CN104038166B - Operational amplifier circuit and method for improving driving capability thereof - Google Patents

Abstract

The present invention provides an operational amplifier circuit and a method for improving its driving capability, which are used to drive a load. The operational amplifier circuit includes an output stage module. The output stage module includes a detection circuit and an output stage circuit. The detection circuit is used to detect a current output voltage and a previous output voltage according to a comparison result between a current input voltage and a current output voltage. Moreover, the detection circuit increases the charging speed or discharging speed of the output stage circuit to the load according to a detection result.

Description

Operational Amplifier Circuit and Method for Improving Its Driving Capability

technical field

The invention relates to an electronic circuit and a method for improving its circuit characteristics, and in particular to an operational amplifier circuit and a method for improving its driving capability.

Background technique

The output stage operational amplifier (operational amplifier) plays a very important role in the design of integrated circuits. It is widely used in radio communication, TV broadcast transmitters and receivers, high-fidelity stereo equipment, microcomputers and other electronic equipment . The function of the output stage operational amplifier is to increase the signal energy to drive the load or the next stage circuit. Traditional linear power amplifiers, such as Class A, Class B and Class AB amplifiers, bias the active components at a fixed DC current, so they have better linearity.

However, in the application of a driver chip for a large-sized panel, if the operating frequency of the driver chip increases or the size of the panel becomes larger, the output-stage operational amplifier often has insufficient charge and discharge for the load or the next-stage circuit. Generally speaking, the chip area of the output stage operational amplifier determines the size of its drive current. Therefore, if it is desired to improve the charge-discharge capability of the driver chip, it can usually be achieved by increasing the area of the output stage operational amplifier, but this method will increase the area of the driver chip, resulting in an increase in cost.

Contents of the invention

The invention provides an operational amplifier circuit, which can dynamically detect the magnitude of the output voltage, so as to improve the driving ability of the output stage circuit.

The invention provides a method for improving the driving ability of the operational amplifier circuit, which can dynamically detect the magnitude of the output voltage to improve the driving ability of the operational amplifier circuit.

The invention provides an operational amplifier circuit for driving a load. The operational amplifier circuit includes an output stage module. The output stage module includes a detection circuit and an output stage circuit. The detection circuit is used for detecting the current output voltage and a previous output voltage according to a comparison result between a current input voltage and a current output voltage. Moreover, the detection circuit increases the charging speed or discharging speed of the load by the output stage circuit according to a detection result.

In an embodiment of the present invention, when the previous output voltage is greater than the current output voltage, the detection circuit increases the charging speed of the output stage circuit to the load according to the detection result.

In an embodiment of the present invention, when the previous output voltage is lower than the current output voltage, the detection circuit increases the discharge speed of the output stage circuit to the load according to the detection result.

In an embodiment of the present invention, the above-mentioned output stage circuit includes a first transistor and a second transistor. The first transistor has a first terminal, a second terminal and a control terminal. The first end of the first transistor is coupled to a first voltage. The second terminal of the first transistor serves as the output terminal of the output stage circuit. The control terminal of the first transistor is coupled to the detection circuit. The detection circuit turns on the first transistor by reducing the voltage of the control terminal of the first transistor, so as to increase the charging speed of the output stage circuit to the load. The second transistor has a first terminal, a second terminal and a control terminal. The first terminal of the second transistor is coupled to the first terminal of the first transistor. The second terminal of the second transistor is coupled to a second voltage. The control terminal of the second transistor is coupled to the detection circuit. The detection circuit turns on the second transistor by increasing the voltage of the control terminal of the second transistor, so as to increase the discharge speed of the output stage circuit to the load.

In an embodiment of the present invention, the above-mentioned output stage circuit further includes a first current source. The first current source has a first terminal and a second terminal. A first terminal of the first current source is coupled to a first voltage. The second terminal of the first current source is coupled to the control terminal of the first transistor. When the first current source is turned on, the voltage at the control terminal of the second transistor rises to turn on the second transistor, thereby increasing the discharge speed of the output stage circuit to the load.

In an embodiment of the present invention, the above output stage circuit further includes a second current source. The second current source has a first terminal and a second terminal. The first terminal of the second current source is coupled to the control terminal of the second transistor. The second terminal of the second current source is coupled to the second voltage. When the second current source is turned on, the voltage at the control terminal of the first transistor drops to turn on the first transistor, thereby increasing the charging speed of the output stage circuit to the load.

In an embodiment of the present invention, the above-mentioned output stage circuit includes a third transistor and a fourth transistor. The third transistor has a first terminal, a second terminal and a control terminal. The first terminal of the third transistor is coupled to a first voltage. The second terminal of the third transistor serves as the output terminal of the output stage circuit. The control terminal of the third transistor is coupled to the detection circuit. The detection circuit turns on the third transistor by increasing the voltage of the control terminal of the third transistor, so as to increase the charging speed of the output stage circuit to the load. The fourth transistor has a first terminal, a second terminal and a control terminal. The first terminal of the fourth transistor is coupled to the first terminal of the third transistor. The second end of the fourth transistor is coupled to a second voltage. The control terminal of the fourth transistor is coupled to the detection circuit. The detection circuit turns on the fourth transistor by reducing the voltage of the control terminal of the fourth transistor, so as to increase the discharge speed of the output stage circuit to the load.

