JP2001332946A - Amplifier circuit and equipment for movable object communication - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve a problem that the dynamic range of a gain controlled amplifier is different with respect to a control voltage determining a fixed variable range for each gain controlled amplifier, since there is individual dispersion among the gain controlled amplifiers and maximum gain is respectively different with respect to control voltage to be applied to a gain control terminal. SOLUTION: A signal attenuator is connected to the input terminal of the gain controlled amplifier having a gain control terminal, a control voltage variable circuit is connected to the gain control terminal and the signal attenuator and control voltage variable circuit are constituted for complementing increase/decrease of the gain of the gain controlled amplifier caused by the signal attenuator and the control-voltage variable circuit. Thus, while maintaining the gain of the gain-controlled amplifier almost at a fixed value, the dynamic range in the gain-controlled amplifier is controlled.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an automatic gain control (A)
The present invention relates to an amplifier circuit used for GC) and a mobile communication device using the amplifier circuit.

[0002]

2. Description of the Related Art Generally, in a mobile communication device such as a portable telephone, an amplifier for amplifying a transmission signal requires a wide dynamic range. However, as described in Japanese Patent Application Laid-Open No. H11-340743, multistage connection is required. In the configuration in which an attenuator is inserted between the amplifiers to adjust the phase distortion between the front and rear amplifiers,
The gain of the amplifier is reduced, and the dynamic range of the amplifier cannot be adjusted.

An example of a mobile communication device will be described with reference to FIG. 9. The mobile communication device includes a high-frequency transmitting / receiving circuit and a baseband processing circuit. The high-frequency transmission / reception circuit includes a reception circuit unit and a transmission circuit unit that are switched and connected to the antenna 2 by the antenna duplexer 1. The reception circuit section includes a low noise amplifier 3 for amplifying a weak reception signal, and a demodulator 4 for demodulating the reception signal amplified by the low noise amplifier 3.
A local oscillator 5 for providing a frequency signal serving as a reference for demodulation, and an intermediate frequency amplifier 6 for amplifying a baseband received signal demodulated by the demodulator 4 and transmitting the amplified signal to a baseband processing circuit 7. . The transmission circuit section includes an intermediate frequency amplifier 8 for amplifying a baseband transmission signal output from the baseband processing circuit 7, for example, an I signal (in-phase signal) and a Q signal (quadrature signal); A modulator 9 that modulates the transmission signal amplified by 8, for example, performs quadrature modulation, a local oscillator 10 that supplies a frequency signal serving as a reference for modulation, and power-amplifies the transmission signal modulated by the modulator 9. A power amplifier 11, connected between the modulator 9 and the power amplifier 11, and connected to the baseband processing circuit 7;
And a transmission power control amplifier 12 for adjusting the transmission power based on the control voltage from The power amplifier 11 and the transmission power control amplifier 12 constitute a power amplifier circuit. The baseband processing circuit 7 includes a D / A converter, an A / D converter, and a digital signal processor (DSP), and performs various processes on a reception signal and a transmission signal.

[0004] The operation of the above-described mobile communication device will be described. The received signal received by the antenna 2 is input to the low-noise amplifier 3 of the receiving circuit unit via the antenna duplexer 1. The received signal amplified by the low noise amplifier 3 is demodulated into a baseband received signal by the demodulator 4 with reference to the oscillation frequency of the local oscillator 5, and then amplified by the intermediate frequency amplifier 6 to the baseband processing circuit 7. Sent. The baseband processing circuit 7 performs, for example, signal processing such as detection of received power intensity and received frequency, extraction of control signals, decryption of encryption, and error correction, and outputs data signals and audio signals. At the time of transmission, the audio signal and data signal to be transmitted are
The baseband processing circuit 7 performs processing on a signal of a predetermined wireless communication system, such as encryption coding and error correction coding.

