KR100657822B1 - Wideband variable gain amplifier - Google Patents

Abstract

A wideband variable gain amplifier is provided to have low distortion and high linearity by performing stable current supply using a bleeding current. In a wideband variable gain amplifier, a transconductance conversion unit(21) controls a gain of a differential input signal by controlling the amplitude of transconductance according to a gain control signal. A load resistor stage(22,23) converts a current type differential signal outputted from the transconductance conversion unit into a voltage type differential signal. An output DC voltage comparison unit(24) detects a DC current of the differential signal converted in the load resistor stage, and sets a bias voltage by comparing the DC voltage with a reference DC voltage. A bleeding current generation unit(25) determines the intensity of a bleeding current according to a bias voltage set in the output DC voltage comparison unit, and supplies the corresponding bleeding current to the transconductance conversion unit.

Description

Wideband variable gain amplifier

1 is a configuration diagram of an embodiment of a conventional variable gain amplifier;

2 is a block diagram of an embodiment of a wideband variable gain amplifier according to the present invention;

3 is a configuration diagram of another embodiment of a wideband variable gain amplifier according to the present invention.

* Explanation of symbols for the main parts of the drawings

21: transconductance conversion section 22, 23: load resistance stage

24: output DC voltage comparator 25: bleeding current generator

The present invention relates to a wideband variable gain amplifier, and more particularly, has a wideband characteristic, a low power consumption characteristic, and a characteristic capable of operating at a low voltage, and having a low distortion and high linearity according to a stable current supply using a bleeding current. It is about a gain amplifier.

1 is a configuration diagram of an embodiment of a conventional variable gain amplifier.

As shown in FIG. 1, the conventional variable gain amplifier includes a transistor M1 11 for converting an input signal V _{in +} received through a gate into a current and an input signal V _in received through a gate. _- transistors for converting) with a current (M2) (12), amplifying the transistor (M1), the converted input current (11) signal (V _{in +)} according to the input through the gate gain control signal (V _CTRL) A transistor M4 for amplifying the input current signal V _in− converted by the transistor M2 12 according to the gain control signal V _CTRL input through the gate and the transistor M3 13. 14, a load resistor for converting the input current signal V _{in +} amplified by the transistors M3 and 13 and the input current signal V _in- amplified by the transistors M4 and 14 into voltage. Stage R _L 15 is included.

In more detail, the differential input signals V _{in +} and V _in− are input to the gates of the transistors M1 and M2 and are converted into differential signals in the form of current. The converted differential current signal is converted into an output voltage differential signal V _out amplified by the load resistor terminal R _L through the cascode-type transistors M3 and M4. At this time, a gain control signal V _CTRL is applied to the gates of the transistors M3 and M4. The gain control signal _VCTRL is applied to adjust the transconductance of the entire circuit according to the voltage signal (gain control signal). Here, the input transistors M1 and M2 operate in the linear region or the saturation region according to the gain control signal, and the cascode type transistors M3 and M4 operate in the saturation region.

Such a conventional variable gain amplifier requires the use of a large load resistor to obtain a large gain and a large dynamic range when the supply voltage VDD of the variable gain cell is low. When the large load resistor R _L is used, the DC voltage of the output V _out is lowered by the voltage between the load resistors, and all the transistors M1 to M4 operate in the linear region or the cutoff region. There is a problem that high gains cannot be obtained.

In addition, the conventional variable gain amplifier can obtain a high gain when the bias current (I _S ) is lowered to prevent the output DC (Direct Current) voltage from falling, but a high differential input signal (V _{in +} , V _in- ) is obtained. When applied, there is a problem of generating severe distortion and destroying the linearity of the circuit.

The present invention has been proposed in order to solve the above problems, and has a wide band characteristic, a low consumption characteristic and a characteristic capable of operating at a low voltage, and a variable power gain amplifier having low distortion and high linearity according to a stable current supply using a bleeding current. The purpose is to provide.

