KR20030079243A - Controlled gain amplifier with improved selectable wide linearity - Google Patents

Abstract

PURPOSE: An amplifier capable of controlling the gain variable improved in a linearity is provided to increase the linearity so as to widely control the gain characteristics for the control voltage. CONSTITUTION: An amplifier capable of controlling the gain variable improved in a linearity includes a differential amplifying block(30), a variable current supplying block(31), a control block(32), a current compensation block(33) and an output block(34). The differential amplifying block(30) generates the output signal(Vout) in proportional to the difference of the input signal(Vin). The variable current supplying block(31) controls the gain of the differential amplifying block(30) by supplying the reference voltage to the differential amplifying block(30). The control block(32) controls the variable current supplying block(31). The current compensation block(33) reduces the width of the change between the reference current(Iref) in response to the change the control voltage so as to secure the linearity of the output signal(Vout) of the differential amplifying block(30) And, the output block(34) outputs the output of the differential amplifying block(30).

Description

Controlled gain amplifier with improved selectable wide linearity

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to an adjustable gain amplifier (hereinafter referred to as CGA). In particular, the gain characteristics of a control voltage can be adjusted in a wide range according to the strength of a specific input signal. The present invention relates to an amplifier having a variable gain control which improves the linearity of the amplifier.

CGA is an amplifier that can control the gain by a voltage or the like, and is commonly used to amplify the signal strength and use it directly in a system or to provide an output signal having a predetermined strength for subsequent signal processing. In radio transceivers such as Mobi1e communication, signal strength may change significantly due to environmental factors.

Therefore, in order to transmit and receive a signal more accurately, power control is required to increase the gain of the amplifier when the signal strength is small and to decrease the gain of the amplifier when the signal strength is large. For this reason, CGA which can change a gain according to signal strength is used.

1 is a detailed circuit diagram illustrating a CGA according to the prior art.

Referring to FIG. 1, in the conventional CGA, the differential amplifier 10 generates an output signal Vout in proportion to the difference between the input signals Vin and the reference current Iref that varies in the differential amplifier 10. A variable current providing unit 11 for adjusting the gain of the differential amplifier 10 by providing a control unit, a control unit 12 for controlling the variable current providing unit 11, and an output signal of the differential amplifier 10. An output unit 13 for amplifying and outputting the bar is configured, and the current of the variable current supply unit 11 is varied using the control voltage Vctrl.

Each component of the above-described conventional CGA will be described in more detail.

The differential amplifier 10 forms a current mirror with each other, serves as a load of the differential amplifier 10, and each emitter is connected to a transistor Q7 and a transistor Q8 connected to a power supply voltage terminal Vcc, and Transistor Q5 is connected to the collector of transistor Q7 and its collector, with the signal Vin being the base input, and a constant voltage V1 is applied to the base, and the collector of transistor Q8 and its collector are connected. Transistor Q6, transistor Q5, transistor Q5 and transistor whose output is differentially amplified by the input signal Vin and whose gain is adjusted in accordance with the current Iref that the transistor Q5 and the emitter are commonly connected. The emitter of Q6 and its collector are connected, and the signal from the variable current supply unit 11 is used as its base input, and the emitter includes a transistor Q4 connected to the ground power supply terminal.

The variable current supply unit 11 has the constant current sources I1 and I2, the outputs of the constant current source I1 as the base inputs, the transistors Q1 having the collector connected to the power supply voltage terminal, and the base and ground of the transistors Q4. Transistor Q3 and transistor Q2, which form a current mirror between the voltage terminals, resistor R1 connected between the collector of transistor Q2 and the emitter of transistor Q1, and the control voltage Vctrl. The transistor Q12 connected with the base of the transistor Q1 and its emitter connected to the collector, and the collector connected to the ground voltage terminal, and the capacitor C1 connected between the base and the ground voltage terminal of the transistor Q12 are used as the base input. Include.

