KR101528405B1 - Input buffer using noise generator - Google Patents

Abstract

The present invention relates to an input buffer for canceling flicker noise and thermal noise generated at an input terminal using a noise generator. The present invention relates to a preamplifier for transmitting an input signal converted from a diaphragm to an A / D converter, the preamplifier comprising: an input buffer circuit for supplying a DC voltage to the input signal; Wherein the input buffer circuit comprises: a CD amplifier including an input terminal made up of a first PMOS transistor for receiving an input signal from the diaphragm; and a second amplifier for removing flicker noise generated at an input terminal of the CD amplifier And a noise generator including a noise generator including a first noise generator generating another flicker noise and a second noise generator generating another thermal noise to remove thermal noise generated at an input terminal of the CD amplifier.

Description

An input buffer using a noise generator {INPUT BUFFER USING NOISE GENERATOR}

The present invention relates to an input buffer using a noise generator, and more particularly to an input buffer of a preamplifier for canceling flicker noise and thermal noise generated at an input terminal by flicker noise and thermal noise generated through a noise generator.

Currently used microphones consist of a diaphragm that converts voice signals into electrical signals and a preamplifier that connects the converted electrical signal to a converter that converts the analog signal to a digital signal with minimal loss. Here, the signal size of the microphone is determined by the ratio between the capacitance produced by the diaphragm and the capacitance produced by the preamplifier, and the noise of the microphone is mostly determined by the noise generated by the preamplifier. Therefore, low noise of the preamplifier is required. The preamplifier consists of an input buffer and an amplifier. 1 shows an input buffer of a preamplifier which is conventionally used. Referring to FIG. 1, a conventional input buffer receives an input signal Vin through an input terminal PMOS transistor M3. As shown in FIG. 1, the conventional input buffer does not have a specific circuit for eliminating noise generated at the input terminal. Just as a general way to eliminate noise is to increase the device size to reduce flicker noise and to increase transconductance to reduce thermal noise. However, the above method has a problem of decreasing the product competitiveness by increasing the area of the preamplifier and increasing the power consumption.

Korean Patent Registration No. 10-0913197 (hereinafter referred to as " Prior Art Document ") relates to a noise canceling apparatus and method for removing a noise signal included in a voice signal using two microphones. The prior art includes a first microphone for converting an ambient noise signal included in a user's voice signal and a voice signal into an electrical signal and outputting the electrical signal, a second microphone for converting the ambient noise signal into an electrical signal and outputting the electrical signal, A second noise canceling unit for canceling the noise signal included in the signal by using the output signal of the second microphone and outputting the canceled noise signal and the noise canceling unit for outputting the output signal of the noise canceling unit through the external sound output unit, And an output unit for outputting the output signal of the first microphone and the output signal of the second microphone, wherein the noise canceling unit includes an inverse conversion unit for inverting and outputting the output signal of the second microphone, And a noise canceling unit. Accordingly, the prior art uses a first microphone receiving a noise signal included in a voice signal and a voice signal, and a second microphone receiving only a noise signal to offset a noise signal included in the voice signal into a noise signal input to the second microphone So that a clear voice signal can be output.

However, since the prior art is composed of the first microphone and the second microphone, the area of the apparatus is increased, and the cost of constructing the apparatus is increased.

1. Noise canceling apparatus and method of claim 1, characterized in that:

SUMMARY OF THE INVENTION The present invention has been made to overcome the above problems, and it is an object of the present invention to provide a flip-flop circuit which generates flicker noise and a thermal noise using resistance by using a MOS transistor and compensates flicker noise and thermal noise generated at an input terminal, And an input buffer circuit using the noise generator.

According to an aspect of the present invention, there is provided an input buffer using a noise generator that supplies a DC voltage to an input signal that is an electrical signal converted from a diaphragm, the input buffer circuit comprising: A first noise generator for generating another flicker noise for removing flicker noise generated at an input terminal of the CD amplifier and a CD amplifier including an input terminal made up of a first PMOS transistor, And a noise generator including a second noise generator for generating another thermal noise for removing the thermal noise.

The noise generator according to the preferred embodiment of the present invention may further include a reference current source for converting the input current into a constant current, and the first noise generator of the noise generator may include a flicker noise generator for generating flicker noise through the first NMOS transistor, And a second noise generator of the noise generator includes a thermal noise generator for generating thermal noise through a first resistor.

The first noise generator according to a preferred embodiment of the present invention further includes a first current transformer including a second NMOS transistor for converting the flicker noise generated from the flicker noise generator into a flicker noise current, The noise generator further includes a second current transformer including a third NMOS transistor for converting thermal noise generated from the thermal noise generating unit into a thermal noise current.