[0005] The transmission signal output from the baseband processing circuit 7 is amplified by the intermediate frequency amplifier 8 and sent to the modulator 9. The modulator 9 performs modulation on the basis of the frequency signal generated by the local oscillator 10, and
Generates a transmission signal of a radio frequency determined by the DSP. The transmission power level of the transmission signal is adjusted in the transmission power control amplifier 12. That is, the baseband processing circuit 7
Generates a control voltage for controlling the transmission power from the control signal terminal 7a in accordance with the reception sensitivity determined by the electric field strength of the reception radio wave, the reception frequency, the temperature condition at the time of reception, and the like, and the gain control terminal of the transmission power control amplifier 12 12a to control the gain of the transmission power control amplifier 12. Transmission power control amplifier 12
Is amplified at a constant amplification factor in the power amplifier 11 and transmitted from the antenna 2 via the antenna duplexer 1.

The mobile communication device is required to communicate at a constant quality level regardless of the distance from the base station. For this reason, it is necessary to control the transmission power of the mobile communication device with high accuracy, for example, in the range of 60 to 80 dB, and the power amplifier circuit needs to operate linearly with a wide dynamic range.

[0007]

However, the transmission power control amplifiers 12 constituting the power amplifying circuit have individual variations, and even if the mobile communication devices are manufactured under the same conditions, the transmission power control amplifiers 12 may be different for each mobile communication device. A difference may occur in the transmission power. FIG. 10 shows the characteristics of the gain with respect to the control voltage in the three transmission power control amplifiers.
c is different from each other. That is, in the amplifier of the characteristic curve a, the gain can be adjusted in the range of Ga with respect to the variable range Vc of the control voltage, but the maximum control voltage Vc determined by the power supply voltage
The maximum gain at m is Gam. On the other hand, in the characteristic curves b and c, the variable adjustment gain ranges are Gb and Gb, respectively.
Gc, and the maximum gains are Gbm and Gcm, respectively.
Respectively.

For this reason, even when the baseband processing circuit 7 outputs a control voltage for controlling the transmission power to an appropriate level, the transmission power control amplifier having the characteristic curves a, b and c is used. The transmission powers of the mobile communication devices are different due to individual differences of the transmission power control amplifiers. For this reason, it is conceivable to adjust the maximum gain of the transmission power control amplifier by connecting an attenuator to the input terminal of the transmission power control amplifier. Since the dynamic range changes, it is necessary to readjust the variable range of the control voltage for each transmission power control amplifier.

In addition, the oscillation frequency of the local oscillator 10 may be mixed in the transmission signal modulated by the modulator 9 accompanying the individual variation of the transmission power control amplifier.
There is a disadvantage that the spurious level of the transmission signal transmitted from the mobile communication device differs for each mobile communication device.

[0010]

In order to solve the above-mentioned problems, an amplifier circuit according to the present invention includes a gain control amplifier having a gain control terminal, and is connected to an input terminal of the gain control amplifier to attenuate an input signal. A signal attenuator, and a control voltage variable circuit that is connected to a gain control terminal of the gain control amplifier and varies a control voltage to be applied;
The configuration is such that the amount of change in the control voltage is determined so that the change in gain in the gain control amplifier with respect to the amount of attenuation of the signal attenuator substantially cancels out.

With this configuration, the gain of the gain control amplifier gradually decreases as the attenuation of the signal attenuator gradually increases. However, the gain of the gain control amplifier increases as the amount of change in the potential of the control voltage by the control voltage variable circuit gradually increases. It gradually increases. Since the rate of change of the gain at this time is made substantially equal, even if both the signal attenuator and the control voltage variable circuit are adjusted, the gain of the gain control amplifier remains almost constant.
In this case, since the attenuation of the signal attenuator is adjusted without changing the variable range of the control voltage, the output power variable range (dynamic range) in the gain control amplifier can be adjusted according to the attenuation. Further, when the signal attenuator and the control voltage variable circuit are adjusted according to the magnitude of the power of the input signal input to the amplifier circuit, the output power variable range can be set wide. Then, when the control voltage is varied within the above-described output power variable range, the gain of the gain control amplifier changes.

