CN114123988B - Constant cross-guide rail to rail input/output operational amplifier - Google Patents
Constant cross-guide rail to rail input/output operational amplifier Download PDFInfo
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- CN114123988B CN114123988B CN202111440330.9A CN202111440330A CN114123988B CN 114123988 B CN114123988 B CN 114123988B CN 202111440330 A CN202111440330 A CN 202111440330A CN 114123988 B CN114123988 B CN 114123988B
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- 230000001502 supplementing effect Effects 0.000 claims description 21
- 230000007423 decrease Effects 0.000 claims description 20
- 230000003313 weakening effect Effects 0.000 claims description 20
- 230000002829 reductive effect Effects 0.000 claims description 18
- 239000013589 supplement Substances 0.000 claims description 10
- 238000013459 approach Methods 0.000 description 4
- 238000010586 diagram Methods 0.000 description 4
- 230000000694 effects Effects 0.000 description 2
- 230000000670 limiting effect Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
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- 230000000087 stabilizing effect Effects 0.000 description 2
- 230000003068 static effect Effects 0.000 description 2
- 230000003247 decreasing effect Effects 0.000 description 1
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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
- H03F1/301—Modifications of amplifiers to reduce influence of variations of temperature or supply voltage or other physical parameters in MOSFET amplifiers
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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
- H03F2203/00—Indexing scheme relating to amplifiers with only discharge tubes or only semiconductor devices as amplifying elements covered by H03F3/00
- H03F2203/45—Indexing scheme relating to differential amplifiers
- H03F2203/45051—Two or more differential amplifiers cascade coupled
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Abstract
The invention discloses a constant cross-guide rail to rail input/output operational amplifier, which comprises an operational amplifier circuit to be stabilized and an auxiliary circuit. The auxiliary circuit is connected between a power rail and a ground rail of the operational amplifier circuit to be stabilized, a first input end of the auxiliary circuit is connected with tail current output ends of differential pair transistors pm1 and pm2 of the operational amplifier circuit to be stabilized, a second input end of the auxiliary circuit is connected with tail current output ends of differential pair transistors nm1 and nm2 of the operational amplifier circuit to be stabilized, a first output end of the auxiliary circuit is connected with an input end of a transistor pm13 of the operational amplifier circuit to be stabilized, and a second output end of the auxiliary circuit is connected with an input end of a transistor pm14 of the operational amplifier circuit to be stabilized. According to the scheme, the auxiliary circuit is additionally arranged in the circuit of the original constant cross-rail to rail input/output operational amplifier, so that the change of the bias state of the output stage when the constant cross-rail to rail input/output operational amplifier is changed in the input common mode level is eliminated, and the operational amplifier bandwidth, the phase margin and the overall power consumption of the constant cross-rail to rail input/output operational amplifier are stabilized.
Description
Technical Field
The invention relates to the technical field of integrated circuit design, in particular to a constant cross-guide rail to rail input/output operational amplifier.
Background
Constant rail-to-rail input-output operational amplifiers are often used in integrated circuit designs. Currently, as shown in fig. 1, the constant rail-to-rail operational amplifier has an operational amplifier structure comprising two input differential pair transistors nm1, nm2 (a pair of N-MOS transistors) and pm1, pm2 (a pair of P-MOS transistors), and the range of the input common-mode voltage vcmin= (vim+vip)/2 should satisfy VSS < VCMIN < VDD. In this circuit:
when the input common-mode voltage VCMIN is close to the power rail voltage VDD, the differential pair transistors pm1 and pm2 are closed, the differential pair transistors nm1 and nm2 work, tail currents of the differential pair transistors pm1 and pm2 flow to the transistor nm6 through the transistor pm3, the tail currents are overlapped to the differential pair transistors nm1 and nm2 through the mirror images of the transistors nm6/nm5 to serve as tail current sources, bias currents of the differential pair transistors nm1 and nm2 are increased, and the overall transconductance of the operational amplifier is kept constant. However, at this time, more current from the current sources pm8, pm9 flows to the differential pair transistors nm1, nm2, so that the current flowing to the transistors pm13, pm14 decreases, and thus the current flowing to the transistors pm7, nm7 decreases, the gate-source voltages of the transistors pm7, nm7 decrease, the gate-source voltages of the output stage transistors pm15, nm15 increase, the static bias currents of the output stage transistors pm15, nm15 increase, the transconductance increases, the bandwidth and the phase margin of the op amp increase, and the static power consumption also increases.
