KR102345764B1 - Variable gain amplifier - Google Patents

Abstract

The variable gain amplifier includes an amplifying unit configured to amplify an input signal by adjusting an amplification gain using the first control signal, wherein the amplifying unit includes: a 1-1 operational amplifier; a 1-1 th resistor having one end connected to an output node of the 1-1 th operational amplifier and the other end connected to one of the input nodes of the 1-1 th operational amplifier; and a first transistor having a drain or a source connected to one of the input nodes of the 1-1 operational amplifier and receiving the first control signal through a gate.

Description

Variable Gain Amplifier {VARIABLE GAIN AMPLIFIER}

The present invention relates to a variable gain amplifier.

A variable gain amplifier capable of outputting by varying the voltage gain with respect to an input analog voltage is important for optical sensor applications.

1 shows a circuit diagram of a general variable gain amplifier 100 .

For reference, FIG. 1 illustrates a variable gain amplifier 100 using a differential signal.

The gain of the variable gain amplifier 100 of FIG. 1 can be expressed as the following [Equation 1].

As can be seen from [Equation 1], the variable gain amplifier 100 may change the gain by changing Rg.

In US Patent No. 5077541 (Variable-gain amplifier controlled by an analog signal and having a large dynamic range), a resistive attenuator (20) is used in Fig. 1 for the resistance corresponding to Rg of Fig. 1 . However, in the case of a resistive attenuator, since the gain of the amplifier is adjusted by selecting some of the resistors arranged in a ladder shape, it is expected that it will be difficult to secure linearity. That is, according to the selection of the resistor, the resistance value of the resistive attenuator does not change gradually, but at an interval.

However, in the case of an optical sensor application product, it is necessary to adjust the voltage gain of the output signal according to the surrounding environment of the product, the reflectance of the reflector, the distance between the light source and the sensor, and the like. To this end, it is required to develop a variable gain amplifier that maintains the linearity and is robust against variations in temperature and manufacturing process.

The present invention aims to solve the technical problem as described above, and an object of the present invention is to provide a variable gain amplifier in which linearity can be maintained.

Another object of the present invention is to provide a variable gain amplifier that is robust to variations in temperature and manufacturing process.

The variable gain amplifier of the present invention includes an amplifying unit configured to amplify an input signal by adjusting an amplification gain using a first control signal, wherein the amplifying unit includes: a 1-1 operational amplifier; a 1-1 th resistor having one end connected to an output node of the 1-1 th operational amplifier and the other end connected to one of the input nodes of the 1-1 th operational amplifier; and a first transistor having one of a drain and a source connected to one of the input nodes of the 1-1 operational amplifier and receiving the first control signal through a gate.

In addition, the variable gain amplifier of the present invention preferably further includes a control signal converter that receives the second control signal, converts it into the first control signal, and outputs the converted signal.

Specifically, the control signal converter may include: a voltage-current conversion circuit for receiving the second control signal, which is a voltage signal, and converting it into a second current; and a 2-2 th operational amplifier receiving signals from the 2-1 th input node and the 2-2 th input node, and outputting the first control signal; The 2-1 voltage level is determined according to a reference current, and the 2-2 second input node is connected to an output node of the voltage-current conversion circuit.

In addition, the control signal converter may include: a 2-2 resistor having one end connected to the 2-1 input node and manufactured using the same type of resistor as the 1-1 resistor in a manufacturing process; and a second 2-3 transistor having one of a drain or a source connected to the 2-2 input node and manufactured using the same type of transistor as the first transistor in a manufacturing process.

In addition, the gate of the 2-3 th transistor is connected to the output node of the 2-2 th operational amplifier.

According to the present invention, it is possible to implement a variable gain amplifier that not only maintains linearity but is also robust against variations in temperature and manufacturing process.

1 is a circuit diagram of a typical variable gain amplifier.
2 is a block diagram of a variable gain amplifier according to a preferred embodiment of the present invention.
3 is an exemplary diagram of an amplification unit by a non-inverting amplifier;
4 is an exemplary implementation diagram of an amplification unit by an inverting amplifier.

Hereinafter, a variable gain amplifier according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings. Of course, the following examples of the present invention are not intended to limit or limit the scope of the present invention only to embody the present invention. What can be easily inferred by an expert in the technical field to which the present invention pertains from the detailed description and examples of the present invention is construed as belonging to the scope of the present invention.

First, FIG. 2 shows a configuration diagram of a variable gain amplifier 200 according to a preferred embodiment of the present invention.

