WO2019113931A1 - Negative feedback amplification circuit - Google Patents

Abstract

Provided in the present application is a negative feedback amplification circuit, relating to the technical field of circuits. The negative feedback amplification circuit comprises an operational amplifier, comprising a reverse input end and an output end; a sampling branch, one end of the sampling branch being used for receiving an input voltage, and a second end of the sampling branch being connected to the reverse input end of the operational amplifier; a feedback branch, one end of the feedback branch being connected to the output end of the operational amplifier, and a second end of the feedback branch being connected to the reverse input end of the operational amplifier; a voltage amplifier, an input end thereof being connected to the reverse input end of the operational amplifier; and a regulating branch, the output end of the voltage amplifier being connected to a second end of a sampling circuit by means of the regulating branch. The embodiments of the present application can achieve higher gain and larger bandwidth whilst consuming less power.

Description

Negative feedback amplifier circuit Technical field

The present application relates to the field of circuit technologies, and in particular, to a negative feedback amplifying circuit.

Background technique

Operational amplifiers are one of the most commonly used modules for analog integrated circuits and have been widely used in devices such as comparators, analog-to-digital converters, oscillators, and analog integrators. The gain-bandwidth product of an op amp is the product of gain and bandwidth used to measure the performance of the op amp.

The inventors have found that the prior art has at least the following problem: the gain-bandwidth product of the operational amplifier is proportional to the power consumption, and if a larger gain-bandwidth product is to be obtained, the power consumption of the operational amplifier is inevitably increased.

Summary of the invention

It is an object of some embodiments of the present application to provide a negative feedback amplifying circuit capable of achieving higher gain and greater bandwidth at the expense of less power consumption.

The embodiment of the present application provides a negative feedback amplifying circuit, including: an operational amplifier including an inverting input end and an output end; a sampling branch, a first end of the sampling branch is configured to receive an input voltage, and the sampling branch a second end of the circuit is coupled to an inverting input of the operational amplifier; a feedback branch, wherein a first end of the feedback branch is coupled to an output of the operational amplifier, and a second end of the feedback branch Connected to an inverting input of the operational amplifier; a voltage amplifier having an input coupled to an inverting input of the operational amplifier; and an adjustment branch, wherein an output of the voltage amplifier is coupled through the adjustment branch At the second end of the sampling circuit.

Compared with the prior art, the embodiment of the present application can control the impedance value of the branch, the gain of the voltage amplifier, the impedance value of the sampling branch, and the impedance value of the feedback branch by increasing the adjustment branch and the voltage amplifier. The size allows the negative feedback amplifying circuit to achieve higher gain and greater bandwidth at the expense of lower power consumption.

In addition, the sampling branch includes one or any combination of a sampling resistor, a sampling capacitor, and a sampling inductor; the feedback branch includes one or any combination of a feedback resistor, a feedback capacitor, and a feedback inductor; and the adjustment branch includes an adjustment resistor and an adjustment. One or any combination of capacitance and adjustment inductance. This embodiment provides a specific type of sampling branch, feedback branch, and adjustment branch.

In addition, the voltage amplifier is an amplifier circuit based amplifier; the positive phase input of the operational amplifier in the voltage amplifier forms the input of the voltage amplifier, and the output of the operational amplifier in the voltage amplifier forms the output of the voltage amplifier. This embodiment provides a specific form of a voltage amplifier.

In addition, the negative feedback amplifying circuit is a switched capacitor circuit, wherein the sampling branch is a sampling capacitor and the feedback branch is a feedback capacitor.

In addition, the negative feedback amplifying circuit is an active low pass filter, wherein the sampling branch is a sampling resistor and the feedback branch is a feedback capacitor.

In addition, the negative feedback amplifying circuit is an active high-pass filter, wherein the sampling branch is a sampling capacitor and the feedback branch is a feedback resistor.

In addition, the negative feedback amplifying circuit is a resistive feedback amplifier, wherein the sampling branch is a sampling resistor and the feedback branch is a feedback resistor.

