JP2006032450A - Power amplifier using bipolar transistor and manufacturing method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem where a power amplifier composed of a bipolar transistor in multi-cell structure is broken as a collector output side thermally runs away as the collector output side becomes high in a heat distribution at high output time. <P>SOLUTION: The base potential of a transistor with large heating value can be suppressed low by making a blast resistance connected to the base of a collector-output side transistor large, and positive feedback of a rise in base potential due to heat generation can be suppressed, so a thermal runaway can be avoided. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a power amplifier using a bipolar transistor, and more particularly to a power amplifier using a heterojunction bipolar transistor (hereinafter referred to as HBT) having excellent high frequency characteristics.

The structure of a commonly used high-power microwave HBT is shown in FIG. It is constituted by a via hole row constituted by a row in which a plurality of HBT cells 1 are arranged and a via hole 8 parallel to the transistor row. The emitter electrode 3 of each HBT is connected to a via hole array formed in the emitter wiring 6, and is connected to the back electrode from the front surface of the HBT transistor and grounded. Therefore, the heat generated in the HBT escapes from the via hole. In such a structure having a via hole in the vicinity of the emitter, the heat generated in the HBT is more easily escaped than the structure having no via hole and the structure in which the via hole is separated from the HBT, and the problem of destruction due to thermal runaway is reduced. The In high-power bipolar transistor power amplifiers, the resistance to breakdown due to this thermal runaway is a problem. A high frequency signal is input to the base wiring 5 as a high frequency amplifier, and the amplified signal is output from the collector electrode 4 to the collector wiring 7. This thermal runaway will be briefly explained here. If heat is generated when each HBT is driven, the base voltage rises due to the heat generation, a collector current flows, and the heat of the transistor rises due to the positive feedback. In the case of a bipolar transistor consisting of multiple cells, if heat non-uniformity occurs, the base voltage of a transistor with a large amount of heat generation rises, and the base current concentrates and flows into the transistor, thereby further increasing the collector current and generating heat. This is a phenomenon in which a positive feedback is applied and the transistor starts a thermal runaway. In order to suppress this non-uniform phenomenon of heat generation, there is a method of arranging a via hole in the vicinity of the HBT to increase the absolute amount of heat escape, but the non-uniformity of heat generation cannot be completely suppressed. Therefore, a method of applying a base bias to each HBT via a ballast resistor is usually performed. FIG. 5 shows the base electrode 2 connected to the base wiring 5 via the ballast resistor 9. This is a method using a mechanism in which, when the heat generation of the transistor increases, the base voltage increases, which lowers the voltage at the ballast resistor end, and as a result, the input base current is suppressed. (See Patent Document 1).
JP 7-176538 A

  However, even in the method of suppressing the non-uniformity of heat generation at the time of high output by inserting this ballast resistor, the non-uniform amount of heat generation occurs. This is because, in the structure as shown in FIG. 5, the collector current of each HBT is collected on the output side at the top of the drawing where the collector wirings are commonly connected, so that the heat distribution on this output side becomes high. Therefore, there has been a problem that the heat generation amount of the HBT on the output side is increased, causing thermal runaway and destruction.

  The present invention solves the above-described problem, and is characterized in that the base ballast resistor is gradually increased toward the output side of the power amplifier. Further, the base ballast resistor is constituted by a thin film resistor, and the base ballast resistor is narrowed as the pattern width of the base ballast resistor approaches the output side of the power amplifier. Furthermore, the base ballast resistor is one or more resistors connected in parallel, and the number thereof decreases as it approaches the output side of the power amplifier.

  Furthermore, in the method of manufacturing a power amplifier using the bipolar transistor of the present invention, the burst ballast resistor is a plurality of resistors connected in parallel, and the number of the resistors is changed by trimming the resistors. The base ballast resistance value connected is changed by the arrangement of the bipolar transistor.

  According to the above method, the HBT that easily generates heat on the collector output side can suppress the base potential by the ballast resistor, suppress the heat generation, and avoid thermal runaway.

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

(First embodiment)
FIG. 1 shows a first embodiment.

