JPH02291709A - Power amplifier circuit - Google Patents

Abstract

PURPOSE:To simplify the overall structure of a power amplifier circuit and also to reduce the overall size of the circuit by controlling the output of a 1st amplifier circuit based on the detection output of a 2nd detection circuit and to keep the output of the 1st amplifier circuit at a fixed level when both 1st and 2nd amplifier circuits are actuated at one time. CONSTITUTION:A circuit part consisting of a 2nd detection circuit 4b and a 2nd amplifier circuit 5b is connected to a high frequency output terminal 7' for increase of the transmission power. Thus the output of a 1st amplifier circuit 5a serves as the input of the circuit 5b. Then the circuit 5b amplified more the output of the circuit 5a and outputs it to a high frequency output terminal 7. As a result, the output of the circuit 5b ds partly detected by a 2nd detection circuit 4b and inputted to a switch circuit 8 as the DC voltage proportional to the output power. The output of the circuit 8 is switched to the detection output of the circuit 4b from that of the circuit 4a and inputted to a maintaining circuit 3A to perform the control in order to always keep the output of the circuit 5a at a fixed level.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention is a power amplification device that is used in a wireless telephone device, etc., and is capable of selectively generating one of a plurality of outputs of different levels. Regarding circuits.

(Prior Art) In recent years, improvements have been made in the miniaturization of wireless telephone devices and the like in consideration of portability, but this has resulted in limitations on battery capacity and the inability to obtain sufficient transmission power in many cases. It's coming.

For this reason, for example, when this type of portable radio telephone device is used as a vehicle-mounted radio telephone device that requires greater transmission power, it is common to connect a booster to increase the output.

FIG. 2 shows the main circuit configuration of a conventional radio telephone device used for such operation, which includes a reference voltage group generation circuit 1, a first selection circuit 2a, a first maintenance circuit 3a, a A circuit portion consisting of a detection circuit 4a and a first amplifier circuit 5a corresponds to the main body of the radio telephone device, and includes a second selection circuit 2b, a second maintenance circuit 3b, a second detection circuit 4b, and a second amplifier circuit 5.
The circuit portion consisting of b corresponds to the booster.

When this wireless telephone device is used for operation that does not require much transmission power (for example, for portable use), the second amplifier circuit 5b
The first amplifier circuit 5a is operated in a state where the booster circuit portion including the booster circuit section is not connected.

At this time, the radio frequency signal input from the high frequency input terminal 6 is amplified by the first amplifier circuit 5a, and the radio frequency signal input from the high frequency output terminal 7 is amplified by the first amplifier circuit 5a.
′ is output.

Along with this, a part of the output of the first amplifier circuit 5a is
The signal is detected by the detection circuit 4a, and is input to the first maintenance circuit 3a as a DC voltage proportional to its output.

On the other hand, the reference voltage group generating circuit 1 is provided with reference voltage groups corresponding to a plurality of output levels, one of which is selected by the first selection circuit 2a and sent to the first sustaining circuit 3.
input to a.

Here, the first sustaining circuit 3a monitors the difference between the reference voltage selected by the first selection circuit 2a and the DC voltage detected by the first detection circuit 4a, and amplifies the difference voltage. By applying voltage to the first amplifier circuit 5a, the output of the first amplifier circuit 5a is controlled to always have a constant value in accordance with the reference voltage.

Next, when this radio telephone device is used for operation requiring larger transmission power (for example, for use in a vehicle), the above-mentioned booster circuit section is connected to the high frequency output terminal 7', and the second amplifier circuit 5b is connected to the high frequency output terminal 7'. make it work.

In this case, the output of the first amplifier circuit 5a, which has been made constant by the above-described control, is supplied as an input to the second amplifier circuit 5b.

As a result, the second amplifier circuit 5b becomes the first amplifier circuit 5.
The output of a is further amplified and output to the high frequency output terminal 7.

Accordingly, a part of the output of the second amplifier circuit 5b is detected by the second detection circuit 4b, and is inputted to the second sustaining circuit 3b as a DC voltage proportional to the output.