When the input common-mode voltage VCMIN is close to the ground rail voltage VSS, the differential pair transistors nm1 and nm2 are closed, tail currents of the differential pair transistors nm1 and nm2 flow to the transistor pm6 after passing through the transistor nm3, the tail currents of the differential pair transistors pm1 and pm2 are increased through mirror images of the transistors pm6 and pm5 and are overlapped to the differential pair transistors pm1 and pm2, transconductance of the differential pair transistors pm1 and pm2 is increased, and the integral transconductance of the operational amplifier is kept constant. However, at this time, the currents of the current sources pm8, pm9 should flow through the differential pair transistors nm1, nm2, and flow to the transistors pm13, pm14, the currents of the transistors pm13, pm14 increase, the currents of the transistors pm7, nm7 increase, the gate-source voltages of the output stage transistors pm15, nm15 decrease, the quiescent current flowing through the output stage transistors pm15, nm15 decreases, the transconductance of the output stage transistors pm15, nm15 decreases, the bandwidth and the phase margin of the op amp decrease, and the quiescent power consumption also decreases.
Based on the analysis, the bias states of the output stages of the conventional constant rail-to-rail input/output operational amplifier are different under different input common-mode voltages, so that the transconductance and the power consumption of the output stages are different, and the bandwidth, the phase margin and the power consumption of the operational amplifier are greatly changed.
Disclosure of Invention
The invention aims to solve the technical problems of unstable output stage bias state, transconductance and power consumption of the conventional constant cross-rail to rail input/output operational amplifier, and provides the constant cross-rail to rail input/output operational amplifier provided with an auxiliary circuit.
Aiming at the technical problems, the invention provides the following technical scheme:
the embodiment of the invention provides a constant cross-guide rail to rail input/output operational amplifier, which comprises an operational amplifier circuit to be stabilized and an auxiliary circuit, wherein:
the auxiliary circuit is connected between a power rail and a ground rail of the operational amplifier circuit to be stabilized, a first input end of the auxiliary circuit is connected with tail current output ends of differential pair transistors pm1 and pm2 of the operational amplifier circuit to be stabilized, a second input end of the auxiliary circuit is connected with tail current output ends of differential pair transistors nm1 and nm2 of the operational amplifier circuit to be stabilized, a first output end of the auxiliary circuit is connected with an input end of a transistor pm13 of the operational amplifier circuit to be stabilized, and a second output end of the auxiliary circuit is connected with an input end of a transistor pm14 of the operational amplifier circuit to be stabilized;
when the differential pair transistors pm1, pm2 are turned off and the input currents of the transistors pm13, pm14 are reduced, the auxiliary circuit supplements the input currents of the transistors pm13, pm 14; the auxiliary circuit attenuates the input current of the transistors pm13, pm14 when the differential pair transistors nm1, nm2 are off and the input current of the transistors pm13, pm14 increases.
In some embodiments of the present invention, the constant rail-to-rail input/output operational amplifier has a first input terminal connected to an input terminal of the transistor nm6 of the operational amplifier to be stabilized and a second input terminal connected to an input terminal of the transistor pm6 of the operational amplifier to be stabilized;
when the input currents of the transistor pm13 and the transistor pm14 decrease, the input current of the transistor nm6 increases, and the auxiliary circuit supplements the input currents of the transistor pm13 and the transistor pm14 with the increased current of the input of the transistor nm 6;
when the input currents of the transistor pm13 and the transistor pm14 increase, the input current of the transistor pm6 decreases, and the auxiliary circuit attenuates the currents of the input terminals of the transistor pm13 and the transistor pm14 with the reduced current of the input terminal of the transistor pm 6.
