JPH05152876A - Power limiting element - Google Patents

Abstract

PURPOSE:To realize the power limiting element with a small size, a high output, and excellent power limiting characteristic in which a matching circuit and a bias circuit are integrated and mounted in a package. CONSTITUTION:The power limiting element is featured that a field effect transistor(TR) chip 2, matching circuits 3, 4 converting an impedance of the TR chip 2 into a desired load impedance, a bias circuit supplying drive power, a resistor 6, a resistive element whose electrode is connected to a metallic member via an insulation film are mounted in a package 1, the element is provided with a microwave input terminal, an output terminal and a drain bias terminal 11, and a voltage applied to a drain bias terminal is fed to a drain electrode of a TR chip via the resistive element fixed to a metallic base of the package by the metallic member.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a microwave circuit component,
In particular, it relates to the structure of a power limiting element used for high power.

[0002]

2. Description of the Related Art In recent years, the output of amplifiers used in the microwave band is becoming higher and higher, and the power gain of each transistor is not so high accordingly, and therefore the circuit configuration thereof is high. The number of stages in the amplifier chain, which is based on the series connection of transistors, is also increasing. In an amplifier having such a circuit configuration, a power limiting element is used in order to stabilize output power against environmental temperature and frequency changes and to avoid damage due to overdrive of transistor elements. In the configuration method of arranging this limiting element in the amplifier chain of the amplifier,
The most common and most efficient method is to place it in the middle position of the amplifier chain, but in the high power amplifier as described above, the temperature gradient caused by the multi-stage transistors placed after the limiting element is It is not possible to ignore the effects of gain fluctuations and output fluctuations on frequency,
Limiting elements are needed near the final stage. Usually, this power limiting element consists of a diode, and a resistor is inserted in the drain bias of the field effect transistor to absorb the change in power due to the change in current by a voltage drop and to bias the transistor at a low voltage bias. There are some that work with and utilize its saturated output.

The former has the advantage that it is easy to design, but has the drawback that since the element itself is passive, the passage loss is large and the power reflection becomes large when limiting occurs.

Since the latter uses an active transistor element for limiting, there is an advantage that the limiting element itself has a gain and the reflection loss is relatively stable regardless of the limiting state. There is a drawback that it is difficult to design and it is difficult to obtain a limiting element with a stable yield.

In both methods, the power withstanding property must be improved when used near the final stage of the high-power amplifier as described above, but in the former case, the junction area of the semiconductor must be large. This inevitably causes a problem that the passing loss and the reflection loss are further increased. In the latter case,
This can be dealt with by increasing the gate width and the operating channel width, but this increases the operating current, and the resistor that determines the limiting characteristics must be upsized in order to have power resistance. It must be connected to the outside of the envelope, and the wiring between the envelope and the resistor must be placed close to avoid the effect of unnecessary inductors, limiting the place of installation. A high-dielectric constant substrate such as a Teflon substrate or a ceramic substrate is usually placed around the envelope, and the resistor placed on such a substrate does not dissipate heat well. It was necessary to use cement resistance or ceramic resistance of.

[0006]

As described above, in order to provide the transistor amplifier with a stable limiting characteristic, it is necessary to provide a resistor having a large current capacity outside the transistor. It has for large resistors, such as when used with DC voltage. Since the influence of inductance becomes visible, there was a possibility of bias oscillation. The present invention solves this problem by mounting a small resistor with good heat dissipation directly on a metal base with good heat dissipation in an envelope, and applying an external drain voltage to the drain electrode via this resistor. It was made to be done. Further, the present invention provides a new resistor having a good heat dissipation characteristic as a resistor structure suitable for this structure.

[0007]

A power limiting element according to the present invention includes a power field effect transistor chip in an envelope, a matching circuit for converting the impedance of the transistor chip into a desired load impedance, and drive power. A bias circuit for supplying and a resistor element in which a resistor and an electrode are formed on a metal member via an insulation film are provided, and a microwave input terminal, an output terminal and a drain bias terminal are provided, and the bias circuit is supplied to the drain bias terminal. Voltage is applied to the drain electrode of the transistor chip through a resistor element fixed to the metal base of the envelope with a metal member.

The resistor element is provided with a metal resistor and an electrode on the upper surface thereof, and the resistor and the electrode are formed on an inorganic insulating film on a metal substrate, and the resistor portion and the electrode portion are connected to each other. It is characterized in that the included shape and dimension are sufficiently small with respect to the wavelength of the operating frequency and there is no difference in the coefficient of thermal expansion between the metal substrate and the insulation film.