On the other hand, the second selection circuit 2b, which is connected to the reference voltage group generation circuit 1 due to the above operation, selects reference voltages corresponding to a plurality of output level groups prepared in the reference voltage group generation circuit 1. Select one of them and input it to the second sustaining circuit 3b.

Here, the second maintenance circuit 3b monitors the difference between the reference voltage selected by the second selection circuit 2b and the DC voltage detected by the second detection circuit 4b, and amplifies the difference voltage to generate the second This second amplifier circuit 5b is
The output of b is controlled so that it always has a constant value in accordance with the reference voltage.

In this way, in the conventional circuit, when a relatively small transmission power is required, only the first amplifier circuit 5a is operated and a constant amplification output is ensured by the first sustaining circuit 3a, and when a larger transmission power is required. In this case, the second amplifier circuit 5b is connected and operated together so that the constant output of the first amplifier circuit 5a is input, and a second sustaining circuit provided exclusively for the output is used. 3b, it was controlled to be constant.

In other words, in this type of conventional power amplifier circuit in which amplifier circuits are connected in multiple stages due to transmission power constraints, a maintenance circuit corresponding to each amplifier circuit is required.

By the way, the maintenance circuit used in this type of power amplification circuit is generally realized by an automatic output control circuit (APC).

Its function is as described above, and it amplifies the error voltage between the DC voltage obtained by detecting a portion of the output power and the reference voltage corresponding to one of a plurality of preset output levels. The output of the power amplifier circuit is controlled to be constant based on the voltage (or current) obtained.

Therefore, the components usually include a differential amplifier that amplifies the difference between the detected voltage and the reference voltage, and a control circuit that controls the power amplifier circuit based on the output of this differential amplifier, resulting in a complex circuit configuration. Moreover, there was a tendency for the circuit scale to become larger.

(Problem to be Solved by the Invention) As described above, in the conventional power amplifier circuit described above, when operating the amplifier circuit by connecting it in multiple stages for the purpose of increasing the transmission power,
Since a large-scale sustaining circuit with a complex circuit configuration was required for each amplifier circuit, the circuit configuration requirements of this sustaining circuit were directly reflected, resulting in a problem that the overall circuit configuration became complicated and large. .

The present invention has been made in view of the above-mentioned circumstances, and allows the entire circuit to have a simple and compact configuration in order to support an operation mode in which amplifier circuits are connected in multiple stages to increase transmission power. The purpose is to provide a power amplifier circuit.

[Structure of the invention]

(Means for Solving the Problems) A power amplifier circuit of the present invention includes: a first amplification means for amplifying a radio frequency signal; a first detection means for detecting the output of the first amplification means; a second amplification means selectively connectable to the output of the first amplification means; a second detection means for detecting the output of the second amplification means; detection output switching means for switching from the detection output of the first detection means to the detection output of the second detection means when the amplification means of the first detection means is connected; power supply voltage applying means for applying one of a second power supply voltage higher than the power supply voltage to the first amplification means; a first output level group; and at least one higher than any one of the first output level group. The first power supply voltage is applied to a reference voltage group generating means for generating a plurality of reference voltages respectively corresponding to each output level of a second output level group including one output level, and the first amplifying means. At times, a reference voltage corresponding to one output level of the first output level group is selected, and when the second power supply voltage is applied to the first amplification means, the reference voltage corresponding to one output level of the first output level group is selected. a reference voltage selection means for selecting and outputting a reference voltage corresponding to one of the output levels; and a detection output of the first or second detection means inputted from the detection output switching means; and output maintaining means for maintaining the output of the first amplifying means so as to match the reference voltage selected by the first amplifying means.

(Function) In the power amplifier circuit of the present invention, when a relatively small transmission power is required, only the first amplifier circuit is operated, and when a larger transmission power is required, the power amplifier circuit is connected to the output of the first amplifier circuit. The output of the second amplifier circuit is also operated to increase the output.

