JPH0878977A - High frequency amplifier circuit - Google Patents

Abstract

PURPOSE: To prevent an oscillation and to obtain a stable high frequency amplifier circuit by connecting an inductor between the source of each FET forming a semiconductor amplifier element and ground and connecting the inter-source of an FET via a resistance. CONSTITUTION: The high frequency signal via an input side matching circuit 11 is amplified by FETT1 and Tn connected in parallel. A ground connection is performed for each of the sources S1 to Sn of the FETT1 to Tn via inductors L1 to Ln , the input impedance of the FETT1 to Tn becomes low and the constitution of the circuit 11 is facilitated. Resistances R1 to Rn-1 are connected between the terminals of the sources S1 to Sn . When the oscillation by the feedback via the drain gates of an FET is generated, a difference is generated in the high frequency voltage in the sources, current flows in the resistances R1 to Rn and the oscillation is suppressed. When a circuit operates as a high frequency amplifier circuit, the source high frequency voltage of the FET is equal, current does not flow to the resistances R1 to Rn and loss, etc., is not generated. Thus, the circuit becomes the stable high frequency amplifier circuit, preventing the oscillation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high frequency amplifier circuit used for amplifying microwaves, for example.

[0002]

2. Description of the Related Art In a high-frequency amplifier circuit, for example, a source-grounded field effect transistor or high electron mobility transistor (HEMT) has a high gate-source impedance in a low frequency band. Therefore, when configuring a low-noise high-frequency amplifier in a low frequency band, it is difficult to realize a compact broadband matching circuit with low loss.

For this reason, in a conventional high frequency amplifier circuit, a plurality of field effect transistors are arranged in parallel, the gates of the field effect transistors are connected to each other, and an inductor is connected between the source and the ground to obtain an input impedance. Is small.

Here, regarding the conventional high-frequency amplifier circuit,
This will be described with reference to FIG.

IN is an input terminal, and a high frequency signal such as a microwave is input from the input terminal IN. This signal passes through the input side matching circuit 31 and is divided into a plurality of field effect transistors T1 to T1 connected in parallel.
n. A power supply 32 supplies a bias voltage to the gates G1 to Gn of the field effect transistors T1 to Tn. Further, the field effect transistors T1 to Tn
The inductors L1 to Ln are connected to the respective sources S1 to Sn of and are grounded.

The amplified signals are output from the drains D1 to Dn of the field effect transistors T1 to Tn. The amplified signals are combined, sent to the output side matching circuit 33, and output from the output terminal OUT. In addition, 34 is a power supply and each drain D of field effect transistors T1-Tn.
Bias voltage is supplied to 1 to Dn.

[0007]

In the case of the above configuration,
For example, the signal input to the gate G1 of the field effect transistor T1 is amplified and output from the drain D1. At this time, the signal output to the drain D1 leaks to the gate G2 side through the drain D2 of another field effect transistor (for example, T2), and a feedback circuit for inputting again to the gate G1 of the field effect transistor T1 is formed. Therefore, depending on the conditions of the field effect transistors T1 to Tn, the input / output matching circuits 31 and 33, and the inductors L1 to Ln, the feedback circuit may function as a positive feedback circuit and cause oscillation.

The present invention solves the above-mentioned drawbacks, and an object of the present invention is to provide a high-frequency amplifier circuit in which oscillation is prevented and stabilized.

[0009]

According to the present invention, a plurality of semiconductor amplifiers each having an input terminal for inputting a signal, a ground terminal for grounding via an inductor, and an output terminal for outputting an amplified signal are provided. In a high frequency amplifier circuit comprising an element, an input side matching circuit connected to each input terminal of the plurality of semiconductor amplifier elements, and an output side matching circuit connected to each output terminal of the plurality of semiconductor amplifier elements, The ground terminal of each of the plurality of semiconductor amplifying elements is connected to a common point via a resistor.

Further, a plurality of semiconductor amplifying elements each having an input terminal for inputting a signal, a ground terminal for grounding via an inductor, and an output terminal for outputting an amplified signal, and the plurality of semiconductor amplifying elements. A high-frequency amplifier circuit comprising an input-side matching circuit connected to each input terminal of an element and an output-side matching circuit connected to each output terminal of the plurality of semiconductor amplifying elements, wherein: A resistor is connected between the ground terminals.

An impedance element other than the resistor is connected to the resistor.

[0012]

According to the above structure, a plurality of field effect transistors are connected in parallel, and an inductor is connected between the source of the field effect transistor and the ground. Therefore, the input impedance of the field effect transistor becomes low and the configuration of the matching circuit becomes easy.

Further, the ground terminals of the plurality of semiconductor amplifying elements are connected to a common point via a resistor, or the resistors are connected between the ground terminals of the plurality of semiconductor amplifying elements. According to this configuration, if oscillation occurs due to feedback between the drain and gate, a difference occurs in the high frequency voltage at the source of each field effect transistor, and a current flows through the resistor connected to the source, resulting in oscillation. Can be suppressed.
When operating as a high-frequency amplifier circuit, since the high-frequency voltage at the source of each field effect transistor is the same, no current flows through the resistor connected to the source. Therefore, no loss occurs. Therefore, a high-frequency amplifier circuit that prevents oscillation and is stable is realized.

The element connected to the source of each field-effect transistor is not limited to a resistor, and the same effect can be obtained by a circuit in which a resistor and an impedance element other than the resistor are combined.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIG.

