JPH06125230A - High frequency band/high output amplifier - Google Patents

Abstract

PURPOSE:To reduce the distortions in a large amplitude input state by controlling the output impression voltage of the amplifier element of the final stage in the feedback of an envelope. CONSTITUTION:With regard to a field-effect transistor FET 1, the output voltage of an error amplifier 7 is increased to the large amplitude input by the operation of an envelope feedback circuit 9 and by the input follow-up. The increased output voltage of the amplifier 7 is reached as the input voltage of the FET 1 via a choke coil 13 which feeds the preceding increased output voltage as the input voltage of an inverted amplifier 10 and an adder 12. Thus the input of the FET 1 (source grounded) is pinched off (B-class) or deeply biased at the negative side (C-class). Meanwhile the output voltage of the amplifier 7 is reduced to the medium amplitude input by the operation of the circuit 9 and by the input follow-up. This reduced output voltage reaches as the input voltage of the FET 1. Thus the input voltage of the FET 1 is shallowly biased in the negative side and an A-class operating point is secured.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-frequency band high-power amplifier, and more particularly to a high-frequency band high-power amplifier improved in order to achieve high efficiency and low distortion of the final amplification stage of the amplifier.

[0002]

2. Description of the Related Art As shown in FIG. 3, the circuit configuration of a conventional high-frequency band high-output amplifier has a high-frequency signal input terminal 15 and
The depletion-type field effect transistor (hereinafter referred to as FET) 1 of the final stage amplification element, the excitation amplifier 2, and the FET are connected between the amplified signal output terminal 16 of the high-power amplifier.
The difference between the output voltage of the output detection circuit 5 including the attenuator 4 provided on the output side of the FET 1 and the output voltage of the output detection circuit 5 Difference detector to extract 6, FET to eliminate the difference
For the FET1, which includes an error amplifier 7 having a function of varying the output voltage to be the output applied voltage of No. 1 in the error direction and an output side voltage feed choke coil 8 for guiding the output voltage of the error amplifier 7 to the output of the FET1. Saturation line feedback circuit 9
And a choke coil 13 that supplies the Vgs voltage 20 to the gate of the FET 1.

Next, the operation of the conventional circuit of FIG. 3 will be described with reference to the operation explanatory diagrams of FIGS. Generally, the efficiency is improved and the distortion is reduced by performing the satiation feedback on the amplifier elements of class B and class C operation, which have excellent efficiency as compared with the amplifier of class A operation. As shown in FIG. 4, the saturating-wire feedback circuit 9 has a constant output applied voltage when there is no feedback along the saturating wire of the modulated wave.
The amplitude element output applied voltage by saturating line feedback is changed according to the small amplitude.

Next, the operation characteristic of the saturated wire feedback circuit 9 including the FET 1 of FIG. 5 will be described with reference to FIG. Figure 5 shows FET1
At the pinch-off points of the B-class and C-class operating points, a small-amplitude, medium-amplitude, and large-amplitude input of approximately half a wave is applied. On the other hand, the VI characteristic has a non-linear region closer to the pinch-off point and a linear region up to V = 0. Medium amplitude and small amplitude, which operate mainly in the non-linear region, are subject to waveform distortion. At medium amplitude, as shown in FIG. 5, the medium amplitude output with waveform distortion is the amplitude of the medium amplitude output with no waveform distortion. It is compressed and output. In this way, the amplified signal distorted by the non-linear operation of class B, class C, etc. is subjected to the saturating line detection, and similarly, the undetected input signal detected on the input side is compared by the difference detector 6, In order to eliminate the difference, the output voltage of the error amplifier 7 is fed back as the output applied voltage of the amplifying element FET1 to control the amplifying element output based on the low distortion input signal, resulting in high efficiency of class B and class C. While holding, the amplitude distortion after amplification due to the non-linearity is reduced by controlling the output voltage of the amplification element. When the saturating line feedback of the conventional example is performed, the output applied voltage to the amplifying element is changed by following the saturating line of the modulation signal.
The average power consumption is reduced, contributing to higher efficiency.

However, the distortion in the case where only the amplification element output voltage control based on the input / output signal saturation detection is performed is F
Since the input applied voltage Vgs voltage 20 to the ET1 is fixed, there is room for improvement in that waveform distortion occurs in the medium output region of the output modulation signal. That is, in the V-I characteristic of the FET 1 itself, at the time of outputting a medium amplitude, the output waveform is distorted because the output half-wave swing and most of it operates in the bending region of the rising characteristic which is a non-linear region when the medium amplitude is output. Occurs. On the other hand, since the signal itself is small, the distortion at the time of a small signal can be ignored as the amount of generation. Also, when a large signal is output, most of the output half-wave swing operates in the linear region, so V
The influence of the non-linear region of the −I characteristic is not surfaced. However,
This is a condition in the input / output state where clipping does not occur.

[0006]

In the above-mentioned conventional high frequency and high output amplifier, the input applied voltage Vgs to the amplifying element is set to B.
Since it is fixed to class C or class C, the V-I of the amplifying element in the medium output region of the modulated signal at the time of medium signal input
There is a drawback that waveform distortion occurs in the nonlinear region of characteristics.

