JP2001036366A - Gain variable amplifier circuit, gain control circuit and communication equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide desired gain performance such that, for example dependence on temperature is reduced. SOLUTION: In a control circuit 42, plural collector currents I1, I2, I3, ..., In flowing corresponding to an AGC voltage VAGC inputted to the plural differential amplifier circuits of a differential amplifier part 45 are combined and on the basis of a combined composite collector current It, the gain of a variable amplifier circuit 41 is controlled. The plural collector currents I1, I2, I3, ..., In have mutually different temperature dependence and are set to values, so as to decrease the temperature dependence corresponding to the AGC voltage VAGC as a result, when the respective currents are combined. Thus, the temperature dependence of the synthetic collector current It is improved, and finally, the temperature dependence of the gain of the variable amplifier circuit 41 is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable gain amplifier having a gain control function, a gain control circuit for performing variable gain control, and a portable apparatus for performing processing related to signal transmission and reception using the variable gain amplifier. The present invention relates to a communication device such as a telephone.

[0002]

2. Description of the Related Art A gain control circuit controls the output signal of an amplifier circuit to a desired level by variably controlling the gain of the amplifier circuit according to an input signal or the like. A circuit that automatically performs such gain control according to an input signal or the like is called an “AGC (Automatic Gain Control) circuit”. A variable gain amplifier circuit (hereinafter, “A”) that variably amplifies the gain using the AGC function of the AGC circuit.
GC amplifier circuit ". ) Is used in, for example, a signal processing circuit of a mobile phone or the like.

For example, CDMA (Code Division Multip
In the mobile phone of the le access (code division multiple access) system, the transmission power is controlled on the basis of the level of the received signal in order to maintain the strength of the received signal and the intensity of the arrival signal at the base station uniform. ing. More specifically, for example, control is performed so as to increase the level of the signal output of the mobile station as the distance between the mobile station (cellular phone) and the base station increases. In order to perform such control, a mobile phone of the CDMA system requires an AGC amplifier circuit capable of linearly varying the gain by 80 dB or more in the receiving circuit and the transmitting circuit. By reflecting the signal level of the received signal on the transmission power, the CDMA mobile phone maintains communication of 40 or more users assigned to one frequency band.

In order to reflect the signal level of the received signal on the transmission power, it is necessary to operate the AGC amplifier circuit on the transmitting side and the AGC amplifier circuit on the receiving side in conjunction with each other. A input to each AGC amplifier circuit over a wide dynamic range of 80 dB or more.
It is necessary that there be an excellent linearity relationship between the value of the GC voltage and the gain in each AGC amplifier circuit.

FIG. 8 shows a configuration example of a general AGC amplifier circuit used for a CDMA type portable telephone or the like. The AGC amplifier circuit shown in FIG.
And a control circuit 102 for controlling the gain of the variable amplifier circuit 101. In the AGC amplifier circuit shown in FIG.
5, an input signal IN is inputted, and an AGC voltage (gain control voltage) V _AGC is inputted through an input terminal 113 of the control circuit 102. Further, in the AGC amplifier circuit shown in FIG.
The output signal OUT amplified by the variable amplifying circuit 101 is output via the elements 7, 118.

The variable amplifying circuit 101 includes resistors R111 and R112 provided as load resistors, a pair of transistors T107 and T108 provided for amplification, and a transistor T104 serving as a current source in the variable amplifying circuit 101.
And The power supply voltage Vcc is applied to the variable amplifier circuit 101 via the input terminal 116.

In this variable amplifier circuit 101, a resistor R
One ends of 111 and R112 are commonly connected to an input terminal 116 to which the power supply voltage Vcc is applied. Resistance R111
Is connected to the collector terminal of the transistor T107. The other end of the resistor R112 is connected to the transistor T1.
08 is connected to the collector terminal. An output terminal 117 for outputting the output signal OUT is connected between the resistor R111 and the collector terminal of the transistor T107. An output terminal 118 for outputting the output signal OUT is connected between the resistor R112 and the collector terminal of the transistor T108. Transistor T107,
The base terminal of T108 is connected to input terminals 114 and 115 to which the input signal IN is input, respectively. The emitter terminals of the transistors T107 and T108 are commonly connected to the collector terminal of the transistor T104.
The emitter terminal of the transistor T104 is grounded. The base terminal of the transistor T104 is connected to the control circuit 102.

[0008] The control circuit 102 is a circuit for realizing a so-called AGC function for the variable amplifier circuit 101. The control circuit 102 includes a pair of transistors T101 and T10 having a voltage / current conversion function.
2 and a transistor T1 forming a current mirror circuit 104 by the transistor T104 of the variable amplifier circuit 101.
03, and a pair of transistors T109 and T110 forming the current mirror circuit 103. The power supply voltage Vcc is applied to the control circuit 102 via input terminals 111 and 112.

In the control circuit 102, the AGC voltage V is applied to the base terminal of the transistor T101.
An input terminal 113 to which _AGC is input is connected. The collector terminal of the transistor T101 is connected to the current mirror circuit 103. Transistor T101,
The emitter terminal of T102 is commonly connected to a current source Ia that supplies a current having a current value I0. Transistor T1
The fixed voltage VB is applied to the base terminal 02. The input terminal 112 to which the power supply voltage Vcc is applied is connected to the collector terminal of the transistor T102.

The base terminals of a pair of transistors T109 and T110 forming the current mirror circuit 103 are commonly connected to each other. The base terminals of the transistors T109 and T110 are diode-connected to the collector terminal of the transistor T109. The emitter terminals of the transistors T109 and T110 are commonly connected to an input terminal 111 to which the power supply voltage Vcc is applied. The collector terminal of the transistor T109 is connected to the collector terminal of the transistor T101. The collector terminal of the transistor T110 is connected to the collector terminal of the transistor T103. The base terminal of the transistor T103 is
Is connected to the base terminal of the transistor T104, and the current mirror circuit 10 is connected to the transistor T104.
4 are formed. The base terminal of the transistor T103 is diode-connected to its own collector terminal. The emitter terminal of the transistor T103 is grounded.

In FIG. 1, the variable amplifier circuit 101 has one
Although only a single-stage variable amplifying circuit 101 is used,
The variable amount of gain obtained by the above is about 30 to 40 dB. Therefore, in order to realize a variable amount of gain of 80 dB or more required for a normal CDMA mobile phone, a circuit equivalent to the variable amplifying circuit 101 is actually provided by three.
It is necessary to cascade more than one step. In this connection, as shown in the figure, the base terminals of the transistors T105, T106,... Corresponding to the transistor T104 are commonly connected to the base terminal of the transistor T104, and also connected to the base terminal of the transistor T103 in the control circuit 102. Then, similarly to the current mirror circuit 104 formed by the transistor T104, the current mirror circuit is formed by the transistor T103 and the transistors T105, T106,.

In the AGC amplifier circuit having the above configuration,
When the AGC voltage V _AGC is input, the control circuit 1
02 by the voltage / current conversion action of the pair of transistors T101 and T102 in the transistor T101.
Collector current I101 according to the magnitude of GC voltage V _AGC
Flows. Further, the transistor T103 is connected to the transistor T103 by the operation of the current mirror circuit 103.
, A collector current I102 flows in conjunction with the collector current I101. Further, the collector current I in the transistor T103 is applied to the transistor T104 of the variable amplifier circuit 101 by the operation of the current mirror circuit 104.
The collector current I _AGC1 flows in conjunction with 102. When a plurality of variable amplifying circuits 101 are cascaded, the transistors T105 and T10 of another cascaded variable amplifying circuit are connected.
6, the transistor T104 of the variable amplifier circuit 101
Similarly, the collector currents I _AGC2 , I _AGC3 ,... Flow in conjunction with the collector current I102 in the transistor T103.