As can be seen from FIG. 2 , the variable gain amplifier 200 according to the preferred embodiment of the present invention includes an amplifier 210a and a control signal conversion unit 220 . In addition, the amplifying unit 210a and the control signal converting unit 220 may be configured using a circuit.

The amplifying unit 210a amplifies the input signals VIP and VIN and outputs VOP and VON. The amplification gain of the amplifier 210a may be adjusted using the first control signal Vcon1.

Also, the control signal converter 220 serves to receive the second control signal Vcon2, convert it into the first control signal Vcon1, and output it. Preferably, the first control signal Vcon1 and the second control signal Vcon2 are voltage signals.

Specifically, the amplifier 210a includes a 1-1 operational amplifier A11, a 1-2 operational amplifier A12, a first gain determination circuit 211a, and a second gain determination circuit 212a. can be

The first gain determining circuit 211a includes a first resistance component that determines the gain of the amplifier 210a. Specifically, it is preferable that the first gain determining circuit 211a includes a 1-1 resistor R11 and a 1-2 th resistor R12. In addition, resistance values of the 1-1th resistor R11 and the 1-2th resistor R12 are the same.

One end of the 1-1 th resistor R11 is connected to the output node of the 1-1 th operational amplifier A11, and the other end of the 1-1 th resistor R11 is an input node of the 1-1 th operational amplifier A11. connected to one of In addition, one end of the 1-2 first resistor R12 is connected to the output node of the 1-2 operational amplifier A12, and the other end of the 1-2 first resistor R12 is connected to the 1-2 operational amplifier A12. connected to one of the input nodes. Specifically, the other end of the 1-1 th resistor R11 is connected to the inverting input node of the 1-1 th operational amplifier A11, and the other end of the 1-2 th resistor R12 is connected to the 1-2 operational amplifier ( It is preferably connected to the inverting input node of A12).

The second gain determining circuit 212a includes a second resistance component that determines the gain of the amplifier 210a. Specifically, the second gain determining circuit 212a has a drain or a source connected to one of the input nodes of the 1-1 operational amplifier A11, and receives the first control signal Vcon1 as a gate. The transistor T1 may be included. In addition, it is preferable that one of the input nodes of the first and second operational amplifiers A12 is connected to the other one of the drain and the source of the first transistor T1. Since the gate voltage of the first transistor T1 varies according to the magnitude of the first control signal Vcon1 that is the voltage signal, the resistance value between the drain and the source of the first transistor T1 also varies. That is, when the first control signal Vcon1 increases, the resistance between the drain and the source of the first transistor T1 decreases, and when the first control signal Vcon1 decreases, the resistance between the drain and the source of the first transistor T1 decreases. resistance value increases. Accordingly, the gain of the amplifying unit 210a is changed.

That is, the gain of the amplifying unit 210a can be expressed as in the following [Equation 2].

Here, Rm represents a resistance value between the drain and the source of the first transistor T1.

The amplifying unit 210a of the present invention may gradually change the resistance value between the drain and the source of the first transistor T1 by the first control signal Vcon1, unlike the case of using a resistive attenuator. Linearity can be ensured.

The first transistor T1 may use a depletion MOS transistor or a JFET.

Hereinafter, the control signal conversion unit 220 of the present invention will be described in detail.

The control signal conversion unit 220 of the present invention is configured to include a voltage-current conversion circuit 221 , a reference current generation unit 222 , and a compensation circuit 223 .

The control signal converter 220 receives the second control signal Vcon2, which is a voltage signal, and converts it into a second current I2 and outputs it. That is, the second current I2 may be set by a value obtained by dividing the second control signal Vcon2 by the 2-1 th resistor R21.

The reference current generator 222 generates a reference current Iref and serves to provide the reference current Iref to the control signal converter 220 . For reference, the reference current generation unit 222 generates a reference current Iref using the 2-1 th resistor R21 and the same type of resistance in the semiconductor manufacturing process, so that the temperature and dispersion in the semiconductor manufacturing process It is preferable to compensate for a difference in characteristics of the 2-1 th resistor R21 according to, for example.

The compensation circuit 223 receives the reference current Iref and the second current I2 as inputs, and receives the feedback of the first control signal Vcon1 as a feedback to the 1-1 resistor R11 and the drain of the first transistor T1 . It serves to compensate for differences in characteristics due to temperature and dispersion in the semiconductor manufacturing process between the resistance and the source.