The controller 12 is configured to selectively switch the base of the constant current source Ia and the constant current source Ib and the transistor Q12 in response to the constant current source Ia and the constant current source Ib and the control signal Vsw. Switches SW1 and SW1B.

The output unit 13 has a transistor Q9 for outputting the output signal Vout through the emitter through a gate connected to an output terminal of the differential amplifier 10 and a collector connected to a power supply voltage terminal, and a transistor ( And a transistor connected to the common base Q11 and connected between the transistor Q9 and the ground voltage terminal.

FIG. 2 is a graph illustrating a relationship between a gain and a control voltage in the CGA of FIG. 1. Hereinafter, an operation of a conventional CGA having the above-described configuration will be described with reference to FIG. 2.

First, when the control signal Vsw is applied as a positive pulse and the switch SW1 is turned on to increase the control voltage Vctrl, the base voltage of the transistor Q12 is increased. Accordingly, the transistor Q12 is applied. Is turned off so that the current path through transistor Q12 is blocked, so that the current flowing along resistor R1 increases. The increased current causes the base current of the transistor Q4 to flow to the ground voltage terminal by mirroring the transistors Q2 and Q3.

Therefore, as the base current of the transistor Q4 decreases, the collector current, that is, the reference current Iref, also decreases, so that the gain of the differential amplifier 10 decreases, as shown in FIG. 2. It can be seen that as Vctrl increases, the base current of the transistor Q4 increases, thereby decreasing the reference current Iref.

On the other hand, when the control signal Vsw is applied as a positive pulse and the switch SW1B is turned on to increase the control voltage Vctrl, the base voltage of the transistor Q12 is decreased, and accordingly, the transistor Q12 is applied. Since the current is turned on to increase the current through the transistor Q12, the current flowing along the resistor R1 decreases. The reduced current causes the base current of the transistor Q4 to increase due to the mirroring of the transistors Q2 and Q3.

Accordingly, as the base current of the transistor Q4 increases, the collector current, that is, the reference current Iref, also increases, so that the gain of the differential amplifier 10 increases. As the control voltage Vctrl decreases, It can be seen that the base current of the transistor Q4 decreases, thereby increasing the reference current Iref.

However, in the conventional CGA as described above, the gain characteristic of the CGA operates to change according to the magnitude of the control voltage Vctrl, but the slope of the gain characteristic curve with respect to the control voltage Vctrl maintains a constant value. In order to change, it is necessary to configure a circuit as a structure capable of trimming a specific value inside the chip or to adjust a specific variable outside the chip. Thus, a problem arises that it is not easy to increase the linearity of the amplifier gain.

The present invention proposed to solve the conventional problems as described above, the object of the present invention is to provide a gain variable adjustable amplifier that can increase the linearity by making it possible to adjust the gain characteristics of the control voltage over a wide range. do.

1 is a detailed circuit diagram illustrating a CGA according to the prior art;

FIG. 2 is a graph showing a relationship between a gain and a control voltage in the CGA of FIG. 1;

3 is a detailed circuit diagram illustrating a CGA according to an embodiment of the present invention;

4 is a block diagram illustrating a CGA according to another embodiment of the present invention;

5 and 6 are graphs showing signal waveforms according to FIG. 4;

7 is a graph showing the linearity of the output signal according to the present invention.

* Explanation of symbols for the main parts of the drawings

30: differential amplifier 31: variable current providing unit

32: control unit 33: current compensation unit

34: output unit

The present invention for achieving the above object, the differential amplifier for generating an output signal in proportion to the difference between the input signal; A variable current providing unit for controlling a gain of the differential amplifier by providing a reference current variable by a control voltage to the differential amplifier; A current compensator for compensating the reference current to ensure linearity of the output signal of the differential amplifier according to the change of the control voltage; A controller for controlling the variable current providing unit; And it provides an amplifier capable of variable gain control including an output unit for amplifying and outputting the output signal of the differential amplifier.