IN is an input terminal, and a high frequency signal such as a microwave is input from the input terminal IN. This signal is applied to the input side matching circuit 11. A plurality of field effect transistors T, which are divided into a plurality of pieces and are connected in parallel,
1 to Tn, respectively. In addition, 12 is a power supply,
Gates G1 to Gn of field effect transistors T1 to Tn
Bias voltage is supplied to. An inductor L is provided in each of the sources S1 to Sn of the field effect transistors T1 to Tn.
1 to Ln are connected and grounded. Further, between the sources S1 to Sn of the field effect transistors T1 to Tn adjacent to each other, for example, the sources S1 to Sn and the inductor L.
The resistors R1 to Rn-1 are connected between the connection points of 1 to Ln.

The signals input to the field effect transistors T1 to Tn are amplified and output from the drains D1 to Dn. The amplified signals are combined and sent from the output side matching circuit 13 to the output terminal OUT and output. In addition,
A power source 14 supplies a bias voltage to the drains D1 to Dn of the field effect transistors T1 to Tn.

According to the above structure, the plurality of field effect transistors T1 to Tn are arranged in parallel, and the inductors L1 to Ln are connected between the sources S1 to Sn of the field effect transistors T1 to Tn and the ground. There is. And
Sources S1 to Sn of the field effect transistors T1 to Tn
Between the terminals, for example, adjacent field effect transistors T1 to T
Resistors R1 to Rn-1 are connected between n sources S1 to Sn.

Therefore, the input impedance becomes low and the structure of the input side matching circuit becomes easy. In addition, resistors R1 to Rn-1 are connected between the sources S1 to Sn of the plurality of field effect transistors T1 to Tn. If the operation of each of the field effect transistors T1 to Tn moves in the direction in which oscillation occurs due to feedback via the drain and gate, a difference occurs in the high frequency voltage at the sources of the plurality of field effect transistors T1 to Tn, and the source S1 ~ S
A current flows through the resistors R1 to Rn-1 connected between n, and as a result, the oscillation power is attenuated and the oscillation is suppressed. Each field effect transistor T1 when operated as an amplifier
The operation of Tn is balanced, the high-frequency voltages at the sources S1 to Sn are equal, and no current flows through the resistors R1 to Rn-1 so that no loss occurs.

Next, another embodiment of the present invention will be described with reference to FIG.
Will be explained. In FIG. 2, parts corresponding to those in FIG. 1 are designated by the same reference numerals, and the description will focus on the configuration different from that in FIG.

In the case of FIG. 1, a resistor is connected between the connection point of the source and the inductor of the field effect transistor adjacent to each other. However, in the embodiment of FIG. 2, the resistors R1 to Rn are connected to the connection points of the sources S1 to Sn and the inductors L1 to Ln of the field effect transistors T1 to Tn, and the resistors R1 to Rn are connected to the common point T. Has been done.

According to the above structure, the input impedance is low, and the structure of the matching circuit is easy. The sources S1 to S of the plurality of field effect transistors T1 to Tn are also included.
The resistors R1 to Rn are connected to n, and the resistors R1 to Rn are connected to the common point T. Also in this case, the resistors R1 to R1
Rn suppresses an unbalanced operation of each of the field effect transistors T1 to Tn, and suppresses oscillation due to feedback passing between the drain and the gate. Also in this case, since the high-frequency voltages at the sources S1 to Sn of the plurality of field effect transistors T1 to Tn are equal, no current flows through the resistors R1 to Rn connected to the sources S1 to Sn, and there is no loss. In the above-described embodiments, a resistor is connected between the connection point of the source of the field effect transistor and the inductor, or each connection point of the source and the inductor is connected to a common point via the resistance. However, the resistor may be connected in the middle of the inductor instead of the connection point between the source and the inductor. Further, the same effect can be obtained by using not only a circuit including only a resistor but also a circuit in which a reactance element other than a resistor is combined with a reactance element such as a transmission line.

[0023]

According to the present invention, it is possible to realize a stable high frequency amplifier circuit which can prevent oscillation.

[Brief description of drawings]

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

FIG. 2 is a circuit diagram showing another embodiment of the present invention.

FIG. 3 is a circuit diagram showing a conventional example.

[Explanation of symbols]

 11 ... Input side matching circuit 12, 14 ... Power source 13 ... Output side matching circuit T1-Tn ... Field effect transistors G1-Gn ... Gate S1-Sn ... Source D1-Dn ... Drain R1-Rn ... Resistor L1-Ln ... Inductor

Claims (3)

[Claims] 1. A plurality of semiconductor amplifier elements each having an input terminal for inputting a signal, a ground terminal grounded via an inductor, and an output terminal for outputting an amplified signal, and a plurality of semiconductor amplifiers. In a high-frequency amplifier circuit including an input-side matching circuit connected to each input terminal of an element and an output-side matching circuit connected to each output terminal of the plurality of semiconductor amplifying elements, each of the plurality of semiconductor amplifying elements A high-frequency amplifier circuit characterized in that the ground terminal is connected to a common point via a resistor. 2. A plurality of semiconductor amplifying elements each having an input terminal for inputting a signal, a ground terminal grounded via an inductor, and an output terminal for outputting an amplified signal, and the plurality of semiconductor amplifying elements. A high-frequency amplifier circuit comprising an input-side matching circuit connected to each input terminal of an element and an output-side matching circuit connected to each output terminal of the plurality of semiconductor amplifying elements, wherein: A high-frequency amplifier circuit characterized by connecting a resistor between ground terminals. 3. The high frequency amplifier circuit according to claim 1, wherein an impedance element other than the resistor is connected to the resistor.