A quasi-complementary class-b output stage circuit configuration

Abstract

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

Description

TECHNICAL FIELD

[0001] The present application relates to the field of integrated circuit design, in particular to a quasi-complementary class B output stage circuit structure. BACKGROUND

[0002] The output stage of the operational amplifier not only needs to provide the specified signal power and sufficient driving current for the load, but also needs to isolate the low resistance load, reduce the output impedance and avoid the voltage gain of the operational amplifier being reduced by the small resistance load. In addition, it also needs to meet the low power consumption, avoid the distortion of the output signal, high bandwidth, and reduce the influence on the frequency response of the operational amplifier.

[0003] Due to the process limitation, the pnp transistor cannot reach the same doping level as the npn transistor in the circuit, and its high current and frequency response performance are slightly worse. The class B complementary output stage circuit can meet the load power application within a few hundred milliwatts. If there is a larger output, the pnp transistor cannot meet the use requirement due to its limited current carrying capacity. A good performance output stage circuit needs to have good signal buffering effect and can provide stable analog signal frequency response for the circuit system. However, the frequency characteristic of the pnp transistor in the current technology is poor, which affects the working frequency of the operational amplifier. SUMMARY

[0004] In order to overcome the defects of the prior art, the purpose of the present application is to provide a quasi-complementary class B output stage circuit structure to solve the technical problem of poor frequency characteristic of the pnp transistor in the current technology.

[0005] The present application is realized by the following technical solutions:

[0006] A quasi-complementary class B output stage circuit structure, comprising a power supply voltage VCC, an analog ground signal GND, an output signal Vout, a bias circuit, a Wollman circuit, a voltage bias circuit, a common source amplification 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 to the power supply voltage VCC, and the other end is grounded; one end of the Wollman circuit is connected to the power supply voltage VCC, and the other end is connected in series with one end of the voltage bias circuit; the other end of the voltage bias circuit is connected in series with one end of the common source amplification stage circuit; the other end of the common source amplification stage circuit is connected to the analog ground signal GND; one end of the output power pull-up tube is connected to the 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 the analog ground signal GND; one end of the Wollman circuit is connected to the bias circuit, and the output power pull-up tube is connected between the Wollman circuit and the voltage bias circuit.

[0007] Preferably, the 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 connected to the positive terminal of the resistor R and the Wollan circuit respectively; and the negative terminal of the resistor R is grounded.

[0008] Further, the Wollan circuit comprises a triode Q1 and a triode QP; the emitter E of the triode Q1 is connected to a power supply voltage VCC, the collector C of the triode Q1 is connected to the emitter E of the triode QP; the base B of the triode Q1 is connected to the cathode of the diode D0; the collector C of the triode QP is connected to the output power pull-up tube and the voltage bias circuit respectively; and the base B of the triode QP is connected to a Vf input signal.

[0009] Still further, the base B of the triode QP can be connected to a bias signal or self-biased according to the pre-stage structure of the operational amplifier; and according to the output saturation high level index, the base B potential of the triode QP can be biased to an applicable potential point.

[0010] Still further, the output power pull-up tube comprises a triode Q2; the base B of the triode Q2 is connected to the collector C of the triode QP, the collector C of the triode Q2 is connected to a power supply voltage VCC, and the emitter E of the triode Q2 is connected to an output signal Vout.

[0011] Still further, the voltage bias circuit comprises a diode Q5 and a diode Q6; the anode of the diode Q5 is connected to the collector C of the triode QP, the cathode of the diode Q5 is connected to the anode of the diode Q6; and the cathode of the diode Q6 is connected to the common source amplification stage circuit and the output composite pnp power pull-down tube respectively.

[0012] Further, the common source amplification stage circuit comprises a triode Q7; the base B of the triode Q7 is connected to a Vb input signal, the collector C of the triode Q7 is connected to the cathode of the diode Q6, and the emitter E of the triode Q7 is connected to an analog ground signal GND.

[0013] Further, the output composite pnp power pull-down tube comprises a triode Q3 and a triode Q4; the base B of the triode Q3 is connected to the cathode of the diode Q6, the collector C of the triode Q3 is connected to the base B of the triode Q4, the emitter E of the triode Q3 is connected to an output signal Vout, the collector C of the triode Q4 is connected to the output signal Vout, and the emitter E of the triode Q4 is connected to an analog ground signal GND.