Other objects and advantages of the present invention can be understood by the following description, and will be more clearly understood by the embodiments of the present invention. Also, it will be readily appreciated that the objects and advantages of the present invention may be realized by the means and combinations thereof indicated in the claims.

According to an aspect of the present invention, there is provided a broadband variable gain amplifier, comprising: transconductance converting means for adjusting gain of a differential input signal by adjusting a magnitude of a transconductance according to a gain control signal (gain control voltage); A load resistance stage for converting a differential signal in the form of current output from the transconductance converting means into a differential signal in the form of a voltage; Output DC voltage comparison means for setting a bias voltage by detecting a DC (Direct Current) voltage of the differential signal converted by the load resistance terminal and comparing it with a reference DC voltage; And bleeding current generating means for determining the bleeding current amount according to the bias voltage set by the output DC voltage comparing means and supplying the bleeding current to the transconductance converting means.

Further, another apparatus of the present invention is a broadband variable gain amplifier, comprising: transconductance converting means for adjusting gain of a differential input signal by adjusting a magnitude of a transconductance according to a gain control signal (gain control voltage); An active load stage for converting a differential signal in the form of current output from the transconductance conversion means into a differential signal in the form of a voltage and improving a frequency characteristic through a capacitor; Output DC voltage comparison means for setting a bias voltage by detecting a DC (Direct Current) voltage of the differential signal converted by the load resistance terminal and comparing it with a reference DC voltage; And bleeding current generating means for determining the bleeding current amount according to the bias voltage set by the output DC voltage comparing means and supplying the bleeding current to the transconductance converting means.

In addition, the present invention is operable even at a low supply voltage, and has a low distortion characteristic and a high linearity characteristic by the broadband characteristics and the bleeding current.

In addition, the present invention is applied to a broadband system such as "Multi-Band UWB", and can be integrated like other components, have a low voltage characteristic and a low power characteristic, and have a small size by simplifying a circuit configuration. In addition, it has a variable gain amplification function for an input signal having a wide variable gain range, and has a wide band operation characteristic by a fixed current bias.

The above objects, features and advantages will become more apparent from the following detailed description taken in conjunction with the accompanying drawings, whereby those skilled in the art may easily implement the technical idea of the present invention. There will be. In addition, in describing the present invention, when it is determined that the detailed description of the known technology related to the present invention may unnecessarily obscure the gist of the present invention, the detailed description thereof will be omitted. Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

2 is a block diagram of an embodiment of a wideband variable gain amplifier according to the present invention.

As shown in FIG. 2, the broadband variable gain amplifier according to the present invention adjusts the magnitude of the transconductance according to a gain control signal (gain control voltage) V _ctrl , thereby providing a differential input signal (first input voltage Vin +). And a transconductance converter 21 for adjusting the gain of the second input voltage Vin− and a differential signal in the form of a current output from the transconductance converter 21 in the form of a voltage output voltage V _{out +.} , V _{out -} bias as compared to) a load resistance stage (22, 23), after detecting the DC voltage of the differential output transform from the load resistance stage (22, 23) based on a direct current voltage (V _cm) for converting The output DC voltage comparator 24 for setting the voltage, and the amount of bleeding current is determined according to the bias voltage set by the output DC voltage comparator 24 and for supplying the bleeding current to the transconductance converter 21. Bleeding current And a part (25).

Looking at this in more detail as follows.

First, the transconductance converter 21 receives and differentially inputs the input signals V _{in +} and V _in- through the differential input transistors Mn1 and Mn2, and outputs them according to the gain control voltage signal V _ctrl . The variable transconductance is used to adjust the variable gain of the input signal.

That is, the cascode type input terminal includes transistors Mn1, Mn2, Mn3, and Mn4. This cascode type input stage minimizes the Miller effect and parasitic capacitance components. At this time, the input transistor Mn1 is connected to the source terminal of the node P1 and the transistor Mn3, and the input transistor Mn2 is connected to the source terminal of the node P1 and the transistor Mn4.