[0009]

In such a transistor amplifier, since the drain bias resistor inserted to obtain a stable limiting characteristic is provided on the metal base inside the envelope, the heat radiation from the resistor is very good. The temperature rise of the resistance is suppressed and the reliability is improved. Further, since the structure of the resistor itself is mainly composed of the metal substrate, the thermal resistance of the resistor is also small, so that even a small resistor can have sufficient power resistance.

[0010]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a top view showing the overall structure of a power limiting amplifier element according to the present invention. In the figure, 1 is an envelope, which is based on an alloy of copper and tungsten. On this metal base, an FET chip 2, an input matching circuit board having an input matching circuit 4 formed thereon, and an output matching circuit board having an output matching circuit 3 formed thereon are provided. Also, F
A gate bias terminal 11 and a drain bias terminal 12 for applying a bias to the gate and drain of the ET are provided in the envelope. On the drain side, first, the terminal is bonded to the resistor 6 and further connected to the output matching circuit pattern 3 near the FET chip via the bias circuit and the chip capacitor 5a. The substrate of the resistor 6 is made of the same copper tungsten as the base metal of the envelope, and the gate side has a bias circuit chip capacitor 5b provided on the base metal of the envelope and an output matching circuit pattern C. It is connected. Here, 7 is a chip capacitor for so-called DC cutting, 6 is a low resistance body, 9 is a high resistance body, 12 is a gate bias terminal, and 13 is an RF terminal.

Next, the structure of the resistor 6 is shown in a perspective view in FIG.

In the figure, the metal substrate 61 is made of Cu20%, W80
% Alloy with a plate thickness of 0.2 mm, the surface of which is sufficiently polished, and then a plasma CVD (chemical vapor deposition) method is used to form a layer of silicon dioxide (SiO 2) having a layer thickness of 0.4 μm.
N) form layer 62. The conditions for forming the SiON layer 62 are such that the temperature and the gas flow rate ratio are set so that the SiON layer 62 comes close to the coefficient of thermal expansion of the metal substrate 61. Further, tantalum (Ta) and gold (Au) are formed by an electron beam evaporation method, and gold in a portion to be a resistance portion is removed by selective etching to form a resistance. In the resistor having this structure, the metal body having a high thermal conductivity is provided immediately below the resistor portion which is the heat source, and therefore the power resistance is high. In addition, since the substrate material of the resistor and the base metal of the envelope on which this resistor is mounted are the same metal, the stress caused by the difference in the coefficient of thermal expansion is not applied to the resistor and the nitrogen oxide SiON is It won't break.

Next, FIG. 3 shows an equivalent circuit of the block diagram shown in FIG.

The power amplifier elements connected as shown in the figure are:
Since the current characteristic and the temperature characteristic with respect to the input / output of the field effect transistor (FET) show the characteristics as shown in FIG. 4, the drain end voltage decreases in proportion to the increase in the current, and the power is stable with respect to the temperature and the input level. Limiting characteristics can be obtained. In addition, all parts are built in one envelope, and by cap-sealing with metal or ceramic material, it is easy to handle as a completely sealed type element, and reliability is improved.

[0016]

As described above, according to the present invention, it is possible to realize a power limiting element which is small in size and has a high output, and which has a matching circuit and a bias circuit integrated with each other and incorporated in an envelope to have excellent power limiting characteristics.

[Brief description of drawings]

FIG. 1 is a top view of a power limiting amplifier element according to an embodiment of the present invention,

2 is a perspective view of the low antibody in FIG. 1,

FIG. 3 is an equivalent circuit diagram of the power limiting amplification element shown in FIG.

FIG. 4 is a diagram showing a current characteristic and a temperature characteristic with respect to an input / output of the FET.

[Explanation of symbols]

 1 Envelope 2 FET Chip 3 Output Matching Circuit 4 Input Matching Circuit 5a, 5b Bias Circuit Chip Capacitor 6 Low Resistor 61 Metal Substrate 62 Inorganic Insulator (SiON) 63 Metal Electrode 64 Resistor 7 DC Cut Chip Capacitor 8 Metal Fine Wire 9 High Resistor 11 Drain Bias Terminal 12 Gate Bias Terminal 13 RF Terminal

Claims (1)

[Claims] 1. A power field-effect transistor chip housed in an envelope, a matching circuit for converting the impedance of the transistor chip into a desired load impedance, a bias circuit for supplying drive power, and a resistor and an electrode made of metal. A member is internally provided with a resistor element configured through an insulation film, and a microwave input terminal, an output terminal and a drain bias terminal are provided, and the voltage supplied to the drain bias terminal is a metal base of an envelope. A power limiting element, which is applied to a drain electrode of the transistor chip via a resistor element fixed by a member.