[0014] Compared with the prior art, the application has the following beneficial technical effects:

[0015] The application provides a quasi-complementary class B output stage circuit structure, a transistor QP is added between a collector C of a transistor Q1 and a base B of a transistor Q2 in an output power pull-up tube, a common-emitter structure of the transistor QP and the transistor Q1 can form a Wollan circuit, high-frequency characteristics are better, and influence of poor frequency characteristics of a pnp tube in a bipolar process on working frequency of an operational amplifier can be compensated. The base B of the transistor QP can be freely biased. When the operational amplifier is used as a current source, if a load is heavy and a load current is large, a current flowing through the transistor Q1 will also increase. If the complementary bipolar process cannot be realized when a chip is manufactured, the npn tube in the overall circuit structure is in a vertical structure, and the pnp tube is mostly a horizontal pnp tube. As can be seen from a layout structure, two parasitic pnp tubes are generated when the emitter and the base of the horizontal pnp tube face an isolation wall and a substrate. If the load current is too large, the base region current of the transistor Q1 increases, which can cause the parasitic pnp tube to be turned on, thereby causing the output saturation high level to be reduced and the application range of the structure to be reduced. After the common-base transistor QP structure is added, according to an output saturation high level index, the base potential of the transistor QP can be biased to an applicable potential point, thereby improving the electrode potential of the transistor Q1 and the transistor QP, and the output saturation high level is clamped.

[0016] Further, the output stage adopts a complementary structure, and under the process limitation, because of the conflict with the npn tube, the doping level of the base region and the emitter of the pnp tube cannot be optimized, which often causes the power handling capacity of the pnp tube to be limited. Therefore, the composite pnp tube power tube composed of the transistor Q3 and the transistor Q4 is used as the pull-down tube in the output structure, the output power can be improved, and the transistor Q4 and the transistor Q2 are the same type of transistors, which can keep good symmetry of the tubes in the layout design.

[0017] Further, the structure is compatible with the bipolar process containing the JFET process, the transistor Q3 can be replaced by the JFET tube, and the diode Q5 or the diode Q6 is replaced by a diode-connected JFET tube, so that the temperature influence is reduced, the bypass current is obtained regardless of the temperature, and the feedback resistor between the emitter and the base of the transistor Q4 can improve the switching speed under high frequency. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 FIG. 1 is a schematic diagram of the quasi-complementary class B output stage circuit structure in the application.

[0019] 1-biasing circuit; 2-Wollan circuit; 3-voltage biasing circuit; 4-common-source amplification stage circuit; 5-output power pull-up tube; 6-output composite pnp power pull-down tube. DETAILED DESCRIPTION

[0020] In order to make the person skilled in the art better understand the technical scheme of the present application, the technical scheme in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work should belong to the protection scope of the present application.

[0021] It should be noted that the terms "first", "second" and the like in the description and claims of the present application and the above drawings are used to distinguish similar objects, and do not necessarily indicate a specific order or sequence. It should be understood that the data thus used can be interchanged under appropriate circumstances, so that the embodiments of the present application described herein can be implemented in an order other than that illustrated or described herein. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion, for example, a process, method, system, product or device including a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but can include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0022] The present application will be described in further detail below in conjunction with the drawings:

[0023] The purpose of the present application is to provide a high stability quasi-complementary class B output stage circuit structure for JFET bipolar process operational amplifier, to solve the technical problem of poor frequency characteristic of pnp tube in bipolar process in the prior art. The common base device structure is added in the quasi-complementary class B output stage to improve the frequency characteristic, and the base can be biased freely to realize free clamping of saturation output voltage, and the clamping voltage can suppress the process fluctuation of output saturation level.

[0024] The power supply voltage VCC is the power supply signal of the output stage, VCC should also be the power supply signal of the operational amplifier to which the structure is applied, GND is the analog ground signal, Vf is the input signal of the common base QP tube, Vb is the output signal of the operational amplifier amplification stage, which is the input signal of the output stage, and Vout is the output signal of the output stage.

[0025] The Vb input signal of the output stage is first amplified by the common source amplifier composed of the transistor Q7. The C, E and B of the transistor Q7 are connected to the cathode of the diode Q6, the GND analog ground signal and the Vb input signal respectively.