本实施例中提供了调节支路的阻抗值Z _x、电压放大器的增益G、采样支路的阻抗值Z _s以及反馈支路的阻抗值Z _f满足的具体关系公式。 In addition, the impedance value Z _{x of the} adjustment branch, the gain G of the voltage amplifier, the impedance value Z _{s of the} sampling branch, and the impedance value Z _{f of the} feedback branch satisfy the following relationship:

In this embodiment, a specific relationship formula for adjusting the impedance value Z _{x of the} branch, the gain G of the voltage amplifier, the impedance value Z _{s of the} sampling branch, and the impedance value Z _{f of the} feedback branch is provided.

本实施例中提供了一种理想情况下的负反馈放大电路。 In addition, the impedance value Z _{x of the} adjustment branch, the gain G of the voltage amplifier, the impedance value Z _{s of the} sampling branch, and the impedance value Z _{f of the} feedback branch satisfy the following relationship:

In this embodiment, a negative feedback amplifying circuit in an ideal case is provided.

DRAWINGS

The one or more embodiments are exemplified by the accompanying drawings in the accompanying drawings, and FIG. The figures in the drawings do not constitute a scale limitation unless otherwise stated.

1 is a circuit configuration diagram of a switched capacitor circuit in the prior art;

2 is a circuit connection diagram of a switching capacitor circuit in a prior art in a conversion cycle;

3 is an equivalent circuit diagram of a switching capacitor circuit in a prior art in a conversion cycle;

4 is a circuit structural diagram of a negative feedback amplifying circuit according to a first embodiment of the present application, which is specifically a switched capacitor circuit;

5 is a circuit connection diagram of the switched capacitor circuit shown in FIG. 4 in a conversion cycle according to the first embodiment of the present application;

6 is a circuit configuration diagram of a negative feedback amplifying circuit according to a first embodiment of the present application;

7 is a circuit configuration diagram of a first type of negative feedback amplifying circuit according to a second embodiment of the present application, which is specifically an active low pass filter;

8 is a circuit configuration diagram of a second negative feedback amplifying circuit according to a second embodiment of the present application, which is specifically an active high-pass filter;

9 is a circuit configuration diagram of a third negative feedback amplifying circuit according to a second embodiment of the present application, which is specifically a resistive feedback amplifier;

Fig. 10 is a circuit configuration diagram of a voltage amplifier of a negative feedback amplifying circuit according to a third embodiment of the present application.

Detailed ways

In order to make the objects, the technical solutions and the advantages of the present application more clear, some embodiments of the present application will be further described in detail below with reference to the accompanying drawings and embodiments. It is understood that the specific embodiments described herein are merely illustrative of the application and are not intended to be limiting.

The first embodiment of the present application relates to a negative feedback amplifying circuit for amplifying an input to produce a large output with a small input. The negative feedback amplifying circuit of the present application includes an operational amplifier including an inverting input end and an output end; a sampling branch, a first end of the sampling branch is for receiving an input voltage, and a second end of the sampling branch is connected An inverting input of the operational amplifier; a feedback branch, wherein a first end of the feedback branch is coupled to an output of the operational amplifier, and a second end of the feedback branch is coupled to the operational amplifier An inverting input; a voltage amplifier having an input coupled to an inverting input of the operational amplifier; and an adjustment branch, wherein an output of the voltage amplifier is coupled to the sampling circuit via the adjustment branch Second end.

Compared with the prior art, the embodiment of the present application can control the impedance value of the branch, the gain of the voltage amplifier, the impedance value of the sampling branch, and the impedance value of the feedback branch by increasing the adjustment branch and the voltage amplifier. The size allows the negative feedback amplifying circuit to achieve higher gain and greater bandwidth at the expense of lower power consumption.

Compared with the existing negative feedback amplifying circuit, the negative feedback amplifying circuit of the present application increases the adjusting branch and the voltage amplifier, thereby realizing higher gain and larger at the cost of lower power consumption. The technical effect of the bandwidth. The negative feedback amplifying circuit includes various types, and different types of negative feedback amplifying circuits are used to implement different functions; the switched capacitor circuit is a common negative feedback amplifying circuit, and the following is a switched capacitor circuit as an example, which will be in the prior art. The switched capacitor circuit and the switched capacitor circuit in the present application are compared and analyzed to illustrate how the present application achieves the above technical effects on the basis of increasing the adjustment branch and the voltage amplifier.

