JP2003188667A - Multi-stage variable gain amplifier - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce consumption current without deteriorating an input intercept point and improve linearity of a gain in a multi-stage variable gain amplifier. <P>SOLUTION: The multi-stage variable gain amplifier is provided with a first variable gain amplification circuit 1 for controlling the gain by first inside control voltage Vg1, a variable current circuit 3 for changing output current by the first inside control voltage Vg1, a second variable gain amplification circuit 2 inputting a signal amplified by the first variable gain amplification circuit 1, driven by output current of the variable current circuit 3 and controlling the gain by second inside control voltage Vg2, and a gain control signal generating circuit 4 for controlling the first and second inside control voltages Vg1 and Vg2 by outside control voltage Vge. Since the gain control and bias current control of the second variable gain amplification circuit 2 can be separately performed by this constitution, the consumption current can be reduced without deteriorating the input intercept point because the current of the second variable gain amplification circuit 2 is lowered as the gain of the first variable gain amplification circuit 1 of a front stage is lowered and output signal strength is lessened. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to, for example, CDMA.
The present invention relates to a multistage variable gain amplifier used for a (code division multiple access) type mobile phone.

[0002]

2. Description of the Related Art Generally, in a CDMA mobile phone,
The receiving unit has a variable gain amplifier having a dynamic range of 80 dB or more for stable reception according to the received input signal level and the transmitting unit for controlling the transmission output signal level. Since the mobile phone is driven by a battery, it is desirable that the current consumption of the variable gain amplifier is as small as possible.

As a variable gain amplifier whose current consumption changes according to a change in gain, a differential amplifier circuit capable of controlling a gain by changing a bias current is well known. It is not generally used because the distortion characteristic deteriorates and the noise characteristic deteriorates. Therefore, a variable gain amplifier, which is a differential amplifier circuit in which the bias current is constant and which changes the gain by controlling the signal current flowing through the load resistance, is often used. This technology is, for example, "IEEE JOURNAL
OF SOLID-STATE CIRCUITS,
VOL35, NO12, DECEMBER 2000,
PP 1942-1948 ”.

Further, in the one-stage differential amplifier circuit, the range in which the gain can be linearly controlled is about 30 to 40 dB.
In order to obtain a dynamic range of 80 dB or more, a method of cascade connecting two or three stages of differential amplifier circuits of the same type is adopted.

FIG. 9 shows the structure of a conventional multistage variable gain amplifier, where 1 is a first variable gain amplifier circuit and 2 is a variable gain amplifier circuit.
Is a second variable gain amplifier circuit, and 4 is a gain control signal generating circuit. The signal input from IN is amplified by the first variable gain amplifying circuit 1 and the second variable gain amplifying circuit 2, and output from OUT. Further, the external control voltage Vge input from GCIN is converted into the internal control voltage Vg1 by the gain control signal generation circuit 4. The internal control voltage Vg1 is supplied to the variable gain amplifier circuits 1 and 2 in parallel,
The gain is controlled to change linearly in a predetermined external control voltage range.

FIG. 10 shows a conventional example of a variable gain amplifier circuit composed of bipolar transistors. Input terminal Sin
The input signal inputted from the transistor Q35, Q3
It is amplified by the differential circuit consisting of 6 and each collector current is Q3.
The differential circuit composed of 1 to Q34 causes only a fixed ratio of current to flow through the load resistors R31 and R32, so that the output signal level is controlled and output from the output terminal Sout. As for the gain, the internal control voltage Vg1 is set by the transistors Q31 to Q34.
It can be changed by controlling the balance of.

[0007]

However, in the above-mentioned conventional configuration, a constant current always flows even when the gain is set so that the non-linear distortion characteristic and the noise characteristic are not required, so that excessive power is consumed more than necessary. There is a problem that the battery life of the mobile phone is shortened.

An object of the present invention is to solve the above-mentioned conventional problems, and an object thereof is to provide a multi-stage variable gain amplifier capable of changing current consumption depending on a gain setting state.

[0009]

In order to achieve this object, a multistage variable gain amplifier according to the present invention comprises a first variable gain amplifier circuit whose gain is controlled by a first internal control voltage, and the first variable gain amplifier circuit. Of the variable current circuit whose output current changes according to the internal control voltage of the second internal control voltage and the signal amplified by the first variable gain amplifier circuit are input and driven by the output current of the variable current circuit. And a gain control signal generating circuit for controlling the first and second internal control voltages by an external control voltage.