[0026] The transistor Q2 is the output power tube pull-up tube, and the C, E and B of the transistor Q2 are connected to the power supply voltage VCC, the output signal Vout and the collector C of the transistor QP respectively.

[0027] Transistors Q3 and Q4 form a composite PNP transistor, which is a power pull-down transistor. The collector, emitter, and base (C, E, B) of transistor Q3 are connected to the base (B) of transistor Q4, the output signal Vout, and the cathode of diode Q6, respectively. The collector, emitter, and base (C, E, B) of transistor Q4 are connected to the output signal Vout, the analog ground signal GND, and the collector (C) of transistor Q3, respectively.

[0028] Diodes Q5 and Q6 are connected in series to provide bias voltage for the output power transistor. The anode of diode Q5 is connected to the base (B) of transistor Q2, and the cathode of diode Q5 is connected to the anode of diode Q6. The anode of diode Q6 is connected to the cathode of diode Q5, and the cathode of diode Q6 is connected to the collector of transistor Q7.

[0029] Transistor Q1 is a tail current transistor. The collector, emitter, and base of transistor Q1 are connected to the emitter E of transistor QP, the power supply voltage VCC, and the cathode of diode D0, respectively.

[0030] The QP transistor is a common-base amplifier circuit. The collector C, emitter E, and base B of the QP transistor are connected to the base of transistor Q2, the collector C of transistor Q1, and the input signal Vf, respectively.

[0031] Diode D0 and resistor R provide bias signals for Q1. The positive terminal of resistor R is connected to the base of Q1, and the negative terminal is connected to GND (analog ground). The anode of diode D0 is connected to VCC (power supply signal), and the cathode of diode D0 is connected to the base of Q1.

[0032] Specifically, according to Figure 1 As shown, 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 Worman circuit 2, a voltage bias circuit 3, a common-source amplifier stage circuit 4, an output power pull-up transistor 5, and an output composite PNP power pull-down transistor 6. One end of the bias circuit 1 is connected to the power supply voltage VCC, and the other end is grounded. One end of the Worman circuit 2 is connected to the power supply voltage VCC, and the other end is connected in series with one end of the voltage bias circuit 3. The other end of the voltage bias circuit 3 is connected in series with one end of the common-source amplifier stage circuit 4, and the other end of the common-source amplifier stage circuit 4 is connected to the analog ground signal GND. One end of the output power pull-up transistor 5 is connected to the power supply voltage VCC. The other end of the output power pull-up transistor 5 is connected in series with one end of the output composite PNP power pull-down transistor 6, and the other end of the composite PNP power pull-down transistor 6 is connected to the analog ground signal GND. One end of the Worman circuit 2 is connected to the bias circuit 1, and the output power pull-up transistor 5 is connected between the Worman circuit 2 and the voltage bias circuit 3.

[0033] 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, and the cathode of the diode D0 is connected to the positive terminal of the resistor R and the Wollman circuit 2 respectively, and the negative terminal of the resistor R is grounded.

[0034] Specifically, the Wollman circuit 2 includes a triode Q1 and a triode QP; the emitter E of the triode Q1 is connected to a power supply voltage VCC, and the collector C of the triode Q1 is connected to the emitter E of the triode QP; the base B of the triode Q1 is connected to the cathode of the diode D0; the collector C of the triode QP is connected to the output power pull-up tube 5 and the voltage bias circuit 3 respectively; and the base B of the triode QP is connected to a Vf input signal.

[0035] Among them, the base B of the triode QP can be biased according to the bias signal or self-bias of the front stage structure of the operational amplifier, and according to the output saturation high voltage index, the base B potential of the triode QP can be biased to the applicable potential point.

[0036] Specifically, the output power pull-up tube 5 includes a triode Q2, the base B of the triode Q2 is connected to the collector C of the triode QP, the collector C of the triode Q2 is connected to a power supply voltage VCC, and the emitter E of the triode Q2 is connected to an output signal Vout.

[0037] 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; the cathode of the diode Q6 is connected to the common source amplification stage circuit 4 and the output composite pnp power pull-down tube 6 respectively.

[0038] Specifically, the common source amplification stage circuit 4 includes a triode Q7; the base B of the triode Q7 is connected to a Vb input signal, the collector C of the triode Q7 is connected to the cathode of the diode Q6; and the emitter E of the triode Q7 is connected to an analog ground signal GND.