In an embodiment of the present invention, the above-mentioned output stage circuit includes a third current source and a fifth transistor. The third current source has a first terminal and a second terminal. The first end of the third current source is coupled to a first voltage. The second terminal of the third current source is coupled to the output terminal of the output stage circuit. When the third current source is turned on, the third current source charges the load, so as to increase the charging speed of the output stage circuit to the load. The fifth transistor has a first terminal, a second terminal and a control terminal. The first terminal of the fifth transistor is coupled to the output terminal of the output stage circuit. The second terminal of the fifth transistor is coupled to a second voltage. The control terminal of the fifth transistor is coupled to the detection circuit. The detection circuit turns on the fifth transistor by increasing the voltage of the control terminal of the fifth transistor, so as to increase the discharge speed of the output stage circuit to the load.

In an embodiment of the present invention, the above-mentioned output stage circuit includes a first control terminal and a second control terminal. Moreover, the detection circuit includes a differential input pair, a first current mirror module and a second current mirror module. The differential input pair has a first end and a second end. The first end of the differential input pair receives the previous output voltage. The second terminal of the differential input pair receives the current output voltage. The first current mirror module is coupled to the differential input pair and controlled by an enable signal. When the previous output voltage is greater than the current output voltage, the first current mirror module provides a first current to the first control terminal according to the enabling signal. The second current mirror module is coupled to the differential input pair and controlled by the enabling signal. When the previous output voltage is lower than the current output voltage, the second current mirror module draws a second current from the second control terminal according to the enabling signal.

In an embodiment of the present invention, the above-mentioned output stage circuit includes a first control terminal and a second control terminal. Moreover, the detection circuit includes a differential input pair, a first switch and a second switch. The differential input pair has a first end and a second end. The first end of the differential input pair receives the previous output voltage. The second terminal of the differential input pair receives the current output voltage. The first switch has a first terminal, a second terminal and a control terminal. The first terminal of the first switch is coupled to the first control terminal via a third current mirror module. The second end of the first switch is coupled to the differential input pair. The control end of the first switch is controlled by an enabling signal. When the previous output voltage is greater than the current output voltage, the enabling signal turns on the first switch, so that the third current mirror module provides a third current to the first control terminal. The second switch has a first terminal, a second terminal and a control terminal. The first terminal of the second switch is coupled to the differential input pair. The second terminal of the second switch is coupled to the second control terminal via a fourth current mirror module. The control end of the second switch is controlled by the enabling signal. When the previous output voltage is lower than the current output voltage, the enabling signal turns on the second switch, so that the fourth current mirror module draws a fourth current from the second control terminal.

In an embodiment of the present invention, the above detection circuit includes a comparator circuit. The comparator circuit is used for comparing the current output voltage with the previous output voltage. The comparator circuit has a first input terminal, a second input terminal, a control terminal and an output terminal. A first input terminal of the comparator circuit receives the previous output voltage. The second input terminal of the comparator circuit receives the current output voltage. The output terminal of the comparator circuit outputs a comparison result between the current output voltage and the previous output voltage. The control terminal of the comparator circuit receives an enabling signal. The comparator circuit determines whether to compare the current output voltage with the previous output voltage according to the enabling signal.

In an embodiment of the present invention, when the current input voltage is greater than or less than the current output voltage, the above detection circuit is enabled to detect the current output voltage and the previous output voltage.

In an embodiment of the present invention, the above operational amplifier circuit further includes a pre-operational amplifier. The pre-operational amplifier is coupled to the output stage module for comparing the current input voltage and the current output voltage, and outputs an enable signal to the detection circuit according to the comparison result. The detection circuit determines whether to detect the current output voltage and the previous output voltage according to the enabling signal.

The present invention provides a method of improving the driving capability of an operational amplifier circuit. The operational amplifier circuit is used to drive a load. The method includes the following steps. A current input voltage is compared with a current output voltage, and an enabling signal is generated according to the comparison result. The current output voltage and a previous output voltage are detected according to the enabling signal. According to a detection result, the charging speed or discharging speed of the output stage circuit to the load is increased.

In an embodiment of the present invention, the step of increasing the charging speed or discharging speed of the output stage circuit to the load includes increasing the charging speed of the output stage circuit to the load when the previous output voltage is greater than the current output voltage according to the detection result.

In an embodiment of the present invention, the step of increasing the charging or discharging speed of the output stage circuit to the load includes increasing the discharge speed of the output stage circuit to the load when the previous output voltage is lower than the current output voltage according to the detection result.

In an embodiment of the present invention, in the step of comparing the current input voltage and the current output voltage, when the current input voltage is greater than or less than the current output voltage, an enable signal is generated to detect the current output voltage and the previous output voltage.

Based on the above, in an exemplary embodiment of the present invention, the output stage module of the operational amplifier circuit includes a detection circuit. The detection circuit can dynamically detect the magnitude of the output voltage to improve the charging and discharging capability of the output stage circuit to the load or the next stage circuit.

In order to make the above-mentioned features and advantages of the present invention more comprehensible, the following specific embodiments are described in detail with reference to the accompanying drawings.