Here, in the variable amplifier circuit 101,
Theoretically, when the collector current I _AGC1 is controlled exponentially, the gains of the transistors T107 and T108 change linearly. Therefore, the control circuit 102
, If the collector current I101 of the transistor T101 flowing according to the AGC voltage V _AGC is controlled exponentially,
_{Since AGC1} is controlled exponentially, the gain of the transistors T107 and T108 can be controlled linearly. The same applies to other variable amplifier circuits when a plurality of variable amplifier circuits 101 are connected in cascade.

Next, the gain PG [dB] obtained by the above AGC amplifier circuit will be described.

In general, the above-mentioned AGC amplifier circuit has a relationship represented by the following equation (A). In the formula (A), q is a unit charge of an electron, k is a Boltzmann constant, and T is an absolute temperature. Equation (A) shows that the variable amplifier circuit 101 includes a transistor T1 corresponding to a constant current source.
When 04 of the collector current I _AGC1 is exponentially controlled transistor T107, T108 of the power gain PG
[DB] linearly changes.

[0016] _{PGα20log (I AGC1 * q / kT} ) ... (A)

In the above-mentioned AGC amplifier circuit, there is a relationship represented by the following equation (B). In the equation (B), Is is a reverse saturation current of the transistor T104. Equation (B) shows a linearly changing AGC
This shows that the collector current I _AGC1 of the variable amplifier circuit 101 changes exponentially with respect to the voltage V _AGC . Or of formula (A), as can be seen from equation (B), the power gain PG of the AGC amplifier circuit shown in FIG. 8, AGC voltage V _AGC
Also changes linearly in accordance with the linear change of.

[0018] _{I AGC1 αIs * exp (V AGC} * q / kT) ... (B)

[0019]

[Problems to be solved by the invention]

As described above, in the AGC amplifier circuit, the collector current I _AGC1 is theoretically generated in the variable amplifier circuit 101 _.
Is controlled exponentially, the transistor T
The gains of 107 and T108 change linearly. At this time, current I _AGC1 Since is exponentially controlled by transistors T101,102 control circuit 102, power gain PG of the AGC amplifier circuit, AG
It changes linearly according to the linear change of the C voltage _VAGC . Here, it is desirable that the relationship between the AGC voltage V _AGC and the gain of the variable amplifier circuit 101 be kept constant even when the external environment such as temperature changes. However, in the conventional AGC amplifier circuit, as described below, for example, the AGC voltage V
There is a problem that the relationship between the _AGC and the gain of the variable amplifier circuit 101 is broken.

FIG. 9 is a diagram showing the relationship between the AGC voltage V _AGC and the temperature dependence of the collector current I101 of the transistor T101. The horizontal axis represents the AGC voltage V _AGC.
The vertical axis indicates the collector current I101.
FIG. 10 shows the AGC voltage V _AGC and the variable amplifier circuit 10.
FIG. 5 is a diagram showing a relationship between temperature dependency and a gain PG of No. 1, in which a horizontal axis indicates an AGC voltage V _AGC and a vertical axis indicates a gain PG. In these figures, the temperatures are respectively 75 ° C. (reference numerals 104 and 107) and 25 ° C. (reference numerals 10 and 10).
3, 106), 3 at -25 ° C (codes 105, 108)
The relationship between the two cases is shown.

As shown in FIG. 9, the relationship between the AGC voltage V _AGC and the collector current I101 of the transistor T101 is as follows: when the temperature is 75 ° C., when the temperature is 25 ° C., -2.
It is different in the case of 5 ° C. At this time, AG
The relationship is such that the temperature characteristic is substantially symmetrical from the point where the value of the C voltage V _AGC is substantially equal to the fixed voltage VB applied to the base terminal of the transistor T102. For example, when the temperature is 75 ° C., the AGC voltage V
_{When AGC} value is smaller than VB, temperature characteristic is 25 ° C
The collector current I101
Decrease. Conversely, when the value of the AGC voltage V _AGC is higher than VB, the temperature characteristic is positive compared to the case of 25 ° C., and the collector current I101 increases. When the temperature is −25 ° C., the tendency is opposite to the temperature characteristic when the temperature is 75 ° C. AGC
When the value of the voltage V _AGC is VB, the transistor T10
1 is equal to the value of the collector current I101 of the transistor T10.
1, 1/2 of the current value I0 supplied from the current source Ia connected to T102. Note that the collector current I
The cause of the temperature dependency of the transistor 101 is that the transistor T10
This is due to the temperature characteristic of the voltage Vbe between the base and the emitter of the first transistor.

As described above, since the collector current I101 of the transistor T101 with respect to the AGC voltage V _AGC has temperature dependence, the gain PG of the transistors T107 and T108 with respect to the AGC voltage V _AGC is, as shown in FIG. It would have similar temperature dependence as the collector current I101 for V _AGC.

As described above, in the conventional AGC amplifier circuit, since the transistors T101 and T102 having a voltage / current conversion function with respect to the AGC voltage V _AGC have temperature dependence, the gain of the AGC amplifier circuit varies depending on the temperature. And
There is a problem that the slope of the gain PG changes with respect to the AGC voltage V _AGC . Such a temperature dependency becomes a more serious problem particularly when a plurality of variable amplifier circuits 101 are cascaded. Also, if the gain PG with respect to the AGC voltage V _AGC has a large temperature dependency, for example, in a CDMA mobile phone, the transmission power is controlled based on the AGC voltage V _AGC , so that an error in the transmission power due to a temperature change is caused. This causes a problem that communication may be hindered. As described above, conventionally, there has been a problem that a desired gain performance has not always been obtained.

The present invention has been made in view of the above problems, and has as its object to provide a variable gain amplifier circuit and a gain control circuit capable of obtaining desired gain performance such as, for example, reducing temperature dependence. Another object of the present invention is to provide a communication device.

[0026]

According to a first aspect of the present invention, there is provided a variable gain amplifying circuit having a variable amplifying circuit capable of changing a gain and a plurality of differential amplifying circuits connected in parallel to each other. A control circuit that combines a plurality of control currents that flow in accordance with the gain control voltage for gain control input to the differential amplifier circuit, and controls the gain of the variable amplifier circuit based on the combined control current. It is a thing.

In this variable gain amplifier circuit, the control circuit combines a plurality of control currents corresponding to the gain control voltages for gain control input to the plurality of differential amplifier circuits, and combines the control currents with the combined current. Based on this, the gain of the variable amplifier circuit is controlled.

The variable gain amplifying circuit according to the second aspect of the present invention is characterized in that, in the variable gain amplifying circuit according to the first aspect, when respective currents are combined in a plurality of differential amplifying circuits, the temperature dependence on the gain control voltage results. In this case, control currents having different temperature dependencies such that the characteristics are reduced flow.

In this variable gain amplifier circuit, control currents having different temperature dependencies flow through the plurality of differential amplifier circuits, and when the respective currents are combined, the temperature dependency on the gain control voltage decreases as a result. Let me do.

According to a third aspect of the present invention, in the variable gain amplifying circuit according to the first or second aspect, when the respective currents are combined in a plurality of differential amplifying circuits, the gain control voltage is consequently reduced. Control currents having different values from each other flow so as to improve the linearity.

In this variable gain amplifier circuit, control currents having different values flow through a plurality of differential amplifier circuits, and when the respective currents are combined, as a result, the linearity with respect to the gain control voltage is improved.

According to a fourth aspect of the present invention, in the variable gain amplifying circuit according to any one of the first to third aspects, each of the plurality of differential amplifying circuits includes a pair of transistors, The gain control voltage is commonly applied to the differential amplifier circuit via the base terminal of the first transistor of the pair of transistors.

In this variable gain amplifier circuit, in a plurality of differential amplifier circuits each including a pair of transistors,
A gain control voltage is commonly applied through a base terminal of a first transistor of the pair of transistors.

According to a fifth aspect of the present invention, in the variable gain amplifying circuit according to the fourth aspect, a current source for supplying a different current to each of the plurality of differential amplifying circuits is connected. Different values of voltage are applied via the base terminal of the second transistor of the pair of transistors.

