively eliminate it by only combining the compensation current and the output resistance.

[0118] In addition, it can be confirmed that the method of the present application does not require trimming circuits or external reference voltages, and can achieve offset compensation only by digital control code, so it is a very effective circuit structure that can realize the self-compensation function for process imbalance and environmental changes.

[0119] As described above, although the embodiments are described by limited drawings, those skilled in the art can make various modifications and variations from the above description. For example, the described techniques can be executed in a different order from the description, and / or the described systems, structures, devices, circuits, etc. components can be combined or combined in a different form from the description, or replaced or replaced by other components or equivalents, and still obtain appropriate results.

[0120] Therefore, other implementations, other embodiments, and equivalents of the claims are also included within the scope of the following claims.

Claims

1. An inverting type operational amplifier circuit for canceling an input offset voltage, characterized by, Comprising: an input resistor for receiving an input voltage; an operational amplifier for inverting amplifying the input voltage and outputting; an output resistor part connected in series between the output terminal of the operational amplifier and the input resistor, the output resistor part being composed of a plurality of output resistors connected in series; a plurality of current sources connected to the nodes between the output resistors of the output resistor part respectively, the current sources being used to compensate for the output offset voltage caused by the input offset voltage of the operational amplifier; and a digital code input part for adjusting the current values of the current sources; wherein the voltage value of the output offset voltage is determined according to the current values of the current sources and the resistance values of the output resistor part.

2. The inverting type operational amplifier circuit for canceling an input offset voltage according to claim 1, wherein The plurality of output resistors are connected in series to form a total output resistor, and the resistance value of the total output resistor satisfies the following relationship with the resistance values of the plurality of output resistors: wherein, is a resistance value of the total output resistance, is a resistance value of the mth output resistance, m is an index of the output resistance, m has a value range of , n is a number of the output resistances.

3. The inverting type operational amplifier circuit for canceling an input offset voltage according to claim 2, characterized by, Each of the current sources applies a predetermined current through its connection node, so as to realize offsetting of an output offset voltage caused by an input offset voltage of the operational amplifier, a current value of the preset current applied for the kth current source, k is an index of the current source, k is in a range of , and n-1 is a number of the current sources.

4. The inverting type operational amplifier circuit for canceling an input offset voltage according to claim 3, characterized by, The digital code input unit is configured to receive a plurality of digital control codes, each of which is configured to set a current value of a corresponding current source output, and a kth digital control code is configured to set a current value of a kth current source output .

5. The inverting type operational amplifier circuit for canceling an input offset voltage according to claim 4, wherein The digital code input part is provided with a corresponding switch for each current source, and the flow of current is controlled by controlling the opening or closing state of the switch through the digital control code. When n-1 switches are simultaneously in the open state, the total current for compensation is the sum of the current values of n-1 current sources simultaneously applied.

6. The inverting type operational amplifier circuit for canceling an input offset voltage according to claim 5, wherein The voltage value of the output offset voltage is equal to: wherein, is the voltage value of the output offset voltage.

7. The inverting type operational amplifier circuit for canceling an input offset voltage according to claim 6, wherein The input offset voltage is generated due to input current imbalance caused by process imbalance or / and package stress, and the output offset voltage is amplified as times of the input offset voltage, wherein, is a resistance value of the input resistance.

8. The inverting type operational amplifier circuit for canceling an input offset voltage according to claim 7, wherein The voltage value of the output voltage satisfies the following calculation formula: where k represents the index of the current source, and m represents the index of the output resistor after the corresponding current source.

9. An inverting type operational amplifier circuit for canceling an input offset voltage, characterized by comprising: Comprising: an input resistor for receiving an input voltage; an operational amplifier for inverting amplifying the input voltage and outputting; an output resistor part connected in series between the output terminal of the operational amplifier and the input resistor, the output resistor part being composed of a first output resistor and a second output resistor connected in series; a current source connected to the node between the first output resistor and the second output resistor, the current source being used to apply a current to compensate for the output offset voltage caused by the input offset voltage of the operational amplifier; a digital current control part comprising a plurality of switches, each switch being connected in series with its corresponding current source, the digital current control part selectively setting the state of a plurality of switches according to a digital control code to form a plurality of current loops; wherein the current control part also determines the effective current applied to the current source according to the digital control code, and compensates for the offset voltage caused by the input offset voltage at the output terminal of the operational amplifier according to the product of the current applied by the current source and the resistance value of the second output resistor.

10. The inverting type operational amplifier circuit for canceling an input offset voltage according to claim 9, wherein The digital current control part is provided with a plurality of parallel switches in the current path of the current source, and each switch is individually controlled to be in the on state or the off state according to the bit value of the digital control code, so that the effective current output by the current source increases in proportion to the number of switches in the on state.

11. The inverting type operational amplifier circuit for canceling an input offset voltage according to claim 9, wherein An output offset voltage compensated by the current source is where N represents a number of switches set to an on state according to the digital control code, a current applied to the single current source, a resistance value of the second output resistance.

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