The switched capacitor circuit in the prior art, as shown in FIG. 1 , includes an operational amplifier OPAMP (Operational Amplifier, OPAMP for short), a sampling capacitor C _s (that is, a sampling branch), and a feedback capacitor C _f (ie, a feedback branch). , switch S1, switch S2, and switch S3. The switched capacitor circuit includes a sampling period and a conversion period. When the switched capacitor circuit is in the sampling period, the switch S1 is switched to V _in , the switch S2 is closed, and the switch S3 is switched to the ground; when the switched capacitor circuit is in the switching cycle, the switch S1 is switched to the ground, the switch S2 is turned on, and the switch S3 is switched. To V _out .

Please refer to FIG. 2 , which is a circuit connection diagram of the switched capacitor circuit of FIG. 1 in a conversion cycle. At this time, the switched capacitor circuit can be equivalent to a single pole system. As shown in FIG. 3, the equivalent circuit diagram of the switched capacitor circuit in the conversion cycle; wherein gm is the overall transconductance of the operational amplifier OPAMP, and R ₀ is the operational amplifier. The impedance corresponding to the main pole, C ₀ is the capacitance corresponding to the main pole of the operational amplifier, V _in is the input, and V _out is the output.

According to the equivalent circuit diagram of the switched capacitor circuit in the conversion cycle in Fig. 3, the following equation can be obtained:

(V _in -V _x )jwC _s =(V _x -V _out )×jwC _f

After the above equation is transformed, it is obtained:

V _in jwC _s =V _x (jwC _s +jwC _f )-jwC _f V _out

After continuing the conversion, the gain of the switched capacitor circuit of Figure 1 can be obtained, as shown in the following formula (1):

Ideally, the impedance R ₀ of the main pole of the operational amplifier OPAMP is infinite, the capacitance C ₀ corresponding to the main pole of the operational amplifier is infinitesimal, and the overall transconductance gm of the operational amplifier is infinite; the gain of the switched capacitor circuit is equal to the preset The gain, ie, the above formula (1) can be simplified as:

与

无法真正相等，即实际工作中的开关电容电路的增益无法达到设计要求(

与

的大小视情况而定；就目前大部分已知的运算放大器而言，

小于

但在低频状态下，也可能

大于

但无论哪种情况，都属于非理想状态)。 However, it should be noted that, in practice, due to manufacturing process limitations, the op amp OPAMP is unlikely to achieve the desired condition, therefore,

versus

Can not be truly equal, that is, the gain of the switched capacitor circuit in actual operation cannot meet the design requirements (

versus

The size depends on the situation; for most current operational amplifiers,

Less than

But in the low frequency state, it is possible

more than the

But in either case, it is a non-ideal state.)

In the present application, referring to FIG. 4, an adjustment branch and a voltage amplifier are added on the basis of the existing switched capacitor circuit (FIG. 1); wherein the input end of the voltage amplifier is connected to the inverting input terminal of the operational amplifier OPAMP. The output of the voltage amplifier is connected to the second end of the sampling branch via an adjustment branch.

When the switched capacitor circuit is in the sampling period, the switch S1 is switched to V _in , the switch S2 is turned on, and the switch S3 is switched to the ground; when the switched capacitor circuit is in the switching cycle, the switch S1 is switched to the ground, the switch S2 is closed, and the switch S3 is switched. To V _out , please refer to FIG. 5 , which is a circuit structure diagram of the switched capacitor circuit in the conversion cycle; wherein the adjustment branch is the adjustment capacitor C _x and the gain of the voltage amplifier is G.

According to the switched capacitor circuit in the conversion cycle of FIG. 5 and in combination with the overall transconductance of the operational amplifier OPAMP described above, the impedance and capacitance corresponding to the main pole (in conjunction with the equivalent circuit diagram of FIG. 3), the following equation can be obtained:

(V _in -V _x )×jwC _s =(V _x -V _out )×jwC _f -(GV _x -V _x )×jwC _x

Obtained by the above equation:

V _in jwC _s =V _x [jwC _s +jwC _f -(G-1)jwC _X ]-jwC _f V _out

Thereby you can get:

After continuing the conversion, the gain of the switched capacitor circuit in Figure 4 can be obtained, as shown in the following formula (2):