In this variable gain amplifier circuit, different currents are supplied to the plurality of differential amplifier circuits, respectively, and the base terminals of the second transistor of the pair of transistors in the plurality of differential amplifier circuits are respectively connected to the plurality of differential amplifier circuits. Since voltages of different values are applied, it is possible to make control currents in a plurality of differential amplifier circuits flowing corresponding to gain control voltages for gain control different from each other. Since the gain of the variable amplifier circuit is controlled based on the current obtained by combining the control currents in the plurality of differential amplifier circuits, the control current in the plurality of differential amplifier circuits is appropriately changed,
The gain can be controlled with desired performance.

According to a sixth aspect of the present invention, in the variable gain amplifying circuit according to the fifth aspect, the voltage value applied to the base terminal of each of the second transistors of the plurality of differential amplifying circuits is V _{1. , V 2, V 3, ...} V n if (n is an integer) to _{"V 1 -V 2 = V 2 -V} 3 = ... = V n-1
−V _n ”.

In this variable gain amplifier circuit, the voltage value applied to the base terminal of each of the second transistors of the plurality of differential amplifier circuits is "V ₁ -V ₂ = V ₂ -V ₃ =... =
By satisfying the conditional expression ₍ Vn _-1- Vn), the temperature dependency on the gain control voltage is mainly improved.

The variable gain amplifying circuit according to claim 7 is the same as the variable gain amplifying circuit according to claim 6, except that “V ₁ −
V ₂ , V ₂ −V ₃ ,..., V _n−1 −V _n ”.

In this variable gain amplifying circuit, the conditional expression "V
_{By making} the values of ₁₋ V ₂ , V ₂ −V ₃ ,..., V _n−1 −V _n partially different, for example, it is possible to partially improve the linearity with respect to the gain control voltage. You.

The variable gain amplifier circuit according to claim 8 is the variable gain amplifier circuit according to claim 5, wherein in the plurality of differential amplifier circuits, the first of each of at least four differential amplifier circuits arranged in series is arranged. Collector currents as control currents flowing through the collector terminals of the transistors are represented by I ₁ , I ₂ ,
... I _n (n is an integer), “(I _n−3 + I _n−2 ) <
(I _n-1 + I _n ) ".

In this variable gain amplifier circuit, in a plurality of differential amplifier circuits, the collector current as a control current flowing through the collector terminal of each first transistor of at least four consecutively arranged differential amplifier circuits is " (I
By satisfying _{n-3 + I n-2} ) <(it n-1 + I n) "condition, linearity is improved with respect to primarily the gain control voltage.

According to a ninth aspect of the present invention, in the variable gain amplifying circuit according to the fourth aspect, the current source is configured to be capable of changing the current supplied to the plurality of differential amplifying circuits. .

In this variable gain amplifier circuit, the current supplied from the current source can be changed as appropriate, for example, the relationship between the gain and the gain control voltage can be changed as appropriate.

According to a tenth aspect of the present invention, there is provided a gain control circuit for controlling a variable amplifying circuit capable of changing a gain, comprising a plurality of differential amplifying circuits connected in parallel with each other. A control circuit that combines a plurality of control currents that flow in accordance with gain control voltages for gain control input to the plurality of differential amplifier circuits, and controls the gain of the variable amplifier circuit based on the combined control current It is provided with.

In this gain control circuit, the control circuit combines a plurality of control currents flowing in accordance with the gain control voltage for gain control input to the plurality of differential amplifier circuits,
The gain of the variable amplifier circuit is controlled based on the combined current.

According to another aspect of the present invention, a communication device is provided in at least one of a transmission device for performing signal processing on a transmission signal, a reception device for performing signal processing on a reception signal, and a transmission device or a reception device. A communication device comprising a variable gain amplifier circuit for variably amplifying a signal, wherein the variable gain amplifier circuit includes a variable amplifier circuit capable of changing a gain, and a plurality of differential amplifiers connected in parallel to each other. A plurality of control currents flowing in accordance with gain control voltages for gain control input to the plurality of differential amplifier circuits, and a gain of the variable amplifier circuit is determined based on the synthesized control current. And a control circuit for controlling.

In this communication device, the control circuit in the variable gain amplifier circuit combines a plurality of control currents flowing in accordance with the gain control voltages for gain control input to the plurality of differential amplifier circuits, and combines the control currents. The gain of the variable amplifier circuit is controlled based on the supplied current. The transmission signal or the reception signal is variably amplified based on the gain controlled by the variable gain amplifier circuit.

[0048]

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

FIG. 1 is a block diagram showing a configuration of a mobile phone as a communication device according to one embodiment of the present invention. In the figure, a CD is used as an example of the configuration of the mobile phone.
The parts having dual modes of the MA system and the FM system are shown mainly with respect to a part handling a high-frequency signal. The mobile phone shown in this figure processes a transmission (TX) circuit 1 that performs signal processing on a transmission signal, a reception (RX) circuit 2 that performs signal processing on a reception signal, and a transmission circuit 1. A modem 3 to which a transmission signal to be transmitted is modulated and output and to which a reception signal processed in the reception system circuit 2 is inputted, a duplexer 4 for separating the transmission signal and the reception signal, and a radiation of a signal radio wave to be transmitted. And a common antenna 5 for receiving signal radio waves from a base station (not shown).

Here, the transmission system circuit 1 and the reception system circuit 2
Correspond to specific examples of the “transmitting device” and the “receiving device” in the present invention, respectively.

The transmission system circuit 1 converts the baseband transmission signal output from the modem 3 into a QPSK (Quadrature Phase S
hift Keying: a QPSK modulation circuit 11 that modulates and outputs an IF (intermediate frequency) transmission signal by four-phase shift, and an IF
Transmits the transmission signal to the transmission side AGC voltage (gain control voltage) V _TX-AGC
AGC amplifier circuit 12 that variably amplifies according to
And a mixer 13 that mixes the amplified IF transmission signal with a local oscillation signal from a local oscillator 16 to convert it to an RF (high frequency) transmission signal and outputs the RF signal, and removes unnecessary signal components included in the RF transmission signal. Bandpass filter 14 for
And a power amplifier (PA) 15 for amplifying the RF transmission signal output from the band-pass filter 14 and outputting the amplified RF transmission signal to the duplexer 4.

The reception system circuit 2 includes a low noise amplifier (LNA) 21 for amplifying the RF reception signal input via the duplexer 4 and a band-pass filter for removing unnecessary signal components included in the RF reception signal. 22 and R
A mixer 23 for mixing the F reception signal with a local oscillation signal from the local oscillator 16 to convert the F reception signal into an IF reception signal, and a CDMA bandpass filter for converting the input IF reception signal into a CDMA signal component. 24 and an F for converting the input IF reception signal into a signal component for FM.
M band-pass filter 25 and selectively input C
A receiving signal for DMA and a receiving signal for FM
A receiving-side AGC amplifier 26 variably amplifies according to a GC voltage (gain control voltage) V _RX-AGC , and a QPSK demodulator 27 for QPSK demodulating the amplified received signal.

Here, each of the transmission-side AGC amplifier circuit 12 and the reception-side AGC amplifier circuit 26 corresponds to a specific example of the “variable gain amplifier circuit” in the present invention.

The modem 3 includes a received signal strength detection circuit (RSSI) 33 for detecting the strength (received strength) of the input received signal, and received strength and strength reference data D11.
And outputs a signal indicative of the difference.
4 and a transmission output correction circuit 35 for controlling the gain of the transmission-side AGC amplifier circuit 12.

The signal indicating the difference from the comparison circuit 34 is supplied to the reception-side AG via a reception-side AGC voltage correction circuit (not shown).
The signal is output to the C amplifier circuit 26. Also,
The signal indicating the difference from the comparison circuit 34 is also output to the transmission output correction circuit 35. The reception-side AGC voltage correction circuit (not shown) outputs the reception-side AGC voltage V _RX-AGC and adjusts the gain of the reception-side AGC amplification circuit 26 so that the difference indicated by the signal from the comparison circuit 34 becomes “0”. Control. The transmission output correction circuit 35 includes the comparison circuit 3
4 based on the signal indicating the difference input from No. 4 and the transmission output correction data D12 separately input so as to control the gain of the transmission-side AGC amplifier circuit 26 by outputting the transmission-side AGC voltage V _TX-AGC. Has become.