The gain control voltage V _ctrl is applied to the gate terminals of the transistors Mn3 and Mn4, and operates as a common gate amplifier according to the gain control voltage V _ctrl . At this time, the transistors Mn1, Mn3, Mn2, Mn4 operate in the linear region or the saturation region according to the gain control voltage signal.

That is, when the gain control voltage is large, the transistors Mn1, Mn2, Mn3, and Mn4 all operate in the saturation region, whereas when the gain control voltage is small, the transistors Mn1 and Mn2 operate in the linear region, and the transistors Mn3 and transistor Mn4 operates in the saturation region.

Therefore, when a small differential input voltage (V _{in +} , V _in- ) is applied, it has a control signal mode that increases the gain control voltage (V _ctrl ), so that two transistor stages (Mn1, Mn3, Mn2 and Only two transistors (Mn1 and Mn2) to which the differential input signal is applied in the linear region are allowed to operate in the saturation region, and the control signal mode is reduced when a large differential input voltage (V _{in +} , V _in- ) is applied. Operation maximizes linearity regardless of the magnitude of the input signal.

This cascode configuration increases the voltage gain by having a large output impedance at output nodes P2 and P3.

)와 트랜스컨덕턴스(

)는 하기의 [수학식 1] 및 [수학식 2]와 같다.Here, the drain current and the transconductance in the linear region and the saturation region are represented by Equations 1 to 4 below.

) And transconductance (

) Is the same as the following [Equation 1] and [Equation 2].

)은

을 만족하고,

이며,

는 트랜지스터의 문턱전압(threshold voltage)을 의미한다. 이때,

는 게이트 전압을 의미한다.Where the drain voltage (

)silver

Satisfying,

Is,

Is the threshold voltage of the transistor. At this time,

Means gate voltage.

)와 트랜스컨덕턴스(

)는 하기의 [수학식 3] 및 [수학식 4]와 같다.Next, the drain current in the saturation region (

) And transconductance (

) Is the same as the following [Equation 3] and [Equation 4].

)은

를 만족한다.Where the drain voltage (

)silver

Satisfies.

Next, the load resistance stages 22 and 23 receive a differential signal in the form of current output from the transconductance converter 21 and output it as an output voltage V _{out +} , V _{out − in the} form of voltage.

Specifically, the load resistance stage (22, 23) is a resistive load (R1, R2) the through transconductance conversion section 21 the differential signal of the electric current form the voltage-output voltage of the output from (V _{out +,} V _{out -)} Convert to In this case, in order to improve the frequency characteristic of the wideband variable gain amplifier, as shown in FIG. 3, an active load may be used instead of a resistor to output an output voltage (V _{out +} , V _{out −} ) in the form of a voltage.

In other words, the inverse of the transconductance value of the transistor Mp1 and the transistor Mp2 becomes an approximate output load, and together with the transistors Mn5 and Mn6, the current sources I _S1 and I _S2 enable low voltage operation and provide a stable bias. .

In addition, the frequency characteristics can be improved by the frequency compensating capacitors C1 and C2, which have greater gain than using a resistive load, and can operate at low voltage and wideband.

Next, the output DC voltage comparator 24 detects the DC voltage at the output node point and compares it with the reference DC voltage (threshold).

That is, the output DC voltage comparator 24 detects the DC voltage values of the differential output nodes P2 and P3 by using the transistors Mp5 and Mp6. Here, the node P6 is an alternating current (AC) virtual ground node of the differential output node, and the DC voltage value is set as the output DC voltage.

The output DC voltage comparator 24 uses a transistor Mn7, a transistor Mn8, a transistor Mp7, a transistor Mp8, and a differential amplifier composed of a resistor R3 and a capacitor C3, which are frequency compensation circuits, and an external reference DC voltage V of the node P6. After comparing _cm , the bias voltage of node P7 is set.