The noise generator according to a preferred embodiment of the present invention includes a current amplification unit including a fourth NMOS transistor for receiving the flicker noise current and the thermal noise current and adding the first addition current to the first addition current, And a third current transformer including a current mirror part composed of a fifth NMOS transistor for copying current and a second PMOS transistor for converting the first added current flowing in the current mirror part into an additive voltage.

The CD amplifier according to the preferred embodiment of the present invention converts the added voltage to a second added current from the third current transforming unit and outputs a third added current for canceling the noise current generated at the input terminal and the second added current. And a fourth current conversion section composed of a PMOS transistor.

The present invention generates thermal noise using flicker noise and resistance using a MOS transistor, and cancels flicker noise and thermal noise generated at an input terminal, thereby minimizing attenuation of a signal of an input signal and reducing noise.

1 is a diagram showing a conventional input buffer circuit.
2 is a diagram illustrating an input buffer circuit including a noise generator according to the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description, well-known functions or constructions are not described in detail since they would obscure the present invention.

The input buffer circuit is a device that provides a DC voltage to the electrical signal so that the amplifier of the preamplifier and the A / D converter can operate normally. The amplifier is a device for amplifying the signal output from the input buffer circuit. The amplifier increases the magnitude of the electrical signal and sends it to the A / D converter.

As shown in FIG. 2, the input buffer circuit according to the present invention includes a noise generator 100 and a CD amplifier 200.

The noise generator 100 is a device for generating flicker noise and thermal noise to remove noise generated at an input terminal. The CD amplifier 200 is an apparatus for receiving an input signal from a diaphragm, receiving a voltage for the noise generator 100 generated noise, and providing a DC voltage to the input signal.

Flicker noise is 1 / f noise, which is inversely proportional to frequency at frequencies below a few kHz, and refers to the noise caused by the oscillation of the anode current as the state of the cathode surface changes over time.

Thermal noise refers to noise generated by irregular movement of electrons in all conductors (resistors), and white noise that appears uniformly in all frequency bands regardless of frequency band.

The noise generator 100 includes a reference current source 110, a first noise generator 120, a second noise generator 130, a current amplifying unit M4, a current mirror unit M5, a low three-current converting unit M6, .

The reference current source 110 is a device for supplying a constant current to the input buffer.

The first noise generator 120 is a circuit that generates flicker noise using an NMOS transistor. 2, the first noise generator 120 includes a flicker noise generating unit M8, a first current converting unit M7, and a first current supplying unit M9. The flicker noise generating unit M8 generates another flicker noise to remove the flicker noise generated at the input terminal from the CD amplifier 200. [ As shown in FIG. 2, the flicker noise generating unit M8 includes a first NMOS (N-channel metal oxide semiconductor) transistor.

The first current converting unit M7 is a device for converting the voltage of the flicker noise generated from the flicker noise generating unit M8 into the flicker noise current. As shown in FIG. 2, the first current converting unit M7 is composed of a second NMOS transistor.

The first current supplying unit M9 is a device for supplying a current to the first noise generator 120. The first current supplying unit M9 is constituted by a fourth PMOS (P-channel metal oxide semiconductor) transistor as shown in FIG.

Referring to the first noise generator 120 of FIG. 2, the first NMOS transistor M8 is formed between the fourth node D and the VSS (ground terminal). The second NMOS transistor M7 is formed between the third node C and the VSS (ground terminal). The fourth PMOS transistor M9 is formed between the fourth node D and VDD (power supply voltage terminal). The gate of the first NMOS transistor M8 and the gate of the second NMOS transistor M7 are connected to each other and the first NMOS transistor M8 and the fourth PMOS transistor M9 are connected in series.

The second noise generator 130 is a circuit that generates thermal noise using a resistor. 2, the second noise generator 130 includes a thermal noise generating unit R, a second current converting unit M10, and a second current supplying unit M11. The thermal noise generating unit R generates another thermal noise to remove the thermal noise generated at the input terminal from the CD amplifier 200. As shown in FIG. 2, the thermal noise generating unit R is composed of a first resistor.

The second current converting unit M10 is a device for converting the voltage of the thermal noise generated from the thermal noise generating unit R into a thermal noise current. As shown in FIG. 2, the second current converting unit M10 is formed of a third NMOS transistor.

The second current supply unit M11 is a device for supplying current to the second noise generator 130. [ As shown in FIG. 2, the second current supply unit M11 is composed of a fifth PMOS transistor.

Referring to the second noise generator 130 of FIG. 2, the third NMOS transistor M10 is formed between the fifth node E and the VSS (ground terminal). The fifth PMOS transistor M11 is formed between the sixth node F and VDD (power supply voltage terminal). A first resistor R is formed between the sixth node F and VSS (ground terminal). The first resistor R is connected to the fifth PMOS transistor M11 through the sixth node F and the first resistor R is connected to the gate of the third NMOS transistor M11.