In the above-mentioned invention, it is preferable that the signal attenuator is formed by a resistance circuit and the control voltage variable circuit is formed by a resistance voltage dividing circuit. This is because the amount of attenuation of the signal attenuator and the amount of change in the potential in the control voltage can be realized by the amount of change in the resistor. For example, this can be realized by linearly increasing or decreasing the resistance value of the resistor, or replacing the resistor with a resistor having a large or small resistance value. In this case, the resistive voltage dividing circuit can be configured by a voltage dividing resistor having a control voltage applied to the gain control terminal with a magnitude that compensates for a decrease in gain of the gain control amplifier due to the resistive circuit. By setting the resistance value of the resistor constituting the resistance voltage dividing circuit to an appropriate value, it is possible to maintain the gain of the gain control amplifier at a constant value.

Further, in the above-mentioned invention, the resistor of the resistor circuit and the voltage-dividing resistor of the resistor voltage dividing circuit can be constituted by variable resistors, and these variable resistors can be varied in conjunction with each other. This eliminates the need to individually adjust the resistor circuit and the resistor voltage divider circuit, and facilitates adjustment of the output power variable range of the gain control amplifier. In this case, the resistor circuit and the resistor voltage divider circuit reduce the gain of the gain control amplifier with respect to the change amount of the variable resistor constituting the resistor circuit, and adjust the gain corresponding to the change amount of the variable resistor in the resistor voltage divider circuit. It is preferable that the configuration be such that the gain is offset by an increase in the gain of the control amplifier. For the resistor circuit and the resistor voltage divider circuit, variable resistors having different rated values can be selected, and the amount of change in the resistance value of each variable resistor is set so that the output power of the gain control amplifier is maintained at a substantially constant value. It is possible to determine.

A mobile communication device according to the present invention includes a high-frequency transmission / reception circuit and a baseband processing circuit, and a transmission circuit of the high-frequency transmission / reception circuit includes a transmission power control amplifier as a preceding stage of a power amplifier. An attenuator for attenuating the transmission signal is connected to the input side of the transmission power control amplifier, and a control voltage variable circuit for varying the control voltage supplied from the baseband processing circuit is connected to the gain control terminal of the transmission power control amplifier. The change of the transmission signal by the attenuator and the change of the control voltage in the control voltage variable circuit are set to values at which the gain of the transmission power control amplifier becomes substantially constant.

[0015] With this configuration, the transmission power at the farthest distance in the definition that communication with the base station is possible, so-called,
The maximum transmission power can be adjusted for each mobile communication device. That is, the maximum gain different for each transmission power control amplifier can be adjusted to ensure the maximum transmission power of the specified value. Further, the spurious mixed into the transmission signal is attenuated by the attenuator, and thus has a level within a specified value.

[0016]

Embodiments of the present invention will be described with reference to the drawings. In FIG. 1, an amplification circuit 20 includes a gain control amplifier 21 having a gain control terminal 21a, and a signal attenuator 2 connected to an input terminal 21b of the gain control amplifier 21.
2 and a control voltage variable circuit 23 connected to the gain control terminal 21a. The signal attenuator 22 and the control voltage variable circuit 23 cooperate with each other to adjust the dynamic range of the gain control amplifier 21.
Is configured. A control voltage source 25 that supplies a control voltage to the gain control amplifier 21 is connected to the control voltage variable circuit 23.

In this configuration, the signal attenuator 22 attenuates the input signal input to the input terminal 20a of the amplifier circuit 20. When the signal attenuator 22 is adjusted alone and its attenuation is changed, the gain of the gain control amplifier 21 increases or decreases linearly or nonlinearly. Further, the control voltage variable circuit 23 varies the level (potential) of the control voltage Vc supplied from the control voltage source 25. When the control voltage variable circuit 23 is independently adjusted and the potential variable range is adjusted, the signal attenuator 22
In contrast to the case, the gain of the gain control amplifier 21 increases or decreases linearly or non-linearly. That is, the signal attenuator 22 and the control voltage variable circuit 23 cooperate with each other, and the signal attenuator 2
2 decreases the input power of the input signal input to the input terminal 21b of the gain control amplifier 21, the control voltage variable circuit 23 controls the control voltage Vic applied to the gain control terminal 21a.
And the gain of the gain control amplifier 21 is maintained at a constant value. In other words, the signal attenuator 22 and the control voltage variable circuit 23 operate in a complementary relationship to compensate for a change in the gain of the gain control amplifier 21, and maintain the gain of the gain control amplifier 21 stably without increasing or decreasing. When the dynamic range variable circuit 24 is adjusted in the stable state of the gain of the gain control amplifier 21, the dynamic range of the gain control amplifier 21 can be varied. The control voltage source 25 can vary the value of the control voltage applied to the gain control terminal 21a of the gain control amplifier 21 within a certain range. This variable range is possible up to a range that gives the maximum gain of the gain control amplifier 21.

