CN115833766A - Quasi-complementary class B output stage circuit structure - Google Patents

Abstract

The invention relates to the field of integrated circuit design, in particular to a quasi-complementary class B output stage circuit structure, wherein a triode QP is added between a collector C of a triode Q1 and a base B of a triode Q2 in an output power pull-up tube, and the triode QP and a triode Q1 cascode structure can form a cascode circuit, so that the high-frequency characteristic of the cascode circuit is better, and the influence of the frequency characteristic difference of a pnp tube in a bipolar process on the working frequency of an operational amplifier can be compensated. The base B input of transistor QP is free to bias. The structure can be compatible with a bipolar process containing a JFET process, the triode Q3 can be replaced by a JFET tube, meanwhile, the diode Q5 or the diode Q6 is replaced by the JFET tube in a diode connection mode, the temperature influence is reduced, a bypass current irrelevant to the temperature is obtained, and the switching speed under high frequency can be improved by adding a feedback resistor between the emitter and the base of the triode Q4.

Description

Quasi-complementary class B output stage circuit structure

Technical Field

The invention relates to the field of integrated circuit design, in particular to a quasi-complementary class B output stage circuit structure.

Background

The output stage of the operational amplifier needs to provide a specified signal power and sufficient driving current for the load, and should isolate the low-resistance load to reduce the output impedance and avoid the voltage gain drop of the operational amplifier caused by the small-resistance load. In addition, the requirements for low power consumption, avoidance of output signal distortion, high bandwidth, and reduced influence on the frequency response of the operational amplifier should be satisfied.

Because pnp transistors are process limited and cannot reach the same doping level as npn transistors in the circuit, their high current and frequency response performance are slightly inferior. The B-type complementary output stage circuit can meet the load power application within hundreds of milliwatts, and if the B-type complementary output stage circuit has larger output requirement, the use requirement cannot be met because the current carrying capacity of the pnp transistor is limited. An output stage circuit with excellent performance needs to have good signal buffering effect and can provide stable analog signal frequency response for a circuit system. However, in the bipolar technology in the prior art, the frequency characteristic of the pnp tube is poor, and the operational frequency of the operational amplifier is affected.

Disclosure of Invention

In order to overcome the defects in the prior art, the invention aims to provide a quasi-complementary class b output stage circuit structure to solve the technical problem of poor frequency characteristics of a pnp tube in a bipolar process in the prior art.

The invention is realized by the following technical scheme:

a quasi-complementary class B output stage circuit structure comprises a power supply voltage VCC, an analog ground signal GND, an output signal Vout, a bias circuit, a cascode circuit, a voltage bias circuit, a common source amplifier stage circuit, an output power pull-up tube and an output composite pnp power pull-down tube; one end of the bias circuit is connected with a power supply voltage VCC, and the other end of the bias circuit is grounded; one end of the cascode circuit is connected with a power supply voltage VCC, the other end of the cascode circuit is connected with one end of a voltage bias circuit in series, the other end of the voltage bias circuit is connected with one end of a common-source amplifier circuit in series, and the other end of the common-source amplifier circuit is connected to an analog ground signal GND; one end of the output power pull-up tube is connected to a power supply voltage VCC; the other end of the output power pull-up tube is connected in series to one end of the output composite pnp power pull-down tube, the other end of the composite pnp power pull-down tube is connected to an analog ground signal GND, one end of the cascode circuit is connected to the bias circuit, and the output power pull-up tube is connected between the cascode circuit and the voltage bias circuit.

Preferably, the bias circuit 1 includes a diode D0 and a resistor R; the anode of the diode D0 is connected to a power supply voltage VCC, the cathode of the diode D0 is respectively connected to the positive end of the resistor R and the cascode circuit, and the negative end of the resistor R is grounded.