Description of drawings

FIG. 1 shows a schematic circuit diagram of an operational amplifier circuit of a related art of the present invention.

FIG. 2 is a schematic circuit diagram of an operational amplifier circuit according to an embodiment of the present invention.

FIG. 3 , FIG. 4 and FIG. 8 are schematic circuit diagrams of operational amplifier circuits of other embodiments of the present invention.

FIG. 5 is a schematic circuit diagram of a detection circuit according to an embodiment of the present invention.

FIG. 6 is a circuit structure diagram of the operational amplifier circuit in FIG. 2 .

FIG. 7 is a circuit structure diagram of the detection circuit in FIG. 6 .

FIG. 9 is a flow chart showing the steps of improving the driving capability of the operational amplifier circuit according to an embodiment of the present invention.

[Description of main component symbols]

100, 200, 300, 400, 800: Operational amplifier circuits

110, 210, 310, 410, 810: pre-operational amplifier

120, 220, 320, 420, 820: Output Stage Operational Amplifiers

130, 230, 330, 430, 830: output stage circuit

140, 240, 340, 440, 840: output switch

222, 322, 422, 822: detection circuit

224: The third current mirror module

226: The fourth current mirror module

510, 710: differential input pair

520: the first current mirror module

522: First current mirror

524, 720: first switch

530: second current mirror module

532: second current mirror

534, 730: second switch

823: Comparator circuit

V1, V2: Gate-to-source voltage across output stage transistors

VIN: input voltage

VIN+: current input voltage

VOUT: output voltage

VOUT-: previous output voltage

VOUT+: current output voltage

VDD: system voltage

Vb1, Vb2, Vb3, Vb4: control voltage

C1, C2: Capacitors

I1, I2, I3: current sources

A: The first control terminal

B: the second control terminal

C, D: node

Nout, Nout2, Nout5, Nout3, N1, N2, N3, N4, N5, N6: N-type transistors

Pout, Pout1, Pout4, P1, P2, P3, P4, P5, P6: P-type transistors:

SW1: switch control signal

EN: enable signal

ENB: Inverted enable signal

IM1: first current

IM2: second current

IM3: third current

IM4: fourth current

S900, S910, S920: Procedures for Improving the Drive Capability of Operational Amplifier Circuits

detailed description

FIG. 1 shows a schematic circuit diagram of an operational amplifier circuit of a related art of the present invention. Please refer to FIG. 1 , the operational amplifier circuit 100 of this example is for example applied in a driver chip of a display panel, and includes a class AB output stage circuit 130 . The driving capability of the class AB output stage circuit 130 , such as the charge and discharge capability of the load or the next stage circuit (not shown), depends on the size of the output stage transistors Pout and Nout. Under this framework, if it is desired to increase the driving capability of the driver chip for the display panel, the only way is to increase the size of the output stage transistors Pout and Nout, but this method will increase the area of the driver chip, resulting in an increase in cost.

In this example, when the class AB output stage circuit 130 is charging and discharging the load or the next stage circuit, its output current value may also depend on the gate-to-source voltages V1 and V2 of the output stage transistors Pout and Nout. Therefore, if a circuit method can be used to adjust the magnitude of the gate-source cross voltage V1, V2, then the output stage transistor of the same size can provide a larger current, thereby increasing the driving capability of the operational amplifier circuit. At least based on this concept, the detection circuit of the present disclosure can dynamically detect the output voltage value of the output stage circuit to adjust the magnitude of the gate-source cross voltage of the output stage transistor. In order to understand the present invention more clearly, at least one exemplary embodiment will be described in detail below with reference to the accompanying drawings.

FIG. 2 is a schematic circuit diagram of an operational amplifier circuit according to an embodiment of the present invention. Please refer to FIG. 2 , the operational amplifier circuit 200 of this embodiment is used to drive loads such as data lines on the display panel. The operational amplifier circuit 200 can be roughly divided into two circuit stages, including a pre-stage and an output stage, wherein the pre-stage includes a pre-operational amplifier 210 , and the output stage includes an output stage module. In this example, the output stage module includes an output stage operational amplifier 220 and an output stage circuit 230 . At least to perform the function of detecting the output voltage value, the output stage operational amplifier 220 internally configures a detection circuit 222 for detecting the current output voltage VOUT+ and the previous output voltage VOUT− of the output stage circuit 230 . Here, the previous output voltage VOUT-, for example, refers to the previous data voltage output by the operational amplifier circuit 200 to drive the data lines on the display panel, and the current output voltage VOUT+, for example, refers to the data voltage to be output by the operational amplifier circuit 200 The next data voltage is also used to drive the data lines on the display panel. Therefore, in order to reduce the mutual influence between the current output voltage VOUT+ and the previous output voltage VOUT-, this embodiment further configures an output switch 240, which can reduce the The current output voltage VOUT+ is affected by the previous output voltage VOUT-. It should be noted that although the present embodiment is illustrated by taking the detection circuit 222 disposed inside the output-stage operational amplifier 220 as an example, the present invention is not limited thereto.