The current multiplying section M4 is a device for adding the currents generated in the first noise generator 120 and the second noise generator 130. Therefore, the current multiplying portion M4 receives the flicker noise current and the thermal noise current from the first current converting portion M7 and the second current converting portion M10 to generate the first added current. As shown in FIG. 2, the current multiplying portion M4 is constituted by a fourth NMOS transistor.

The current mirror section M5 is a device for copying the first added current in which the current is added to the peak section. Therefore, a current amount equal to that of the current portion flows through the current mirror portion M5. As shown in FIG. 2, the current mirror section M5 is composed of a fifth NMOS transistor.

The third current conversion section M6 is a device for converting the first added current flowing in the current mirror section M5 into the added voltage. As shown in FIG. 2, the third current converter M6 is formed of a second PMOS transistor.

The CD amplifier 200 is a device for receiving an electrical signal Vin from a diaphragm and for providing a DC voltage to a received input signal and for receiving an added voltage generated from the noise generator 100. Referring to FIG. 2, the CD amplifier 200 includes an input terminal M12 and a fourth current transformer M13.

The input terminal M12 is a device for receiving the electric signal Vin from the diaphragm. As shown in FIG. 2, the input terminal M12 is composed of a first PMOS transistor.

The fourth current converting section M13 receives the added voltage from the third current converting section M6 and converts it into a second added current. In addition, the fourth current transforming unit M13 removes the noise by canceling the flicker noise current and the thermal noise current generated at the input terminal M12 and the flicker noise current and the thermal noise current received at the second addition current. As shown in FIG. 2, the fourth current converting unit M13 is composed of a third PMOS transistor.

The conventional input buffer configured as in FIG. 1 generates flicker noise and thermal noise for the electrical signal Vin. In the conventional input buffer, noise is generated in the PMOS transistor M3, which is the input terminal of the CD amplifier. The noise generated in the conventional input buffer is expressed by Equation (1).

[Equation 1]

은 CD증폭기의 입력단자인 PMOS 트랜지스터(M3)에서 발생하는 열잡음을 의미하며, 나머지

은 플리커잡음을 의미한다. Here,

Denotes the thermal noise generated in the PMOS transistor M3, which is the input terminal of the CD amplifier,

Means flicker noise.

은 MOS(Metal Oxide Semiconductor)의 게이트 산화막의 단위면적당 커패시턴스, W는 MOS의 넓이, L은 MOS의 길이, f는 주파수, gm은 입력신호를 받는 PMOS 트랜지스터(M3)의 트랜스컨덕턴스(Transconductance)이다. 트랜스컨덕턴스(gm)은 다음의 수학식 2와 같다.k is the Boltzmann constant, T is the absolute temperature,

W is the width of the MOS, L is the length of the MOS, f is the frequency, and gm is the transconductance of the PMOS transistor M3 receiving the input signal. The transconductance (gm) is given by the following equation (2).

&Quot; (2) "

은 종횡비,

는 PMOS 트랜지스터에 흘러가는 전류를 의미한다. 수학식 1와 같이, 종래의 CD 증폭기에 발생하는 잡음을 낮추기 위해서는 수학식 2의 트랜스컨덕턴스(gm)의 값을 크게 해야한다. 따라서 수학식 2의 트랜스컨덕턴스(gm)의 값을 크게 하기 위해서는

(종횡비)를 크게 하고,

(PMOS 트랜지스터에 흘러가는 전류)를 크게 해야한다. 하지만 이와 같이 종횡비와 PMOS에 흘러가는 전류의 크기를 크게 하면, 전류의 크기가 증가함에 따라 전류의 소모가 증가하며 전치증폭기의 입력 신호(Vin)이 감소하게 된다.

The aspect ratio,

Quot; refers to the current flowing to the PMOS transistor. As shown in Equation (1), the transconductance (gm) of Equation (2) must be increased in order to lower the noise generated in the conventional CD amplifier. Therefore, in order to increase the value of the transconductance gm of the equation (2)

(Aspect ratio) is increased,

(The current flowing into the PMOS transistor) must be increased. However, if the aspect ratio and the magnitude of the current flowing through the PMOS are increased, the consumption of the current increases and the input signal Vin of the preamplifier decreases as the magnitude of the current increases.

Accordingly, as shown in FIG. 2, the present invention generates flicker noise and thermal noise through the noise generator 100, and lowers the noise of the preamplifier by canceling the flicker noise and the thermal noise generated in the input terminal PMOS transistor M12 of the preamplifier . 2, the flicker noise generated in the first noise generator 120 and the thermal noise generated in the second noise generator 130 are supplied to the fourth current transformer (gate of the third PMOS transistor) of the CD amplifier 200 . Therefore, the input to the fourth current transforming unit M13 becomes a CS amplifier (common source amplifier), and the CS amplifier inverts its input and output. On the other hand, since the noise is 0 V and the input signal is calculated as power, the noise power output from the fourth current transforming unit M13 is expressed by Equation (3). The square of the voltage becomes the power.