Further, the cascode circuit includes a transistor Q1 and a transistor QP; an emitter E of the triode Q1 is connected with a power supply voltage VCC, and a collector C of the triode Q1 is connected with an emitter E of the triode QP; the base electrode B of the triode Q1 is connected to the cathode of the diode D0; a collector C of the triode QP is connected with an output power pull-up tube and a voltage bias circuit respectively; the base B of the transistor QP is connected to the Vf input signal.

Furthermore, a base B of the triode QP can be accessed with a bias signal or self-biased according to the pre-stage structure of the operational amplifier, and the potential of the base B of the triode QP can be biased to an applicable potential point according to the output saturation high-level index.

Further, the output power pull-up tube includes a transistor Q2, a base B of the transistor Q2 is connected to a collector C of the transistor QP, the collector C of the transistor Q2 is connected to the power voltage VCC, and an emitter E of the transistor Q2 is connected to the output signal Vout.

Further, the voltage bias circuit includes a diode Q5 and a diode Q6; the anode of the diode Q5 is connected to the collector C of the triode QP, and the cathode of the diode Q5 is connected to the anode of the diode Q6; and the cathode of the diode Q6 is respectively connected to the common source amplifier stage circuit and the output composite pnp power pull-down tube.

Further, the common-source amplification stage circuit comprises a triode Q7; a base electrode B of the triode Q7 is connected with a Vb input signal, and a collector electrode C of the triode Q7 is connected with a cathode of the diode Q6; the emitter E of the transistor Q7 is connected to an analog ground signal GND.

Further, the output composite pnp power down tube comprises a triode Q3 and a triode Q4; the base electrode B of the triode Q3 is connected to the cathode of the diode Q6; the collector C of the triode Q3 is connected with the base B of the triode Q4; the emitter E of the triode Q3 is connected to the output signal Vout; the collector C of the transistor Q4 is connected to the output signal Vout, and the emitter E of the transistor Q4 is connected to the analog ground signal GND.

Compared with the prior art, the invention has the following beneficial technical effects:

the invention provides a quasi-complementary class B output stage circuit structure, wherein a triode QP is added between a collector C of a triode Q1 and a base B of a triode Q2 in an output power pull-up tube, and the triode QP and a triode Q1 co-emitting structure can form a cascode circuit, so that the high-frequency characteristic is better, and the influence of the frequency characteristic difference of a pnp tube in a bipolar process on the working frequency of an operational amplifier can be compensated. The base B input of transistor QP is free to bias. When the operational amplifier is used as a current source, if the load is heavy and the load current is large, the current flowing through the transistor Q1 will also increase. If the complementary bipolar process can not be realized during sheet flowing, the npn tube in the whole circuit structure is a longitudinal structure, and the pnp tube mostly uses a transverse pnp tube, and as can be known from a layout structure, the emitter and the base of the transverse pnp tube can generate two parasitic pnp tubes when facing the isolation wall and the substrate, and if the load current is too large, the base current of the triode Q1 is increased, so that the parasitic pnp tube is conducted, the output saturation high level is reduced, and the application range of the structure is reduced. After the common base triode QP structure is added, the base potential of the triode QP can be biased to an applicable potential point according to the output saturation high level index, so that the potentials of the triode Q1 and the triode QP electrode are improved, and the clamped output saturation high level is achieved.

Furthermore, the output stage adopts a complementary structure, and under the condition of limited process, because of conflict with the npn tube, the doping levels of a base region, emission and the like of the pnp tube cannot be optimized, so that the power processing capability of the pnp tube is limited. Therefore, the composite pnp tube power tube composed of the triode Q3 and the triode Q4 is used as a pull-down tube in an output structure, the output power can be improved, the triode Q4 and the triode Q2 are transistors of the same type, and the good symmetry of the tube can be kept in layout design.

Furthermore, the structure can be compatible with a bipolar process containing a JFET process, the triode Q3 can be replaced by a JFET tube, meanwhile, the diode Q5 or the diode Q6 is replaced by the JFET tube in a diode connection mode, the temperature influence is reduced, a bypass current irrelevant to the temperature is obtained, and the switching speed under high frequency can be improved by adding a feedback resistor between the emitter and the base of the triode Q4.