With this configuration, it is possible to obtain a multistage variable gain amplifier capable of changing the current consumption depending on the gain setting state.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION According to the first aspect of the present invention, the gain is controlled by the first internal control voltage.
Variable gain amplifier circuit, a variable current circuit whose output current changes according to the first internal control voltage, and a signal amplified by the first variable gain amplifier circuit, and an output current of the variable current circuit. A second variable gain amplifier circuit driven by a second internal control voltage and having a gain controlled by a second internal control voltage; and a gain control signal generation circuit for controlling the first and second internal control voltages by an external control voltage. It is characterized by that.

Therefore, according to the multistage variable gain amplifier of the first aspect of the present invention, the gain control and the bias current control of the second variable gain amplifier circuit can be separately performed.
For this reason, the current of the second variable gain amplifier circuit can be set to decrease as the gain of the first variable gain amplifier circuit in the previous stage decreases and the output signal strength decreases, so that the non-linear distortion characteristic deteriorates. It is possible to reduce the current consumption without doing so.

The invention according to claim 2 of the present invention comprises a mixer circuit for frequency-converting the signal amplified by the first variable gain amplifier circuit, and the signal after frequency conversion is supplied to the second variable gain amplifier circuit. It is characterized by being input. As a result, even in the variable gain amplifier circuits that operate in different frequency bands, the current of the second variable gain amplifier circuit decreases as the gain of the first variable gain amplifier circuit in the previous stage decreases and the output signal strength decreases. Therefore, the consumption current can be reduced without deteriorating the non-linear distortion characteristic.

According to a third aspect of the present invention, the first and second internal control voltages do not change at the same time, and the gain of the first variable gain amplifier circuit is controlled by the first internal control voltage. And the second internal control voltage is changed after the output current of the variable current circuit decreases.
As a result, in the state where the gain of the second variable gain amplifier circuit is controlled, the current consumption during that period is sufficiently small, so that the average value of the current consumption over the entire external control voltage range can be reduced. it can.

According to a fourth aspect of the present invention, the gain of the first variable gain amplifier circuit is configured to have a constant minimum value in a partial range of the external control voltage. As a result, the gain control range of the second variable gain amplifier circuit is
Since the gain of the first variable gain amplifier circuit can be adjusted to a range in which the minimum value is constant, the overall gain of the multistage variable gain amplifier can be linearly changed in a wide range of the external control voltage.

According to a fifth aspect of the present invention, in the first variable gain amplifier circuit, a resistor and a capacitor are connected in parallel between respective collectors, and a resistor is connected between at least one collector and a constant voltage terminal. The first internal control voltage is applied between the respective bases, a signal is input from the common emitter, and a signal is output from the other collector. As a result, the resistance and the capacitance connected between the collectors of the differential transistor pair can be set to be similar to the resistive impedance and the parasitic capacitance of the element and the line connected to the collector that outputs the signal. Even if the gain of the first variable gain amplifier circuit changes, frequency dependence of the transfer characteristic can be prevented.

According to a sixth aspect of the present invention, the variable current circuit has a configuration in which the output current does not drop below a certain value with respect to a change in the external control voltage. This allows
It is possible to prevent the circuit from becoming inoperative because the bias current of the second variable gain amplifier circuit is completely eliminated.

Embodiments of the present invention will be described in detail below with reference to the drawings.

(Embodiment 1) FIG. 1 shows the configuration of a multistage variable gain amplifier according to Embodiment 1 of the present invention. In FIG. 1, 1 is a first variable gain amplifier circuit,
Reference numeral 2 is a second variable gain amplifier circuit, 3 is a variable current circuit, and 4 is a gain control signal generating circuit.

The signal input from the input terminal IN is the first
Variable gain amplifier circuit 1 and second variable gain amplifier circuit 2
Is amplified by and output from the output terminal OUT. The gain of the first variable gain amplifying circuit 1 is controlled by the internal control voltage Vg1, and the gain of the second variable gain amplifying circuit 2 is the internal control voltage Vg1.
It is controlled by g2. Internal control voltages Vg1 and Vg2
Is controlled in the gain control signal generation circuit 4 according to the external control voltage Vge input from the external control voltage input terminal GCIN. The output current of the variable current circuit 3 supplies the bias current of the second variable gain amplifier circuit 2, and the output current thereof depends on the internal control voltage Vg1 for controlling the gain of the first variable gain amplifier circuit 1. Change.

Next, the circuits of the first variable gain amplifier circuit 1, the second variable gain amplifier circuit 2 and the variable current circuit 3 will be described in detail with reference to FIGS.