Specifically, the pre-operational amplifier 210 of this embodiment is coupled to the output-stage operational amplifier 220 of the output-stage module to compare the current input voltage VIN+ with the current output voltage VOUT+, and output the enable signal EN to VOUT+ according to the comparison result. The detection circuit 222 is configured to perform the function of dynamically detecting the output voltage value. Therefore, the detection circuit 222 determines whether to detect the current output voltage VOUT+ and the previous output voltage VOUT− according to the enable signal EN. In this embodiment, when the current input voltage VIN+ is greater than or less than the current output voltage VOUT+, it indicates that the driving capability of the operational amplifier circuit 200 needs to be adjusted, so the detection circuit 222 is enabled to detect the difference between the current output voltage VOUT+ and the previous The output voltage VOUT-, so as to achieve the purpose of enhancing the driving capability. On the contrary, if the current input voltage VIN+ is equal to the current output voltage VOUT+, the detection circuit 222 will not perform the operation of enhancing the driving capability. In addition, the specific implementation manner of the pre-operational amplifier 210 may be, for example, the circuit structure of the pre-operational amplifier 110 as shown in FIG. 1 , which will not be repeated here.

In this embodiment, the detection circuit 222 detects the current output voltage VOUT+ and the previous output voltage VOUT- after being enabled, and increases the charging or discharging speed of the output stage circuit 230 to the load according to the detection result. In this example, according to the detection result, when the previous output voltage VOUT− is greater than the current output voltage VOUT+, the detection circuit 222 will increase the charging speed of the output stage circuit 230 to the load. On the contrary, according to the detection result, when the previous output voltage VOUT− is smaller than the current output voltage VOUT+, the detection circuit 230 will increase the discharge speed of the output stage circuit 230 to the load. The manner in which the detection circuit 230 enhances the driving capability of the output stage circuit 230 is specifically described as follows.

Taking the class AB output stage circuit as an example, the output stage circuit of this embodiment includes a P-type transistor Pout1 and an N-type transistor Nout2. The source of the P-type transistor Pout1 is coupled to the system voltage VDD. The drain of the P-type transistor Pout1 serves as the output terminal of the output stage circuit 230 . The gate of the P-type transistor Pout1 is coupled to the detection circuit 222 as the first control terminal A. The drain of the N-type transistor Nout2 is coupled to the drain of the P-type transistor Pout1 . The source of the N-type transistor Nout2 is coupled to the ground voltage. The gate of the N-type transistor Nout2 is coupled to the detection circuit 222 as the second control terminal B.

In this embodiment, the detection circuit 222 turns on the P-type transistor Pout1 by reducing the gate voltage of the P-type transistor Pout1 , so as to increase the charging speed of the output stage circuit 230 to the load. Similarly, the detection circuit 222 turns on the N-type transistor Nout2 by increasing the gate voltage of the N-type transistor Nout2, so as to increase the discharge speed of the output stage circuit 230 to the load. From another point of view, reducing the gate voltage of the P-type transistor Pout1 means increasing the gate-source voltage V1 of the P-type transistor Pout1 . Increasing the gate voltage of the N-type transistor Nout2 means increasing the gate-source voltage V2 of the N-type transistor Nout2.

To sum up, in the transient response of the operational amplifier circuit 200 , the switch control signal SW1 will first turn off the output switch 240 , so that the previous output voltage VOUT− maintains the charged voltage value at the last driving time point. Next, after the enable signal EN enables the detection circuit 222 , the detection circuit 222 compares the magnitude relationship between the current output voltage VOUT+ and the previous output voltage VOUT−. If the current output voltage VOUT+ is greater than the previous output voltage VOUT-, the detection circuit 222 will reduce the voltages of the first control terminal A and the second control terminal B, so that the voltage difference V1 between the gate and source of the P-type transistor Pout1 increases, accelerating The charging capability of the output stage circuit 230 to the load. Similarly, if the current output voltage VOUT+ is lower than the previous output voltage VOUT-, the detection circuit 222 will increase the voltages of the first control terminal A and the second control terminal B, so that the voltage difference between the gate and source of the N-type transistor Nout2 is V2 increase to speed up the discharge capability of the output stage circuit 230 to the load. .

In this embodiment, the output stage circuit 230 is an example of an AB class output stage circuit, but the present invention is not limited thereto. The concept of dynamically detecting the output voltage value of the output stage circuit in the present disclosure can also be applied to the output stage circuit is The implementations of the class A output stage circuit or the class B output stage circuit are respectively described as follows.

FIG. 3 is a schematic circuit diagram of an operational amplifier circuit according to another embodiment of the present invention. Please refer to FIG. 2 and FIG. 3, the operational amplifier circuit 300 of the present embodiment is similar to the operational amplifier circuit 200 of FIG. The circuit structure is described in detail as follows.

In this embodiment, the output stage circuit 330 includes a current source I3 and an N-type transistor Nout5. One end of the current source I3 is coupled to the system voltage VDD. The other terminal of the current source I3 is coupled to the output terminal of the output stage circuit 330 . In this example, when the current source I3 is turned on, the current source I3 will charge the load, so as to increase the charging speed of the output stage circuit 330 to the load. The drain of the N-type transistor Nout5 is coupled to the output terminal of the output stage circuit 330 . The source of the N-type transistor Nout5 is coupled to the ground voltage. The gate of the N-type transistor Nout5 is coupled to the detection circuit 322 as the second control terminal B. In this example, the detection circuit 322 turns on the N-type transistor Nout5 by increasing the gate voltage of the N-type transistor Nout5 , so as to increase the discharge speed of the output stage circuit 330 to the load.