Then, the bleeding current generator 25 determines the bleeding current amount according to the node P7 voltage, and the transconductance converter 21 adjusts the DC voltages of the output nodes P2 and P3 according to the determined current amount. Through this process, the external reference voltage V _cm is equal to the DC voltages of the output nodes P2 and P3.

As described above, the output DC voltage comparator 24 and the bleeding current generator 25 form a negative feedback to stably set the bias current and the output DC voltage. In this case, the resistor R3 and the capacitor C3 serve as compensating circuits so that the output DC voltage comparator 24 operates stably.

Since the output DC voltage can be adjusted externally, the DC voltage level of the input and output of the wideband variable gain amplifier is the same, so that the cascade connection can be made.

Next, the bleeding current generator 25 directly receives the DC voltage of the node P7 set by the output DC voltage comparator 24 through the gate terminal of the transistor Mp3 and the transistor Mp4 to determine the amount of bleed current, and then converts the corresponding bleed current. Supply to conductance conversion section 21.

Here, the transistors Mp3 and Mp4 operate as current sources, which do not affect the performance of the circuit because the impedances at the output nodes P2 and P3 are very large. That is, the bleeding current generator 25 causes the bias current to flow small in the load of the circuit, and the larger the current flows, the larger the bias current flows to the transconductance converter 21 having linearity, thereby providing low distortion and high linearity characteristics. Improve.

In addition, the bleeding current generator 25 allows a small current to flow through the load resistors R1 and R2 to enable a large resistance, obtain a large gain and a large variable gain range, and enable low voltage operation. .

3 is a configuration diagram of another embodiment of a wideband variable gain amplifier according to the present invention.

As shown in FIG. 3, the wideband variable gain amplifier according to the present invention adjusts the magnitude of the transconductance according to a gain control signal (gain control voltage) V _ctrl to provide a differential input signal (first input voltage Vin +). and a second input voltage (Vin-)) transfected's conductance conversion unit 31, the transconductance conversion unit 31 a differential signal of a current form of the voltage in the form of the output voltage (V _out output from for controlling the gain of _+, V _{out -)} by then converting and detecting the DC voltage of the differential output conversion in the active part at the bottom (32, 33), said active part at the bottom (32, 33) to improve the frequency characteristics through the capacitor the reference The output DC voltage comparator 34 for setting the bias voltage in comparison with the DC voltage V _cm , and the amount of bleeding current is determined according to the bias voltage set by the output DC voltage comparator 34 and the corresponding bleed current is converted into the transformer. Conductance And a bleeding current generator 35 for supplying the converter 31.

Here, one active load 32 includes transistor Mp1, transistor Mn5, current source I _S1 and capacitor C1. At this time, the transistor Mp1 is connected between the power supply voltage source VDD and the output node P2 and operates in accordance with the potential of the node P4. In addition, the transistor Mn5 is connected between the power source voltage source and the node P4, and operates in accordance with the potential of the node P2. In addition, transistor Mp1 and transistor Mn5 constitute mutual negative feedback. In addition, current source I _S1 is connected between ground and node P4 and sets the current bias of the active load. In addition, the frequency compensation capacitor C1 is connected in parallel with the current source I _S1, and improves the frequency characteristic.

Looking more closely at this, transistor Mp1 acts as a load. In addition, the active load 34 determines the stable bias current through the sizes of the transistors Mp1 and Mn5 and the current source I _S1 , thereby increasing the common mode rejection ratio (CMRR) than when using the resistive load. Accordingly, the output voltage at the output node P2 is maintained at a more stable voltage level. Capacitor C1 has a zero frequency along with the output impedance in output mode P2, and by adjusting the size of the capacitor, the desired gain can be obtained at the desired operating frequency.

This operation is similarly performed in other active loads 33 including transistor Mp2, transistor Mn6, current source I _S2 , capacitor C2, and output node P3.