First, a circuit diagram of the first variable gain amplifier circuit 1 is shown in FIG. Resistor R3 and capacitance C1 are transistor Q
1 and Q2 are connected in parallel to each other, a resistor R2 is connected between the collector of the transistor Q2 and the power supply terminal VCC, and the emitters of the transistors Q1 and Q2 are commonly connected. Configuration,
A first internal control voltage Vg1 is applied between the bases of the transistors Q1 and Q2, a signal is input from the common emitter, and a signal is output from the collector of the transistor Q1.

The resistor R1 may or may not be additionally connected for gain adjustment. In FIG. 3, a differential transistor pair composed of the transistors Q4 and Q5 is similarly configured so that the input signal and the output signal can be handled in the two-phase format, the two-phase signal is input from the input terminal IN, and the output terminal OUT. However, it is also possible to use only one pair of differential transistor pairs for single-phase operation.

When the first internal control voltage Vg1 is positive and the gain is maximum, the signal current input from the input terminal Sin flows through the transistors Q1 and Q4 and is output from the output terminal Sout connected to the collector. . When the first internal control voltage Vg1 is negative and the gain is minimum, the input terminal Sin
The signal current input from the transistors flows through the transistors Q2 and Q3, and the collectors of the signal currents form resistors R3 and R6 and capacitors C1 and C2.
It is attenuated through the output and output from the output terminal Sout.

Next, a circuit diagram of the second variable gain amplifier circuit 2 is shown in FIG. The configuration is similar to that of the conventional variable gain amplifier circuit shown in FIG. 10, and the input signal input from the input terminal Sin passes through the DC blocking capacitors C11 and C12 and is amplified by the differential circuit including the transistors Q17 and Q18. , The output signal level of each collector current is controlled by the differential circuit composed of Q13 to Q16 so that only a constant current flows through the load resistors R18 and R19, and is output from the output terminal Sout.

The gain is variable by controlling the balance of the transistors Q13 to Q16 by the internal control voltage Vg2. Unlike the conventional example, the currents flowing in the transistors Q17 and Q18 are the same as those in the transistors Q11 and Q12 and the resistor R1.
It is controlled by the bias circuit composed of 1 to R14, and is changed by the bias current Ibias.

Subsequently, a circuit diagram of the variable current circuit 3 is shown in FIG. By inputting the internal control voltage Vg1 to the bases of the differential transistors Q21 and Q22 biased by the constant current I21, the collector current of the transistor Q22 is adjusted, and the current flows through the current mirror circuit composed of the transistors Q23 and Q24. After that, it is output as the output current Ibias. The current of the constant current circuit I22 is also added to the output current.

The operation of the multistage variable gain amplifier according to the first embodiment configured as described above will be described below with reference to FIGS. 6 to 8. FIG. 6 shows how the internal control voltages Vg1 and Vg2 change with respect to the external control voltage Vge. The internal control voltage Vg1 changes to a,
The internal control voltage Vg2 changes according to b. As the external control voltage Vge is lowered, the internal control voltage Vg1 starts to decrease before the internal control voltage Vg2.

FIG. 7 is a diagram showing how the gains of the first variable gain amplifier circuit 1 and the second variable gain amplifier circuit 2 change. The gain of the first variable gain amplifying circuit 1 changes according to c and the gain of the second variable gain amplifying circuit 2 changes according to d, and the change of the overall gain of the multistage variable gain amplifier including the two variable gain amplifying circuits is changed. Is as in e.

FIG. 8 is a diagram showing the current consumption of the entire multistage variable gain amplifier and the change in the input intercept point representing the non-linear distortion characteristic. The current consumption changes according to f and the input intercept point changes according to g.

As described above, according to the first embodiment, as shown in FIG. 6, the first and second internal control voltages Vg1, Vg are set.
g2 does not change at the same time, and the first internal control voltage Vg1
After the gain of the first variable gain amplifier circuit 1 and the output current of the variable current circuit 3 are decreased by the above, the second internal control voltage V
With the configuration in which g2 is changed, as shown in FIG. 8, in the state where the gain of the second variable gain amplifier circuit is controlled, the current consumption during that period is sufficiently small. Therefore, it is possible to significantly reduce the average current consumption over the entire gain control range. Moreover, since the gain of the first variable gain amplifier circuit 1 and the output current of the variable current circuit 3 decrease at the same time, the input intercept point does not deteriorate even in the control voltage range where the current consumption is small.

Further, as shown in FIG. 7C, the gain of the first variable gain amplifier circuit 1 is configured to have a constant minimum value in a partial range of the external control voltage Vge. Thereby, the gain control range of the second variable gain amplifier circuit 2 is
Since the gain of the first variable gain amplifier circuit 1 can be adjusted to a range in which the minimum value is constant, the overall gain of the multistage variable gain amplifier can be linearly changed in a wide range of the external control voltage.