In addition, the present invention for achieving the above object, the first amplifier for outputting a signal amplified by a variable gain in accordance with the first control signal; Second and third amplifiers for amplifying the outputs of the first amplifier with different gains; First and second highest value detectors detecting their highest values from respective outputs of the second and third amplifiers; And a comparator configured to compare outputs of the first peak detector and the second peak detector to form a feedback loop for outputting a second control signal for adjusting the gain of the first amplifier to the first amplifier. Provide an adjustable amplifier.

The technical feature of the present invention is to secure a linearity of gain by adding a simple current compensator to the CGA and compensating for a sudden decrease in the reference current provided to the differential amplifier according to the decrease in the de-stabilization voltage.

Hereinafter, the most preferred embodiments of the present invention will be described with reference to the accompanying drawings so that those skilled in the art may easily implement the technical idea of the present invention. 3 is a detailed circuit diagram illustrating a CGA according to an embodiment of the present invention, FIG. 4 is a block diagram illustrating a CGA according to another embodiment of the present invention, and FIGS. 5 and 6 are signals according to FIG. 4. Figure 7 is a graph showing the waveform, Figure 7 is a graph showing the linearity of the output signal according to the present invention.

Referring to FIG. 3, the CGA of the present invention includes a differential amplifier 30 generating an output signal Vout in proportion to the difference between the input signals Vin and a reference current Iref that is changed by a control voltage Vctrl. ) Is provided to the differential amplifier 30 to adjust the gain of the differential amplifier 30, and the output signal of the differential amplifier 30 according to the variation of the control voltage (Vout) Output signal Vout of the current compensator 33 for compensating the reference current (Iref), the control unit 32 for controlling the variable current providing unit 31, and the differential amplifier 30 to ensure the linearity of the ) Is provided with an output unit 34 for amplifying and outputting.

Here, the current compensation unit 33 reduces the width of the variation of the reference current (Iref) according to the variation of the control voltage (Vctrl) in order to secure the linearity of the output signal (Vout) of the differential amplifier 30, A current source I3 having one side connected to the first voltage terminal (eg, VCC), a transistor Q12 controlled by the control voltage Vctrl, and having one side thereof in contact with the other side of the current source I3, and a transistor Q12. And a diode (D1) connected in the forward direction between the other side of the circuit and the node (X) in contact with the differential amplifier 30 and the variable current providing unit 31, the transistor Q12 is a PMOS or NMOS in addition to the BJT shown It can also be implemented as a transistor.

The differential amplifier 30 forms a current mirror with each other, serves as a load of the differential amplifier 30, and each emitter is connected to a transistor Q7 and a transistor Q8 connected to the power supply voltage terminal Vcc, and Transistor Q5 is connected to the collector of transistor Q7 and its collector, with the signal Vin being the base input, and a constant voltage V1 is applied to the base, and the collector of transistor Q8 and its collector are connected. Transistor Q6, transistor Q5, transistor Q5 and transistor whose output is differentially amplified by the input signal Vin and whose gain is adjusted in accordance with the current Iref that the transistor Q5 and the emitter are commonly connected. The emitter of Q6 and its collector are connected, and the signal from the variable current supply part 31 is used as its base input, and the emitter includes transistor Q4 connected to the ground power supply terminal.

The variable current supply unit 31 has the constant current sources I1 and I2, the output of the constant current source I1 as a base input, the transistor Q1 having a collector connected to the power supply voltage terminal, the base and ground of the transistor Q4. Transistor Q3 and transistor Q2, which form a current mirror between the voltage terminals, resistor R1 connected between the collector of transistor Q2 and the emitter of transistor Q1, and the control voltage Vctrl. Transistor Q13 connected to the base of the transistor Q1 and its emitter, the collector connected to the ground voltage terminal, and the capacitor C1 connected between the base of the transistor Q13 and the ground voltage terminal. Include.

The control unit 32 selectively switches the constant current source Ia and the constant current source Ib and the base of the constant current source Ia and the constant current source Ib and the transistor Q13 in response to the control signal Vsw. Switches SW1 and SW1B.