FIG. 2 shows the dynamic range D of the amplifier circuit 20, where the power of the input signal input to the input terminal 20a of the amplifier circuit 20 is Pin and the power of the output signal output from the output terminal 20b is Po. The coordinate axis Ra indicates the adjustment amount of the dynamic range variable circuit 24, and the dynamic range D can be changed in the range of Dv by adjusting the dynamic range variable circuit 24. Thus, when a plurality of amplifier circuits 20 are configured, the dynamic range of the gain control amplifier 21 is
Even in the case where each amplifier circuit differs, the dynamic range of each amplifier circuit 20 can be adjusted to match the dynamic range of all amplifier circuits 20.

FIG. 3 shows an embodiment of an amplifier circuit 30 in which a signal attenuator and a control voltage variable circuit are specifically configured.
The same parts as those in the embodiment of FIG. 1 are denoted by the same reference numerals, and the description is referred to. A variable resistor 31 is used as the signal attenuator 22 in FIG.
As 3, a resistance voltage dividing circuit 32 is configured. The variable resistor 31 and the resistance voltage dividing circuit 32 constitute a dynamic range variable circuit. The resistor voltage dividing circuit 32 connects resistors 33 and 34 in series between the gain control terminal 21a of the gain control amplifier 21 and the control voltage source 25, and a connection point between the resistor 33 and the resistor 34 has one end. Variable resistor 35 grounded
Are connected to each other. And the variable resistor 31
The slider 31a of the variable resistor 35 and the slider 35a of the variable resistor 35 work together to increase or decrease the resistance value of the variable resistors 31 and 35.

In this configuration, since the resistance of the variable resistor 31 can be increased by moving the slider 31a, the power of the input signal input to the input terminal 30a of the amplifier circuit 30 should be reduced linearly. Can be. Thereby, as shown in FIG. 4, the gain of the gain control amplifier 21 decreases with a linear gradient k1 with respect to the amount of change of the variable resistor 31. On the other hand, the resistance voltage dividing circuit 32 includes a slider 35 of the variable resistor 35.
By moving a, the voltage at both ends, in other words, the voltage at the connection point between the variable resistors 34 and 35 can be increased. The inside of the gain control amplifier 21 viewed from the gain control terminal 21a may be regarded as high impedance,
Further, the internal impedance does not change depending on the application of the input signal and the control voltage.
Can be regarded as the voltage across the variable resistor 35. In this case, the resistor 33 becomes a protection resistor.

When the resistance value of the variable resistor 35 is increased,
Although the control voltage Vic increases, the gain of the gain control amplifier 21 is adjusted by using a variable resistor such as a gain slope k2 shown in FIG. 4 by using a resistance value in a range in which the control voltage Vic changes linearly. The characteristic increases linearly with respect to the change amount of 35. The gain gradient k2 is determined so as to compensate for the decrease in gain (gradient k1) due to the variable resistor 31 by appropriately determining the resistance values of the resistors 34 and 35 (k1 +
k2 = 0). Therefore, when the variable resistor 31 and the variable resistor 35 are linked and both resistance values are changed at the same time, the gain of the gain control amplifier 21 can be maintained at a constant value as shown by a broken line k in FIG. . Dashed line k in FIG.
2 indicates a dynamic range that can be adjusted by changing the variable resistors 31 and 35. This range corresponds to the dynamic range adjustment range Dv in FIG.
Becomes For example, if the resistance value is set to Rx on the coordinate axis of the resistor R in FIG. 4, the dynamic range becomes Dx, and the dynamic range is adjusted to be narrower by (Dv-Dx).