[0039] Specifically, the output composite pnp power pull-down tube 6 includes a triode Q3 and a triode Q4; the base B of the triode Q3 is connected to the cathode of the diode Q6; the collector C of the triode Q3 is connected to the base B of the triode Q4; the emitter E of the triode Q3 is connected to an output signal Vout; the collector C of the triode Q4 is connected to the output signal Vout, and the emitter E of the triode Q4 is connected to an analog ground signal GND.

[0040] According to the application structure, the Vf signal is given a bias voltage that meets the output saturation high voltage index requirement, so that the QP tube can work normally. The base bias currents of the power pull-up tube Q2 and the composite pnp power pull-down tubes Q3 and Q4 are all provided by the tail current source Q1 tube.

[0041] The quasi-complementary class B output stage circuit structure provided by the application has the advantages that:

[0042] When the input signal Vb rises, the collector voltage of the transistor Q7 decreases, causing the emitter voltage of the transistor Q3 to decrease, and the output signal Vout to decrease. When the input signal Vb rises to the lowest saturation voltage of the output signal Vout, the output voltage value is the saturation voltage drop between the collector and the emitter of the transistor Q4, the transistor Q2 is turned off, the operational amplifier works in the current sink state, and the transistors Q3 and Q4 draw current from the output signal Vout port to the GND analog ground signal. The current carrying capacity of the common pnp tube is limited, and the current carrying capacity is improved because the transistors Q3 and Q4 are combined into a composite pnp tube.

[0043] When the input signal Vb decreases, the collector voltage of the transistor Q7 increases, causing the base voltage of the transistor Q2 to increase, and the output signal Vout to increase. When the input signal Vb decreases to the highest saturation voltage of the output signal Vout, the output voltage value is the power supply voltage signal minus the saturation voltage drop between the collector and the emitter of the transistor QP and the transistor Q1, and then minus the base-emitter turn-on voltage drop of the transistor Q2. The transistors Q3 and Q4 are turned off, the operational amplifier works in the current source state, and the transistor Q2 delivers current from the VCC power signal to the load through the output signal Vout.

[0044] The diodes Q5 and Q6 are diode-connected transistors. These two tubes can be pnp tubes or npn tubes. The diodes Q5 and Q6 provide a bias voltage for the output power tube to avoid crossover distortion of the output signal.

[0045] The diode D0 and the resistor R provide a bias signal for the tail current transistor Q1, so that the output structure generates stable static current.

[0046] The transistors QP and Q1 are connected in series, the collector output signal of the transistor Q1 is connected to the emitter of the transistor QP, and then the collector output of the transistor QP is connected to the base of the transistor Q2, and finally to the Vout output signal. The transistor QP is a common-base amplification circuit that does not amplify current and functions as a current follower. This structure has excellent high-frequency characteristics and improves the high-frequency performance of the output stage.

[0047] The base voltage of the transistor QP can be connected to a bias signal or self-biased according to the pre-stage structure of the operational amplifier.

[0048] The transistor Q1 in the output structure is a pnp tube, and in general bipolar technology, its frequency characteristics are far inferior to those of an npn tube. The transistor QP added to the structure is a common-base amplifier that has good frequency characteristics and can improve the stability of the frequency response of the output structure.

[0049] The base voltage potential of the triode QP in the output structure is not explicitly required, and can be self-biased according to application conditions, and the output saturation high level is freely set.

[0050] When a large load current is provided, the output saturation high level is affected by the process level, and the collector-emitter saturation voltage of the triode Q1 is easily increased, resulting in a decrease in the output saturation high level. At this time, the base potential of the triode QP can be connected to a higher voltage node, so as to increase the output saturation high level and play a clamping role.

[0051] In summary, the application provides a quasi-complementary class-B output stage circuit structure. The triode QP is added between the collector C of the triode Q1 and the base B of the triode Q2 in the output power pull-up tube, and a Wollan circuit can be formed by the common-emitter structure of the triode Q1 and the triode QP, so that the high-frequency characteristics are better, and the influence of the poor frequency characteristics of the pnp tube in the bipolar process on the operating frequency of the operational amplifier can be compensated. The base B input of the triode QP can be freely biased. 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 triode Q1 will also increase. If the complementary bipolar process cannot be realized during the wafer fabrication, the npn tube in the overall circuit structure is in a vertical structure, and the pnp tube is mostly a lateral pnp tube. As can be seen from the layout structure, the emitter and the base of the lateral pnp tube will generate two parasitic pnp tubes when facing the isolation wall and the substrate. If the load current is too large, the base region current of the triode Q1 will increase, which will cause the parasitic pnp tube to be turned on, thereby causing the output saturation high level to decrease and the application range of the structure to decrease. 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 as to increase the electrode potential of the triode Q1 and the triode QP, and the output saturation high level is clamped.