FIG. 4 is a schematic circuit diagram of an operational amplifier circuit according to another embodiment of the present invention. Please refer to FIG. 2 and FIG. 4, the operational amplifier circuit 400 of the present embodiment is similar to the operational amplifier circuit 200 of FIG. The circuit structure is described in detail as follows.

In this embodiment, the output stage circuit 430 includes an N-type transistor Nout3 and a P-type transistor Pout4 . The drain of the N-type transistor Nout3 is coupled to the system voltage. The source of the N-type transistor Nout3 serves as the output terminal of the output stage circuit. The gate of the N-type transistor Nout3 is coupled to the detection circuit as the first control terminal A. The detection circuit turns on the N-type transistor Nout3 by increasing the gate voltage of the N-type transistor Nout3, so as to increase the charging speed of the output stage circuit to the load. The source of the P-type transistor Pout4 is coupled to the drain of the N-type transistor Nout3 . The drain of the P-type transistor Pout4 is coupled to the ground voltage. The gate of the P-type transistor Pout4 is coupled to the detection circuit as the second control terminal B. The detection circuit turns on the P-type transistor Pout4 by reducing the gate voltage of the P-type transistor Pout4, so as to increase the discharge speed of the output stage circuit 430 to the load.

FIG. 5 is a schematic circuit diagram of a detection circuit according to an embodiment of the present invention. Please refer to FIG. 5 , the detection circuit 500 of this embodiment, for example, can at least be applied to the operational amplifier circuit disclosed in any one of the above embodiments. In this embodiment, the detection circuit 500 includes a differential input pair 510 , a first current mirror module 520 and a second current mirror module 530 . Wherein, the first current mirror module 520 includes a first current mirror 522 and a first switch 524 . The second current mirror module 530 includes a second current mirror 532 and a second switch 534 .

Two ends of the differential input pair 510 in this embodiment respectively receive the previous output voltage VOUT− and the current output voltage VOUT+. Moreover, the magnitude relationship between the previous output voltage VOUT− and the current output voltage VOUT+ will determine which transistor N1 or P1 is turned on. The first current mirror 522 is coupled to the differential input pair 510 , and the first switch 524 is controlled by the inverted enable signal ENB. The second current mirror 532 is coupled to the differential input pair 510, and the second switch 534 is controlled by the enable signal EN. In this embodiment, when the previous output voltage VOUT− is greater than the current output voltage VOUT+, the transistor N1 is turned on, and the first switch 524 is turned on by the inverted enable signal ENB. At this moment, the first current mirror 522 provides the first current IM1 to the first control terminal A of the output stage circuit, so as to decrease or increase the voltage of the first control terminal A. On the contrary, when the previous output voltage VOUT− is lower than the current output voltage VOUT+, the transistor P1 will be turned on, and the second switch 534 will be turned on by the enable signal EN. At this moment, the second current mirror 532 draws the second current IM2 from the second control terminal B of the output stage circuit to increase or decrease the voltage of the second control terminal B.

In detail, taking the class AB output stage circuit as an example, in this embodiment, the transistors N1 and P1 determine the magnitude relationship between the previous output voltage VOUT− and the current output voltage VOUT+. If the previous output voltage VOUT− is greater than the sum of the current output voltage VOUT+ and the threshold voltage Vtn of the transistor N1, the transistor N1 is turned on. The detection circuit 500 generates the first current IM1 to the operational amplifier circuit through the transistors P2, P3, and P4, and the first current IM1 charges the first control terminal A and the second control terminal B of the output stage circuit, so that the voltage of both rises and accelerates Its driving ability to discharge the load. If the voltage difference between the previous output voltage VOUT- and the current output voltage VOUT+ is larger, the turn-on range of the transistor N1 will be larger, and as a result, the first current IM1 provided to the operational amplifier will be increased, and the transistor of the output stage will increase. The gate voltage dynamically adjusts its driving capability according to the relationship between the previous output voltage VOUT- and the current output voltage VOUT+. Conversely, if the previous output voltage VOUT- is smaller than the difference between the current output voltage VOUT+ and the absolute threshold voltage |Vtp| of the transistor P1, the transistor P1 will draw a current from the terminal receiving the current output voltage VOUT+ of the differential input pair 510 to the transistor N2 , and then the transistors N3 and N4 draw the second current IM2 to the output stage circuit. The voltages of the first control terminal A and the second control terminal B of the output stage circuit will drop due to the current being drawn, thereby accelerating the charging speed of the output stage transistor. On the other hand, if the previous output voltage VOUT- is greater than the difference between the current output voltage VOUT+ and the absolute value of the threshold voltage |Vtp| The transistors N1 and P1 of the 510 are not turned on, so there is no additional current injection or output to the output stage circuit. Therefore, the driving capability of the output stage circuit remains unregulated, and its output waveform will not overshoot.