The constant cross rail to rail input output operational amplifier described in some embodiments of the invention, the auxiliary circuit comprises:
the input end of the current supplementing circuit is connected with the input end of the transistor nm6 of the operational amplifier circuit to be stabilized, the first output end of the current supplementing circuit is connected with the first output end of the auxiliary circuit, and the second output end of the current supplementing circuit is connected with the second output end of the auxiliary circuit; when the input current of the transistor nm6 increases and the input currents of the transistor pm13 and the transistor pm14 decrease, the increased current of the input of the transistor nm6 is output to the transistor pm13 and the transistor pm14 through the current supplementing circuit to ensure that the current flowing through the transistor pm13 and the transistor pm14 is a constant value.
The constant rail-to-rail input-output operational amplifier of some embodiments of the invention, the auxiliary circuit further comprises:
the input end of the current weakening circuit is connected with the input end of the transistor pm6 of the operational amplifier circuit to be stabilized, the first output end of the current weakening circuit is connected with the first output end of the auxiliary circuit, and the second output end of the current weakening circuit is connected with the second output end of the auxiliary circuit; when the input current of the transistor pm6 decreases and the input currents of the transistor pm13 and the transistor pm14 increase, the reduced current of the input of the transistor pm6 is outputted to the transistor pm13 and the transistor pm14 through the current weakening circuit to ensure that the currents flowing through the transistor pm13 and the transistor pm14 are constant values.
The constant cross-rail to rail input/output operational amplifier in some embodiments of the present invention, the current supplementing circuit comprises a transistor nm20, the transistor nm20 is in mirror connection with the transistor nm6, and the current increased at the input end of the transistor nm6 is connected to the current supplementing circuit through the transistor nm20 mirror.
The constant rail-to-rail input-output operational amplifier of some embodiments of the present invention, the current supplementing circuit further comprises a transistor pm21, a pair of mirror transistors pm22 and pm23;
the input terminal of the transistor pm21 is connected to the output terminal of the transistor nm20, the input terminals of a pair of the mirror transistors pm22 and pm23 are connected to the output terminal of the transistor pm21, the output terminal of the transistor pm22 is connected to the input terminal of the transistor pm14, and the output terminal of the transistor pm23 is connected to the input terminal of the transistor pm 13.
The constant cross rail to rail input output operational amplifier described in some embodiments of the present invention, the current weakening circuit comprises a transistor pm20, the transistor pm20 being mirror connected to the transistor pm 6; the reduced current at the input of transistor pm6 is mirrored through transistor pm20 into the current weakening circuit.
The constant cross rail to rail input output operational amplifier described in some embodiments of the present invention, the current weakening circuit further comprises a transistor nm21, a pair of mirror transistors nm22 and nm23;
the input terminal of the transistor nm21 is connected to the output terminal of the transistor pm20, the input terminals of a pair of the mirror transistors nm22 and nm23 are connected to the output terminal of the transistor nm21, the output terminal of the transistor nm22 is connected to the input terminal of the transistor pm13, and the output terminal of the transistor nm23 is connected to the input terminal of the transistor pm 14.
The constant rail-to-rail input-output operational amplifier of some embodiments of the present invention, the sources of the transistor pm20, the transistor pm21, the transistor pm22, and the transistor pm23 are all connected to the voltage rail.
The constant cross rail to rail input output operational amplifier of some embodiments of the present invention, the sources of the transistor nm20, the transistor nm21, the transistor nm22, and the transistor nm23 are all connected to the ground rail.
