JPH11340747A - Mmic low noise amplifier - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an MMIC low noise amplifier capable of reducing a component cost and an assembly cost. SOLUTION: A circuit in which the gate terminal of an FET 1 is grounded through a feedback resistor 8 and a resistor 11 for gate grounding serially connected to it, a drain terminal is grounded through the connection point of the feedback resistor 8 and the resistor 11 for gate grounding and a first capacitor 10 for output matching, the connection point and a signal output terminal are connected through a second capacitor 12 for output matching and a source terminal is grounded through a self bias circuit is monolithically formed. Then, a signal input terminal 4 and the gate terminal of the FET 1 are connected through an input matching circuit 14 and the drain voltage of the FET 1 is supplied through an external inductor 9.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an MMIC low-noise amplifier using an FET and mainly used in a frequency band of a microwave band, and more particularly to a component cost and an assembly cost by reducing the number of components of an external matching circuit. The present invention relates to an MMIC low-noise amplifier capable of reducing noise.

[0002]

2. Description of the Related Art FIG. 4 is a circuit diagram of a self-biased MMIC low-noise amplifier in which a conventionally used input matching circuit 14 and output matching circuit 20 are constituted by external components. If the inductors 6, 7, 16 and 17 constituting the input matching circuit 14 and the output matching circuit 20 are formed in a GaAs chip, the chip size is greatly increased and the chip cost is increased. , The output matching circuit 20 is constituted by external components.

The source of the FET 1 is grounded via a self-bias circuit comprising a parallel circuit of a bias resistor 2 and a bypass capacitor 3. FET1, bias resistor 2, and bypass capacitor 3 are formed in the same chip.
The MMIC chip 19 is configured.

The gate of the FET 1 is connected to a signal input terminal 4 via a capacitor 5 and an inductor 7.
The inductor 6 is connected between the connection point of the inductor 7 and the ground. These capacitors 5, inductors 6, 7
Are composed of external components such as chip capacitors and chip inductors, and constitute the input matching circuit 14.

On the other hand, the drain of the FET 1 is connected to the signal output terminal 13 via the inductor 16 and the capacitor 18, and the inductor 17 is connected between the connection point between the inductor 16 and the capacitor 18 and the drain voltage (VDD) supply terminal 21. I have. The inductors 16 and 17 and the capacitor 18 are also formed of external components as described above, and the output matching circuit 20
Is composed.

[0006]

However, in the above-mentioned MMIC low-noise amplifier, the number of external components constituting the input matching circuit and the output matching circuit is as large as six in total, and the parts cost and the assembly cost are increased. There is.

It is an object of the present invention to provide an MMIC low-noise amplifier which solves the above-mentioned problem and which can reduce the cost of parts and the cost of assembly by reducing the number of external parts.

[0008]

In order to achieve the above object, the present invention provides an FET, an input matching circuit connected between a gate terminal of the FET and a signal input terminal, a drain terminal of the FET and a signal output. An MMIC low-noise amplifier comprising an output matching circuit connected between terminals and a self-bias circuit connected between the source of the FET and ground, wherein the output matching circuit is monolithic with the FET and the self-bias circuit. A feedback resistor and a gate grounding resistor are connected in series between the gate terminal and ground formed in
The drain terminal is connected to a connection point between the feedback resistor and the gate grounding resistor via a first output matching capacitor,
A circuit comprising the connection point and the signal output terminal connected via a second output matching capacitor, and an inductor connected between a drain terminal of the FET and a drain voltage supply terminal. MMIC low noise amplifier.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. The same or corresponding components are denoted by the same reference symbols throughout the drawings.

FIG. 1 shows a first embodiment of the present invention.
As shown in this figure, the source of the FET 1 is grounded via a self-bias circuit composed of a parallel circuit of a bias resistor 2 and a bypass capacitor 3 as in the conventional device shown in FIG.

The gate of the FET 1 is grounded via a feedback resistor 8 and a gate grounding resistor 11. Further FE
The drain of T1 is connected via a first output matching capacitor 10 to a connection point between the feedback resistor 8 and the gate grounding resistor 11, and the connection point is connected via a second output matching capacitor 12 to a signal output terminal. 13.

Each of the constituent elements described above is monolithically formed in the same chip to constitute the MMIC chip 15. As described above, the feedback resistor 8, the gate grounding resistor 11, the first output matching capacitor 10, and the second output matching capacitor 12 constitute a part of an output matching circuit. Since both of them have a small occupied area, even if they are formed in the same chip, there is almost no effect on the chip area. It is important that the feedback resistor 8 has a high resistance value that does not deteriorate the noise characteristics of the FET 1.

