JPH09106994A - Microwave transistor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power feeding method that enables unit microwave transistors of comb-shaped structure to be set zero in phase difference between them, prevents deteriorating in gain, and keeps high output. SOLUTION: Provided that the m-th gate finger 5 from an input point is Zum in length, and a gate pitch is represented by GP, an electric length difference ΔL2 between a gate (first) nearest to the input point and a farthest gate (m-th) from the input point is represented by a formula, ΔL2=2(m-1)GP +2(Zum-Zu1), where M is an integer above 1. Therefore, the gate fingers 5 are varied in length Zum, whereby ΔL2 can be reduced to zero. By this setup, signals can be set identical to each other in phase from an input point, so that a problem of phase difference can be solved. Moreover, a gate bus line 4 and bypass wire 7 are provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention provides a power supply method for a microwave transistor having a comb structure, which eliminates a phase difference between unit transistors, maintains a high output, and prevents a decrease in gain. About things.

[0002]

2. Description of the Related Art In a high-output transistor intended for high-frequency power, in order to obtain a large output, a method of connecting many cells in a lateral direction is employed. However,
In a device having many cells, a problem of a phase difference between a cell closest to the input point and a cell farthest from the input point may occur, and the device characteristics may be degraded. To solve this problem, there is a structure in which the bypass line is extended in the direction of the gate 3 so that the cell 6 is prevented from expanding in the lateral direction as much as possible, as in the conventional example of FIG. According to such a method, the phase difference can be reduced as compared with the case where the cell 6 is expanded only in the horizontal direction by the width of the gate 3, and an element having a high synthesis efficiency can be configured.

[0003] 1 is a drain, 2 is a source, 8 is an input point, and 9 is an output point.

Incidentally, the following can be cited as this kind of conventional technology.

(1) In a high frequency field effect transistor, a plurality of gate bus lines and drain bus lines are extended in the short side direction of the chip, and fingers extending from the respective bus lines in the long side direction of the chip are provided. By projecting, the length of the gate bus line with respect to the length of the FET chip can be shortened, and a decrease in output due to the phase difference in the FET chip can be suppressed. Further, in each cell, the path between the gate electrode and the drain electrode can be made uniform, and the combined loss of the output due to the phase difference can be reduced (JP-A-5-251479).

(2) In the structure of the field-effect transistor, the input terminal is connected to one end of the gate-impedance converter, and the output terminal is connected to the other end of the drain-impedance converter which is farthest from one end of the gate-impedance converter. (See Japanese Patent Laid-Open No. 6-151471).

(3) An active element of a microwave integrated circuit having a finger structure in which electrodes of a drain, a gate and a source are alternately arranged and connected by wiring, wherein the active element is in the signal propagation direction. , A microwave integrated circuit element formed by forming a plurality of vertically arranged fingers (Japanese Patent Laid-Open No. 3-289143).

[0008]

According to this method, as shown in FIG. 5, when the gate width is the same, the lateral spread can be suppressed to half of the normal width. 1 farthest from the input point
The electrical lengths (phases) viewed from the output points of the signals passing through the gates at the second and the second stages are in phase. However, in the first stage, the electrical length difference ΔL1 between the gate closest to the input point (first) and the farthest gate (mth) is represented by the gate pitch G
Assuming that p, ΔL1 = 2 (m−1) Gp, m> 1, and an integer (number of fingers), so that ΔL1 ≠ 0 always holds, and the problem of the phase difference cannot be solved.

Further, as shown in FIG. 6, there is a problem that the phase difference between cells becomes more remarkable even when multi-cells are formed for higher output than the basic cell structure.

Accordingly, the present invention provides a microwave transistor which improves the drawbacks of the prior art, eliminates the phase difference between unit transistors, and maintains a high output while preventing a decrease in gain. What you want to do.

[0011]

According to the present invention, in a microwave transistor having a comb structure which generates a large output, a bypass line 7 is extended in the direction of the gate 3 in order to suppress the lateral expansion of the cell 6, and a two-stage structure is provided. At the same time, there is provided a transistor structure characterized in that the length of adjacent gate fingers 5 is changed in each stage.

[0012]

Next, the operation of the present invention will be described. According to the above-described means, firstly, in order to arrange two bus lines 4 of the gate 3 in the direction of the gate finger 5, the bus line 4 at the farthest finger is larger than the usual laterally enlarged structure having the same total gate. The phase difference can be reduced. Further, by arranging the finger lengths of the respective gate fingers 5 shorter than the center by an amount corresponding to the length of the gate pitch in order, the phase difference between all the fingers can be made completely zero. Therefore, the high-frequency characteristics and the like of the element are significantly improved.

[0013]

FIG. 1 shows an embodiment of the structure of a microwave transistor according to the present invention. FIG. 2 is a diagram showing the appearance of an embodiment of the gate structure of the microwave transistor of the present invention. Assuming that the m-th gate finger length from the input point 8 is Zum, the electrical length difference Δ between the gate closest to the input point (first) and the gate farthest (m-th) is Δ
L2 is: ΔL2 = 2 (m−1) Gp + 2 (Zum−Zu1), where Gp is the gate pitch.
m> 1, an integer. Therefore, by changing each gate finger length Zum, ΔL2 can be completely set to zero. In addition, as shown in FIG. 3, even when a multi-cell configuration is used for higher output than the basic cell structure, the phase difference can be made completely zero.

[0014]

As is apparent from the above description, according to the present invention, it is shown that the phase of the signal as viewed from the input point becomes the same in each finger, and the problem of the phase difference is solved. Further, since the lateral spread of the gate is suppressed by using a two-stage configuration, a reduction in output, a deterioration in gain, and a reduction in combined loss due to a phase difference are significantly reduced while maintaining a large total gate width. doing. This structure largely contributes to obtaining a large output without deteriorating the gain of the microwave transistor. This method is particularly effective in increasing the output of a microwave transistor.

[Brief description of the drawings]

FIG. 1 is a plan view of one embodiment of a microwave transistor of the present invention.

FIG. 2 is a plan view of a gate structure in one embodiment of the microwave transistor of the present invention.

FIG. 3 is a plan view of an embodiment of the multi-cell structure of the microwave transistor of the present invention.

FIG. 4 is a plan view of a conventional microwave transistor.

FIG. 5 is a plan view of a gate structure of a conventional microwave transistor.

FIG. 6 is a plan view of a multi-cell structure of a conventional microwave transistor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Drain 2 Source 3 Gate 4 Gate bus line 5 Gate finger 6 Cell 7 Bypass line 8 Input point 9 Output point

Claims (3)

[Claims] 1. A finger structure transistor in which electrodes of a drain, a source, and a gate are alternately arranged and connected by wiring, wherein the transistor has two bus lines of the gate arranged in parallel with each other in a gate finger direction. A microwave transistor having a structure in which a finger length of each finger from a central portion to an end of a bus line is sequentially shortened by a gate pitch. 2. The microwave transistor according to claim 1, wherein the gate bus line has a two-stage structure. 3. The microwave transistor according to claim 1, wherein a plurality of cells are arranged in the direction of the bus line of the gate to have a multi-cell structure.