Further, as shown in FIG. 3, in the first variable gain amplifier circuit 1, the path through which the signal flows among the transistors Q1 to Q4 changes depending on the value of the first internal control voltage Vg1. In general, the element and the line connected to the output terminal Sout have a capacitive impedance, so that when the gain is reduced, the signal passes through the resistors R3 and R6, so that the high frequency signal is attenuated and the frequency characteristic is deteriorated. However, by connecting the capacitors C1 and C2 to the resistors R3 and R6 in parallel, it is possible to prevent the frequency dependence of the transfer characteristic from occurring.

Let cL be the value of the capacitive impedance connected to the output terminal Sout, r1 be the values of the resistors R1 and R5, r3 be the values of the resistors R3 and R6, c1 be the values of the capacitors C1 and C2, and ω be the operating angular frequency. Y1 = jωc1 + 1 / r3, Y
If 2 = jωcL + 1 / r1 is set, the attenuation caused by passing through the resistors R3 and R6 is 1 / Y2 / (1 / Y1 + 1 /
Y2), which varies depending on the angular frequency ω. Capacity C
If the value c1 of 1 and C2 is selected so that c1 = (r1 / r3) · cL, the attenuation becomes 1 / (1 + r3 / r1), which is a constant value regardless of the frequency. In this way, the capacitance C1,
When C2 is present, the effect that the frequency dependence of the transfer characteristic does not occur is clear. In addition, since the first variable gain amplifier circuit 1 shown in FIG. 3 is configured to supply the bias current from the input terminal Sin, it is possible to share the bias current with the block in the previous stage, and it is easy to reduce the current consumption. There is also an advantage.

Moreover, the variable current circuit 3 has the configuration shown in FIG. 5, so that the output current does not drop below the current value of the constant current source I22 even if the external control voltage Vge changes. This can prevent the bias current of the second variable gain amplifier circuit 2 from running out and the circuit from becoming inoperative.

(Second Embodiment) Next, FIG. 2 shows a configuration of a multistage variable gain amplifier according to a second embodiment. The first variable gain amplifying circuit, the second variable gain amplifying circuit, the second variable gain amplifying circuit, the variable current circuit, and the gain control signal generating circuit of 1, 2, 3 and 4 have the same configurations and functions as those of the first embodiment. The second embodiment further includes a mixer circuit 5,
First variable gain amplifier circuit 1 and second variable gain amplifier circuit 2
Placed between.

The signal amplified by the first variable gain amplifier circuit 1 is mixed by the mixer circuit 5 with the local signal input from the local terminal LO, frequency-converted, and then input to the second variable gain amplifier circuit 2. Take a configuration. As a result, even in the variable gain amplifier circuits that operate in different frequency bands, as the gain of the first variable gain amplifier circuit 1 in the preceding stage decreases and the output signal strength decreases, the second variable gain amplifier circuit 2 Since the current is reduced, the current consumption can be reduced without deteriorating the non-linear distortion characteristic.

In the above description of the first and second embodiments, the multi-stage variable gain amplifier has the two-stage configuration including the first and second variable gain amplifying circuits. However, the multi-stage variable gain amplifier has three or more stages. It goes without saying that it is acceptable.

[0039]

As described above, according to the multistage variable gain amplifier according to the first aspect of the present invention, the gain control and the bias current control of the second variable gain amplifier circuit can be performed separately. For this reason, the gain of the first variable gain amplifier circuit at the preceding stage is lowered, and the current of the second variable gain amplifier circuit can be set to be lowered as the output signal strength is reduced, so that the nonlinear distortion characteristic is not deteriorated and consumed. The current can be reduced.

According to the second aspect of the present invention,
The signal amplified by the first variable gain amplifier circuit is frequency-converted by the mixer circuit and then input to the second variable gain amplifier circuit. As a result, even in the variable gain amplifier circuits that operate in different frequency bands, the current of the second variable gain amplifier circuit decreases as the gain of the first variable gain amplifier circuit in the preceding stage decreases and the output signal strength decreases. Therefore, the consumption current can be reduced without deteriorating the non-linear distortion characteristic.

According to the invention of claim 3 of the present invention,
The first and second internal control voltages do not change at the same time,
The second internal control voltage is changed after the gain of the first variable gain amplifier circuit and the output current of the variable current circuit are reduced by the first internal control voltage. As a result, in the state where the gain of the second variable gain amplifier circuit is controlled, the current consumption during that period is sufficiently small, so that the average value of the current consumption over the entire external control voltage range can be reduced. it can.