In addition to being directly connected to the first control terminal A and the second control terminal B of the output stage circuit, the detection circuit of this embodiment can also be connected to an operational amplifier circuit that will affect the flow into or out of the first control terminal A and the second control terminal. The operating point of the terminal B current.

Taking the class AB output stage circuit as an example again, FIG. 6 shows a circuit structure diagram of the operational amplifier circuit in FIG. 2 , and FIG. 7 shows a circuit structure diagram of the detection circuit in FIG. 6 . Please refer to FIG. 6 and FIG. 7 , the detection circuit 222 of this embodiment includes a differential input pair 710 , a first switch 720 and a second switch 730 . Two ends of the differential input pair respectively receive the previous output voltage VOUT− and the current output voltage VOUT+. The first terminal of the first switch 720 is coupled to the first control terminal A via the node C and the third current mirror module 224 inside the output stage operational amplifier 220 . The second terminal of the first switch 720 is coupled to the differential input pair 710 . The control terminal of the first switch 720 is controlled by the enable signal EN. A first end of the second switch 730 is coupled to the differential input pair 710 . The second terminal of the second switch is coupled to the second control terminal B via the node D and the fourth current mirror module 226 inside the output stage operational amplifier 220 . The control terminal of the second switch is controlled by the inverted enabling signal ENB. In this embodiment, when the previous output voltage VOUT− is greater than the current output voltage VOUT+, the enable signal EN turns on the first switch 720 to allow the third current mirror module 224 to provide the third current IM3 to the first control terminal A. When the previous output voltage VOUT− is smaller than the current output voltage VOUT+, the inverted enable signal ENB turns on the second switch 730 so that the fourth current mirror module 226 draws the fourth current IM4 from the second control terminal B.

In detail, when the voltage difference between the previous output voltage VOUT− and the current output voltage VOUT+ is large enough to turn on the transistor N1, a voltage is generated between the node C and the terminal of the differential input pair 710 receiving the current output voltage VOUT+. The current is conducted to the terminal of the differential input pair 710 receiving the current output voltage VOUT+ via the node C, the transistors N2 and N1. Then, the detection circuit 222 uses the transistors P5 and P6 of the third current mirror module 224 to map the same current IM3 into the first control terminal A and the second control terminal B to charge them, so that the voltage of the second control terminal B rises, Thus, the discharge capability of the N-type transistor Nout2 is accelerated. Conversely, when the voltage difference between the previous output voltage VOUT- and the current output voltage VOUT+ is large enough to turn on the transistor P1, another current will be generated between the terminal of the differential input pair 710 receiving the current output voltage VOUT+ and node D , this current receives the terminal of the current output voltage VOUT+ through the differential input pair 710 , and the transistors P1 and P2 are turned on to the node C. Next, the detection circuit 222 uses the transistors N5 and N6 of the fourth current mirror module 226 to draw the same current IM4 from the first control terminal A and the second control terminal B to discharge it, so that the voltage of the first control terminal A drops, Thus, the charging capability of the P-type transistor Pout1 is accelerated.

In addition, in the present disclosure, the detection circuit is used to compare the previous output voltage with the current output voltage, and respond a proper current to the inside of the output stage operational amplifier, so the detection circuit can also be implemented by using a comparator circuit.

FIG. 8 is a schematic circuit diagram of an operational amplifier circuit according to another embodiment of the present invention. Please refer to FIG. 2 and FIG. 8, the operational amplifier circuit 800 of this embodiment is similar to the operational amplifier circuit 200 of FIG. A circuit structure is implemented, and the detection circuit 822 includes a comparator circuit 823, which is described in detail below.

In this embodiment, compared with the output stage circuit 230 , the output stage circuit 830 further includes current sources I1 and I2 . The first end of the current source I1 is coupled to the system voltage VDD. The second terminal of the current source I1 is coupled to the gate of the P-type transistor Pout1 , that is, the first control terminal A. When the current source I1 is turned on, the voltages of the first control terminal A and the second control terminal B will rise to turn on the N-type transistor Nout2 , thereby increasing the discharge speed of the output stage circuit 830 to the load. On the other hand, the first terminal of the current source I2 is coupled to the gate of the N-type transistor Nout2 , that is, the second control terminal B. The second terminal of the current source I2 is coupled to the ground voltage. When the current source I2 is turned on, the voltages of the first control terminal A and the second control terminal B will drop to turn on the P-type transistor Pout1 , thereby increasing the charging speed of the output stage circuit 830 to the load.

In addition, in this embodiment, the comparator circuit 823 is controlled by the enable signal EN to compare the current output voltage VOUT+ with the previous output voltage VOUT-, and output a comparison result accordingly. In detail, the comparator circuit 823 has a first input terminal, a second input terminal, a control terminal and an output terminal. The first input terminal receives the previous output voltage VOUT-. The second input terminal receives the current output voltage VOUT+. The output end outputs the comparison result of the two. The control end receives the enabling signal EN. Therefore, the comparator circuit 823 determines whether to compare the current output voltage VOUT+ with the previous output voltage VOUT− according to the enable signal EN.