越接近于零，表示运算放大器OPAMP越接近于理想状态，则现有技术中的负反馈电路的增益越大；同理，公式(2)中，分母中的部分公式

越接近于零，则负反馈电路的增益越大；而本实施例中可以通过上述部分公式的分子

中的

进行调节，以使得上述部分公式尽可能接近于零，从而使得负反馈电路的增益尽可能接近于理想状态。因此可知，当满足以下公式时， It can be seen from the above analysis that the denominator of formula (1) is closer to 1, that is, the partial formula in the denominator

The closer to zero, the closer the operational amplifier OPAMP is to the ideal state, the greater the gain of the negative feedback circuit in the prior art; similarly, the partial formula in the denominator in equation (2)

The closer to zero, the greater the gain of the negative feedback circuit; in this embodiment, the numerator of the above partial formula can be passed.

middle

The adjustment is made such that the above partial formula is as close as possible to zero, so that the gain of the negative feedback circuit is as close as possible to the ideal state. Therefore, it can be seen that when the following formula is satisfied,

The transformation can be obtained by the following formula (3):

The gain of the switched capacitor circuit in this embodiment can be made to be ideal, that is,

而公式(2)中为

Further, the gain of the switched capacitor circuit of the regulating branch and the voltage amplifier is compared with that of the existing switched capacitor circuit, that is, by comparing the formula (1) with the formula (2), the formula (1) can be obtained. The difference in formula (2) is only that the partial formula on the denominator is different: in equation (1)

And in formula (2)

的模对开关电容电路的增益影响较大，而

的正负对开关电容电路的增益影响相对于次要，可以忽略。因此，只要公式(2)中的

的绝对值小于公式(1)中的

那么，公式(2)的分母中的部分公式

就小于公式(1)的分母中的部分公式

从而使得本实施例的开关电 容电路的增益相对于现有技术得到提高。因此，只要满足下列公式(4)，便可以使增加了调节支路与电压放大器的开关电容电路的增益大于现有的开关电容电路的增益，即，在相同的输入下，达到更高的输出。 In formula (1), due to

The mode has a large influence on the gain of the switched capacitor circuit, and

The positive and negative effects on the gain of the switched capacitor circuit are relatively minor and can be ignored. Therefore, as long as in formula (2)

The absolute value is less than that in equation (1)

Then, the partial formula in the denominator of formula (2)

Is smaller than the partial formula in the denominator of formula (1)

Thereby, the gain of the switched capacitor circuit of the present embodiment is improved relative to the prior art. Therefore, as long as the following formula (4) is satisfied, the gain of the switched capacitor circuit with the adjustment branch and the voltage amplifier can be increased larger than that of the existing switched capacitor circuit, that is, the higher output can be achieved under the same input. .

Change is available,

0<(G-1)C _X <2C _s +2C _f

Without loss of generality, if the existing negative feedback amplifying circuit is of other types, in order to make the negative feedback amplifying circuit of the present application equally applicable, please refer to FIG. 6, and each branch is represented by impedance, where Z _x To adjust the impedance value of the branch, G is the gain of the voltage amplifier, Z _s is the impedance value of the sampling branch, and Z _f is the impedance value of the feedback branch.

According to the negative feedback amplifying circuit in Fig. 6, the following equation can be obtained:

(V _in -V _x )/Z _s =(V _x -V _out )/Z _f -(GV _x -V _x )/Z _x

From the above, we can see:

V _in /Z _s =V _x [1/Z _s +1/Z _f -(G-1)/Z _x ]-1/Z _f V _out

Thereby you can get:

After the transformation, the gain of the negative feedback amplifying circuit of FIG. 6 can be obtained, as shown in the following formula (5):

From the foregoing analysis, it can be seen that when the formula (6) is satisfied, the gain of the negative feedback amplifying circuit in which the adjustment branch and the voltage amplifier are increased can be made larger than the gain of the conventional negative feedback amplifying circuit.