Drawings

Fig. 1 is a schematic diagram of a quasi-complementary class b output stage circuit structure according to the present invention.

1-a bias circuit; a 2-cascode circuit; 3-a voltage bias circuit; 4-common source amplifier stage circuit; 5-output power up-pulling the tube; 6-output composite pnp power down tube.

Detailed Description

In order to make the technical solutions of the present invention better understood, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

It should be noted that the terms "first," "second," and the like in the description and claims of the present invention and in the drawings described above are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used is interchangeable under appropriate circumstances such that the embodiments of the invention described herein are capable of operation in sequences other than those illustrated or described herein. Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed, but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.

The invention is described in further detail below with reference to the accompanying drawings:

the invention aims to provide a high-stability quasi-complementary class-B output stage circuit structure for a combined JFET bipolar process operational amplifier, and aims to solve the technical problem that a pnp tube in a bipolar process is poor in frequency characteristic in the prior art. A common base device structure is added in a quasi-complementary class B output stage to improve the frequency characteristic, the base of the quasi-complementary class B output stage can be freely biased to realize free clamping of saturated output voltage, and the clamping voltage can inhibit the fluctuation of the output saturated level along with the process.

The power supply voltage VCC is a power supply signal of the output stage, VCC is also a power supply signal of an operational amplifier applied to the structure, GND is a ground analog signal, vf is an input signal of the common base QP tube, vb is an output signal of the amplification stage of the operational amplifier, and is an input signal of the output stage, and Vout is an output signal of the output stage.

The Vb input signal of the output stage passes through a common source amplifier formed by a triode Q7, and C, E, B of the triode Q7 are respectively connected with the cathode of a diode Q6, a GND analog ground signal GND and a Vb input signal.

The triode Q2 is an output power tube pull-up tube, and C, E, B of the triode Q2 are respectively connected with the power supply voltage VCC, the output signal Vout, and the collector C of the triode QP.

Triode Q3 and triode Q4 pipe constitute a compound pnp pipe, for the power pull-down pipe, C, E, B of triode Q3 connects base B, output signal Vout and the negative pole of diode Q6 of triode Q4 respectively, C, E, B of triode Q4 connects output signal Vout, analog ground signal GND and collector C of triode Q3 respectively.

The diode Q5 and the diode Q6 are connected in series to provide bias voltage for the output power tube, the anode of the diode Q5 is connected with the base B of the triode Q2, and the cathode of the diode Q5 is connected with the anode of the diode Q6. The anode of the diode Q6 is connected with the cathode of the diode Q5, and the cathode of the diode Q6 is connected with the collector of the triode Q7.

Triode Q1 is the tail current pipe, and the C, E, B of triode Q1 connects emitter E, mains voltage VCC and the negative pole of diode D0 respectively of triode QP.

The QP tube is a common base amplification circuit, and a collector C, an emitter E and a base B of the QP tube are respectively connected with a base of the triode Q2, a collector C of the triode Q1 and Vf input signals.

Diode D0 and resistor R provide a bias signal for Q1. The positive end of the resistor R is connected with the base of the Q1, the negative end of the resistor R is connected with a GND analog ground signal, the anode of the diode D0 is connected with a VCC power supply signal, and the cathode of the diode D0 is connected with the base of the Q1 tube.