In other words, when the comparator circuit 823 determines the relationship between the current output voltage VOUT+ and the previous output voltage VOUT−, it dynamically adjusts the current values of the current sources I1 and I2. If the previous output voltage VOUT− is greater than the current output voltage VOUT+, the comparator circuit 823 turns on the current source I1 and switches off the current source I2. Therefore, the first control terminal A and the second control terminal B are charged to a high potential through the current source I1, so that the discharge capability of the N-type transistor Nout2 is increased. On the contrary, if the previous output voltage VOUT− is smaller than the current output voltage VOUT+, the comparator circuit 823 will turn off the current source I1 and turn on the current source I2. Therefore, the first control terminal A and the second control terminal B are discharged to a low potential through the current source I2, so that the charging capability of the P-type transistor Pout1 is increased.

FIG. 9 is a flow chart showing the steps of improving the driving capability of the operational amplifier circuit according to an embodiment of the present invention. Please refer to FIG. 2 and FIG. 9 at the same time. The method for improving the driving capability of this embodiment is at least applicable to the operational amplifier circuit disclosed in the above embodiments. In step S900 , the pre-operational amplifier 210 compares the current input voltage VIN+ and the current output voltage VOUT+, and generates an enable signal EN according to the comparison result. Next, in step S910 , the detection circuit 222 detects the current output voltage VOUT+ and the previous output voltage VOUT− according to the enable signal EN. Afterwards, in step S920 , the detection circuit 222 increases the charging speed or discharging speed of the load by the output stage circuit 230 according to the detection result.

In addition, the dynamic image detection method of the embodiment of the present invention can obtain sufficient teachings, suggestions and implementation descriptions from the descriptions of the embodiments in FIG. 2 to FIG. 8 , so details are not repeated here.

To sum up, in an exemplary embodiment of the present invention, in an exemplary embodiment of the present invention, the output stage module of the operational amplifier circuit includes a detection circuit. The detection circuit can dynamically detect the magnitude of the output voltage to adjust the gate-source cross voltage of the output stage transistor, thereby improving the charge and discharge capability of the output stage circuit to the load or the next stage circuit.

Although the present invention has been disclosed as above with the embodiments, it is not intended to limit the present invention. Those skilled in the art can make some changes and modifications without departing from the spirit and scope of the present invention, so the protection scope of the present invention The scope defined by the appended claims shall prevail.

Claims (15)

1. a kind of operation amplifier circuit, to drive a load, it is characterised in that the operation amplifier circuit includes：

One output level module, including a detection circuit and an output-stage circuit, the detection circuit are used to electric according to an input at present Pressure detects the current output voltage and a previous output voltage with a comparative result of a current output voltage, and according to one Testing result increases charging rate or the velocity of discharge of the output-stage circuit to the load；And

One preamplifier, is coupled to the output level module, to compare the current output electricity of the current input voltage and this Pressure, and an enable signal is exported to the detection circuit when the current input voltage is more than or less than the current output voltage,

Wherein the detection circuit decides whether to detect the current output voltage and the previous output voltage according to the enable signal.

2. operation amplifier circuit as claimed in claim 1, it is characterised in that according to the testing result, when the previous output When voltage is more than the current output voltage, the detection circuit increases charging rate of the output-stage circuit to the load.

3. operation amplifier circuit as claimed in claim 1, it is characterised in that according to the testing result, when the previous output When voltage is less than the current output voltage, the detection circuit increases the velocity of discharge of the output-stage circuit to the load.

4. operation amplifier circuit as claimed in claim 1, it is characterised in that the output-stage circuit includes：

One the first transistor, with first end, the second end and control end, the first end of the first transistor is coupled to one first electricity Pressure, the second end of the first transistor is as the output end of the output-stage circuit, and the control end of the first transistor is coupled to this Circuit is detected, the wherein detection circuit turns on the first transistor by reducing the control terminal voltage of the first transistor, with Increase charging rate of the output-stage circuit to the load；And

One second transistor, with first end, the second end and control end, the first end of the second transistor is coupled to first crystalline substance The first end of body pipe, the second end of the second transistor is coupled to a second voltage, and the control end of the second transistor is coupled to The detection circuit, wherein the detection circuit turn on the second transistor by improving the control terminal voltage of the second transistor, To increase the velocity of discharge of the output-stage circuit to the load.

5. operation amplifier circuit as claimed in claim 4, it is characterised in that the output-stage circuit also includes：

One first current source, with first end and the second end, the first end of first current source is coupled to the first voltage, and this Second end of one current source is coupled to the control end of the first transistor, wherein when first current source is opened, second crystalline substance The control terminal voltage of body pipe rises, to turn on the second transistor, so as to increase electric discharge speed of the output-stage circuit to the load Degree.

6. operation amplifier circuit as claimed in claim 4, it is characterised in that the output-stage circuit also includes：

One second current source, with first end and the second end, the first end of second current source is coupled to the second transistor Control end, the second end of second current source is coupled to the second voltage, wherein when second current source is opened, first crystalline substance The control terminal voltage of body pipe declines, to turn on the first transistor, so as to increase charging speed of the output-stage circuit to the load Degree.

