JPS59131208A - Microwave monolithic amplifier - Google Patents

Abstract

PURPOSE:To avoid an effect of variation of a circuit parameter by setting the conductor thickness of a transmission line of each matching circuit at a value larger and smaller the skin thickness due to a skin effect at the input side and the interstage/output side respectively for a microwave monolithic amplifier which contains an input matching circuit and an interstage/output matching circuit. CONSTITUTION:An input matching circuit consisting of an RF by-pass capacity 13 and series/parallel transmission lines 7 and 8 is provided between a gate electrode 1 of the 1st-stage FET formed on a semi-insulated GaAs substrate 31 and an upper electrode of a DC block capacitor 9 which is used as an input terminal of an amplifier. An interstage matching circuit consisting of a series transmission line 18, etc. is set between an FET drain 3 and the 2nd-stage FET gate 4. Furthermore an output matching circuit consisting of series/parallel transmission lines 22, 23, etc. is provided between the 2nd-stage FET drain 6 and an output terminal. The thickness of each transmission line is set larger than the skin thickness of a high frequency current produced by a skin effect with an input affecting the noise exponent and smaller than said skin thickness with the interstage/output in order to lower the circuit Q respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to microwave low noise monolithic amplifiers.

In recent years, with the aim of mass producing microwave amplifiers, research and development of microwave amplifiers having a monolithic IC configuration has been actively conducted. However, with monolithic ICs, the circuit trimming that is normally done with hybrid ICs is not possible, so even if the band shifts slightly due to fluctuations in circuit parameters, this cannot be corrected, resulting in a defective product. there were.

SUMMARY OF THE INVENTION An object of the present invention is to provide a microwave monolithic amplifier which solves the above-mentioned problems, has uniform amplifier characteristics, and can be mass-produced.

The configuration of the present invention provides a microwave monolink amplifier equipped with an input matching circuit, an interstage matching circuit, and an output matching circuit each including one or more circuit elements of a distributed constant line, an inductor, and a capacitor. The conductor thickness of the transmission line is thicker than the skin thickness through which high-frequency current flows in the skin effect, and the conductor thickness of the transmission line between the stages and the output matching circuit is thinner than the skin thickness.

According to the present invention, the conductor thickness of each transmission line is thinner than the skin thickness in the skin effect, except for the input matching circuit, which has a large effect on the noise figure, so the Q of each matching circuit decreases, causing fluctuations in circuit parameters. It is possible to reduce the influence of the noise on the amplifier characteristics, thereby making the characteristics of the amplifier uniform, and eliminating the need for circuit trimming. This feature has a great effect since it is used as a means of mass production of monolithic microwave amplifiers.

The present invention will be explained in detail below with reference to Figure TK+.

FIG. 1 is a plan view of an embodiment of the present invention, in which the shaded areas are plated with gold. Further, FIG. 4 shows an equivalent circuit diagram of FIG. 1. This embodiment is a microwave monolithic amplifier including two stages of FETs, the first stage FET has a gate pole 1, a source electrode 2 and a drain electrode 3, and the second stage FET has a gate electrode 4, a source electrode 5 and a drain electrode 3. It has a drain electrode, and is provided on a semi-insulating GaAs substrate 31 together with an input matching circuit, a two-stage matching circuit, and an output matching circuit. Dielectrics 11, 12, 16, 19, 24, 26 are provided on the lines of these matching circuits, respectively, and upper electrodes are formed by plating gold on these, respectively. Therefore, capacitors 9, 13, 15, 20, 27, respectively
．． It forms 28.

In FIG. 1, an RF bypass capacitor 13 is provided at the tip between the gate electrode 1 of the first-stage FET configured on a semi-insulating GaAs substrate 31 and the upper electrode of a DC block capacitor 9 that serves as the input terminal of the amplifier. An input matching circuit consisting of a parallel transmission line 8 and a series transmission line 7 is provided. The drain electrode 3 of this FET and the second stage FET
An interstage matching circuit consisting of a series transmission line 18 and a parallel transmission line 17 equipped with an RF bypass capacitor 15 at the tip is provided between the gate electrode 3 and the gate electrode 4. A DC block capacitor 20 is provided for DC isolation from the connected pad 21. A resistive layer 41 is provided between this pad 21 and a gate bias power supply bonding pad 42.

Further, between the drain electrode 6 of the second stage FET and the upper electrode of the DC block capacitor 27 constituting the output terminal, a series transmission line 22 and a parallel transmission line 23 having R and F bypass capacitors 28 at the tips are connected. An output matching circuit is provided.