Compared with the prior art, the technical scheme of the invention has the following technical effects:
the constant cross guide rail-to-rail input/output operational amplifier provided by the invention takes a circuit in a conventional constant cross guide rail-to-rail input/output operational amplifier as an operational amplifier circuit to be stabilized, and an auxiliary circuit is additionally arranged on the basis of the operational amplifier circuit to be stabilized. The auxiliary circuit is connected between a power rail and a ground rail of the operational amplifier circuit to be stabilized, a first input end of the auxiliary circuit is connected with tail current output ends of differential pair transistors pm1 and pm2 of the operational amplifier circuit to be stabilized, a second input end of the auxiliary circuit is connected with tail current output ends of differential pair transistors nm1 and nm2 of the operational amplifier circuit to be stabilized, a first output end of the auxiliary circuit is connected with an input end of a transistor pm13 of the operational amplifier circuit to be stabilized, and a second output end of the auxiliary circuit is connected with an input end of a transistor pm14 of the operational amplifier circuit to be stabilized; when the differential pair transistors pm1, pm2 are turned off and the input currents of the transistors pm13, pm14 are reduced, the auxiliary circuit supplements the input currents of the transistors pm13, pm 14; when the differential pair transistors nm1, nm2 are turned off and the input currents of the transistors pm13, pm14 increase, the auxiliary circuit attenuates the input currents of the transistors pm13, pm 14. In the above scheme, when the input common-mode voltage VCMIN of the operational amplifier circuit to be stabilized is close to the power rail voltage VDD, the tail currents of the transistors pm1 and pm2 in the operational amplifier circuit to be stabilized are supplemented by the added auxiliary circuit through the transistor pm3 to supplement the reduced currents of the transistors pm13 and pm14, and the currents flowing through the transistors pm13 and pm14 are kept constant. When the input common-mode voltage VCMIN of the operational amplifier circuit to be stabilized is close to the ground rail voltage VSS, the transistors nm1 and nm2 are closed, and the tail currents of the transistors nm1 and nm2 are subtracted by the transistor nm3 and the auxiliary circuit to correspondingly increase currents of the transistors pm13 and pm14, so that the currents flowing through the transistors pm13 and pm14 are kept constant. According to the scheme, the change of the bias state of the output stage when the constant cross guide rail-to-rail input-output operational amplifier changes in the input common mode level is eliminated, the effects of stabilizing the operational amplifier bandwidth, the phase margin and the overall power consumption of the constant cross guide rail-to-rail input-output operational amplifier are achieved, and the operational amplifier bandwidth, the phase margin and the power consumption of the constant cross guide rail-to-rail input-output operational amplifier are not changed along with the input common mode level.
Drawings
The objects and advantages of the present invention will be better understood by describing in detail preferred embodiments thereof with reference to the accompanying drawings in which:
FIG. 1 is a schematic diagram of a circuit connection of a conventional constant rail-to-rail input/output operational amplifier;
FIG. 2 is a schematic diagram of a circuit connection of a constant rail-to-rail input/output operational amplifier according to an embodiment of the present invention;
FIG. 3 is a schematic diagram of an auxiliary circuit according to an embodiment of the invention;
fig. 4 is a schematic diagram of circuit connection of a constant cross rail to rail input/output operational amplifier according to another embodiment of the present invention.
Detailed Description
The following description of the embodiments of the present invention will be made apparent and fully in view of the accompanying drawings, in which some, but not all embodiments of the invention are shown. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
In the description of the present invention, it should be noted that the directions or positional relationships indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. are based on the directions or positional relationships shown in the drawings, are merely for convenience of describing the present invention and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a specific orientation, be configured and operated in a specific orientation, and thus should not be construed as limiting the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.
In the description of the present invention, it should be noted that, unless explicitly specified and limited otherwise, the terms "mounted," "connected," and "connected" are to be construed broadly, and may be either fixedly connected, detachably connected, or integrally connected, for example; can be directly connected or indirectly connected through an intermediate medium, and can be communication between two elements. The specific meaning of the above terms in the present invention will be understood in specific cases by those of ordinary skill in the art.
In addition, the technical features of the different embodiments of the present invention described below may be combined with each other as long as they do not collide with each other.