[0007]

The high frequency band high output amplifier of the present invention is an excitation amplifier for amplifying a small amplitude, medium amplitude and large amplitude high frequency signal to be inputted, and a part of the output level of this excitation amplifier. An input detection circuit for detecting the input signal, a high-frequency amplification element for inputting and amplifying the power of the output signal of the excitation amplifier, an output detection circuit for branching and detecting a part of the output signal of the high-frequency amplification element, and the input A difference detector for detecting the difference level by inputting the detection level of the detection circuit and the detection level of the output detection circuit, and an output terminal of the high frequency amplification element through a choke coil after amplifying the output of the difference detector. In a high frequency band high power amplifier for supplying a first level to be fed back, an inverting amplifier for inverting the first level to generate a second level, and a gate source of the high frequency amplifying element A third level and the second level and to additive the adder becomes the offset voltage corresponding to the voltage, and supplies the output level of the adder to the input terminal of the high-frequency amplifying device.

[0008]

The present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the circuit configuration of an embodiment of the present invention. 1, the same reference numerals as those in the conventional example of FIG. 3 have the same configurations and functions. That is, in this embodiment, the operating point control circuit 14 is added. This operating point control circuit 14
Is a DC amplifier 10 that inverts and amplifies the output voltage of the error amplifier 7, and an input offset applied voltage (Vgs) 1 at the time of a small signal.
Adder 12 for adding 1 to the output voltage of the DC amplifier 10
And an operating point control circuit 14 for the FET 1 including an input side voltage feed line having a choke coil 13 for guiding the output voltage of the adder 12 which is the input applied voltage of the FET 1 to the input of the FET 1.

Next, the operation of this embodiment will be described. FET1
For a large-amplitude input, the output voltage of the error amplifier 7 is large by following the input by the operation of the saturation line feedback circuit 9, and the choke coil 13 that feeds this as the input side voltage of the inverting amplifier 10 and the adder 12 is used. After that, the voltage reaches the input voltage of the FET1 and the input of the FET1 (source ground) is pinched off (class B) or further deeply biased to the negative side (class C). Here, the setting of B and C is the inverting amplifier 10
This is done by changing the gain of. By the input applied voltage, the FET 1 is in the B or C class, and the output voltage of the FET 1 is fed back by the operation of the saturating line feedback similarly to the conventional example, and the efficiency and the distortion are reduced. Similarly, for a medium-amplitude input, the output voltage of the error amplifier 7 is small by following the input by the operation of the saturating wire feedback circuit 9, and this reaches as the input voltage of the FET 1, so that the input voltage of the FET 1 is negative. Is biased to the side of, and the operating point is class A. Therefore, since the medium amplitude swing is performed in the linear operation region on the VI characteristic, the waveform distortion is improved as compared with the conventional class B and class C fixed input bias. The above-mentioned movement of the operating point is shown on the VI characteristic of FIG. Further, when a small amplitude is input, the input voltage applied to the FET1 moves in the direction of 0V to reach a shallower operating point, but even if the output voltage of the inverting amplifier 10 becomes 0V, the input added to the adder 12 is added. The input applied voltage is shallower than the offset applied voltage 11, and the class A operation is guaranteed from the medium amplitude input to the small amplitude input. As described above, the present invention has little merit of increasing the efficiency with respect to small and medium amplitude inputs, and therefore aims at improving the characteristics with a focus on reducing distortion. It should be noted that the input / output applied voltage control circuit of the final-stage amplifying element which is dynamic with respect to this input signal amplitude can realize high efficiency and low distortion of the high-frequency band high-power amplifier that immediately responds to various modulated wave amplitudes. .

[0010]

As described above, according to the present invention, by controlling the output applied voltage of the final stage amplifier element in the saturating line feedback, distortion can be reduced at the time of inputting a large amplitude, and amplification can be performed corresponding to the input signal amplitude. By controlling the element input applied voltage as well, the operation of the final stage amplification element is set to class B for high efficiency input, and the operating point is changed to class A for medium amplitude to small amplitude input to reduce waveform distortion. It has the effect of making things possible. Therefore, the present invention is also effective for realizing a system requiring small channel spacing, which is a problem in that the communication terminal station is small and lightweight, and interference between adjacent channels due to side waves of modulated waves due to distortion is a problem.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is an operation explanatory diagram of the present embodiment.

FIG. 3 is a block diagram of a conventional example.

FIG. 4 is an explanatory diagram comparing this embodiment with a conventional example.

FIG. 5 is an operation explanatory diagram of a conventional example.

[Explanation of symbols]

 1 Amplifier element (FET) 2 Excitation amplifier 3 Input detection circuit 4 Attenuator 5 Output detection circuit 6 Difference detection circuit 7 Error amplifier 8,13 Choke coil 9 Saturation line feedback circuit 10 Inversion amplifier 11 Offset applied voltage 12 Adder 14 Operation Point control circuit 15 Input terminal 16 Output terminal 17 Capacitor 18 Tuning circuit

Claims (2)

[Claims] 1. An excitation amplifier that amplifies a high-frequency signal of small amplitude, medium amplitude, and large amplitude that is input, an input detection circuit that branches and detects a part of the output level of the excitation amplifier, and an excitation amplifier of the excitation amplifier. A high frequency amplifying element for inputting an output signal to amplify the power, an output detecting circuit for branching and detecting a part of the output signal of the high frequency amplifying element, a detection level of the input detecting circuit and a detection level of the output detecting circuit. And a high-frequency band high output for supplying a first level which is fed back to the output terminal of the high-frequency amplifier element through a choke coil after amplifying the output of the difference detector. In the amplifier, an inverting amplifier that inverts the first level to generate a second level, and a third level that becomes an offset voltage corresponding to a gate-source voltage of the high-frequency amplifier element. A high-frequency band high-output amplifier, wherein an adder for adding the second level and the output level of the adder is supplied to an input terminal of the high-frequency amplification element. 2. The high frequency amplifying device is controlled in the direction of class B or class C operation in accordance with the input small and medium amplitudes of the output level of the adder. High frequency high power amplifier.