The transformation is available:

Preferably, it can be

The transformation is available:

Thereby, the negative feedback amplifying circuit of FIG. 6 can be made to achieve an ideal situation, that is,

带入公式(8)可以得到： It should be noted that when the negative feedback amplifying circuit is a switched capacitor circuit,

Bring into equation (8) to get:

C _X (G-1)=C _s +C _f

After the transformation, the above formula (3) can be obtained:

When designing a negative feedback amplifying circuit, the designer usually designs Z _f and Z _s according to the gain requirement of the negative feedback amplifying circuit; if the embodiment of the present invention is used, after determining the above Z _f and Z _s according to the usual method, The impedance value Z _{X of the} adjustment branch and the gain G of the voltage amplifier can be determined based on Z _f and Z _S in combination with equation (7), that is, only the impedance value Z _{x of the} branch and the gain G of the voltage amplifier are satisfied. Equation (7) can increase the gain of the negative feedback amplifier circuit. Wherein, when actually designing the circuit, the designer can determine the impedance value Z _{x of the} adjustment branch and the gain G of the voltage amplifier according to the ideal situation; that is, after determining Z _f and Z _s , calculating according to formula (8) The impedance value Z _x of the regulating branch and the gain G of the voltage amplifier are taken out; therefore, if the problem of the precision of the manufacturing process is neglected, the ideal state can be achieved; however, even if the manufacturing process accuracy problem does not reach the ideal state, in the usual manufacturing process Within the error range of the accuracy, the impedance value Z _{x of the} adjustment branch, the gains G and Z _f , Z _{s of the} voltage amplifier can also satisfy the formula (7). Therefore, the accuracy requirement of the gain G of the voltage amplifier in this embodiment is not very high, and even if the gain G of the voltage amplifier has a small deviation, the performance of the negative feedback amplifying circuit can be improved; thereby establishing the speed requirement of the voltage amplifier Lower, the voltage amplifier consumes very little power.

Compared with the prior art, the present embodiment increases the adjustment branch and the voltage amplifier, and controls the impedance value Z _{x of the} adjustment branch, the gain G of the voltage amplifier, the impedance value Z _{s of the} sampling branch, and the feedback branch. The satisfaction of the impedance value Z _f as shown by the formula allows the negative feedback amplifying circuit to achieve higher gain and larger bandwidth at the expense of less power consumption.

The second embodiment of the present application relates to a negative feedback amplifying circuit. The present embodiment is a refinement based on the first embodiment. The main refinement is that a specific implementation of a plurality of different types of negative feedback amplifying circuits is provided. the way.

In this embodiment, the sampling branch includes one or any combination of a sampling resistor, a sampling capacitor, and a sampling inductor; the feedback branch includes one or any combination of a feedback resistor, a feedback capacitor, and a feedback inductor; and the adjustment branch includes an adjustment One or any combination of a resistor, a regulating capacitor, and an adjusting inductor.

In the prior art, a commonly used negative feedback amplifying circuit further includes an active low pass filter, an active high pass filter, and a resistive feedback amplifier. In this embodiment, an adjustment branch and a voltage amplifier are added on the basis of the existing three kinds of negative feedback amplifying circuits, as follows:

First, please refer to FIG. 7 , which is a circuit structure diagram of a negative feedback amplifying circuit, which is specifically an active low-pass filter; wherein, the sampling branch is a sampling resistor R _s1 and the feedback branch is a feedback capacitor C _f1 .

Secondly, please refer to FIG. 8 , which is a circuit structure diagram of a negative feedback amplifying circuit, which is specifically an active high-pass filter, wherein the sampling branch is a sampling capacitor C _s2 and the feedback branch is a feedback resistor R _f2 .

Third, please refer to FIG. 9 , which is a circuit structure diagram of a negative feedback amplifying circuit, which is specifically a resistive feedback amplifier, wherein the sampling branch is a sampling resistor R _s3 and the feedback branch is a feedback resistor R _f3 .

Compared with the first embodiment, the present embodiment provides three different types of negative feedback amplifying circuits, and sampling branches and feedback branches corresponding to the respective negative feedback amplifying circuits. However, it is not limited to this. Any negative feedback amplifying circuit can achieve higher gain and larger bandwidth by increasing the regulating branch and voltage amplifier at the cost of less power consumption.

The third embodiment of the present application relates to a negative feedback amplifying circuit. The present embodiment is a refinement based on the first embodiment. The main refinement is as follows: Referring to FIG. 10, the voltage amplifier is an amplifying circuit based on an operational amplifier. .