The present embodiment provides a constant rail-to-rail input/output operational amplifier, as shown in fig. 2, including an operational amplifier circuit 10 to be stabilized and an auxiliary circuit 20. The auxiliary circuit 20 is connected between a power rail and a ground rail of the operational amplifier circuit 10 to be stabilized. The auxiliary circuit 20 is connected between the power rail and the ground rail of the operational amplifier circuit 10 to be stabilized, a first input end of the auxiliary circuit is connected with tail current output ends of differential pair transistors pm1 and pm2 of the operational amplifier circuit 10 to be stabilized, a second input end of the auxiliary circuit is connected with tail current output ends of differential pair transistors nm1 and nm2 of the operational amplifier circuit 10 to be stabilized, a first output end of the auxiliary circuit is connected with an input end of a transistor pm13 of the operational amplifier circuit 10 to be stabilized, and a second output end of the auxiliary circuit is connected with an input end of a transistor pm14 of the operational amplifier circuit 10 to be stabilized; when the differential pair transistors pm1, pm2 are turned off and the input currents of the transistors pm13, pm14 are reduced, the auxiliary circuit supplements the input currents of the transistors pm13, pm 14; the auxiliary circuit attenuates the input current of the transistors pm13, pm14 when the differential pair transistors nm1, nm2 are off and the input current of the transistors pm13, pm14 increases.
Specifically, a first input terminal of the auxiliary circuit 20 is connected to an input terminal of the transistor nm6 of the to-be-stabilized operational amplifier circuit 10, a second input terminal of the auxiliary circuit 20 is connected to an input terminal of the transistor pm6 of the to-be-stabilized operational amplifier circuit 10, a first output terminal of the auxiliary circuit 20 is connected to an input terminal of the transistor pm13 of the to-be-stabilized operational amplifier circuit 10, and a second output terminal of the auxiliary circuit 20 is connected to an input terminal of the transistor pm14 of the to-be-stabilized operational amplifier circuit 10. When the input currents of the transistor pm13 and the transistor pm14 decrease, the input current of the transistor nm6 of the operational amplifier circuit to be stabilized 10 increases, and the auxiliary circuit 20 supplements the input currents of the transistor pm13 and the transistor pm14 with the increased current of the input of the transistor nm 6; when the input currents of the transistor pm13 and the transistor pm14 increase, the input current of the transistor pm6 of the operational amplifier circuit 10 to be stabilized decreases, and the auxiliary circuit 20 attenuates the currents of the input terminals of the transistor pm13 and the transistor pm14 with the reduced current of the input terminal of the transistor pm 6.
The conventional circuit in the constant cross rail-to-rail input/output operational amplifier is used as the circuit 10 to be stabilized, and the auxiliary circuit 20 is added on the basis of the circuit 10 to be stabilized. When the input common mode voltage VCMIN of the to-be-stabilized operational amplifier circuit 10 approaches the power rail voltage VDD, the tail currents of the transistors pm1, pm2 in the to-be-stabilized operational amplifier circuit 10 flow through the transistor pm3 to the transistor nm6 when the transistors pm1, pm2 are turned off, after which the reduced currents of the transistors pm13, pm14 are supplemented back by the added auxiliary circuit 20, keeping the currents flowing through the transistors pm13, pm14 constant. When the input common mode voltage VCMIN of the operational amplifier circuit 10 to be stabilized approaches the ground rail voltage VSS, the transistors nm1, nm2 are turned off, the tail currents of the transistors nm1, nm2 flow through the transistor nm3 to the transistor pm6, and then the currents added by the transistors pm13, pm14 are subtracted by the added auxiliary circuit 20 accordingly, keeping the currents flowing through the transistors pm13, pm14 constant.
The scheme in the embodiment eliminates the change of the bias state of the output stage when the input common mode level of the constant cross guide rail to rail input/output operational amplifier changes, plays the roles of stabilizing the operational amplifier bandwidth, the phase margin and the overall power consumption of the constant cross guide rail to rail input/output operational amplifier, and ensures that the operational amplifier bandwidth, the phase margin and the power consumption of the constant cross guide rail to rail input/output operational amplifier do not change along with the input common mode voltage.