Specifically, the compensation circuit 223 includes a 2-2 th operational amplifier A22, a 2-2 th resistor R22, and a 2-3 th transistor T23.

The 2-2 th operational amplifier A22 receives signals from the 2-1 th input node and the 2-2 th input node, and outputs the first control signal Vcon1. In addition, the 2-2 th resistor R22 has one end connected to the 2-1 th input node, and has the same type of resistance as the 1-1 th resistor R11 and the 1-2 th resistor R12 in the semiconductor manufacturing process. It is characterized in that the difference in characteristics according to temperature, dispersion in the semiconductor manufacturing process, etc. is the same as that of the 1-1 resistor R11 and the 1-2 resistor R12.

In addition, the 2-3 th transistor T23 has either a drain or a source connected to the 2-2 input node, and is manufactured using the same type of transistor as the 1 st transistor T1 in a semiconductor manufacturing process, , it is preferable that the characteristic difference according to dispersion in the semiconductor manufacturing process is the same as that of the first transistor T1 .

In addition, the 2-1 th voltage level V1 which is the voltage of the 2-1 th input node is determined according to the reference current Iref, and the 2-2 th input node is connected to the output node of the voltage-current conversion circuit 221 and connected For reference, the voltage V1 of the 2-1 th input node and the voltage V2 of the 2-2 th input node become the same due to the characteristics of the 2-2nd operational amplifier A22.

In addition, the gate of the 2-3 th transistor T23 is connected to the output node of the 2-2 th operational amplifier A22. Accordingly, the output of the 2-2nd operational amplifier A22 is fed back to the input of the 2-2nd operational amplifier A22.

In the amplification unit 210A, the 1-1 resistance R11 and the 1-2 resistance R12 composed of general resistors and the resistance Rm composed of the first transistor T1 have different resistance characteristics with respect to temperature. . In this case, there is a problem in that the output signal varies according to the temperature for the same input signal. In addition, the 1-1 resistor R11, the 1-2 resistor R12, and the resistor Rm composed of the first transistor T1 greatly increase the dispersion of the gain of the amplifier 210a due to manufacturing process dispersion. can make

In order to improve characteristics such as temperature and process dispersion, a current is applied to the 1-1 resistor R11 and the 1-2 resistor R12 and the 2-2 resistor R22, which is the same type of resistance in the process. to output a constant voltage V1, convert the second control signal Vcon2 into a current, compare the voltage V2 applied to the resistor Rm composed of the 2-3th transistor T23, and 3 It is input to the gate of the transistor T23 so that the voltage V1 of the 2-1th input node and the voltage V2 of the 2nd-2nd input node become the same with respect to the second control signal Vcon2 of the same voltage level. A first control signal Vcon1 that is a feedback voltage is generated.

The first control signal Vcon1 is input to the gate of the first transistor T1 to implement the resistor Rm formed by the first transistor T1 in the amplifier 210a.

Hereinafter, the voltage and current values of the main points of the variable gain amplifier 200 of the present invention will be described by way of example.

The voltage V1 of the 2-1 th input node is determined by the reference current Iref and the 2-2 th resistor R22. That is, it can be expressed as V1=Iref×R22.

In addition, the voltage V2 of the second-second input node is determined according to the second current I2 and the resistance value Rm between the drain and the source of the second-third transistor T23. That is, it can be expressed as V2=I2×Rm. Here, it can be expressed as I2=Vcon2/R21.

V1=V2 and Iref×R22=Vcon2/R21×Rm by the feedback loop using the 2-2nd operational amplifier A22.

In addition, the gate voltage value of the 2-3th transistor T23 is output so that the resistance value of Rm in the 2-2nd operational amplifier A22 of the feedback loop satisfies Iref×R22=Vcon2/R21×Rm. When the second control signal Vcon2 rises, the feedback loop operates so that the value of Rm is decreased, thereby increasing the gain of the amplifier 210a.

For example, if Iref=100uA, R21=100Ω, Vcon2=2.4V, R21=12KΩ, R11=R12=100KΩ, I2=2.4V/12KΩ=200uA, Rm=50Ω.

Accordingly, the voltage gain of the amplifying unit 210a is 2×100K/50, and a gain of 4,000 times can be obtained. If 1.2V is applied to the second control signal Vcon2, the voltage gain of the amplifier 210a is 2,000 times.

In addition, the amplifying unit 210a of the present invention may be implemented in the form of a differential amplifier receiving a differential signal as shown in FIG. 2, but also by an inverting amplifier or a non-inverting amplifier using one input signal, the amplifying unit ( 210b, 210c) may be implemented.

