JPH06244645A - Amplifier circuit - Google Patents

Abstract

PURPOSE:To reduce power consumption at an amplifier. CONSTITUTION:An input signal to a power amplifier 1 is envelope-detected in an input detection part 2. The level of an output signal from the amplifier 1 is attenuated by an attenuator 4 and then envelope-detected in a output detection part 3. Difference between these detected results is detected by a difference detector 5 and the amplifying operation point of the amplifier 1 is changed by an error amplifier 6. Corresponding to this difference, power consumption can be optimized in accordance with output power by changing the amplifying operation point by changing and controlling a voltage impressed to the amplifier 1. Thus, when the output power is low, the power consumption can be suppressed low.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an amplifier circuit, and more particularly to a high frequency band high output amplifier circuit used in mobile communication terminals and the like.

[0002]

2. Description of the Related Art Conventionally, an amplifier circuit of this type has been constructed so that output power can be controlled from the outside. Then, the output power is changed and controlled according to the type of signal to be transmitted such as a control signal and a voice signal.

The conventional amplifier circuit will be described with reference to the drawings. FIG. 3 is a block diagram showing the configuration of a conventional amplifier circuit. In the figure, a conventional amplifier circuit amplifies a signal input to a high frequency input connector 7 and outputs a high frequency output connector 8.
And a high-frequency band high-power amplifier 1 to be sent to, an output detector 3 for envelope-detecting the output of the amplifier 1, and an operational amplifier 9 for amplifying the detected voltage.

Further, the conventional amplifier circuit includes an adder 10 for adding the output of the operational amplifier 9 and the output power change control voltage 200, and a PIN diode attenuator 11 for attenuating the input signal to the amplifier 1 by the added output. It is configured to include.

In the conventional amplifying circuit having such a configuration, the output of the amplifier 1 is detected by the detecting section 3 and the detected voltage is amplified by the operational amplifier 9. Then, by applying the output of the operational amplifier 9 to the PIN diode attenuator 11, negative feedback for keeping the output voltage of the amplifier 1 constant is applied. That is, the well-known ALC (Automatic L)
and an (ever control) circuit will be configured.

An adder 10 is inserted between the operational amplifier 9 and the PIN diode attenuator 11 in the negative feedback loop, and the output voltage change control voltage 200 is applied to the adder 10. As a result, the attenuation amount of the PIN diode attenuator 11 is controlled according to the control voltage, and the output power of the amplifier 1 changes.

That is, in this conventional amplifier circuit, the AL
By inserting an adder in the C circuit, the output power of the amplifier is stabilized and the output power change is controlled.

[0008]

However, in the above-described conventional amplifier circuit, the voltage applied to the amplifier 1 is fixed, and the circuit configuration is such that a stabilized voltage is simply supplied. Therefore, in this conventional amplifier circuit, the voltage applied to the amplifier 1 was not changed under the bias condition (operating condition) at which the maximum set output power could be taken out. There was a drawback that power consumption did not decrease. About this,
Will be described with reference to.

FIG. 4 is a characteristic diagram showing the operation of the amplifier circuit shown in FIG. In the figure, the applied voltage V to the amplifier 1 is
And the applied current I and the output power P of the amplifier 1 are shown. As shown in the figure, in the conventional amplifier circuit, the voltage V applied to the amplifier is always a constant value. That is, even if the input power is attenuated by the PIN diode attenuator 11 as indicated by the arrow, the applied voltage I is changed as indicated by the arrow and the applied voltage V is constant as indicated by the arrow. In the figure, □ is the applied current, ◯ is the applied voltage, and × is the output power.

As a result of the applied current I changing as shown by the arrow, the output power P changes as shown by the arrow, but the applied voltage V remains at a constant value as shown by the arrow. Therefore, even if the PIN diode attenuator 11 is controlled by the output power change control voltage 200 to set it to a low output power, the power consumption does not decrease so much and the power consumption corresponding to the set output power is obtained. There was a drawback that it could not.

The present invention has been made to solve the above-mentioned conventional drawbacks, and an object thereof is to provide an amplifier circuit which can reduce power consumption when a low output power is set.

[0012]

An amplifier circuit according to the present invention comprises a power amplifier for performing power amplification operation, first detecting means for detecting a level of an input signal to the amplifier, and an output signal from the amplifier. A second detection means for detecting the level with a detection sensitivity according to an external command, and an amplification operation of the amplifier according to the difference between the detection result of the second detection means and the detection result of the first detection means. And a change control means for changing the point.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of an embodiment of an amplifier circuit according to the present invention, and the same portions as those in FIG. 3 are designated by the same reference numerals. In the figure, an amplifier circuit according to an embodiment of the present invention has a configuration in which the applied voltage (Vcc) to the amplifier 1 is controlled to change its amplification operating point. An input detection unit 2 and an output detection unit 3 for performing envelope detection are provided respectively, and a difference detector 5 detects the difference between the detection results by these detection units, and the error amplifier 6 outputs the difference to the amplifier 1 according to the detection result. That is, the applied bias voltage of is changed.