Further, as shown in fig. 3, the auxiliary circuit 20 may include a current supplementing circuit 21, an input terminal of which is connected to an input terminal of the transistor nm6 of the to-be-stabilized operational amplifier circuit 10 (i.e., an input terminal of the current supplementing circuit 21 may be connected to a first input terminal of the auxiliary circuit 20), a first output terminal of which is connected to a first output terminal of the auxiliary circuit 20, and a second output terminal of which is connected to a second output terminal of the auxiliary circuit 20; when the input current of the transistor nm6 increases and the input currents of the transistors pm13 and pm14 decrease, the increased current of the input of the transistor nm6 is output to the transistors pm13 and pm14 through the current supplementing circuit 21 to ensure that the currents flowing through the transistors pm13 and pm14 are constant. The auxiliary circuit 20 may further comprise a current weakening circuit 22 having an input connected to an input of the transistor pm6 of the circuit 10 to be stabilized (i.e. the input of the current weakening circuit 22 may be connected to a second input of the auxiliary circuit 20), a first output connected to a first output of the auxiliary circuit 20 and a second output connected to a second output of the auxiliary circuit 20; when the input current of the transistor pm6 decreases and the input currents of the transistor pm13 and the transistor pm14 increase, the reduced current of the input of the transistor pm6 is outputted to the transistor pm13 and the transistor pm14 through the current weakening circuit to ensure that the currents flowing through the transistor pm13 and the transistor pm14 are constant values.
In this scheme, the current reduced by the transistors pm13 and pm14 is directly and equitably supplemented back by the current supplementing circuit 21, and the current increased by the transistors pm13 and pm14 is directly and equitably subtracted by the current weakening circuit 22, so that the stability of the bias state from the constant rail to the rail input/output operational amplifier output stage can be ensured when any change occurs in the common-mode input voltage.
Preferably, as shown in fig. 4, in the constant rail-to-rail input/output operational amplifier, the current supplementing circuit 21 includes a transistor nm20, the transistor nm20 is in mirror connection with the transistor nm6, and the current increased at the input terminal of the transistor nm6 is mirrored through the transistor nm20 to the current supplementing circuit. The current supplementing circuit 21 further comprises a transistor pm21, a pair of mirror transistors pm22 and pm23; the input terminal of the transistor pm21 is connected to the output terminal of the transistor nm20, the input terminals of a pair of mirror transistors pm22 and pm23 are connected to the output terminal of the transistor pm21, the output terminal of the transistor pm22 is connected to the input terminal of the transistor pm14, and the output terminal of the transistor pm23 is connected to the input terminal of the transistor pm13, wherein the sources of the transistor pm20, the transistor pm21, the transistor pm22 and the transistor pm23 are all connected to the voltage rail. As shown in the figure, when the input common-mode voltage VCMIN of the constant rail-to-rail input-output operational amplifier approaches the power rail voltage VDD, the differential pair transistors pm1 and pm2 are turned off, tail currents of the differential pair transistors pm1 and pm2 flow to the transistor nm6 through the transistor pm3, the transistor nm6 flows to the differential pair transistors nm1 and nm2 through the mirror image of the transistor nm5, transconductance of the differential pair transistors nm1 and nm2 is increased, and the overall transconductance of the operational amplifier is kept constant. The current through the differential pair of transistors nm1, nm2 increases, resulting in a decrease in the current through transistors pm13, pm14, while the current through transistor nm6 is mirrored to transistor pm21 through the newly added transistor nm20 in the auxiliary circuit 20, and transistor pm21 supplements back the decreased current through transistors pm13, pm14 through the mirroring of transistors pm22, pm23, maintaining a constant current through transistors pm13, pm 14.