The gain control amplifier 21 can be configured such that even if the resistance value of the variable resistor 31 changes linearly by itself due to individual variations, temperature characteristics, frequency characteristics, and the like, mainly due to variations at the time of manufacturing. As shown in FIG. 5, the gain gradient k1r may be non-linear. In this case, the resistor voltage dividing circuit 3
2, the gain slope k2r becomes non-linear with respect to the control voltage Vic due to 2. Accordingly, by determining the gain slope k2r with respect to the gain slope k1r in line symmetry, the gain of the gain control amplifier 21 is set to a constant value k as in the linear case of FIG.
Can be determined.

FIG. 6 shows an embodiment in which the amplifier circuit of the present invention is used in a mobile communication device. The same parts as those in the conventional example of FIG. 9 are denoted by the same reference numerals, and the description will be referred to. A signal attenuator 26 is provided between the modulator 9 and the transmission power control amplifier 12.
Is connected. The control signal terminal 7a of the baseband processing circuit 7 and the gain control terminal 1 of the transmission power control amplifier 12
The control voltage variable circuit 27 is connected between the control voltage control circuit 2a and the control voltage variable circuit 27.
The signal attenuator 26 and the control voltage variable circuit 27 cooperate to form a dynamic range variable circuit 28 as in FIG.

In this configuration, the signal attenuator 26 acts to attenuate the power of the transmission signal of the modulator 9 to reduce the gain of the transmission power control amplifier 12, and the control voltage variable circuit 27 Gain control terminal 12a of processing circuit 7
Increases the gain of the transmission power control amplifier 12 by increasing the level of the control voltage supplied by With the addition of the dynamic range variable circuit 28 having such a complementary relation, the output power of the transmission power control amplifier 12 is kept constant, in other words, the power of the transmission signal output from the power amplifier 11 is set to the specified value. The output power variable range can be increased or decreased while maintaining the same. That is, even if the dynamic range of the transmission power control amplifier 12 varies for each mobile communication device, the dynamic range variable circuit 28
Is adjusted, the dynamic range of the transmission power control amplifier 12 can be adjusted without lowering the output power of the transmission power control amplifier 12. Therefore,
In any manufactured mobile communication device, the control power from the baseband processing circuit 7 can control the output power of the transmission power control amplifier 12 within a range of, for example, 0 to -30 dB. Further, since the level of spurious signals input to the transmission power control amplifier 12 is reduced by the signal attenuator 26, the noise level can be kept within a certain range.

In FIG. 3, the signal attenuator and the resistor divider 3
Although the variable resistors 31 and 35 were used for 2, the individual variation of the transmission power control amplifier can be measured, so that the resistance value necessary for the variation correction is obtained by calculation, and the variable resistors 31 and 3 are calculated.
Instead of 5, a fixed resistor or a semi-fixed resistor may be used. Thereby, the signal attenuator and the resistance voltage dividing circuit can be configured at low cost. As shown in FIG. 7, a plurality of resistors 41, 42, 43 having different resistance values are juxtaposed, one end is connected to a common terminal 45, and the other end of the resistors 41, 42, 43 is connected to a switch 44. To the switch terminal 46 via
A switching resistor circuit 40 for switching the resistors 41, 42, and 43 may be configured by these switches, and may be replaced with the variable resistors 31 and 35 in FIG. The switch 44 may be a mechanical changeover switch or an electronic switch using a switching transistor or the like.

FIG. 8 shows an embodiment of an amplifier circuit for automatically adjusting the dynamic range of a gain control amplifier.
The same parts as those in the embodiment of FIG. 1 are denoted by the same reference numerals, and the description is referred to. In the amplifier circuit 50, a dynamic range detection circuit 51 is connected between the output terminal 21c of the gain control amplifier 21 and the output terminal 20b. The dynamic signal detected by the dynamic range detection circuit 51 is input to the CPU 52. The CPU 52 calculates the dynamic range of the gain control amplifier 21 from the dynamic signal, and sends a correction command signal to the controller 53 when the dynamic range is not the predetermined value. The controller 53 controls the signal attenuator 22 and the control voltage variable circuit 23 based on the content of the command signal. That is, the controller 53 controls the amount of attenuation of the signal attenuator 22 and controls the control voltage variable circuit 23.
Control voltage Vic. Also, the CPU 52
Sends a command signal for determining the maximum gain of the gain control amplifier 21 to the control voltage source 25.

