JP2006294901A - Power amplifier - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power amplifier capable of delivering high power output, while maintaining superior heat dissipation and grounding performance. <P>SOLUTION: An emitter electrode 4 of bipolar transistor elements is provided with a bump 8, and these are grounded with each other at a short distance. A unit cell 7 is formed as a single configuration unit by combining these arrangements. This method achieves the power amplifier capable of delivering high power output, while maintaining superior heat dissipation and grounding performance. <P>COPYRIGHT: (C)2007,JPO&INPIT

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) used in high frequency applications such as a cellular phone.

  The structure of a conventional HBT power amplifier will be described below with reference to the drawings.

  FIG. 2 is a plan view showing an example of a conventional HBT power amplifier. The HBT element 1 is a unit and is constituted by repeating this unit.

  In the case of the configuration of FIG. 2, an example of 32 cells in which HBT elements 1 are arranged in two rows of 16 cells is shown, but it is configured by arranging two of these in the case of 64 cells and three of them in the case of 96 cells. Become.

  In the figure, 2 is a base electrode, 3 is a collector electrode, and 4 is an emitter electrode. HBT elements 1 composed of these electrodes are arranged in a line, and the emitter electrode 4 is grounded via a via hole 5. The base electrode 2 has a DC bias supply and a high-frequency input. In many cases, the bias supply is provided with a resistor, and the high-frequency input is provided with a capacitor serving as a match. These resistors and capacitors are omitted and are simply shown as the base electrode 2. As for the collector electrode 3, there is a column for collecting outputs, and these columns are arranged on both sides of the via hole 5 and are combined with the collector extraction electrode 6 and output. The actual via holes 4 are arranged with a diameter of 70 μm and a via hole center distance of 100 μm.

  In this HBT power amplifier, heat is radiated from the via hole 5 and emitter grounding is performed by a wiring connected to the column of the via holes 5. However, in this case, the connection line between the collector extraction electrode 6 and the collector electrode 3 for extracting the collector electrode 3 to the outside becomes thin and the resistance is increased. As a result, the output will be attenuated.

An example of a conventional structure corresponding to the above-described problem is the structure of a high-frequency amplifier described in Patent Document 1.
JP 2000-106386 A

  However, in the structure of the conventional HBT power amplifier, there are two problems that conflict with each other as will be described later. That is, in this HBT power amplifier, the heat generated in each HBT element is dissipated from the via hole 5 and the emitter ground is formed by the wiring connected to the row of the via holes 5, so that the shorter the distance to the emitter ground, the more the heat dissipates. Performance will be improved and grounding will be improved. Although shortening this distance can be realized by reducing the collector width W1 shown in FIG. 2 as much as possible, it is also necessary to reduce the collector output resistance of the HBT in order to increase the collector output. Thus, two contradictory problems arise that the collector width W1 of the collector electrode 3 is required to be as wide and low resistance as possible.

  Although it is desirable that there are as many via holes 5 as possible and the arrangement pitch is as narrow as possible, there are limitations on the manufacturing method.

  The present invention solves the above-mentioned conventional problems, and an object of the present invention is to provide a power amplifier capable of increasing the output while maintaining good heat dissipation and grounding.

  In order to solve the above-mentioned problems, a power amplifier according to the present invention is provided with a bump on the emitter electrode of a bipolar transistor element and grounded at a short distance, and a plurality of these are combined to form a unit cell as one constituent unit. Formed.

  Further, the collector electrode of the bipolar transistor element is formed by branching from the common collector electrode and arranged in a row.

  According to the power amplifier of the present invention, the bump provided in each unit cell has a function of grounding the emitter and dissipating heat, and the bump can be arranged with a smaller pitch than the via hole. The emitter electrode can be installed in the immediate vicinity, and the heat radiation effect is higher than that of the via hole due to the large number of installed electrodes and the closeness of the distance. In addition, since the via hole is formed by etching the semiconductor substrate, no other pattern can be formed at the location of the via hole, but when using a bump, it is formed on the emitter electrode, so the semiconductor under the emitter electrode Pattern formation is possible on the surface side, and if a collector electrode with a large area is arranged in this part, the collector electrode can be dramatically thicker than before, and high output can be achieved while maintaining good heat dissipation and grounding It is possible to provide the obtained power amplifier.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a plan view showing an example of a power amplifier according to an embodiment of the present invention, and shows an example of a power amplifier using an HBT having a frequency of 400 MHz or more and an output of 20 dBm or more. Note that components corresponding to the components described in FIG. 2 and having substantially the same functions are denoted by the same reference numerals. The following embodiment is an example embodying the present invention, and does not limit the technical scope of the present invention.

  As shown in FIG. 1, a unit cell 7 in which four HBT elements 1 are combined is configured, and one bump 8 is provided for the unit cell 7. The bump 8 is flip-chip mounted and grounded, and has an effect of grounding and heat dissipation. Unlike the prior art, since the distance to the ground plane is also the shortest, the grounding characteristics and heat dissipation characteristics are improved. The collector electrodes are branched from the common collector electrode 9 and are arranged in rows.

  Since the common collector electrode 9 can be arranged by utilizing the space below the emitter electrode 4, the collector width W2 is widened and can be several times larger than the conventional collector width W1. By increasing the collector width W2, the collector resistance can be reduced, so that the output can be increased, and the output loss is also reduced and the efficiency is improved.

  The method of grouping the unit cells of the HBT is determined by how many base terminals of each HBT element are grouped, and the number of groups is preferably 3 to 5.

  INDUSTRIAL APPLICABILITY The present invention is applied to a power amplifier that requires excellent grounding characteristics and heat radiation characteristics of an electrode, high output, and high efficiency, and is used in a mobile phone or a mobile device, and more particularly, a hetero amplifier used in high frequency applications. This is useful for a power amplifier using a junction bipolar transistor.

The top view which shows an example of the power amplifier in embodiment of this invention Plan view showing an example of a conventional power amplifier

Explanation of symbols

1 HBT element 2 Base electrode 4 Emitter electrode 6 Collector lead electrode 7 HBT unit cell 8 Bump 9 Common collector electrode W1 Collector width W2 Collector width

Claims (2)

  A single bump is provided on the combined emitter electrode of a plurality of bipolar transistor elements, and the bipolar transistor elements are grounded to each other at a short distance, and the plurality of bipolar transistor elements and the bump are integrally formed. Is a new structural unit.   2. The power amplifier according to claim 1, wherein the structural unit composed of the plurality of bipolar transistor elements and the bumps is branched from the common collector electrode array.

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