Specifically, as shown in fig. 1, the quasi-complementary class b output stage circuit structure includes a power supply voltage VCC, an analog ground signal GND, an output signal Vout, a bias circuit 1, a cascode circuit 2, a voltage bias circuit 3, a common-source amplifier stage circuit 4, an output power pull-up tube 5, and an output composite pnp power pull-down tube 6; one end of the bias circuit 1 is connected with a power supply voltage VCC, and the other end is grounded; one end of the cascode circuit 2 is connected with a power supply voltage VCC, the other end of the cascode circuit is connected with one end of the voltage bias circuit 3 in series, the other end of the voltage bias circuit 3 is connected with one end of the common-source amplifier circuit 4 in series, and the other end of the common-source amplifier circuit 4 is connected with an analog ground signal GND; one end of the output power pull-up tube 5 is connected to a power supply voltage VCC; the other end of the output power pull-up tube 5 is connected in series to one end of the output composite pnp power pull-down tube 6, the other end of the composite pnp power pull-down tube 6 is connected to the analog ground signal GND, one end of the cascode circuit 2 is connected to the bias circuit 1, and the output power pull-up tube 5 is connected between the cascode circuit 2 and the voltage bias circuit 3.

Specifically, the bias circuit 1 includes a diode D0 and a resistor R; the anode of the diode D0 is connected to a power supply voltage VCC, the cathode of the diode D0 is respectively connected to the positive end of the resistor R and the cascode circuit 2, and the negative end of the resistor R is grounded.

Specifically, the cascode circuit 2 includes a transistor Q1 and a transistor QP; an emitter E of the triode Q1 is connected with a power supply voltage VCC, and a collector C of the triode Q1 is connected with an emitter E of the triode QP; the base electrode B of the triode Q1 is connected to the cathode of the diode D0; a collector C of the triode QP is connected with an output power pull-up tube 5 and a voltage bias circuit 3 respectively; the base B of the transistor QP is connected to the Vf input signal.

The base B of the triode QP can be accessed with a bias signal or self-biased according to the operational amplifier pre-stage structure, and the potential of the base B of the triode QP can be biased to an applicable potential point according to the output saturation high-level index.

Specifically, the output power pull-up tube 5 includes a triode Q2, a base B of the triode Q2 is connected to a collector C of the triode QP, the collector C of the triode Q2 is connected to a power supply voltage VCC, and an emitter E of the triode Q2 is connected to the output signal Vout.

Specifically, the voltage bias circuit 3 includes a diode Q5 and a diode Q6; the anode of the diode Q5 is connected to the collector C of the triode QP, and the cathode of the diode Q5 is connected to the anode of the diode Q6; and the cathode of the diode Q6 is respectively connected to the common source amplifier stage circuit 4 and the output composite pnp power down tube 6.

Specifically, the common-source amplifier stage circuit 4 includes a triode Q7; a base electrode B of the triode Q7 is connected with a Vb input signal, and a collector electrode C of the triode Q7 is connected with a cathode of the diode Q6; the emitter E of the transistor Q7 is connected to an analog ground signal GND.

Specifically, the output composite pnp power pull-down tube 6 includes a triode Q3 and a triode Q4; the base electrode B of the triode Q3 is connected to the cathode of the diode Q6; the collector C of the triode Q3 is connected with the base B of the triode Q4; the emitter E of the triode Q3 is connected to the output signal Vout; the collector C of the transistor Q4 is connected to the output signal Vout, and the emitter E of the transistor Q4 is connected to the analog ground signal GND.

According to the application structure, a bias voltage meeting the requirement of outputting a saturated high-voltage index is given to the Vf signal, so that the QP tube can work normally. Base electrode bias currents of the power pull-up tube Q2, the composite pnp power pull-down tube Q3 and the Q4 are provided by the tail current source Q1.

When the quasi-complementary class B output stage circuit structure provided by the invention is used:

when the input signal Vb rises, the collector voltage of the transistor Q7 decreases, which causes the emitter of the transistor Q3 to decrease, and the output signal Vout decreases. When the input signal Vb is increased to the state that the output signal Vout is reduced to the lowest saturation level voltage, the output voltage value is the saturation voltage drop of the collector electrode of the triode Q4, the triode Q2 is turned off, the operational amplifier works in a current sinking state, the triode Q3 and the triode Q4 draw current from the port of the output signal Vout to GND analog ground signals, the current carrying capacity of a common pnp tube is limited, and the current drawing capacity is improved because the triode Q3 and the triode Q4 are combined into a composite pnp tube.