As a result, the inverse of the transconductance values of the transistors Mp1 and Mp2 becomes an approximate output load, and as the current flows through the transistors Mp1 and Mp2, the transconductance decreases, so that the value of the output load increases, resulting in a large gain and a large variable gain. Considering that the range can be obtained, the bleeding current generator 35 is implemented with the output DC voltage comparator 34 to have characteristics such as low voltage operation, high gain, and high variable gain range.

As described above, the method of the present invention may be implemented as a program and stored in a recording medium (CD-ROM, RAM, ROM, floppy disk, hard disk, magneto-optical disk, etc.) in a computer-readable form. Since this process can be easily implemented by those skilled in the art will not be described in more detail.

The present invention described above is capable of various substitutions, modifications, and changes without departing from the technical spirit of the present invention for those skilled in the art to which the present invention pertains. It is not limited by the drawings.

The present invention as described above has the effect of providing a variable gain amplification function for the input signal having a wide range by the external control voltage signal at a low supply voltage.

In addition, the present invention can operate at a small supply voltage using a CMOS transistor has the effect that can be embedded into the IC.

Claims (8)

In a wideband variable gain amplifier, Transconductance converting means for adjusting the gain of the differential input signal by adjusting the magnitude of the transconductance according to a gain control signal (gain control voltage); A load resistance stage for converting a differential signal in the form of current output from the transconductance converting means into a differential signal in the form of a voltage; Output DC voltage comparison means for setting a bias voltage by detecting a DC (Direct Current) voltage of the differential signal converted by the load resistance terminal and comparing it with a reference DC voltage; And A bleeding current generating means for determining the bleeding current amount according to the bias voltage set by the output DC voltage comparing means and supplying the bleeding current to the transconductance converting means. Broadband variable gain amplifier comprising a. The method of claim 1, The transconductance converting means, It consists of transistors (Mn1, Mn2, Mn3, Mn4), which are cascode type input terminals, When the gain control voltage is large, the transistors Mn1, Mn2, Mn3, and Mn4 all operate in a saturation region. When the gain control voltage is small, the transistors Mn1 and Mn2 operate in a linear region, and transistors Mn3 and Mn4. Is a wideband variable gain amplifier, characterized in that operating in the saturation region. The method of claim 2, The drain current of each transistor in the linear region

) And transconductance (

) Is a wide band variable gain amplifier, characterized in that represented by the following equation (A) and (Equation B). Equation A

Equation B

Where the drain voltage (

)silver

Satisfying,

Is,

Is the threshold voltage of the transistor. At this time,

Means gate voltage. The method of claim 2, The drain current of each transistor in the saturation region (

) And transconductance (

) Is a wide band variable gain amplifier, characterized in that represented by the following [Equation C] and [Equation D]. Equation C

[Equation D]

Where the drain voltage (

)silver

Satisfies. The method according to any one of claims 1 to 4, The output DC voltage comparison means, Frequency compensation means consisting of resistors and capacitors Broadband variable gain amplifier, characterized in that it further comprises. The method of claim 5, And said output DC voltage comparing means and said bleeding current generating means constitute a negative feedback. In a wideband variable gain amplifier, Transconductance converting means for adjusting the gain of the differential input signal by adjusting the magnitude of the transconductance according to a gain control signal (gain control voltage); An active load stage for converting a differential signal in the form of current output from the transconductance conversion means into a differential signal in the form of a voltage and improving a frequency characteristic through a capacitor; Output DC voltage comparison means for setting a bias voltage by detecting a DC (Direct Current) voltage of the differential signal converted by the load resistance terminal and comparing it with a reference DC voltage; And A bleeding current generating means for determining the bleeding current amount according to the bias voltage set by the output DC voltage comparing means and supplying the bleeding current to the transconductance converting means. Broadband variable gain amplifier comprising a. The method of claim 7, wherein The active load stage, And a frequency compensating capacitor connected in parallel with a current source to improve frequency characteristics.

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