In this configuration, while the power of the input signal at the input terminal 20a of the amplifier circuit 50 is maintained at a constant value,
In response to a command from the CPU 52, the control voltage source 25 outputs the maximum value (maximum control voltage) of the control voltage determined by the power supply voltage. As a result, the gain control amplifier 21 shows the maximum gain for the input signal of constant power, and the CPU 52
Recognizes the end of the fluctuation of the dynamic range. The controller 53 determines the amount of attenuation of the signal attenuator 22 based on the recognition contents, and determines the control voltage Vic input to the gain control terminal 21a by the control voltage variable circuit 23, and adjusts the dynamic range of the gain control amplifier 21. . When the amplifying circuit 50 is applied to the mobile communication device of FIG. 6, a control signal terminal 7a of the baseband processing circuit 7 is used instead of the dynamic signal output from the dynamic range detecting circuit 51.
Of the baseband processing circuit 7
This can be realized by adding the function of the CPU 52 to the SP.

[0028]

According to the amplifier circuit of the first aspect, by setting the signal attenuator and the control voltage variable circuit in cooperation with each other,
The dynamic range of the gain control amplifier can be increased or decreased while maintaining the gain of the gain control amplifier at a substantially constant value. Therefore, due to individual variation of the gain control amplifier,
Even if the maximum gains of the gain control amplifiers are different, the dynamic range of the gain control amplifier can be standardized to a predetermined value. There is no need to adjust the variable range of the control voltage for controlling the gain of the control amplifier, and the adjustment of the amplifier circuit is facilitated. Further, by adjusting the signal attenuator and the control voltage variable circuit according to the magnitude of the power of the input signal, a wide dynamic range can be set.

According to the second aspect of the present invention, since the signal attenuator is constituted by a resistor circuit and the control voltage variable circuit is constituted by a resistor voltage dividing circuit, the dynamics of the gain control amplifier can be changed by changing the resistance value of the resistor. By adjusting the range, individual variations of the gain control amplifier can be corrected, and the dynamic range can be expanded and adjusted.

According to the third aspect of the present invention, the voltage dividing resistor constituting the resistance voltage dividing circuit can be set to a desired resistance value, so that the reduction in gain due to the resistance circuit is offset. The resistance of the amplifier can be set to maintain the gain of the gain control amplifier at a constant value.

According to the fourth aspect of the present invention, since the resistor circuit and the resistor voltage dividing circuit are constituted by linked variable resistors, the dynamic range of the gain control amplifier is increased by increasing or decreasing the resistance value of the variable resistor. It can be easily adjusted.

According to the fifth aspect of the present invention, the output power of the gain control amplifier can be maintained at a substantially constant value even when the resistance values of the variable resistors of the resistance circuit and the resistance voltage dividing circuit are changed, and the gain control amplifier can be maintained. Can be easily realized by varying the resistance value of the variable resistor.

According to the mobile communication device of the sixth aspect, by adjusting the attenuator and the control voltage variable circuit, a wide dynamic range is maintained while maintaining the transmission power of the power amplification circuit composed of the transmission power control amplifier and the power amplifier. You can get a range. Therefore, it is possible to transmit with optimal transmission power regardless of whether the mobile communication device is near or far from the base station. Further, even if the maximum gain of the transmission power control amplifier is adjusted by the attenuator, the dynamic range of the transmission power control amplifier in the variable range of the control voltage does not change.
There is no need to readjust the control voltage variable range as in the past,
Adjustment of the transmission power of the mobile communication device is facilitated. Furthermore,
The spurious mixed into the transmission signal input from the modulator to the transmission power control amplifier is attenuated by the attenuator, and can be kept within a specified value.

[Brief description of the drawings]

FIG. 1 is a block diagram of an amplifier circuit according to the present invention.

FIG. 2 is an explanatory diagram of a dynamic range in the amplifier circuit of FIG.