According to the invention of claim 4 of the present invention,
The gain of the first variable gain amplifier circuit is configured to have a constant minimum value in a partial range of the external control voltage. As a result, the gain control range of the second variable gain amplifier circuit can be adjusted to the range in which the gain of the first variable gain amplifier circuit is constant at the minimum value, so that the entire multi-stage variable gain amplifier can be used in a wide range of the external control voltage. The gain can be changed linearly.

According to the invention of claim 5 of the present invention,
The first variable gain amplifier circuit includes a differential transistor pair in which a resistor and a capacitor are connected in parallel between collectors and a resistor is connected between at least one collector and a constant voltage terminal, and the first variable gain amplifier circuit is provided between the bases. Internal control voltage of
A signal is input from the common emitter and a signal is output from the other collector. As a result, the resistance and the capacitance connected between the collectors of the differential transistor pair can be set to be similar to the resistive impedance and the parasitic capacitance of the element and the line connected to the collector that outputs the signal. Even if the gain of the first variable gain amplifier circuit changes, frequency dependence of the transfer characteristic can be prevented.

According to the invention of claim 6 of the present invention,
The variable current circuit is configured such that the output current does not drop below a certain value with respect to the change in the external control voltage. As a result, it is possible to prevent the circuit from becoming inoperative because the bias current of the second variable gain amplifier circuit is completely lost.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a multistage variable gain amplifier according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram of a multistage variable gain amplifier according to a second embodiment of the present invention.

FIG. 3 is a circuit diagram of a first variable gain amplifier circuit 1 in FIG.

FIG. 4 is a circuit diagram of a second variable gain amplifier circuit 2 in FIG.

5 is a circuit diagram of a variable current circuit 3 in FIG.

FIG. 6 is a diagram showing how internal control voltages Vg1 and Vg2 in FIG. 1 change.

FIG. 7 is a diagram showing how the gain of each stage in FIG. 1 changes.

FIG. 8 is a diagram showing changes in current consumption and input intercept point in FIG. 1.

FIG. 9 is a configuration diagram of a conventional multistage variable gain amplifier.

FIG. 10 is a circuit diagram of a variable gain amplifier circuit in FIG.

[Explanation of symbols]

1 First variable gain amplifier circuit 2 Second variable gain amplifier circuit 3 Variable current circuit 4 Gain control signal generation circuit 5 mixer circuit IN input terminal OUT output terminal GCIN External control voltage input terminal LO local terminal

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 5J069 AA01 AA12 CA21 CA36 FA10                       HA08 HA25 HA29 HA32 KA00                       KA02 KA05 KA08 MA08 MA21                       SA13 TA01 TA02                 5J100 JA00 LA00 QA01 QA03 SA01                       SA02                 5J500 AA01 AA12 AC21 AC36 AF10                       AH08 AH25 AH29 AH32 AK00                       AK02 AK05 AK08 AM08 AM21                       AS13 AT01 AT02

Claims (6)

[Claims] 1. A first variable gain amplifier circuit whose gain is controlled by a first internal control voltage, a variable current circuit whose output current is changed by the first internal control voltage, and said first variable gain. A second variable gain amplifier circuit, to which the signal amplified by the amplifier circuit is input, is driven by the output current of the variable current circuit, and whose gain is controlled by a second internal control voltage; A multi-stage variable gain amplifier, comprising: a gain control signal generating circuit for controlling the first and second internal control voltages. 2. A mixer circuit for frequency-converting the signal amplified by the first variable gain amplifier circuit, wherein the frequency-converted signal is input to the second variable gain amplifier circuit. 1. The multistage variable gain amplifier according to 1. 3. The first and second internal control voltages do not change at the same time, and the first internal control voltage reduces the gain of the first variable gain amplifier circuit and the output current of the variable current circuit. 3. The multistage variable gain amplifier according to claim 1, wherein the second internal control voltage is changed later. 4. The gain of the first variable gain amplifier circuit has a constant minimum value in a partial range of the external control voltage, according to claim 1. Multi-stage variable gain amplifier. 5. The first variable gain amplifier circuit includes a differential transistor pair in which a resistor and a capacitor are connected in parallel between collectors and a resistor is connected between each collector and a constant voltage terminal, and each base has a base. The first internal control voltage is applied between them, a signal is input from a common emitter, and a signal is output from one collector, The multistage according to any one of claims 1 to 4. Variable gain amplifier. 6. The multi-stage variable gain amplifier according to claim 1, wherein the variable current circuit has an output current which does not drop below a certain value with respect to a change in an external control voltage. .