The output unit 13 has a gate connected to the output terminal of the differential amplifier unit 30 and its collector connected to the power supply voltage terminal VCC and the transistor Q9 for outputting the output signal Vout through the emitter. And a transistor Q10 connected to the transistor Q11 with a common base and connected between the transistor Q9 and the ground voltage terminal.

Referring to FIG. 4, the CGA of the present invention includes a first amplifier 40 and a first amplifier for outputting a signal amplified by a variable gain according to the first control signal Vctrl shown in FIG. 3. Second and third amplifiers 41a and 41b for amplifying the output of 40 with different gains, and first and second peaks from the respective outputs of the second and third amplifiers 41a and 41b, respectively. The second control signal Va for adjusting the gain of the first amplifier 40 by comparing the outputs of the second peak detector 42a and 42b with the first peak detector 42a and the second peak detector 42b. ) Is provided with a comparator 43 for forming a feedback loop for outputting a) to the first amplifier 40.

Meanwhile, FIG. 4 is an embodiment block diagram for implementing the second control signal Va of FIG. 3 described above. The operation of the CGA of the present invention having the above-described configuration will be described in detail with reference to FIGS. 3 to 7. Take a look.

In the case of the present invention, as shown in FIG. 3, the switches SW1 and SW1B reversely switch by a pulse applied to Vsw as in the related art, and maintain a constant control voltage Vctrl at the capacitor C1. .

As the control voltage Vctrl increases, the voltage applied to R1 increases and the collector currents of Q2 and Q1 increase. At this time, when the second control voltage Va is "first logic (eg, logic high)", Q12 is turned off, and increasing the collector current of Q3 decreases the base current of Q4 to decrease the gain of the CGA. As shown in FIG. 7, the gain characteristic of the control voltage Vctrl is 'A' in FIG. 7 and maintains the linearity as in the prior art.

On the other hand, when Va is "second logic (eg, logic high)" Q12 is turned on and the base current of Q3 is compensated by current source I3. Accordingly, since the base current of Q4 can be compensated compared with the conventional case in which the increase amount of the base current of Q4 decreases with the increase of the collector current of Q3, 'B' of FIG. 3 showing a gain characteristic curve compared to the control voltage Vctrl. Since these characteristics are shown, the linearity of gain is increased.

In FIG. 4, the output Vout of the first amplifier 40 is amplified while passing through the second amplifier 41a and the third amplifier 41b. For example, at this time, if the gain of the second amplifier 41a is greater than the gain of the third amplifier 41b, the amplitude of the signal amplified while passing through the second amplifier 41a is increased by the third amplifier 41b. As it passes through, it becomes relatively larger than the amplitude of the amplified signal.

Therefore, by appropriately adjusting the gain magnitude of each of the second amplifier 41a and the third amplifier 41b, the difference value ΔV between the input signals 'C' and 'D' compared in the comparator 43 is adjusted. Adjustable

Signals A and B passing through the second amplifier 41a and the third amplifier 41b pass through the two highest peak detectors 42a and 42b, respectively, as shown in FIGS. While being converted into a DC voltage having a small ripple, the two DC voltages are respectively input to the input terminal of the comparator 43 and the comparator 43 according to the value of the difference between the two signals C and D that are input. ) Will maintain "logic high" or "logic low". At this time, if the difference between the applied signals does not exceed a predetermined value, the output of the comparator 43, that is, Va becomes "logic high", and when it exceeds a predetermined value, it is inverted to "logic low". The output Va of 43) is fed back to the first amplifier 40 so that Vout has a characteristic of 'ga' or 'b' shown in FIG.

Meanwhile, the current compensator 33 of FIG. 3 may be configured in the form of a current source and a switch in addition to the form of replacing the BJT with NPN or PNP as described above.