&Quot; (3) "

는 CS증폭기의 이득이며, CS증폭기의 입력과 출력은 반전되기 때문에 수학식 3과 같이 음(-)이 된다. here

Is the gain of the CS amplifier, and the input and output of the CS amplifier are inverted.

The flicker noise is expressed by the following equation (4).

&Quot; (4) "

은 플리커잡음을 생성하는 제1 NMOS 트랜지스터(M8)의 트랜스컨덕턴스(Transconductance)이다. k는 볼츠만 상수, T는 절대온도, W는 MOS의 넓이, L은 MOS의 길이, f는 주파수이다.

Is the transconductance of the first NMOS transistor M8 that produces flicker noise. k is the Boltzmann constant, T is the absolute temperature, W is the width of the MOS, L is the length of the MOS, and f is the frequency.

The thermal noise is expressed by the following equation (5).

&Quot; (5) "

k is the Boltzmann constant, T is the absolute temperature, and R is the resistance.

+

)을 상쇄한 값이 된다. Thus, the output Voutpre is subtracted from the input signal Vin to the second noise current < RTI ID = 0.0 >

+

) Is canceled.

Meanwhile, the noise generated at the input terminal M12 is expressed by Equation (6).

&Quot; (6) "

은 MOS(Metal Oxide Semiconductor)의 게이트 산화막의 단위면적당 커패시턴스, W는 MOS의 넓이, L은 MOS의 길이, f는 주파수,

은 입력신호를 받는 PMOS 트랜지스터(M12)의 트랜스컨덕턴스(Transconductance)이다.k is the Boltzmann constant, T is the absolute temperature,

Is the capacitance per unit area of the gate oxide film of MOS (Metal Oxide Semiconductor), W is the width of the MOS, L is the length of the MOS, f is the frequency,

Is the transconductance of the PMOS transistor M12 receiving the input signal.

Therefore, the noise from the output (Voutpre ^ 2) of the input buffer is expressed by the following equations (7) and (8).

&Quot; (7) "

Equation (7) is a value obtained by canceling the noise (Equation (3)) generated by the first noise generator and the second noise generator in the noise (Equation 6) generated at the input terminal M12. The final expression from the output (Voutpre) of the input buffer of Equation (7) becomes Equation (8).

&Quot; (8) "

The aspect ratio (W / L) of the first PMOS transistor M12 of the input terminal uses a small value in circuit design. If the value of the aspect ratio (W / L) of the first terminal PMOS transistor M12 of the input terminal is designed to be large, the transconductance treshold is increased (see Equations 1 and 2) and the noise is reduced. However, if the value of the aspect ratio (W / L) of the first terminal PMOS transistor M12 of the input terminal is designed to be large, the attenuation of the input signal becomes large and it falls short of the design specification. Therefore, according to the present invention, since the aspect ratio (W / L) of the input terminal first PMOS transistor M12 is designed to be small, the large noise generated is canceled by the noise generated by the noise generator to lower the noise of the preamplifier.

100: Noise generator 110: Reference current source
120: first noise generator 130: second noise generator
200: CD amplifier

Claims (6)

An input buffer using a noise generator for supplying a DC voltage to an input signal, which is an electrical signal converted from a diaphragm,
The input buffer
A CD amplifier including an input terminal made up of a first PMOS transistor for receiving the input signal from the diaphragm; And
A reference current source for converting the input current into a constant current; A flicker noise generating unit for generating another flicker noise to remove flicker noise generated at an input terminal of the CD amplifier through a first NMOS transistor and a second NMOS transistor for converting the another flicker noise into a flicker noise current, A first noise generator including a first current transformer comprising: And a second current source comprising a thermal noise generating unit for generating another thermal noise to remove thermal noise generated at an input terminal of the CD amplifier through a first resistor and a third NMOS transistor for converting the another thermal noise into a thermal noise current, And a second noise generator including a second noise generator and a second noise generator.
delete delete delete 2. The apparatus of claim 1, wherein the noise generator
A current amplifier including a fourth NMOS transistor for receiving the flicker noise current and the thermal noise current and adding the flicker noise current and the thermal noise current as a first addition current;
A current mirror unit including a fifth NMOS transistor for radiating a first addition current in which the current is added to the peak; And
A third current transformer comprising a second PMOS transistor for converting the first addition current flowing in the current mirror portion to an addition voltage; Wherein the input buffer further comprises a noise generator. 6. The method of claim 5,
Wherein the CD amplifier is configured to convert the added voltage to a second added current from the third current conversion unit and to convert the noise current generated at the input terminal and the second added current into a fourth current conversion part; Wherein the input buffer further comprises a noise generator.

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