At this time, the outputs of the first and second amplifier circuits are respectively detected by the first and second detection circuits according to the above-mentioned operating conditions, and the detected outputs are switched by the switching circuit and input to the maintenance circuit.

Here, when operating only the first amplifier circuit, the sustain circuit controls the output of the first amplifier circuit to be constant based on the detection output of the first detector circuit, and also controls the output of the second amplifier circuit at the same time. When operating, the first detection circuit is detected based on the detection output of the second detection circuit.
The output of the second amplifier circuit, that is, the input of the second amplifier circuit, is controlled, and as a result, the output is kept constant.

As a result, in the present invention, the number of sustaining circuits that were conventionally required for each of the first and second amplifier circuits can be reduced to one, and the overall circuit configuration can be simplified.

Furthermore, since the gain of the second amplifier circuit does not need to be varied by the method of controlling the input and making the output constant as described above, the second amplifier circuit can be configured with a fixed gain of 1, for example. At the same time, the structure of the circuit itself can be simplified, such as by using a single transistor having the following characteristics.

(Example) Hereinafter, an example of the present invention will be described in detail based on the accompanying drawings.

FIG. 1 shows the configuration of a power amplifier circuit according to an embodiment of the present invention, and parts that perform the same functions as those of the conventional circuit shown in FIG. 2 are given the same reference numerals. There is.

In FIG. 1, one selection circuit 2A is provided for the reference voltage group generation circuit 1, and its output is connected to one input of a sustaining circuit 3A, which is also provided with only one selection circuit 2A.

A switching circuit 8 is connected to the other input of the sustaining circuit 3A, and switches between the output of the first detection circuit 4a and the output of the second detection circuit 4b, and connects the output to the sustaining circuit 3A.

Furthermore, the first detection circuit 4a is connected to the output of the first amplifier circuit 5a, while the second detection circuit 4b is connected to the output of the second amplifier circuit 5b.

Here, the circuit portion consisting of the second detection circuit 4b and the second amplifier circuit 5b is used, for example, when switching the wireless telephone device from portable operation to vehicle-mounted operation, which requires higher transmission power. , it is used by being connected to the preceding stage circuit section through the high frequency output terminal 7' (corresponding to the above-mentioned booster).

Next, the operation will be explained in detail.

First, a case will be described in which a wireless telephone device including the circuit of the present invention is used as a portable device.

In this case, only the first amplifier circuit 5a is operated without connecting the circuit portion consisting of the second detection circuit 4b and the second amplifier circuit 5b described above to the high frequency output terminal 7'.

At this time, the radio frequency signal input from the high frequency input terminal 6 is amplified by the first amplifier circuit 5a and output to the high frequency output terminal 7'.

Along with this, a part of the output of the first amplifier circuit 5a is
The wave is detected by the detection circuit 4a, and is input to the switching circuit 8 as a DC voltage proportional to the output power.

Here, the switching circuit 8 is switched to be connected to the output of the detection circuit 4a, and the detection output of the detection circuit 4a is inputted to the sustaining circuit 3A through this switching circuit 8.

On the other hand, the reference voltage group generation circuit 1 is provided with reference voltage groups corresponding to a plurality of output levels, one of which is selected by the selection circuit 2A and supplied to the other input of the sustain circuit 3A.

Here, the sustaining circuit 3A is connected to a detection circuit 4a which receives the reference voltage selected by the selection circuit 2A and the switching circuit 8.
The output of the first amplifier circuit 5a is always kept at a constant value by monitoring the DC voltage which is the detection output of
control so that the DC voltage matches the reference voltage).

Next, a case will be described in which a wireless telephone device including the circuit of the present invention is used for car cultivation.

In this case, a larger transmission power is required, so in order to increase this transmission power, a circuit section consisting of a second detection circuit 4b and a second amplifier circuit 5b is connected to the high frequency output terminal 7'. Become.

In this state, the output of the first amplifier circuit 5a becomes the input of the second amplifier circuit 5b.

Here, the second amplifier circuit 5b further amplifies the output of the first amplifier circuit 5a and outputs it to the high frequency output terminal 7.