3 is an exemplary implementation diagram of the amplification unit 210b by a non-inverting amplifier.

As can be seen from Fig. 3, the amplification unit 210b by the non-inverting amplifier includes a 1-1 operational amplifier A11, a first gain determination circuit 211b, and a second gain determination circuit 212b. do.

The gain of the amplifying unit 210b by the non-inverting amplifier can be expressed as in Equation 3 below.

4 is an exemplary implementation diagram of the amplifying unit 210c by an inverting amplifier.

As can be seen from FIG. 4 , the amplification unit 210c by an inverting amplifier includes a 1-1 operational amplifier A11, a first gain determination circuit 211c, and a second gain determination circuit 212c. .

The gain of the amplifying unit 210c by the inverting amplifier can be expressed by the following [Equation 4].

As described above, according to the present invention, it can be seen that the variable gain amplifier 200 can be implemented which not only maintains linearity but is also robust against variations in temperature and manufacturing process.

200: variable gain amplifier
210a, 210b, 210c: amplification unit
220: control signal conversion unit
A11: No. 1-1 operational amplifier
A12: No. 1-2 op amp
211a, 211b, 211c: first gain determining circuit
212a, 212b, 212c: second gain determination circuit
221 voltage-current conversion circuit
222: reference current generator
223: compensation circuit

Claims (11)

A variable gain amplifier comprising:
an amplifier for amplifying an input signal by adjusting an amplification gain using the first control signal; and a control signal conversion unit that receives a second control signal and converts it into the first control signal and outputs it;
The amplifying unit may include: a 1-1 operational amplifier; a 1-1 th resistor having one end connected to an output node of the 1-1 th operational amplifier and the other end connected to one of the input nodes of the 1-1 th operational amplifier; and a first transistor having a drain or a source connected to one of the input nodes of the 1-1 operational amplifier and receiving the first control signal through a gate;
The control signal converter may include: a voltage-current conversion circuit for receiving the second control signal, which is a voltage signal, and converting it into a second current; a 2-2 th operational amplifier that receives signals from the 2-1 th input node and the 2-2 th input node and outputs the first control signal; a 2-2 resistor having one end connected to the 2-1 input node and manufactured using the same type of resistor as the 1-1 resistor in a manufacturing process; and a 2-3 th transistor having one of a drain or a source connected to the 2-2 input node and manufactured using the same type of transistor as the first transistor in a manufacturing process;
The 2-1 th voltage level, which is the voltage of the 2-1 th input node, is determined according to a reference current,
The 2-2 second input node is connected to an output node of the voltage-current conversion circuit,
A gate of the second-third transistor is connected to an output node of the second-second operational amplifier. delete delete delete delete A variable gain amplifier comprising:
an amplifier for amplifying an input signal by adjusting an amplification gain using the first control signal; and a control signal conversion unit that receives a second control signal and converts it into the first control signal and outputs it.
The amplifying unit may include: a 1-1 operational amplifier; a first gain determining circuit including a first resistance component for determining a gain of the amplifier; and a second gain determining circuit including a second resistance component for determining a gain of the amplifying unit.
The first gain determining circuit includes a 1-1 resistor having one end connected to an output node of the 1-1 operational amplifier and the other end connected to one of the input nodes of the 1-1 operational amplifier,
The second gain determining circuit includes a first transistor having a drain or a source connected to one of the input nodes of the 1-1 operational amplifier and receiving the first control signal through a gate;
The control signal conversion unit may include: a voltage-current conversion circuit for receiving the second control signal, which is a voltage signal, and converting it into a second current; and a compensation circuit that receives a reference current and the second current, receives the feedback of the first control signal, and compensates for a characteristic difference between the 1-1 resistor and the resistance between the drain and the source of the first transistor ,
The compensation circuit may include: a 2-2 operational amplifier receiving signals from a 2-1 input node and a 2-2 input node and outputting the first control signal; a 2-2 resistor having one end connected to the 2-1 input node and manufactured using the same type of resistor as the 1-1 resistor in a manufacturing process; and a 2-3 th transistor having one of a drain or a source connected to the 2-2 input node and manufactured using the same type of transistor as the first transistor in a manufacturing process;
The 2-1 th voltage level, which is the voltage of the 2-1 th input node, is determined according to the reference current,
The 2-2 second input node is connected to an output node of the voltage-current conversion circuit,
A gate of the second-third transistor is connected to an output node of the second-second operational amplifier. delete delete delete delete delete

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