Here, the portable telephone according to the present embodiment is always in operation to detect the signal level of the received signal irrespective of the presence or absence of substantial communication. Here, the “substantial communication” refers to communication involving a telephone call. Further, in the present embodiment, the “received signal” includes a signal for simply checking the signal level without an incoming call.

FIG. 2 is a circuit diagram showing a configuration example of an AGC amplifier circuit applied to the transmitting AGC amplifier circuit 12 and the receiving AGC amplifier circuit 26. The AGC amplifier circuit shown in this figure includes a variable amplifier circuit 41 capable of variably amplifying an input signal IN, and a control circuit 42 for controlling the gain of the variable amplifier circuit 41. The input signal IN is input to the AGC amplifier circuit shown in FIG. 10 via input terminals 54 and 55 of the variable amplifier circuit 41, and the transmission-side AGC voltage V _TX-AGC or The receiving-side AGC voltage V _RX-AGC (hereinafter, these voltages are collectively referred to as “AGC voltage V _AGC ”) is input. Also, the AG shown in FIG.
In the C amplifier circuit, an output signal OUT amplified by the variable amplifier circuit 41 is output via output terminals 57 and 58. Here, the control circuit 42 corresponds to a specific example of the “gain control circuit” in the present invention.

The variable amplifier circuit 41 has resistors R11 and R12 provided as load resistors, a pair of transistors T27 and T28 provided for amplification, and a transistor T24 serving as a current source in the variable amplifier circuit 41. ing. The power supply voltage Vcc is applied to the variable amplifier circuit 41 via an input terminal 56.

In the variable amplifier circuit 41, the resistor R1
1 and one end of R12 are commonly connected to an input terminal 56 to which a power supply voltage Vcc is applied. The other end of the resistor R11 is
Connected to the collector terminal of transistor T27.
The other end of the resistor R12 is connected to the collector terminal of the transistor T28. Resistor R11 and transistor T27
And an output terminal 57 for outputting the output signal OUT. An output terminal 58 for outputting the output signal OUT is connected between the resistor R12 and the collector terminal of the transistor T28. The base terminals of the transistors T27 and T28 are connected to input terminals 54 and 55, respectively, to which an input signal IN is input. The emitter terminals of the transistors T27 and T28 are commonly connected to the collector terminal of the transistor T24. The emitter terminal of the transistor T24 is grounded. The base terminal of the transistor T24 is connected to the control circuit 42.

The control circuit 42 includes the variable amplifying circuit 4
1 is a circuit for realizing a so-called AGC function for 1. The control circuit 42 includes a pair of transistors T21 and T22 forming a current mirror circuit 44.
And a transistor T23 forming a current mirror circuit 46 with the transistor T24 of the variable amplifier circuit 41, and a differential amplifier 45 in which a plurality of differential amplifier circuits having a voltage / current conversion action are connected in parallel. , Ra _{n +1} (n is an integer of 2 or more) connected to a plurality of resistors Ra ₁ , Ra ₂ ,. This control circuit 42 includes:
A power supply voltage Vcc is applied via input terminals 51 and 52. A plurality of resistors Ra ₁ , Ra ₂ ,.
Ra _{n + 1} divides the voltage applied to the plurality of differential amplifier circuits of the differential amplifier 45.

The differential amplifier 45 includes a plurality of transistors T
a _1, Ta _2, ..., has a Ta _2n. Differential amplifier 4
5, two transistors (Ta ₁ , T ₁
a ₂ ), (Ta ₃ , Ta ₄ ),... (Ta _2n−1 , Ta _2n )
Are formed as a set, a plurality of differential amplifier circuits are formed, and the plurality of differential amplifier circuits are connected in parallel. The number of stages of the plurality of differential amplifier circuits is
5 is determined according to the dynamic range of the output current It.

Transistor pairs (Ta ₁ , Ta ₂ ), (Ta ₃ , Ta ₄ ),... (Ta
_2n-1, first in the Ta _2n), the emitter terminal of the second transistor, for each set, a current source for supplying different currents respectively Ia _1, Ia _2, ..., are connected in common to Ia _n.

The transistor pairs (Ta ₁ , Ta ₂ ), (T
a ₃ , Ta ₄ ),... (Ta _2n−1 , Ta _2n )
The base terminals of the transistors Ta ₁ , Ta ₃ ,... Ta _2n-1 are connected to the input terminal 53 so that the AGC voltage V _AGC is commonly input. Transistor pairs (Ta ₁ , Ta ₂ ), (Ta ₃ , Ta ₄ ),.
_2n-1, Ta _2n) first transistor Ta _1, T in
The collector terminals of a ₃ ,..., Ta _2n−1 are commonly connected to a current mirror circuit 44.

The transistor pairs (Ta ₁ , Ta ₂ ), (T
a ₃ , Ta ₄ ),... (Ta _2n−1 , Ta _2n )
The collector terminals of the transistors Ta ₂ , Ta ₄ ,... Ta _2n are connected to an input terminal 51 to which a power supply voltage Vcc is applied,
Transistors T21 and T2 in current mirror circuit 44
2 are commonly connected to two emitter terminals. Further, a transistor pair (Ta ₁ , Ta ₂ ), (Ta ₃ , Ta ₄ ),
.. The second transistor T in (Ta _2n-1 , Ta _2n )
a _2, Ta _4, ... each base terminal of Ta _2n, respectively between the resistors Ra ₁ and the resistor Ra _2, between resistors Ra ₂ and the resistor Ra _3, connecting ... between the resistor Ra _n of resistors Ra _{n + 1} Thus, different voltages V ₁ , V ₂ ,..., V _n are applied. The voltages V ₁ , V ₂ ,
..., it will be described in detail later set value of V _n.

[0065] Each of the current sources Ia ₁ for a plurality of differential amplifier circuits, Ia _2, Ia _3, ..., the current value of Ia _n is
For example, I0, I0 / 2, I0 / 4, ..., I0 / 2 ^n-1
Is set to The current sources Ia ₁ , Ia ₂ ,.
The specific configuration example of Ia _n, will be described with reference to the drawings later.

The base terminals of a pair of transistors T21 and T22 forming the current mirror circuit 44 are commonly connected to each other. The base terminals of the transistors T21 and T22 are connected to the transistor T21.
Is diode-connected to the collector terminal. The emitter terminals of the transistors T21 and T22 are connected to the power supply voltage Vcc.
Are connected in common to an input terminal 51 to which is applied. The collector terminal of the transistor T21 is connected to a pair of transistors (Ta ₁ , Ta ₂ ), (Ta
_{3, Ta 4), ... (} Ta 2n-1, Ta 2n first transistor Ta _1), Ta _3, and is connected ... to each collector terminal of Ta _2n-1. The collector terminal of the transistor T22 is connected to the collector terminal of the transistor T23. The base terminal of the transistor T23 is connected to the base terminal of the transistor T24 in the variable amplifier circuit 41, and forms a current mirror circuit 46 with the transistor T24. The base terminal of the transistor T23 is diode-connected to its own collector terminal.
The emitter terminal of the transistor T23 is grounded.

Here, in the present embodiment, as described above, the plurality of differential amplifier circuits in the differential amplifier 45 are:
Different voltages V ₁ , V ₂ ,..., V _n are applied, and different current sources Ia ₁ , Ia ₂ , I
a _3, ..., the current is supplied from Ia _n, transistor pair _{(Ta 1, Ta 2),} (Ta 3, Ta 4), ...
(Ta _2n−1 , Ta _2n ), the first transistor Ta
_1, Ta _3, ... Ta collector current I ₁ flowing through _2n-1, I
_{2, I 3, ..., I} n is a different value.