Voltage amplifier positive input terminal of the operational amplifier 1 to form an input of the voltage amplifier, which is connected to the inverting input terminal of the operational amplifier OPAMP for receiving the voltage V _x; output of the voltage amplifier is a voltage of the operational amplifier 1 amplifier output, by adjusting the Z _x branch connected to the second terminal of the sampling branches; negative voltage amplifier inverting input of the operational amplifier 1 is grounded.

Preferably, the voltage amplifier further includes a first voltage dividing resistor R ₁ and a second voltage dividing resistor R ₂ . The first end of the first voltage dividing resistor R ₁ is connected to the output end of the operational amplifier 1 in the voltage amplifier, and the second end of the first voltage dividing resistor R ₁ is grounded and connected to the voltage through the second voltage dividing resistor R _{2 .} The inverting input of op amp 1 in the amplifier.

The gain G of the voltage amplifier in this embodiment is:

This embodiment provides a relatively simple implementation of the voltage amplifier with respect to the first embodiment; however, it is not limited thereto. It should be noted that the present embodiment can also be refined on the basis of the second embodiment, and the same technical effects can be achieved.

A person skilled in the art can understand that the above embodiments are specific embodiments of the present application, and various changes can be made in the form and details without departing from the spirit and scope of the application. range.

Claims (10)

A negative feedback amplifying circuit, comprising: An operational amplifier comprising an inverting input and an output; a sampling branch, a first end of the sampling branch is for receiving an input voltage, and a second end of the sampling branch is connected to an inverting input end of the operational amplifier; a feedback branch, wherein a first end of the feedback branch is connected to an output end of the operational amplifier, and a second end of the feedback branch is connected to an inverting input end of the operational amplifier; a voltage amplifier having an input coupled to an inverting input of the operational amplifier; and An adjustment branch, wherein an output of the voltage amplifier is coupled to the second end of the sampling circuit via the adjustment branch. A negative feedback amplifying circuit according to claim 1, wherein The sampling branch includes one or any combination of a sampling resistor, a sampling capacitor, and a sampling inductor; The feedback branch includes one or any combination of a feedback resistor, a feedback capacitor, and a feedback inductor; The adjustment branch includes one or any combination of an adjustment resistor, an adjustment capacitance, and an adjustment inductance. A negative feedback amplifying circuit according to claim 1, wherein said voltage amplifier is an operational amplifier-based amplifying circuit; and a non-inverting input terminal of said operational amplifier in said voltage amplifier forms an input terminal of said voltage amplifier, said voltage amplifier The output of the operational amplifier in the form forms the output of the voltage amplifier. The negative feedback amplifying circuit according to claim 3, wherein the voltage amplifier further comprises a first voltage dividing resistor and a second voltage dividing resistor; a first end of the first voltage dividing resistor is connected to an output end of an operational amplifier in the voltage amplifier, and a second end of the first voltage dividing resistor is grounded through the second voltage dividing resistor and connected to the The inverting input of the op amp in the voltage amplifier. The negative feedback amplifying circuit according to claim 1, wherein the negative feedback amplifying circuit is a switched capacitor circuit, wherein the sampling branch is a sampling capacitor and the feedback branch is a feedback capacitor. The negative feedback amplifying circuit according to claim 1, wherein said negative feedback amplifying circuit is an active low pass filter, wherein said sampling branch is a sampling resistor and said feedback branch is a feedback capacitor. The negative feedback amplifying circuit according to claim 1, wherein said negative feedback amplifying circuit is an active high pass filter, wherein said sampling branch is a sampling capacitor and said feedback branch is a feedback resistor. The negative feedback amplifying circuit according to claim 1, wherein the negative feedback amplifying circuit is a resistive feedback amplifier, wherein the sampling branch is a sampling resistor and the feedback branch is a feedback resistor. The negative feedback amplifying circuit according to any one of claims 1 to 8, characterized in that the impedance value Z _{x of} the adjustment branch, the gain G of the voltage amplifier, and the impedance value Z _{s of} the sampling branch And the impedance value Z _{f of} the feedback branch satisfies the following relationship:

A negative feedback amplifying circuit according to claim 9, wherein an impedance value Z _{x of} said adjustment branch, a gain G of said voltage amplifier, an impedance value Z _{s of} said sampling branch, and said feedback branch The impedance value Z _{f of the} road satisfies the following relationship:

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