Further, as shown in fig. 4, in the constant rail-to-rail input-output operational amplifier, the current-weakening circuit 22 comprises a transistor pm20, the transistor pm20 being mirror connected to the transistor pm 6; the reduced current at the input of transistor pm6 is mirrored through transistor pm20 into the current weakening circuit. Wherein the current weakening circuit 22 further comprises a transistor nm21, a pair of mirror transistors nm22 and nm23; the input terminal of the transistor nm21 is connected to the output terminal of the transistor pm20, the input terminals of a pair of the mirror transistors nm22 and nm23 are connected to the output terminal of the transistor nm21, the output terminal of the transistor nm22 is connected to the input terminal of the transistor pm13, and the output terminal of the transistor nm23 is connected to the input terminal of the transistor pm14, wherein the sources of the transistor nm20, the transistor nm21, the transistor nm22, and the transistor nm23 are all connected to the ground rail. As shown, when the input common-mode voltage VCMIN of the constant rail-to-rail input-output operational amplifier approaches the ground rail voltage VSS, the differential pair transistors nm1, nm2 are turned off, the tail current of the differential pair transistors nm1, nm2 flows through the transistor nm3 to the transistor pm6, the transistor pm6 mirrors the current to the differential pair transistors pm1, pm2 through the transistor pm5, and the transconductance of the differential pair transistors pm1, pm2 increases, so that the overall transconductance of the operational amplifier remains constant. Meanwhile, the turning-off of the differential pair transistors nm1 and nm2 increases the currents of the transistors pm13 and pm14, the transistor pm6 mirrors the current to the transistor nm21 through the newly added transistor pm20 in the auxiliary circuit 20, the transistors nm22 and nm23 mirror the current of the transistor nm21, and the currents increased by the transistors pm13 and pm14 are correspondingly subtracted, so that the currents of the transistors pm13 and pm14 are kept constant.
In the scheme in the above embodiment of the invention, when the differential pair transistors pm1 and pm2 are turned off, the constant cross-rail-to-rail input-output operational amplifier supplements the reduced currents of the transistors pm13 and pm 14; when the differential pair nm1 and nm2 is turned off, the increased currents of the transistors pm13 and pm14 are correspondingly subtracted, so that the currents flowing through the transistors pm13 and pm14 are unchanged regardless of the fact that the input common-mode voltage VCMIN is close to the power rail voltage VDD or the ground rail voltage VSS, the currents of the transistors pm7 and nm7 are unchanged, the bias voltages, bias currents and transconductance of the output-stage transistors pm15 and nm15 are unchanged, and therefore the operational amplifier bandwidth, the phase margin and the power consumption of the constant rail-to-rail input-output operational amplifier are unchanged.
It is apparent that the above examples are given by way of illustration only and are not limiting of the embodiments. Other variations or modifications of the above teachings will be apparent to those of ordinary skill in the art. It is not necessary here nor is it exhaustive of all embodiments. While obvious variations or modifications are contemplated as falling within the scope of the present invention.
Claims (7)
1. The constant cross-rail-to-rail input/output operational amplifier is characterized by comprising an operational amplifier circuit to be stabilized and an auxiliary circuit, wherein:
the auxiliary circuit is connected between a power rail and a ground rail of the operational amplifier circuit to be stabilized, a first input end of the auxiliary circuit is connected with tail current output ends of differential pair transistors pm1 and pm2 of the operational amplifier circuit to be stabilized, a second input end of the auxiliary circuit is connected with tail current output ends of differential pair transistors nm1 and nm2 of the operational amplifier circuit to be stabilized, a first output end of the auxiliary circuit is connected with an input end of a transistor pm13 of the operational amplifier circuit to be stabilized, and a second output end of the auxiliary circuit is connected with an input end of a transistor pm14 of the operational amplifier circuit to be stabilized;
when the differential pair transistors pm1, pm2 are turned off and the input currents of the transistors pm13, pm14 are reduced, the auxiliary circuit supplements the input currents of the transistors pm13, pm 14; the auxiliary circuit attenuates the input current of the transistors pm13, pm14 when the differential pair transistors nm1, nm2 are off and the input current of the transistors pm13, pm14 increases;