The collector currents I ₁ , I ₂ , I ₃ ,..., I flowing through the plurality of differential amplifier circuits in the differential amplifier 45
_n is finally added and combined. The combined collector current It is controlled exponentially with respect to the AGC voltage V _AGC by the operation of the differential amplifier circuit. The collector currents I ₁ , I ₂ , I
_3, ..., I _n, when obtained by combining the respective current, resulting such that the temperature dependence of the AGC voltage V _AGC is decreased have different temperature dependencies to each other. The collector current _{I 1, I 2, I 3} , ..., I n , when obtained by combining the respective current result as an AGC voltage V
The currents have different values so that the linearity with respect to the _AGC is improved. Such collector currents _{I 1, I 2, I 3} , ..., for the effects exerted by I _n, with reference to FIG. 5 or the like will be described later. Incidentally, the collector currents _{I 1, I 2, I 3} , ..., I n corresponds to a specific example of "a plurality of control current" in the present invention.

The combined collector current It is input to the variable amplifier circuit 41 via the current mirror circuit 44 and the current mirror circuit 46, and is used for controlling the variable amplifier circuit 41. As described above, in the present embodiment, the collector currents I ₁ , I ₂ , I ₃ ,
..., based on the combined collector current It obtained by combining the I _n,
Transistors T27 and T2 for amplification of the variable amplifier circuit 41
8 is controlled so that the transistor T
27, the gain of T28 is controlled. Therefore, if the temperature dependency and the linearity of the combined collector current It with respect to the AGC voltage V _AGC are improved, the AGC voltage V
The temperature dependence and the linearity of the gain of the variable amplifier circuit 41 with respect to the _AGC are improved.

In FIG. 2, the variable amplifier circuit 41 has only one stage, but the variable amount of gain obtained by the single-stage variable amplifier circuit 41 is about 30 to 40 dB. Therefore, in order to realize a variable amount of gain of 80 dB or more required for a normal CDMA mobile phone, it is actually necessary to cascade three or more circuits equivalent to the variable amplifier circuit 41. . This connection is made by a transistor T24 corresponding to the transistor T24 as shown in FIG.
The base terminals of the transistors T25 and T26 are commonly connected to the base terminal of the transistor T24.
And the transistor T23 and the transistor T23, like the current mirror circuit 46 formed by the transistor T24.
The current mirror circuit is formed by each of T25 and T26.

[0071] Figure 3 is a current source Ia _1, Ia ₂ in the AGC amplifier circuit shown in FIG. 2, ..., is a circuit diagram showing a structural example of a current circuit applied to Ia _n. The current circuit shown in this figure includes a resistor R51 and transistors T51 and T5.
2 and transistors Tb ₁ , Ib ₂ ,..., Tb _n . The current circuit shown in FIG.
Is applied via the power supply voltage Vcc.

In the circuit shown in the figure, one end of a resistor R51 is connected to an input terminal 61 to which a power supply voltage Vcc is applied. The other end of the resistor R51 is connected to a transistor T5
2 collector terminal. Transistor T5
The second base terminal is diode-connected to its own collector terminal. The emitter terminal of the transistor T52 is
It is connected to the collector terminal of transistor T51.
The emitter terminal of the transistor T51 is grounded. The base terminal of the transistor T51 is diode-connected to its own collector terminal.

The base terminal of the transistor T51 is further commonly connected to the base terminals of the transistors Tb ₁ , Ib ₂ ,..., Tb _n . Transistors Tb ₁ and Ib
The base terminals of ₂ ,..., Tb _n are commonly connected to each other. Transistors Tb ₁ , Ib ₂ ,..., T
The respective emitter terminals of b _n are grounded. In the circuit shown in the figure, the transistor Tb _1, T
Each of b ₂ ,..., Tb _n and the transistor T51 form a plurality of current mirror circuits.

[0074] In the circuit shown in the figure, the transistor Tb _1, Ib _2, ..., the collector current of Tb _n, the current source shown in FIG. _{2 Ia 1, Ia 2, Ia} 3, ..., the current Ia _n Is equivalent. Therefore, the transistors Tb ₁ , Tb
_2, Tb _3, ..., the value of the collector current of Tb _n, for example, I0, I0 / 2, I0 / 4, ..., are set to I0 / 2 ^n-1. Such setting of the current value, the transistor Tb _2, Tb _3, ..., the element size of the Tb _n, the element size of the transistor Tb _1, respectively 1/2,
.., 1/2 ⁿ⁻¹ .

Here, the resistor R51 and the transistor T5
2. If the current I51 determined by T51 has a temperature characteristic, a characteristic curve of a combined collector current It shown in FIG.
The amplifier circuit can have any temperature characteristics.

[0076] Figure 4 is a current source Ia _1, Ia ₂ in the AGC amplifier circuit shown in FIG. 2, ..., is a circuit diagram showing another configuration example of the current circuit applied to Ia _n. The current source circuit shown in this diagram is the same as the resistor R51 in the circuit shown in FIG.
Is equivalent to the switch section SW1 and the resistors R57 to R57.
60. Other components are the same as those in the circuit shown in FIG.

In the current circuit shown in the figure, the switch section SW1 has a plurality of switches S1 to S4.
The switches S1 to S4 are, for example, CMOS (Metal-Oxid
e Semiconductor) It is composed of switching elements such as transistors. The switches S1 to S4 are respectively arranged in parallel. One ends of the switches S1 to S4 are commonly connected to an input terminal 62 to which the power supply voltage Vcc is applied. The resistors R57 to R60 are respectively arranged in parallel, and one end is connected to the switches S1 to S4. The other ends of the resistors S1 to S4 are connected to a transistor T
52 is connected to the collector terminal.

In the current source circuit shown in FIG.
The current I51 can be changed by selectively turning on / off 1 to S4. By making the current I51 changeable, the current sources Ia ₁ , Ia ₂ , Ia ₃ ,
..., the transistor Tb ₁ which corresponds to the current of Ia _n, Tb
_Since the collector currents of ₂ ,..., Tb _n are changed, FIG.
The collector currents I ₁ and I ₁ in the differential amplifier 45 shown in FIG.
_2, I _3, ..., is changed I _n, as shown in Figure 5 to be described later, "AGC voltage V _AGC relative to the synthetic collector current It '
The gain PG of the variable amplifying circuit 41 shown in FIG. 2 can be changed while maintaining the slope of “AGC voltage V _AGC vs. gain PG” corresponding to the relationship. For example, by selectively turning on / off the switches S1 to S4 to reduce the current I51, the gain with respect to the AGC voltage V _AGC is maintained while maintaining the slope of “AGC voltage V _AGC vs. gain PG”. P
G can be reduced as a whole. That is, the relationship between “AGC voltage V _{AGC and} combined collector current It” as shown in FIG. 5 described later can be shifted up and down as a whole.

Next, the operation of the portable telephone having the above configuration will be described.

First, the operation at the time of transmission will be described. The baseband transmission signal modulated by the modem 3 is first input to the QPSK modulation circuit 11 of the transmission system circuit 1. The QPSK modulation circuit 11 QPSK-modulates the baseband transmission signal, converts it to, for example, a 130 MHz IF transmission signal, and outputs the IF transmission signal to the transmission-side AGC amplifier circuit 12. Next, the transmission-side AGC amplifier circuit 12 amplifies the IF transmission signal and outputs the amplified signal to the mixer 13. The mixer 13 mixes the amplified IF transmission signal with the local oscillation signal from the local oscillator 16, converts it to, for example, an 800 MHz RF transmission signal, and outputs the RF transmission signal to the bandpass filter 14. The band-pass filter 14 removes an unnecessary signal component included in the RF transmission signal, and outputs the signal to the power amplifier 15. The power amplifier 15 amplifies the RF transmission signal from which the unnecessary signal component has been removed, and outputs the amplified RF transmission signal to the duplexer 4. The RF transmission signal output to the duplexer 4 is radiated from the shared antenna 5 into space.