When the input signal Vb decreases, the collector voltage of the transistor Q7 increases, which causes the base voltage of the transistor Q2 to increase, and the output signal Vout increases. When the input signal Vb is reduced to the state that the output signal Vout is increased to the highest saturation level voltage, the output voltage value is the power supply voltage signal minus the saturation voltage drop of the emitter of the collector of the triode QP and the emitter of the collector of the triode Q1, then the base of the triode Q2 is conducted and dropped, the transistors of the triode Q3 and the triode Q4 are switched off, the operational amplifier works in a current source state, and the triode Q2 transmits current to a load from the VCC power supply signal through the output signal Vout.

The diode Q5 and the diode Q6 are triodes connected in a diode mode, the two pipes can be pnp pipes or npn pipes, and the diode Q5 and the diode Q6 provide bias voltage for the output power pipe to avoid output signals from generating crossover distortion.

The diode D0 and the resistor R provide bias signals for the tail current triode Q1, so that the output structure generates stable quiescent current.

The triode QP is connected with the triode Q1 in series, and a collector output signal of the triode Q1 is connected to an emitter of the triode QP and then output to a base of the triode Q2 from the collector of the triode QP, and finally a Vout output signal is obtained. The triode QP is a common base amplification circuit, does not amplify current and acts as a current following function, and the structure has excellent high-frequency characteristics and improves the high-frequency performance of an output level.

The base voltage of the QP can be switched in a bias signal or self-biased according to the front-end structure of the operational amplifier.

The triode Q1 in the output structure is a pnp tube, the frequency characteristic of the triode Q is far inferior to that of an npn tube in the common bipolar process, and the triode QP added in the structure is a common base amplifier which has good frequency characteristic and can improve the stability of frequency response of the output structure.

The base voltage potential of the triode QP in the output structure has no clear requirement, and can be self-biased according to application conditions, and the output saturation high level can be freely set along with the base voltage potential.

When a large load current is supplied, the output saturation high level is influenced by the process level, the collector emitter saturation voltage of the triode Q1 is easily increased, the output saturation high level is reduced, and the base potential of the triode QP can be connected to a higher voltage node at the moment, so that the output saturation high level is increased and plays a clamping role.

In summary, the quasi-complementary class B output stage circuit structure provided by the invention is characterized in that a triode QP is added between a collector C of a triode Q1 and a base B of a triode Q2 in an output power pull-up tube, and the triode QP and the triode Q1 in a cascode structure can form a cascode circuit, so that the high-frequency characteristic of the cascode circuit structure is better, and the influence of the frequency characteristic difference of a pnp tube in a bipolar process on the working frequency of an operational amplifier can be compensated. The base B input of transistor QP is free to bias. When the operational amplifier is used as a current source, if the load is heavy and the load current is large, the current flowing through the transistor Q1 will also increase. If complementary bipolar technology can not be realized during chip flowing, an npn tube in the whole circuit structure is of a longitudinal structure, and most pnp tubes use transverse pnp tubes, and it can be known from a layout structure that two parasitic pnp tubes can be generated when an emitter and a base of each transverse pnp tube face a partition wall and a substrate, and if load current is too large, base current of a triode Q1 is increased, so that the parasitic pnp tubes are conducted, output saturation high level is reduced, and the application range of the structure is reduced. After the common base triode QP structure is added, the base potential of the triode QP can be biased to an applicable potential point according to the output saturation high level index, so that the potentials of the triode Q1 and the triode QP electrode are improved, and the clamped output saturation high level is achieved.

Finally, it should be noted that: the above embodiments are only for illustrating the technical solutions of the present invention and not for limiting the same, and although the present invention is described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: modifications and equivalents may be made to the embodiments of the invention without departing from the spirit and scope of the invention, which is to be covered by the claims.