Connections with other circuits in this embodiment are made via gold-plated bonding pads to input/output terminals and one wiring layer of the multilayer wiring layer. That is, the upper electrodes of the capacitors 9 and 27, which are input/output terminals, are connected to the signal input/output terminals as bonding pads, and the FE
Each source electrode 2, 5 and each drain electrode 3, 6 of F
Gold plating is applied to reduce the parasitic resistance of the ET itself, and each of the bonding pads 29 and 30 connected to the source voltage %i2.5 is connected to a ground wiring layer. Furthermore, the bonding pads 14 and 25 are also connected to other wiring layers.

2 and 3 are cross-sectional views of the lines of the input matching circuit and the crotch matching circuit in FIG. 1, which explain the present invention in detail. In the figure, 31 is a semi-insulating GaAs substrate, 32 is a back electrode, 33 is a gold plating layer with a thickness of 2 to 3 μm, 34 is a power supply metal necessary for gold plating, and 35 and 36 are formed on the substrate 31 by vapor deposition. It is a metal conductor with a thickness of 0.02 to 0.3 μm.

Generally, high-frequency current flows only on the surface of a multi-conductor due to the skin effect, and the thickness δ of the surface layer through which this current flows is called the skin thickness.If the electrical conductivity of the metal is σ, the magnetic permeability is μ1, and the frequency f is It is expressed by the following formula.

The skin thickness in the case of gold is about 0.8 μm at IQGHz.

In this embodiment, the input matching circuit line has a gold plating layer 33 thicker than the skin thickness as shown in FIG. 2, but the other matching circuit lines are as shown in FIG. 3. The thickness of the metal thin film 36 is made thinner than the skin thickness. Therefore, although it depends on the conductor width and the type of metal, it is possible to make the series resistance of the stage plane and the line of the output matching circuit much larger than that of the line of the input matching circuit, and the Q of the input matching circuit can be made larger. The Q of the interstage and output matching circuits can be lowered. Since this matching circuit with a low Q has broadband characteristics, it is possible to suppress the influence of fluctuations in circuit parameters on amplifier characteristics.

On the other hand, since the input matching circuit, which tends to affect the noise characteristics, has a conductive metal thicker than the skin thickness, the series resistance is small and low noise characteristics can be maintained. The amplification band of this amplifier is mainly determined only by the relatively high Q input circuit,
In other words, it can be said that fluctuations in the amplification characteristics are mainly determined only by parameter fluctuations of the input circuit.

In this way, in the present invention, the conductor thickness of the line is made thinner than the skin thickness, except for the input matching circuit, which has a large effect on the noise figure, so the circuit Q is lowered, and fluctuations in circuit parameters are affected by amplifier characteristics. It is possible to reduce the impact on As a result, the characteristics of the amplifier can be made uniform and the circuit trimming can be reduced, which is particularly effective in making it possible to mass-produce identical circuits in monolithic microwave amplifiers.

Although the embodiment of the present invention has been described using a two-stage amplifier, the number of amplifier stages is not limited to two and may be any number of stages. Furthermore, the semiconductor substrate is not limited to GaAs, but may also be InP or 8i.

[Brief explanation of the drawing]

FIG. 1 is a plan view of an amplifier according to an embodiment of the present invention, FIG.
3 is a sectional view taken along line AA and BB of the matching circuit portion shown in FIG. 1, and FIG. 4 is an equivalent circuit of FIG. 1. In the figure, 1.4...gate electrode, 2,5...source electrode 3.6...drain electrode s7,8
,17,18,22゜23...transmission line, 9,
13, 15, 20, 27.28... Capacitance, 11, 12.16, 19.24.26...
・Dielectric, 14, 25, 29.30...Ponding pad (gold plating), 21...Pad,
31... Semi-insulating substrate, 32... Back electrode, 33... Gold plating layer, 34...
Power supply metal, 35.36...Metal conductor, 41...
. . . Resistance layer, 42 . . . Bonding pad.

Claims (1)

[Claims:] An input matching circuit comprising one or more circuit elements of a distributed constant line, an inductor, and a capacitor. In a microwave monolithic N-width amplifier equipped with an inter-stage matching circuit and an output matching circuit, the conductor thickness of the transmission line of the input matching circuit is set to be less than the skin thickness through which a high-frequency current flows due to the skin effect, and the inter-stage and output matching circuits are A microwave monolithic amplifier characterized in that the conductor thickness of the transmission line of the circuit is made thinner than the skin thickness.