The output detector 3 is provided with an attenuator 4, and the output power change control signal 100 to the attenuator 4 controls the sensitivity of the envelope detector of the output detector 3. . That is, the input detection unit 2 and the output detection unit 3 are
In both cases, the signal level is detected by envelope detection. However, since the output detection unit 3 performs envelope detection after it has been attenuated by the attenuator 4, the output power change control signal 100 determines the detection sensitivity. Will be controlled.
Note that it may be attenuated after envelope detection.

In such a configuration, the input power to the amplifier 1 is envelope-detected by the input detection section 2 and converted into a voltage. Further, the output power from the amplifier 1 is the output detection unit 3
After being attenuated by the attenuator 4, the envelope is detected and converted into a voltage. Both of these voltages are input to the difference detector 5 and the difference voltage between them is detected.

The error amplifier 6 operates based on the difference voltage detected by the difference detector 5, and the output voltage of the error amplifier 6 changes so as to correct the difference voltage. Error amplifier 6
Is output to the amplifier 1 as an applied voltage. As a result, negative feedback is applied, and the applied voltage to the amplifier 1 is controlled so that the detected voltage on the input side and the detected voltage on the output side match.

At this time, by setting the absolute value of the attenuation amount of the attenuator 4 to be equal to the gain desired to be set in the amplifier 1,
The gain in the amplifier 1 is set equal to the absolute value of the attenuation amount. Further, in order to correct the above-mentioned error between the input and output detection voltages, negative feedback is applied to the applied voltage Vcc of the amplifier 1 to stabilize the gain of the amplifier.

The operation of the amplifier circuit of this embodiment having such a configuration will be described with reference to FIG. FIG. 2 is a characteristic diagram showing the operation of the amplifier circuit of FIG. In the figure, the applied voltage V1 and applied current I1 to the amplifier 1 and the output power P1 of the amplifier 1 are shown. As shown in the figure, the applied voltage V1 is different from the conventional characteristic diagram (FIG. 4).
The characteristic is that the value changes according to the input power.

Here, when the input power is kept constant and the attenuation amount of the attenuator 4 in the output detector 3 is controlled, the gain of the amplifier 1 changes as shown by the arrow, and the characteristic of the output power P1 becomes as shown by the arrow. It is relatively shifted to P2. As a result, the applied voltage to the amplifier 1 changes as shown by the arrow,
The characteristic of the applied voltage V1 is relatively deviated to V2.

Further, as the applied voltage is changed from V1 to V2, the applied current to the amplifier is I1 as shown by the arrow.
Changes from I2 to I2. This is because the operating point of the transistor, that is, the amplifying operating point is changed by changing the voltage applied to the transistor which is the active element for amplification in the amplifier 1, and the current applied to the transistor is changed. Therefore, according to the configuration of this embodiment, when the attenuation amount in the attenuator 4 is changed, the applied voltage and the applied current to the amplifier 1 also change.

Therefore, since the applied voltage and applied current to the amplifier 1 dynamically change in proportion to the set output power, the power consumption in the amplifier 1 should be optimized according to the set output power. become. Therefore, when the output power is set low, the power consumption can be suppressed lower than that of the conventional circuit, and the power consumption can be significantly reduced.

In short, unlike the conventional system in which the attenuation amount control by the PIN diode attenuator on the input side and the fixed bias to the amplifier are adopted, the power consumption of the amplifier is
It can be optimized according to the set output power. Therefore, not only the mobile communication terminal, but also various devices that require change control of the output power of the high-frequency band high-power amplifier can realize downsizing and low power consumption.

[0024]

As described above, according to the present invention, the envelope detection of the input and output of the amplifier is performed and the amplifier is fed back by the applied voltage according to the difference between the input side and the output side. The output power can be easily changed by stabilizing the output power of the device and controlling the sensitivity of detection, and at the same time, the amplification operating point can be changed by simultaneously changing the voltage and current applied to the amplifier. This has the effect of achieving low power consumption.

[Brief description of drawings]

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

FIG. 2 is a characteristic diagram showing an operation of the amplifier circuit of FIG.

FIG. 3 is a block diagram showing a configuration of a conventional amplifier circuit.

FIG. 4 is a characteristic diagram showing an operation of the amplifier circuit of FIG.

[Explanation of symbols]

 1 Amplifier 2 Input Detection Section 3 Output Detection Section 4 Attenuator 5 Difference Detector 6 Error Amplifier

Claims (4)

[Claims] 1. A power amplifier that performs a power amplification operation, a first detection unit that detects a level of an input signal to the amplifier, and a level of an output signal from the amplifier with a detection sensitivity according to an external command. Second detecting means for detecting, and the second
And a change control means for changing the amplification operating point of the amplifier according to the difference between the detection result of the detection means and the detection result of the first detection means. 2. The change control means controls the operating voltage of the amplifier according to the difference between the detection result of the second detection means and the detection result of the first detection means. The amplifier circuit according to item 1. 3. The first detecting means includes first envelope detecting means for envelope detecting an input signal to the amplifier, and the second detecting means detects an output voltage from the amplifier. 3. The amplifier circuit according to claim 1, further comprising a second envelope detection unit that performs envelope detection. 4. The second detecting means further comprises attenuating means for attenuating the level of the output signal from the amplifier according to the external command, and applying the attenuated output to the envelope detecting means. The amplifier circuit according to claim 3, wherein the amplifier circuit is configured as described above.