Next, the operation at the time of reception will be described. The signal radio wave captured by the common antenna 5 is converted into an electric RF reception signal via the duplexer 4 and output to the low noise amplifier 21 of the reception circuit 2. The low noise amplifier 21 amplifies the input RF reception signal and outputs the amplified signal to the bandpass filter 22. The bandpass filter 22 removes an unnecessary signal component included in the RF reception signal and outputs the signal to the mixer 23a. The mixer 23
The RF reception signal is mixed with the local oscillation signal from the local oscillator 16 and converted into, for example, an IF reception signal of 85 MHz,
Output to the CDMA bandpass filter 24 and the FM bandpass filter 25. The CDMA band-pass filter 24 and the FM band-pass filter 25 convert the input IF reception signal into a CDMA signal component and an FM signal component, respectively. The CDMA reception signal and the FM reception signal converted by the CDMA band-pass filter 24 and the FM band-pass filter 25 have only one of the signal components according to the setting mode. The signal is selectively output to the AGC amplifier circuit 26. The reception-side AGC amplification circuit 26 amplifies the selectively input CDMA reception signal or FM reception signal and outputs the amplified signal to the QPSK demodulation circuit 27. QPS
K demodulation circuit 27 performs QPSK demodulation on the amplified received signal and outputs it to modem 3.

The reception intensity (signal level) of the reception signal input into the modem 3 is detected by the reception signal intensity detection circuit 33. A signal indicating the reception strength detected by the reception signal strength detection circuit 33 is output to the comparison circuit 34. The comparison circuit 34 compares the received intensity with the separately input intensity reference data D11, and outputs a signal indicating the difference to the reception-side AGC amplifier circuit 26 via a reception-side AGC voltage correction circuit (not shown). The signal indicating the difference from the comparison circuit 34 is also output to the transmission output correction circuit 35. The reception-side AGC voltage correction circuit (not shown) receives the signal such that the difference indicated by the signal from the comparison circuit 34 becomes “0”, that is, the output of the reception signal strength detection circuit 33 matches the strength reference data D11. It outputs the side AGC voltage V _RX-AGC and controls the gain of the reception side AGC amplifier circuit 26.

The transmission output correction circuit 35 controls the gain of the transmission-side AGC amplifier circuit 12 based on the signal indicating the difference input from the comparison circuit 34 and the separately input transmission output correction data D12. The transmission output correction data D
Reference numeral 12 denotes data according to the line status between the mobile phone and a base station (not shown). Also, the transmission output correction circuit 35
Is controlled by the transmission-side AGC amplifier circuit 12 so that the modulated signal is inversely proportional to the level of the received signal, and is controlled in accordance with the transmission output correction data D12.
_Is output by outputting the transmission side AGC voltage V _TX-AGC .

Next, the transmission side AG which is a characteristic part of the present invention
The operation of the AGC amplification circuit applied to the C amplification circuit 12 and the reception AGC amplification circuit 26 will be described.

In the AGC amplifier circuit shown in FIG.
The voltage V _AGC is input to the differential amplifier 45 of the control circuit 42 via the input terminal 53. More specifically, the AGC voltage V _AGC is _supplied to the transistor pair (Ta ₁ , Ta ₁ ,
Ta ₂ ), (Ta ₃ , Ta ₄ ),... (Ta _2n−1 , T
a _2n ) of the first transistors Ta ₁ , Ta ₃ ,.
Input to each base terminal of _2n-1 . A is used for the differential amplifier 45
When the GC voltage V _AGC is input, the transistor pair (Ta
₁ , Ta ₂ ), (Ta ₃ , Ta ₄ ),... (Ta _2n−1 , T
a _2n ), each transistor T
a _1, Ta _3, ... in Ta _2n-1, the collector current I ₁ corresponding to the magnitude of the AGC voltage _{V AGC, I 2, I 3} , ..., flows I _n.

Here, different voltages V ₁ , V ₂ ,...
With V _n are applied, different current sources I
_{a 1, Ia 2, Ia 3} , ..., because the current from the Ia _n is supplied, the transistor pair _{(Ta 1, Ta 2),} (T
a ₃ , Ta ₄ ),... (Ta _2n−1 , Ta _2n )
Transistors Ta _1, Ta _3, ... in the Ta _2n-1, the collector current of different values _{I 1, I 2, I 3} , ..., flows I _n. Collector currents _{I 1, I 2, I 3} , ..., I n has a different temperature dependent with each other, synthetic collector current It obtained by combining the respective current temperature dependence on the AGC voltage V _AGC as a result Decrease. The collector current _{I 1, I 2, I 3} , ..., I n , when obtained by combining the respective current has a current value that linearity is improved with respect to the AGC voltage V _AGC, synthetic The linearity of the collector current It with respect to the AGC voltage V _AGC is improved.

[0087] collector current _{I 1, I 2, I 3} , ..., I n
Is given as a collector current of the transistor T23 by the operation of the current mirror circuit 44. Due to the action of the current mirror circuit 46, the transistor T24 of the variable amplifier circuit 41
The collector current _IAGC1 flows in conjunction with the combined collector current It flowing through the transistor T23. Variable amplification circuit 41
Are connected in cascade, the transistors T25, T26,... Of the other cascade-connected variable amplifier circuits are linked to the combined collector current It flowing through the transistor T23, similarly to the transistor T24 of the variable amplifier circuit 41. Collector currents I _AGC2 , I _AGC3 ,... _Flow .

Here, in the variable amplifier circuit 41, theoretically, when the collector current I _AGC1 is controlled exponentially, the gains of the transistors T27 and T28 change linearly. Therefore, if the combined collector current It of the transistors Ta ₁ , Ta ₃ ,... Ta _{2n -1} of the differential amplifier 45 flowing in accordance with the AGC voltage V _AGC is controlled exponentially in the control circuit 42, The collector current I _AGC1 in the amplifier circuit 41 is controlled exponentially, and the transistors T27, T2
8 can be linearly controlled. The same applies to other variable amplifier circuits when a plurality of variable amplifier circuits 41 are connected in cascade.

As described above, in the present embodiment, the collector currents I ₁ , I ₂ , I ₂ flowing through the plurality of differential amplifier circuits are provided.
_3, ..., based on the combined collector current It obtained by combining the I _n, transistor for amplification of the variable amplifier circuit 41 T27,
The current of T28 is controlled, and consequently the gain of transistors T27, T28 is controlled. At this time, the temperature dependence and linearity of the combined collector current It with respect to the AGC voltage V _AGC are determined by the collector currents I ₁ , I ₂ , I ₃ ,.
_Since the temperature characteristics and the current value of _n are improved by optimizing the temperature characteristics, the temperature dependence and the linearity of the gain of the variable amplifier circuit 41 with respect to the AGC voltage _VAGC are finally improved.

[0090] Next, with reference to FIGS. 5 to 7, a plurality of collector currents _{I 1, I 2, I 3} , ..., a description will be given of the operation exerted by I _n. In FIGS. 5 to 7,
The horizontal axis indicates the AGC voltage V _AGC [V], and the vertical axis indicates the current [μA]. As shown in these figures, for example, 10 [μA] to 100
The change amount of [μA] corresponds to 20 [dB] of the gain change amount ΔPG per stage of the variable amplifier circuit 41.

FIG. 5 shows the AGC voltage V_AGCFor each kore
Current I₁, I_Two, I_Three, ..., I _nAnd synthetic collections
3 shows the relationship between the current It. The function shown in the figure
In the control circuit 2 shown in FIG.
Is obtained by satisfying the conditional expressions (1) and (2).
Things. In conditional expression (1), V₁, V_Two,
V_Three, ... V_nIs a differential amplifier 45 as shown in FIG.
Of the second transistor Ta_Two, Ta_Four, ... Ta_2nEach
Voltage applied to the source terminal.