According to the above, the conventional technique exhibits a linear characteristic of a constant gain regardless of the intensity of the input signal, and if you want to increase the linearity, add a circuit for trimming inside the chip or apply a specific variable outside the chip. The method of increasing the linearity by using a control method has been used, and thus, a constraint that cannot be easily adjusted in an amplifier in which the linearity of gain is important is provided. However, the present invention adds a simple circuit, that is, a current compensation unit, according to the strength of the input signal. The gain linear characteristics of the CGA were to exhibit two characteristics, and it was found through the examples that the gain variable characteristics could be improved as compared with the conventional art.

Although the technical idea of the present invention has been described in detail according to the above preferred embodiment, it should be noted that the above-described embodiment is for the purpose of description and not of limitation. In addition, those skilled in the art will understand that various embodiments are possible within the scope of the technical idea of the present invention.

According to the present invention made as described above, it is possible to increase the linearity by allowing the gain characteristics of the control voltage to be extensively adjusted without the addition of a separate complicated circuit to the amplifier functioning with the gain variable adjustment, ultimately product performance. We can expect the outstanding effect of securing competitiveness through improvement.

Claims (10)

Differential amplifying means for generating an output signal in proportion to the difference between the input signals; Variable current providing means for providing a reference current variable by a control voltage to the differential amplifying means to adjust the gain of the differential amplifying means; Current compensation means for compensating the reference current to ensure linearity of the output signal of the differential amplifying means according to the change of the control voltage; Control means for controlling the variable current providing means; And Output means for amplifying and outputting the output signal of said differential amplifier means Adjustable gain adjustable amplifier comprising a. The method of claim 1, The current compensation means, Gain-variable control amplifier, characterized in that for reducing the width of the variation of the reference current according to the change in the control voltage in order to ensure the linearity of the output signal of the differential amplifier means. The method of claim 1, The current compensation means, A first current source having one side connected to the first voltage terminal; A transistor controlled by the control voltage and whose one side is in contact with the other side of the first current source; And A diode connected in a forward direction between the other side of the transistor and a node in contact with the differential amplifying means and the variable current providing means; A gain adjustable adjustable amplifier comprising a. The method of claim 3, wherein The transistor of claim 1, wherein the transistor includes any one of PMOS, NMOS, and BJT. First amplifying means for outputting a signal amplified by a variable gain according to the first control signal; Second and third amplifying means for amplifying the outputs of the first amplifying means with different gains; First and second highest value detecting means for detecting the highest value from each output of the second and third amplifying means; And Comparison means for forming a feedback loop for outputting a second control signal for adjusting the gain of the first amplifying means to the first amplifying means by comparing the outputs of the first highest detecting means and the second highest detecting means. Adjustable gain adjustable amplifier comprising a. The method of claim 5, The comparison means, When the difference between the output of the first highest value detecting means and the second highest value detecting means is equal to or less than a predetermined level, " first logic " And outputting the second control signals each having a "second logic" when the difference between the outputs of the first highest value detecting means and the second highest value detecting means is greater than or equal to a predetermined level. The method of claim 5, The first amplification means, A differential amplifier for generating an output signal in proportion to the difference between the input signals; A variable current providing unit for adjusting a gain of the differential amplifying unit by providing a reference current varying by the first control signal to the differential amplifying unit; A current compensator for compensating the reference current to ensure linearity of the output signal of the differential amplifier according to the variation of the first control signal; A controller for controlling the variable current providing unit; And Output unit for amplifying and outputting the output signal of the differential amplifier A gain adjustable adjustable amplifier comprising a. The method of claim 7, wherein The current compensation unit, Gain-variable control amplifier, characterized in that for reducing the width of the variation of the reference current according to the variation of the first control signal in order to ensure the linearity of the output signal of the differential amplifier means. The method of claim 7, wherein The current compensation unit, A first current source having one side connected to the first voltage terminal; A transistor controlled by the first control signal and whose one side is in contact with the other side of the first current source; And A diode connected in a forward direction between the other side of the transistor and a node in contact with the differential amplifier and the variable current providing unit; A gain adjustable adjustable amplifier comprising a. The method of claim 9, The transistor of claim 1, wherein the transistor includes any one of PMOS, NMOS, and BJT.