  A plurality of HBT cells 1 are arranged and a via hole row 8a constituted by a via hole 8 parallel to the transistor row. The emitter electrode 3 of each HBT is connected to a via hole array formed in the emitter wiring 6, a high frequency signal is input to the base wiring 5 as a high frequency amplifier, and the amplified signal is output from the collector electrode 4 to the collector wiring 7. . As shown in FIG. 5 of the prior art, the base electrode 2 is connected to the base wiring 5 via the ballast resistor 9. In the present invention, the width of the ballast resistor 9 connected to each HBT is narrowed toward the output side, and the resistance value is increased. As a result, the HBT that easily generates heat on the output side can suppress the base potential by the ballast resistor, suppress the heat generation, and avoid thermal runaway.

  The material of the thin film resistor is TaN, WSiN, NiCr or the like, and the sheet resistance is designed to give a desired resistance value. Since the thin film resistor is deposited by vapor deposition, etching, or lift-off, the above structure is realized by changing the pattern width of photolithography.

(Second Embodiment)
FIG. 2 shows a second embodiment.

  FIG. 2 shows a structure in which the length of the ballast resistor 9 is increased toward the output side. This is a structure in which the resistance value increases as the resistance of the thin film increases toward the output side. As a result, the HBT that easily generates heat on the output side can suppress the base potential by the ballast resistor, suppress the heat generation, and avoid thermal runaway.

  Since the thin film resistor is deposited by vapor deposition, etching, or lift-off, the above structure is realized by changing the pattern length of photolithography.

(Third embodiment)
FIG. 3 shows a third embodiment.

  FIG. 3 shows a structure in which the ballast resistor is a parallel-connected ballast resistor 10 in which a plurality of thin-film resistors 11 of equal width are arranged in parallel and the number of the arranged ballast resistors decreases toward the collector output side. The structure in which the resistance value is changed by changing the number of columns of the resistors of the ballast resistor module in FIG. 5 provides a new method for manufacturing a power amplifier of the HBT.

  The manufacturing method will be described with reference to FIG. First, as shown in (A), the same number of thin film resistors 11 are connected in parallel to all HBTs in parallel-connected ballast resistors 10. Next, as shown in (B), trimming by means of a laser or the like changes the number of thin film resistors 11 and changes the ballast resistance value. This method is advantageous because it allows fine adjustment after the HBT is completed.

  The power amplifier using the bipolar transistor according to the present invention is useful as a power amplifier excellent in high-frequency characteristics because heat generation of the transistor cell on the output side can be suppressed and thermal runaway can be avoided.

The figure which shows the amplifier using the bipolar transistor which has a ballast resistance which shows the 1st Embodiment of this invention The figure which shows the amplifier using the bipolar transistor which has a ballast resistance which shows the 2nd Embodiment of this invention The figure which shows the amplifier using the bipolar transistor which has a ballast resistance which shows the 3rd Embodiment of this invention The figure which showed the manufacturing method in the 3rd Embodiment of this invention The figure which shows the amplifier using the bipolar transistor which has the conventional ballast resistance

Explanation of symbols

1 HBT cell 2 Base electrode 3 Emitter electrode 4 Collector electrode 5 Base wiring 6 Emitter wiring 7 Collector wiring 8 Via hole 9 Ballast resistance

Claims (5)

In the structure of a power amplifier comprising a transistor row in which a plurality of cells of bipolar transistors are arranged and a via hole row comprising a plurality of via holes arranged in parallel with the transistor row, the bipolar transistor is provided with a base ballast resistor. A power amplifier using a bipolar transistor, wherein a ballast resistor is gradually increased toward an output side of the power amplifier. 2. The power amplifier according to claim 1, wherein the base ballast resistor is formed of a thin film resistor, and becomes narrower as the pattern width of the base ballast resistor approaches the output side of the power amplifier. 2. The power amplifier according to claim 1, wherein the base ballast resistor is formed of a thin film resistor, and the length of the pattern of the base ballast resistor becomes longer as it approaches the output side of the power amplifier. 2. The power according to claim 1, wherein the base ballast resistor connected to each bipolar transistor is one or more resistors connected in parallel, and the number thereof decreases as it approaches the output side of the power amplifier. amplifier. The base ballast resistor connected to each bipolar transistor is a plurality of resistors connected in parallel. By trimming the resistors, the number of the resistors is changed, and the base ballast resistors are connected by the arrangement of the bipolar transistors. 2. The method of manufacturing a power amplifier using a bipolar transistor according to claim 1, wherein the base ballast resistance value is changed.

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