the first input end of the auxiliary circuit is connected with the input end of the transistor nm6 of the operational amplifier circuit to be stabilized, and the second input end of the auxiliary circuit is connected with the input end of the transistor pm6 of the operational amplifier circuit to be stabilized;
when the input currents of the transistor pm13 and the transistor pm14 decrease, the input current of the transistor nm6 increases, and the auxiliary circuit supplements the input currents of the transistor pm13 and the transistor pm14 with the increased current of the input of the transistor nm 6;
when the input currents of the transistor pm13 and the transistor pm14 are increased, the input current of the transistor pm6 is reduced, and the auxiliary circuit attenuates the currents of the input terminals of the transistor pm13 and the transistor pm14 with the reduced current of the input terminal of the transistor pm 6;
the auxiliary circuit includes: the input end of the current supplementing circuit is connected with the input end of the transistor nm6 of the operational amplifier circuit to be stabilized, the first output end of the current supplementing circuit is connected with the first output end of the auxiliary circuit, and the second output end of the current supplementing circuit is connected with the second output end of the auxiliary circuit; when the input terminal current of the transistor nm6 increases and the input currents of the transistors pm13 and pm14 decrease, the increased current of the input terminal of the transistor nm6 is output to the transistors pm13 and pm14 through the current supplementing circuit so as to ensure that the currents flowing through the transistors pm13 and pm14 are constant values;
the auxiliary circuit further includes: the input end of the current weakening circuit is connected with the input end of the transistor pm6 of the operational amplifier circuit to be stabilized, the first output end of the current weakening circuit is connected with the first output end of the auxiliary circuit, and the second output end of the current weakening circuit is connected with the second output end of the auxiliary circuit; when the input current of the transistor pm6 decreases and the input currents of the transistor pm13 and the transistor pm14 increase, the reduced current of the input of the transistor pm6 is outputted to the transistor pm13 and the transistor pm14 through the current weakening circuit to ensure that the currents flowing through the transistor pm13 and the transistor pm14 are constant values.
2. The constant rail-to-rail input output operational amplifier of claim 1, wherein:
the current supplementing circuit comprises a transistor nm20, wherein the transistor nm20 is in mirror connection with the transistor nm6, and the current increased at the input end of the transistor nm6 is connected into the current supplementing circuit through the transistor nm20 in mirror connection.
3. The constant rail-to-rail input output operational amplifier of claim 2, wherein:
the current supplementing circuit further comprises a transistor pm21, a pair of mirror transistors pm22 and pm23;
the input terminal of the transistor pm21 is connected to the output terminal of the transistor nm20, the input terminals of a pair of the mirror transistors pm22 and pm23 are connected to the output terminal of the transistor pm21, the output terminal of the transistor pm22 is connected to the input terminal of the transistor pm14, and the output terminal of the transistor pm23 is connected to the input terminal of the transistor pm 13.
4. A constant rail-to-rail input-output operational amplifier according to any one of claims 1-3, wherein:
the current weakening circuit comprises a transistor pm20, the transistor pm20 being mirror connected to the transistor pm 6; the reduced current at the input of transistor pm6 is mirrored through transistor pm20 into the current weakening circuit.
5. The constant rail-to-rail input output operational amplifier of claim 4, wherein:
the current weakening circuit further comprises a transistor nm21, a pair of mirror transistors nm22 and nm23;
the input terminal of the transistor nm21 is connected to the output terminal of the transistor pm20, the input terminals of a pair of the mirror transistors nm22 and nm23 are connected to the output terminal of the transistor nm21, the output terminal of the transistor nm22 is connected to the input terminal of the transistor pm13, and the output terminal of the transistor nm23 is connected to the input terminal of the transistor pm 14.
6. The constant rail-to-rail input output operational amplifier of claim 5, wherein:
the sources of the transistor pm20, the transistor pm21, the transistor pm22 and the transistor pm23 are all connected to the power supply rail.
7. The constant rail-to-rail input output operational amplifier of claim 6, wherein:
the sources of the transistor nm20, the transistor nm21, the transistor nm22 and the transistor nm23 are all connected to the ground rail.
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| CN114123988A (en) | 2022-03-01 |
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