[0052] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the application and not to limit it, although the application has been described in detail with reference to the above examples, those skilled in the art should understand that the specific embodiments of the application can be modified or replaced, and any modification or equivalent replacement without departing from the spirit and scope of the application should be covered within the protection scope of the claims of the application.

Claims

1. A quasi-complementary class-AB output stage circuit structure, characterized by The application relates to a power amplifier circuit, which comprises a power supply voltage VCC, an analog ground signal GND, an output signal Vout, a bias circuit (1), a Wollman circuit (2), a voltage bias circuit (3), a common-source amplification 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 to the power supply voltage VCC, and the other end is grounded; one end of the Wollman circuit (2) is connected to the power supply voltage VCC, and the other end is connected in series with one end of the voltage bias circuit (3); the other end of the voltage bias circuit (3) is connected in series with one end of the common-source amplification stage circuit (4); the other end of the common-source amplification stage circuit (4) is connected to the analog ground signal GND; one end of the output power pull-up tube (5) is connected to the power supply voltage VCC; the other end of the output power pull-up tube (5) is connected in series with 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 Wollman circuit (2) is connected to the bias circuit (1); the output power pull-up tube (5) is connected between the Wollman circuit (2) and the voltage bias circuit (3). The Wollman circuit (2) comprises a transistor Q1 and a transistor QP; the emitter E of the transistor Q1 is connected to the power supply voltage VCC; the collector C of the transistor Q1 is connected to the emitter E of the transistor QP; the base B of the transistor Q1 is connected to the cathode of a diode D0; the collector C of the transistor QP is connected to the output power pull-up tube (5) and the voltage bias circuit (3) respectively; the base B of the transistor QP is connected to a Vf input signal. The base B of the transistor QP can be connected to a bias signal or self-biased according to the structure of a pre-operational amplifier; according to an output saturation high level index, the base B potential of the transistor QP can be biased to an applicable potential point.

2. A quasi-complementary Class AB output stage circuit arrangement as claimed in claim 1, characterized in that The bias circuit 1 comprises a diode D0 and a resistor R; the anode of the diode D0 is connected to the power supply voltage VCC; the cathode of the diode D0 is connected to the positive end of the resistor R and the Wollman circuit (2) respectively; and the negative end of the resistor R is grounded.

3. A quasi-complementary Class AB output stage circuit arrangement as claimed in claim 1, characterized in that The output power pull-up tube (5) comprises a transistor Q2; the base B of the transistor Q2 is connected to the collector C of the transistor QP; the collector C of the transistor Q2 is connected to the power supply voltage VCC; and the emitter E of the transistor Q2 is connected to the output signal Vout.

4. A quasi-complementary Class AB output stage circuit arrangement as claimed in claim 1, characterized in that The 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 transistor QP; the cathode of the diode Q5 is connected to the anode of the diode Q6; and the cathode of the diode Q6 is connected to the common-source amplification stage circuit (4) and the output composite pnp power pull-down tube (6) respectively.

5. A quasi-complementary Class-E output stage circuit arrangement according to Claim 4, characterised in that, The common-source amplification stage circuit (4) comprises a transistor Q7; the base B of the transistor Q7 is connected to a Vb input signal; the collector C of the transistor Q7 is connected to the cathode of the diode Q6; and the emitter E of the transistor Q7 is connected to the analog ground signal GND.

6. A quasi-complementary Class-E output stage circuit arrangement according to Claim 4, characterised in that, The output composite pnp power pull-down tube (6) comprises a triode Q3 and a triode Q4; the base B of the triode Q3 is connected to the cathode of a diode Q6; the collector C of the triode Q3 is connected to the base B of the triode Q4; the emitter E of the triode Q3 is connected to an output signal Vout; the collector C of the triode Q4 is connected to the output signal Vout, and the emitter E of the triode Q4 is connected to an analog ground signal GND.

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