Claims (8)

1. A quasi-complementary class B output stage circuit structure is characterized by comprising a power supply voltage VCC, an analog ground signal GND, an output signal Vout, a bias circuit (1), a cascode circuit (2), a voltage bias circuit (3), a common source amplifier stage circuit (4), an output power pull-up tube (5) and an output composite pnp power pull-down tube (6); one end of the bias circuit (1) is connected with a power supply voltage VCC, and the other end of the bias circuit is grounded; one end of the cascode circuit (2) is connected with a power supply voltage VCC, the other end of the cascode circuit is connected with one end of the voltage bias circuit (3) in series, the other end of the voltage bias circuit (3) is connected with one end of the common-source amplifier circuit (4) in series, and the other end of the common-source amplifier circuit (4) is connected to an analog ground signal GND; one end of the output power pull-up tube (5) is connected to a power supply voltage VCC; the other end of the output power pull-up tube (5) is connected in series to one end of the output composite pnp power pull-down tube (6), the other end of the composite pnp power pull-down tube (6) is connected to an analog ground signal GND, one end of the cascode circuit (2) is connected to the bias circuit (1), and the output power pull-up tube (5) is connected between the cascode circuit (2) and the voltage bias circuit (3).

2. The quasi-complementary class b output stage circuit structure of claim 1, wherein said bias circuit 1 comprises a diode D0 and a resistor R; the anode of the diode D0 is connected to a power supply voltage VCC, the cathode of the diode D0 is respectively connected to the positive end of the resistor R and the cascode circuit (2), and the negative end of the resistor R is grounded.

3. The quasi-complementary class b output stage circuit structure according to claim 2, wherein said cascode circuit (2) comprises a transistor Q1 and a transistor QP; an emitter E of the triode Q1 is connected with a power supply voltage VCC, and a collector C of the triode Q1 is connected with an emitter E of the triode QP; the base electrode B of the triode Q1 is connected to the cathode of the diode D0; a collector C of the triode QP is connected with an output power pull-up tube (5) and a voltage bias circuit (3) respectively; the base B of the transistor QP is connected to the Vf input signal.

4. The structure of claim 3, wherein the base B of the transistor QP is biased to an applicable potential point according to an output saturation high level indicator by a bias signal or self-bias according to an operational amplifier pre-stage structure.

5. A quasi-complementary class B output stage circuit arrangement according to claim 3, wherein said output power pull-up transistor (5) comprises a transistor Q2, wherein the base B of said transistor Q2 is connected to the collector C of a transistor QP, the collector C of the transistor Q2 is connected to the supply voltage VCC, and the emitter E of the transistor Q2 is connected to the output signal Vout.

6. A quasi-complementary class b output stage circuit arrangement according to claim 3, wherein said voltage bias circuit (3) comprises a diode Q5 and a diode Q6; the anode of the diode Q5 is connected to the collector C of the triode QP, and the cathode of the diode Q5 is connected to the anode of the diode Q6; and the cathode of the diode Q6 is respectively connected to the common source amplifier stage circuit (4) and the output composite pnp power pull-down tube (6).

7. A quasi-complementary class B output stage circuit structure according to claim 6, characterized in that said common source amplifier stage circuit (4) comprises a transistor Q7; a base electrode B of the triode Q7 is connected with a Vb input signal, and a collector electrode C of the triode Q7 is connected with a cathode of the diode Q6; the emitter E of the transistor Q7 is connected to an analog ground signal GND.

8. A quasi-complementary class B output stage circuit structure according to claim 6, wherein said output composite pnp power down-pipe (6) comprises a transistor Q3 and a transistor Q4; the base electrode B of the triode Q3 is connected to the cathode of the diode Q6; the collector C of the triode Q3 is connected with the base B of the triode Q4; the emitter E of the triode Q3 is connected to the output signal Vout; the collector C of the transistor Q4 is connected to the output signal Vout, and the emitter E of the transistor Q4 is connected to the analog ground signal GND.

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