On the other hand, the drain voltage (VDD) of the FET 1
Is an inductor 9 externally connected to the drain voltage supply terminal 21.
Is supplied via The inductor 9 also has a function as an output matching circuit element. That is, M
In the MIC low-noise amplifier, the only external component required to constitute the output matching circuit is the inductor 9, that is, only one point of the choke coil, and the total number of external components is four. It becomes 2. Although not described, the input matching circuit 14 is the same as the conventional one shown in FIG.

FIG. 2 shows the state of output matching in the first embodiment described above using a Smith chart. As shown in this figure, the drain impedance of the FET 1 is 5 due to the function of each element constituting the output matching circuit.
It can be seen that the impedance matches 0Ω. Point A in FIG. 2 is the drain impedance of the FET, and moves to point B by the inductor 9. Further, the impedance moves from the point B to the point C by the first output matching capacitor 10, and moves from the point C to the point D by the feedback resistor 8 and the gate grounding resistor 11. Finally, the second output matching capacitor 12 moves from the point D to the point E, which becomes the output impedance of the amplifier in FIG. That is, the output impedance of the amplifier is matched to 50Ω which is the characteristic impedance of the line.

The eigenvalue of each element constituting the output matching circuit should be appropriately selected in accordance with the set frequency of the amplifier. However, if a specific example serving as a guide for implementation is given, The following are mentioned. That is, when the set frequency of the amplifier is 1.5 GHz, the feedback resistor 8 and the gate grounding resistor 11 are 50 kΩ and 2 kΩ, respectively.
The first output matching capacitor 10 and the second output matching capacitor 12 are 2 pF and 0.6 pF, respectively, and the inductor 9 is 10 nH. This is an example in which good characteristics have been obtained by experiments of the inventor.

FIG. 3 shows a second embodiment of the present invention, in which the circuit type is the same as that of the first embodiment, but is formed in the same chip 25 including all external parts. The difference between this figure and FIG. 1 is that the inductors 6, 7,
9 are three spiral inductors 22, 2 in FIG.
3 and 24 are being replaced.

Conventionally, as a method of placing an inductor, which is an external component, in a chip, a method of replacing the inductor with a spiral inductor has been used. However, the spiral inductor occupies a large area, and the number of the spiral inductor greatly affects the chip area, so that an expensive GaAs substrate is often used. For example, in the conventional low noise amplifier shown in FIG. 4, when all external components are formed in a chip, it is necessary to replace four inductors 6, 7, 16, and 17 with spiral inductors. As described above, since the cost cannot be justified, the matching circuit provided for the input and output must be constituted by external components.

However, in the second embodiment of the present invention,
As shown in the figure, the area of one spiral inductor can be reduced, so that the chip cost can be reduced and the entire amplifier can be reduced, so that good cost performance is realized.

[0019]

As described above, according to the present invention,
Since the number of components of the external matching circuit can be reduced, it is possible to provide an MMIC low-noise amplifier that can reduce component costs and assembly costs.

Also, when the input / output matching circuit is formed in the same chip, the chip area can be reduced and the chip cost can be reduced.

[Brief description of the drawings]

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

FIG. 2 is a diagram illustrating a state of output matching according to the first embodiment of the present invention.

FIG. 3 is a diagram showing a second embodiment of the present invention.

FIG. 4 shows a circuit diagram of a conventional MMIC low noise amplifier.

[Explanation of symbols]

 Reference Signs List 1 FET 2 Bias resistor 3 Bypass capacitor 4 Signal input terminal 5 Capacitor 6, 7, 9 Inductor 8 Feedback resistor 10 First output matching capacitor 11 Gate grounding resistor 12 Second output matching capacitor 13 Signal output terminal 14 Outside Input matching circuit 15 MMIC chip 20 External output matching circuit 21 Drain voltage supply terminal

Claims (1)

[Claims] An input matching circuit connected between a gate terminal of the FET and a signal input terminal; an output matching circuit connected between a drain terminal of the FET and a signal output terminal; and a source of the FET. And a self-biasing circuit connected between ground and a ground, wherein the output matching circuit comprises a feedback resistor and a gate between ground and the gate terminal formed monolithically with the FET and the self-biasing circuit. A grounding resistor is connected in series, the drain terminal is connected to a connection point between the feedback resistor and the gate grounding resistor via a first output matching capacitor, and the connection point and the signal output terminal are connected to a second output terminal. A circuit connected via a matching capacitor, and an inductor connected between the drain terminal of the FET and a drain voltage supply terminal. MMIC low noise amplifier according to claim.