Along with this, a part of the output of the second amplifier circuit 5b is
The wave is detected by the detection circuit 4a, and input into the switching circuit 8 as a DC voltage proportional to the output power.

Here, the switching circuit 8 is switched to a state in which the circuit portion consisting of the second detection circuit 4b and the second amplifier circuit 5b is connected to the high frequency output terminal 7' and simultaneously connected to the output of the detection circuit 4b. There is.

Therefore, in the subsequent operation, the output of this switching circuit 8 is switched from the detection output of the first detection circuit to the detection output of the detection circuit 4b, and is input to the sustaining circuit 3A.

At this time, one of the reference voltage groups corresponding to a plurality of output levels prepared in the reference voltage group generation circuit 1 is selected by the selection circuit 2A and inputted to the other input of the sustaining circuit 3A. .

Here, the sustain circuit 3A inputs the reference voltage selected by the selection circuit 2A and the detection circuit 4b through the switching circuit 8.
The output of the first amplifier circuit 5a is always kept at a constant value by monitoring the DC voltage which is the detection output of
control so that the DC voltage matches the reference voltage).

According to the above operation mode, the constant output of the first amplifier circuit 5a becomes an input to the second amplifier circuit 5b through the high frequency output terminal 7', and is amplified with a predetermined gain of the second amplifier circuit 5b. and output to the high frequency output terminal 7.

In this way, in the circuit of the present invention, when the second amplifier circuit 5b is connected and operated simultaneously with the first amplifier circuit 5a, the second amplifier circuit 5b is operated simultaneously with the first amplifier circuit 5a.
Based on the detection output of the detection circuit 4b, the second amplifier circuit 5
This second amplifier circuit 5b indirectly while controlling the input of
The output is kept constant.

In such a circuit of the present invention, only one maintenance circuit 3A having a complicated circuit configuration is required, so the overall configuration of this circuit can of course be simplified. Since there is no need to directly variable control the gain of the second amplifier circuit 5b, it is possible to simplify the configuration of the second amplifier circuit itself by, for example, configuring it with one stage of transistors having a fixed gain. can.

〔Effect of the invention〕

As explained above, according to the power amplifier circuit of the present invention, when only the first amplifier circuit is operated, the output of the first amplifier circuit is determined based on the detection output of the first detection circuit connected to the output of the first amplifier circuit. If the output is directly maintained constant and the second amplifier circuit is also operated at the same time for the purpose of output enhancement, the output of the first amplifier circuit, that is, the Since the output of the second amplifier circuit is maintained at a constant level through an indirect method of controlling the input, the number of maintenance circuits in a complicated circuit structure is reduced to one, simplifying and downsizing the overall circuit structure. It has the excellent advantage of being achievable.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of a power amplifier circuit according to an embodiment of the present invention, and FIG. 2 is a block diagram showing the configuration of a conventional power amplifier circuit of this type.

Claims (1)

[Scope of Claims] A first amplifying means for amplifying a radio frequency signal, a first detecting means for detecting the output of the first amplifying means, and selectively connected to the output of the first amplifying means. second detection means for detecting the output of the second amplification means; and when the second amplification means is connected to the output of the first amplification means, the second amplification means detects the output of the second amplification means; detection output switching means for switching and outputting the detection output of the first detection means to the detection output of the second detection means; a first power supply voltage; and a second power supply voltage greater than the first power supply voltage; a first output level group, and a second output level including at least one output level larger than any of the first output level group; reference voltage group generation means for generating a plurality of reference voltages corresponding to each output level of the group; and when the first power supply voltage is applied to the first amplification means, one of the first output level group A reference voltage corresponding to one output level of the second output level group is selected, and when the second power supply voltage is applied to the first amplifying means, the reference voltage corresponding to one output level of the second output level group is selected. a reference voltage selection means for selecting and outputting a voltage; and a detection output of the first or second detection means inputted from the detection output switching means so that it matches the reference voltage selected by the reference voltage selection means. and output maintaining means for maintaining the output of the first amplifying means.