7. operation amplifier circuit as claimed in claim 1, it is characterised in that the output-stage circuit includes：

One third transistor, with first end, the second end and control end, the first end of the third transistor is coupled to one first electricity Pressure, the second end of the third transistor is as the output end of the output-stage circuit, and the control end of the third transistor is coupled to this Circuit is detected, the wherein detection circuit turns on the third transistor by improving the control terminal voltage of the third transistor, with Increase charging rate of the output-stage circuit to the load；And

One the 4th transistor, with first end, the second end and control end, the first end of the 4th transistor is coupled to the 3rd crystalline substance The first end of body pipe, the second end of the 4th transistor is coupled to a second voltage, and the control end of the 4th transistor is coupled to The detection circuit, wherein the detection circuit turn on the 4th transistor by reducing the control terminal voltage of the 4th transistor, To increase the velocity of discharge of the output-stage circuit to the load.

8. operation amplifier circuit as claimed in claim 1, it is characterised in that the output-stage circuit includes：

One the 3rd current source, with first end and the second end, the first end of the 3rd current source is coupled to a first voltage, and this Second end of three current sources is coupled to the output end of the output-stage circuit, wherein when the 3rd current source is opened, the 3rd electricity Stream source is charged to the load, to increase charging rate of the output-stage circuit to the load；And

One the 5th transistor, with first end, the second end and control end, the first end of the 5th transistor is coupled to the output stage The output end of circuit, the second end of the 5th transistor is coupled to a second voltage, and the control end of the 5th transistor is coupled to The detection circuit, wherein the detection circuit turn on the 5th transistor by improving the control terminal voltage of the 5th transistor, To increase the velocity of discharge of the output-stage circuit to the load.

9. operation amplifier circuit as claimed in claim 1, it is characterised in that the output-stage circuit includes one first control end And one second control end, and the detection circuit includes：

One differential input pair, with first end and the second end, the differential input to first end receive the previous output voltage, should It is differential input to the second end receive the current output voltage；

One first current mirror module, is coupled to the differential input pair, is controlled by the enable signal, when the previous output voltage is more than During the current output voltage, first current mirror module provides one first electric current to first control end according to the enable signal； And

One second current mirror module, is coupled to the differential input pair, is controlled by the enable signal, when the previous output voltage is less than During the current output voltage, second current mirror module draws one second electric current according to the enable signal from second control end.

10. operation amplifier circuit as claimed in claim 1, it is characterised in that the output-stage circuit includes one first control End and one second control end, the output-stage circuit also include an output stage operational amplifier, and the detection circuit includes：

One differential input pair, with first end and the second end, the differential input to first end receive the previous output voltage, should It is differential input to the second end receive the current output voltage；

One first switch, with first end, the second end and control end, the first end of the first switch is via an internal current mirror Module couples to first control end, the second end of the first switch is coupled to the differential input pair, the control of the first switch End is controlled by the enable signal, wherein when the previous output voltage is more than the current output voltage, the enable signal conduction should First switch, to allow the current mirror module to provide one the 3rd electric current to first control end；And

One second switch, with first end, the second end and control end, the first end of the second switch is coupled to the differential input Right, the second end of the second switch is coupled to second control via another current mirror module inside the output stage operational amplifier End processed, the control end of the second switch is controlled by the enable signal, wherein when the previous output voltage is less than the current output electricity During pressure, enable signal conduction second switch, to allow another current mirror module to draw one the 4th electricity from second control end Stream.

11. operation amplifier circuit as claimed in claim 1, it is characterised in that the detection circuit includes：

One comparator circuit, to compare the current output voltage and the previous output voltage, with first input end, second defeated Enter end, control end and output end, the first input end of the comparator circuit receives the previous output voltage, the comparator circuit Second input receives the current output voltage, and it is previously defeated with this that the output end of the comparator circuit exports the current output voltage Go out a comparative result of voltage, the control end of the comparator circuit receives the enable signal, and the comparator circuit is according to the enable Signal decides whether to compare the current output voltage and the previous output voltage.

12. operation amplifier circuit as claimed in claim 1, it is characterised in that when the current input voltage is more than or less than During the current output voltage, the detection circuit is enabled, to detect the current output voltage and the previous output voltage.

13. it is a kind of improve operation amplifier circuit driving force method, the operation amplifier circuit to drive a load, Characterized in that, methods described includes：

Compare a current input voltage and a current output voltage, and produce according to the comparative result enable signal；

The current output voltage and a previous output voltage are detected according to the enable signal；And

Increase charging rate or the velocity of discharge of the output-stage circuit to the load according to a testing result,

Wherein in the step of enable signal is produced according to the comparative result, it is somebody's turn to do when the current input voltage is more than or less than During current output voltage, the enable signal is produced, to detect the current output voltage and the previous output voltage.

14. the method for the driving force of operation amplifier circuit is improved as claimed in claim 13, it is characterised in that increase should The step of output-stage circuit is to charging rate or the velocity of discharge of the load includes：

According to the testing result, when the previous output voltage is more than the current output voltage, increase the output-stage circuit to this The charging rate of load.

15. the method for the driving force of operation amplifier circuit is improved as claimed in claim 13, it is characterised in that increase should The step of output-stage circuit is to charging rate or the velocity of discharge of the load includes：

According to the testing result, when the previous output voltage is less than the current output voltage, increase the output-stage circuit to this The velocity of discharge of load.