V ₁ −V ₂ = V ₂ −V ₃ =... = V _n−1 −V _n (1) (I _n−3 + I _n−2 ) <(I _n−1 + I _n ) (2) )

Here, conditional expression (1) is mainly based on AGC
This contributes to improving the temperature dependency of the combined collector current It with respect to the voltage V _AGC . In conditional expression (1), for example,
V _n-1 -V _n = 50 mV is set. Conditional expression (2) mainly contributes to improving the linearity of the combined collector current It with respect to the AGC voltage V _AGC . As shown in FIG. 5, each collector current I ₁ , I ₂ , I ₃ ,.
_n is not linear with respect to the AGC voltage V _AGC , but according to the conditional expression (2), each collector current I ₁ , I ₂ , I ₃ ,
..., synthetic collector current It obtained by combining the I _n is a straight line with respect to the AGC voltage V _AGC.

Next, the principle of improving the temperature dependency of the combined collector current It will be described with reference to FIGS. 6, the temperature characteristics of the synthetic collector current It, shows the temperature characteristics of the collector current I ₁ in the first-stage differential amplifier of the differential amplifier 45. Below,
The point of V _AGC = 1.9 V in FIGS. 5 and 6 will be described.

As shown in FIG. 5, the combined collector current It at V _AGC = 1.9 V is equal to the collector currents I ₁ and I
₂ , I ₃ and I ₄ . Here, the collector currents I ₁ and I ₂ have negative temperature coefficients at the point of V _AGC = 1.9V. Conversely, the collector current I
₃ and I ₄ have positive temperature coefficients at the point of V _AGC = 1.9V. The negative temperature coefficient is, for example, a coefficient that gives a characteristic that the current output for the same AGC voltage V _AGC decreases when the temperature rises. Further, the positive temperature coefficient is a coefficient that provides a characteristic opposite to the characteristic of the negative temperature coefficient. For example, as shown in FIG. 6, the collector current I ₁ is V _AGC = 1.
At the point of 9 V, the current I _{1B at} the temperature of 75 ° C. is smaller than the current I _1A at the temperature of 25 ° C., indicating that the current I _1B has a negative temperature coefficient. . Note that even if the collector current I ₁ is the same, the AGC
At the position where the voltage V _AGC is different, it has the opposite temperature coefficient. For example, as shown in FIG. 6, the collector current I ₁ is 25 ° C. at the point of V _AGC = 2.0 V.
It can be seen that the current I _1B when the temperature is 75 ° C. is higher than the current I _1A in the case C and has a positive temperature coefficient.

[0096] Thus, by combining the collector currents _{I 1, I 2, I 3} , I 4 having a positive temperature coefficient and negative opposite characteristics, the collector current I ₁ caused by the temperature change, I ₂ (ΔI ₁ + ΔI ₂ ) and the variations (ΔI ₃ + ΔI ₄ ) of the collector currents I ₃ , I ₄ act so as to cancel each other out. As a result, the temperature dependency of the combined collector current It is small. Become. This is clear from the temperature characteristics shown in FIG. That is, the collector current I
₁ alone shows a large difference between a case where the temperature is 25 ° C. (current I _1A ) and a case where the temperature is 75 ° C. (current I _1B ). It has a temperature characteristic of 25 ° C. (current It
A) and the case where the temperature is 75 ° C. (current ItB), the amount of change is small, and the temperature dependency is small.

[0097] In this embodiment, on the basis of small synthetic collector current It temperature dependency was as shown in FIG. 6, the transistor T27, T28 in the variable amplifier 41 is controlled, with respect to the AGC voltage V _AGC Thus, it has excellent gain variable slope and excellent temperature characteristics.

Note that “V ₁ ” shown in the above conditional expression (1) is satisfied.
−V ₂ , V ₂ −V ₃ ,..., V _n−1 −V _n ”are individually set for each of the differential amplifier circuits of the differential amplifying unit 45, so that the AGC voltage _VAGC It is possible to arbitrarily change the slope of the combined collector current It.

FIG. 7 shows an AGC obtained by setting V ₁ -V ₂ = 40 mV and setting 50 mV for the other parts, ie, V ₂ -V ₃ =... = V _n-1 -V _n. It shows the relationship between the voltage V _AGC and the combined collector current It. In the figure, the portion indicated by the symbol It1 corresponds to the characteristic of the combined collector current It shown in FIG. 5, and the portion indicated by the symbol It2 represents the characteristic obtained by setting only V ₁ -V _{2 to} 40 mV. Is shown. In the same figure, the portion indicated by reference numeral I ₁ ′ is V ₁ −V ₂ = 40 m
By by V, shows a change with collector current I ₁ of the characteristic. As described above, when only V ₁ -V ₂ is set to 40 mV, the AGC voltage V _AGC near 2 V
The linearity of the combined collector current It with respect to the AGC voltage V _AGC is improved.

By the way, in a general high-frequency circuit device, in a high frequency range, a change in gain is small at a large current and a change in gain is large at a small current due to the influence of stray capacitance and residual inductance. There is a tendency. Therefore, the AG shown in FIG.
In the C amplifying circuit, for example, the gain of the transistors T27 and T28 of the variable amplifying circuit 41 is AGC voltage _VAGC =
It does not change exponentially with respect to the combined collector current It near 2V. In such a region, the condition of “V ₁ −V ₂ , V ₂ −V ₃ ,..., V _n−1 −V _n ” is made different from the other regions, so that the AGC voltage V
_The gain can be improved so that the slope of the gain with respect to the _AGC becomes linear.

As described above, according to the AGC amplifier circuit or the portable telephone according to the present embodiment, in control circuit 42, AGC voltage V _AGC input to a plurality of differential amplifier circuits in differential amplifier 45 is provided. , I _n, and a plurality of collector currents I ₁ , I ₂ , I ₃ ,..., In flowing in response to the above, and the gain of the variable amplifier circuit 41 is controlled based on the synthesized collector current It. , For example, a plurality of collector currents I ₁ , I ₂ , I ₃ ,
..., by appropriately adjusting the I _n, it becomes possible to obtain a desired gain performance as for example, temperature dependence, etc. is reduced.

[0102] For example, according to this embodiment, a plurality of collector currents _{I 1, I 2, I 3} , ..., when I _n has a different temperature dependent with each other, were synthesized respective current, As a result, the temperature dependency on the AGC voltage V _AGC is set to be reduced.
, The temperature dependency of the combined collector current It for controlling the gain of the variable amplifier circuit 41 can be improved. Further, according to this embodiment, for example, a plurality of collector currents _{I 1, I 2, I 3} , ..., if I _n is, has a different current, obtained by combining the respective current, as a result Since the linearity with respect to the AGC voltage _VAGC is set to be improved, the linearity of the combined collector current It for controlling the gain of the variable amplifier circuit 41 with respect to the AGC voltage _VAGC can be improved. By AG
The linearity of the gain of the variable amplifier circuit 41 with respect to the C voltage V _AGC can be improved.

As described above, according to the portable telephone according to the present embodiment, the linearity and the temperature dependency with respect to the AGC voltage V _AGC are improved. Can be prevented, and a good communication state can be maintained.

The present invention is not limited to the above-described embodiment, and various modifications can be made. For example, in the above embodiment, a case has been described in which operation is performed in the dual mode of the CDMA system and the FM system.
The present invention can also be applied to a case where only one of the MA system and the FM system operates. In addition to the CDMA method and the FM method, for example, TDM
A (Time Division Multiple Access) system and FDMA (Frequency Division Multiple Acc
It can be applied to other types of communication equipment such as the ess (frequency division multiplexing) system. Further, the variable gain amplifier circuit and the gain control circuit of the present invention are applicable not only to communication equipment but also to any other equipment which requires a circuit for controlling the gain inside.

[0105]

As described above, claims 1 to 9 are described.
According to the variable gain amplifier circuit according to any one of the above, the gain control circuit according to claim 10, or the communication device according to claim 11, the control circuit uses the variable gain amplifier circuit for controlling the gain input to the plurality of differential amplifier circuits. A plurality of control currents flowing in accordance with the gain control voltages are combined, and the gain of the variable amplifier circuit is controlled based on the combined control current. By appropriately adjusting the current, it is possible to obtain a desired gain performance in which, for example, the temperature dependency is reduced.