FIG. 3 is a circuit connection diagram showing another embodiment of the amplifier circuit according to the present invention.

FIG. 4 is a characteristic diagram of a gain with respect to a change in a resistance value in the amplifier circuit of FIG. 3;

5 is another characteristic diagram of a gain with respect to a change in a resistance value in the amplifier circuit of FIG. 3;

FIG. 6 is a circuit block diagram of a mobile communication device according to the present invention.

FIG. 7 is a configuration diagram showing another embodiment of the resistance circuit used in the amplifier of FIG. 3;

FIG. 8 is a circuit block diagram showing another embodiment of the amplifier circuit according to the present invention.

FIG. 9 is a circuit block diagram of a conventional mobile communication device.

FIG. 10 is a characteristic curve diagram of gain with respect to control voltage of a gain control amplifier in a conventional mobile communication device.

[Explanation of symbols]

 5, 10 local oscillator 6, 8 intermediate frequency amplifier 7 baseband processing circuit 9 modulator 11 power amplifier 12 transmission power control amplifier 20, 30, 50 amplifier circuit 21 gain control amplifier 21a gain control terminal 22, 26 signal attenuator 23, 27 Control voltage variable circuit 24, 28 Dynamic range variable circuit 25 Control voltage source 31, 35 Variable resistor 32 Resistance voltage dividing circuit

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5J090 AA01 AA41 AA51 CA14 CA32 CA81 CA88 FA08 FA10 GN01 GN07 HA26 HA38 HN14 HN15 KA12 KA48 KA49 MA14 MA22 SA14 TA01 TA02 5J100 AA02 AA03 AA09 AA14 AA16 CA01 BB08 CA29 DA06 EA02 FA01 JA01 KA05 LA09 LA10 QA01 QA02 SA01 5K060 BB07 DD04 HH32 JJ00 JJ02 LL01

Claims (6)

[Claims] 1. A gain control amplifier having a gain control terminal, a signal attenuator connected to an input terminal of the gain control amplifier for attenuating an input signal, and a control connected to and applied to a gain control terminal of the gain control amplifier. A control voltage variable circuit for varying the voltage, wherein the control voltage variable circuit is configured to determine the amount of change in the control voltage so as to substantially cancel the change in gain in the gain control amplifier with respect to the amount of attenuation of the signal attenuator. An amplifier circuit characterized by the above-mentioned. 2. The amplifying circuit according to claim 1, wherein the signal attenuator is constituted by a resistance circuit, and the control voltage variable circuit is constituted by a resistance voltage dividing circuit. 3. The resistance voltage dividing circuit according to claim 2, wherein the control voltage applied to the gain control terminal is constituted by a voltage dividing resistor having a magnitude sufficient to compensate for a decrease in gain of the gain control amplifier due to the resistance circuit. 2. The amplifier circuit according to 1. 4. The variable resistor according to claim 2, wherein the resistor of the resistor circuit and the voltage dividing resistor of the resistor voltage dividing circuit are composed of variable resistors, and these variable resistors are interlocked and varied. 2. The amplifier circuit according to 1. 5. The resistor circuit and the resistor voltage divider circuit correspond to a decrease in the gain of the gain control amplifier with respect to a change amount of the variable resistor constituting the resistor circuit, in accordance with a change amount of the variable resistor in the resistor voltage divider circuit. 5. The amplification circuit according to claim 4, wherein the amplification circuit is configured to offset the gain by increasing the gain of the gain control amplifier. 6. An input side of a transmission power control amplifier in a mobile communication device including a high frequency transmission / reception circuit and a baseband processing circuit, wherein the transmission circuit of the high frequency transmission / reception circuit includes a transmission power control amplifier as a preceding stage of the power amplifier. An attenuator for attenuating a transmission signal is connected to a gain control terminal of the transmission power control amplifier, and a control voltage variable circuit for varying a control voltage supplied from a baseband processing circuit is connected to the transmission power control amplifier. Wherein the amount of change in the control voltage and the amount of change in the control voltage in the control voltage variable circuit are set to values at which the gain of the transmission power control amplifier becomes substantially constant.