In particular, according to the variable gain amplifying circuit according to the second aspect, in the variable gain amplifying circuit according to the first aspect, when each of the currents is combined with a plurality of differential amplifier circuits, the gain control results. Since the control currents having different temperature dependencies such that the temperature dependency on the voltage is reduced flow, it is possible to improve the temperature dependency of the combined control current for controlling the gain of the variable amplifier circuit. Accordingly, there is an effect that the temperature dependence of the gain of the variable amplifier circuit can be improved.

According to the variable gain amplifying circuit according to the third aspect, in the variable gain amplifying circuit according to the first or second aspect, when the respective currents are combined in a plurality of differential amplifying circuits, a result is obtained. Since the control currents of different values are made to flow such that the linearity with respect to the gain control voltage is improved, the linearity of the combined control current for controlling the gain of the variable amplifier circuit with respect to the gain control voltage is improved. Therefore, the linearity of the gain of the variable amplifier circuit with respect to the gain control voltage can be improved.

In particular, according to the variable gain amplifying circuit according to the fifth aspect, in the variable gain amplifying circuit according to the fourth aspect, a current source for supplying a different current to each of the plurality of differential amplifier circuits is connected. At the same time, voltages of different values are applied via the base terminal of the second transistor of the pair of transistors, so that a plurality of differential amplifiers flowing corresponding to the gain control voltage for gain control are provided. The control currents in the circuits can be made different from each other. Since the gain of the variable amplifier circuit is controlled based on the current obtained by combining the control currents in the plurality of differential amplifier circuits, the gain of the desired performance can be obtained by appropriately varying the control current in the plurality of differential amplifier circuits. Control can be performed.

According to the variable gain amplifier circuit of the eighth aspect, in the variable gain amplifier circuit of the sixth aspect, "V ₁ -V ₂ = V ₂ -V ₃ =... = V _n-1- "V ₁ -V ₂ , V ₂ -V ₃ ,... V _n-1- " in the conditional expression of "V _n ".
Since the value of “V _n ” is made partially different, for example, it is possible to partially improve the linearity with respect to the gain control voltage.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a schematic configuration of a mobile phone as a communication device according to an embodiment of the present invention.

FIG. 2 is a circuit diagram showing a detailed configuration example of an AGC amplifier circuit in the mobile phone shown in FIG.

FIG. 3 is a circuit diagram showing a configuration example of a current circuit applied to a current source in the AGC amplifier circuit shown in FIG.

FIG. 4 is a circuit diagram showing another configuration example of the current circuit applied to the current source in the AGC amplifier circuit shown in FIG.

FIG. 5 is an explanatory diagram showing a control current flowing through each part of the AGC amplifier circuit shown in FIG. 2;

FIG. 6 is a characteristic diagram for describing temperature characteristics of a control current flowing through each unit of the AGC amplifier circuit shown in FIG. 2;

FIG. 7 is an explanatory diagram showing a modification of a method of setting a control current flowing through each part of the AGC amplifier circuit shown in FIG. 2;

FIG. 8 is a block diagram showing a configuration of a conventional general AGC amplifier circuit.

9 is a characteristic diagram for describing temperature dependency of a control current flowing in a control circuit in the AGC amplifier circuit shown in FIG.

FIG. 10 is a characteristic diagram for describing temperature dependency of gain in the AGC amplifier circuit shown in FIG. 8;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Transmission circuit 2 Receiving circuit 3 Modem 4 Duplexer 5 Shared antenna 11 QPSK modulation circuit 12 Transmission side AGC amplifier circuit 15 Power amplifier (PA) 16 Local oscillator 21 Low noise amplifier (LNA) 24 CDMA bandpass filter 25 FM band Pass filter 26 Receiver AGC amplifier circuit 27 QPSK demodulator circuit 33 Received signal strength detection circuit (RSSI) 34 Comparison circuit 41 Variable amplifier circuit 42 Control circuit 44, 46 Current mirror circuit 45 Differential amplifier

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5J066 AA03 AA12 AA43 CA02 CA14 FA05 HA01 HA25 KA02 KA06 KA09 KA44 KA68 MA13 ND24 SA13 TA01 TA02 5J090 AA03 AA12 AA43 AA59 CA02 CA14 CN01 FA05 FN10 FN11 KA08 HA01 HA25 KA68 MA13 MN01 NN06 SA13 TA01 TA02 5J100 AA18 BA05 BB01 BB07 BB22 BC05 CA01 CA05 CA19 CA21 CA31 DA06 FA01 FA02 JA01 LA03 QA01 QA03 SA01 SA02

Claims (11)

[Claims] 1. A variable amplifier circuit capable of changing a gain, a plurality of differential amplifier circuits connected in parallel to each other, and gain control for gain control input to the plurality of differential amplifier circuits. A variable gain amplifier circuit comprising: a control circuit that combines a plurality of control currents that flow in accordance with a voltage, and controls a gain of the variable amplifier circuit based on the combined control current. 2. Control currents having different temperature dependencies, such that when the respective currents are combined, the temperature dependency on the gain control voltage is reduced in the plurality of differential amplifier circuits. 2. The variable gain amplifier circuit according to claim 1, wherein said variable gain amplifier circuit flows. 3. When a plurality of currents are combined in the plurality of differential amplifier circuits, control currents having different values from each other so that linearity with respect to the gain control voltage is improved as a result. 3. The variable gain amplifier circuit according to claim 1, wherein: 4. The plurality of differential amplifier circuits each include a pair of transistors, and the plurality of differential amplifier circuits are connected via a base terminal of a first transistor of the pair of transistors. 4. The variable gain amplifier circuit according to claim 1, wherein a common gain control voltage is applied. 5. A current source for supplying a different current to each of the plurality of differential amplifier circuits, and a base terminal of a second transistor of the pair of transistors. 5. The variable gain amplifier circuit according to claim 4, wherein voltages of different values are applied. 6. A voltage applied to a base terminal of a second transistor of each of the plurality of differential amplifier circuits is represented by V
_{1, V 2, V 3,} ... the (n is an integer) V _n to a satisfies the _{V 1 -V 2 = V 2 -V} 3 = ... = V n-1 -V n conditional expressions The variable gain amplifier circuit according to claim 5. 7. The condition “V ₁ −V ₂ , V ₂ ” in the conditional expression
-V _3, ... variable gain amplifier circuit according to claim 6, wherein the value of V _n-1 -V n "is characterized in that partially different. 8. In the plurality of differential amplifier circuits, a collector current as a control current flowing through a collector terminal of a first transistor of each of at least four differential amplifier circuits arranged in series is defined as I ₁ , I ₂ , ... When I _n (n is an _{integer), (I n-3 +} I n-2) <(I n-1 + I n) variable gain amplifier circuit according to claim 5, characterized by satisfying the condition of . 9. The variable gain amplifier circuit according to claim 4, wherein said current source is configured to change a current supplied to said plurality of differential amplifier circuits. 10. A gain control circuit for controlling a variable amplifier circuit capable of changing a gain, comprising: a plurality of differential amplifier circuits connected in parallel to each other; A control circuit that combines a plurality of control currents that flow in accordance with the gain control voltage for gain control input to the amplifier, and controls the gain of the variable amplifier circuit based on the combined control current. Gain control circuit. 11. A transmission device for performing signal processing on a transmission signal, a reception device for performing signal processing on a reception signal,
A variable gain amplifier circuit variably amplifying the transmission signal or the reception signal, the communication device being provided in at least one of the transmission device and the reception device, wherein the variable gain amplifier circuit has a gain of: A variable amplifier circuit capable of changing, a plurality of differential amplifier circuits connected in parallel to each other, and a plurality of differential amplifier circuits flowing in correspondence with a gain control voltage for gain control input to the plurality of differential amplifier circuits. And a control circuit for controlling the gain of the variable amplifier circuit based on the combined control current.