JPS6328074A - Microwave field effect transistor - Google Patents

Abstract

PURPOSE:To improve gain characteristics by a method wherein respective distances from a gate pad to the crossing points of the respective fingers of a gate electrode and the edge of an active layer are equal and respective distances from drain pads to the crossing points of the respective fingers of drain electrodes end the edge of the active layer are equal. CONSTITUTION:The lengths of the fingers 4B of a gate electrode 4 which is formed on an active layer 1 and connected to a gate pad 2 are getting longer in proportion to be counted toward the center so as to make the distamces OA, OC, ...OM from the end point 0 of the gate pad 2 to the crossing points A, C, ... M of the edge of the active layer 1 and the fingers 4B equal. In the same manner, the distances PB, PD, ...PL from the end points P of drain pads 3 to the cross points B, D, ...L of the edge of the active layer 1 and the fingers 5B of drain electrodes 5 are made to be equal. RF signals inputted from the gate pad 2 are divided and the divided signals are propagated as far as the respective crossing points A, C, ...M with the same phase and amplified by an MESFET and the amplified RF signals are propagated in the respective fingers 5B of the drain electrodes 5 with the same phase and synthesized at the points P 100 % and outputted from the drain pads 3.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a microwave field effect transistor, and particularly relates to an electrode structure of a microwave field effect transistor having a comb-shaped electrode structure.

[Conventional technology]

In recent years, microwave field effect transistors (MESFE)
Due to its good properties, it has become widely used in microwave communications and other applications. In particular, since MESFEs and Ts made of GaAs substrates that require high output require a large gate width, a comb-shaped electrode structure is generally adopted.

FIG. 2 is a plan view of the electrode section of a conventional MESFET,
A comb-shaped gate electrode 4 consisting of a buspar 4A and a finger 4B formed on the active layer 1, a buspar 5A, and a finger 5.
A comb-shaped drain electrode 5 made of B is shown.

[Problem that the invention seeks to solve]

As shown in FIG. 2, in the MESFET cr) electrode of the conventional structure described above, fingers 4B of the gate electrode are arranged periodically on the rectangular active layer 1, so that the gate electrode, which is the input position of the RF multiplied signal, From the 0 point of the pad to the intersection point A of each finger 4B forming the gate electrode 4 and the end of the active layer 1
,C,E,G.

The distances from I to M are not equal. Similarly, the distances from the intersections B, D, F, H, J, and L of each finger, 5B, and active layer 1, which constitute the drain electrode 5, to the point P of the drain pad, which is the RF multiplication signal output position, are also equal. do not have. Therefore, the amplification section of MESFET consisting of each electrode etc.
There is a problem in that it does not operate in the same phase with respect to the RF multiplied signal input to the RF signal.

For example, with respect to the RF multiplied signal input to point ○ in FIG. 2, the distance between points OA and the distance between points 00 has a difference of 3 times the distance a between the fingers 4B, that is, 3a. Therefore, the input signal applied to the finger 4B closest to the gate pad 2 and the input signal applied to the farthest finger 4B are 3
A phase difference of a/λ is generated. Also, regarding the output signal, point P
Since there is a distance difference of 2a between B and point PF, 2a/λ
A phase difference occurs. Therefore, the signal manually applied to the gate pad 2 and the signal output from the drain pad 3 contain PF multiplied signals with a maximum phase shift of 5a/λ, and the M E S composed of each finger r'E
The output amplified by the amplification/width section of T is not 100% combined and is output from the drain pad. This is the cause of not being able to fully bring out the good gain characteristics inherent in the MESFET.

An object of the present invention is to provide a microwave field effect transistor with improved gain characteristics.

[Means for solving problems]

The microwave field effect transistor of the present invention has a comb-shaped gate electrode and a drain electrode formed on an active layer, in which the gate electrode is formed from a gate pad connected to the gate electrode. The distance from the intersection between each finger constituting the drain electrode and the end of the active layer is equal, and the distance from the drain pad connected to the drain electrode is equal to the intersection between each finger constituting the drain electrode and the end of the active layer. The distances up to the point are the same.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a plan view of an electrode section according to an embodiment of the present invention.

In FIG. 1, the length of the fingers 4B constituting the gate electrode 4 connected to the gate pad 2 and formed on the active layer 1 increases toward the center, and starts from the point ○ at the end of the gate pad 2. , the distance OA to the intersection of the finger 4B and the end of the active layer 1.

○C...OMs are formed to have the same length. Similarly, from the point P at the end of the drain band 3, the drain electrode 5
The distances PB, PD, . . . , PL to the intersections of the fingers 5B constituting the active layer 1 and the ends of the active layer 1 are also formed to have the same length.

In this embodiment configured in this way, the PF multiplied signal input from the gate pad 2 is divided and sent to each finger 4B.
The intersection points A, C, . . . with the active layer 1 of
The signal is amplified by a MESFET amplification section consisting of fingers of each electrode. Then, the amplified RF multiplied signal passes through each finger 5B of the drain electrode 5 in the same phase and reaches 100 at point P.
% is combined and output from the drain pad 3. Therefore, the gain characteristics are further improved.

〔Effect of the invention〕

As explained above, the present invention is based on the distance from the gate pad to the intersection of each finger constituting the gate electrode and the edge of the active layer, and the distance from the drain pad to the intersection of each finger constituting the drain electrode and the edge of the active layer. By making the distances to the intersections with the gate and drain electrodes equal, the amplifying section of the MESFET consisting of each finger of the gate electrode and the drain electrode can be operated with input signals of the same phase. The inherently good gain characteristics of the transistor can be further improved.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view of an electrode portion of an embodiment of the present invention, and FIG. 2 is a plan view of an electrode portion of a conventional microwave field effect transistor. DESCRIPTION OF SYMBOLS 1... Active layer, 2-- Gate pad, 3... Drain pad, 4... Gate electrode, 4A... Bus bar, 4B... Finger, 5... Drain electrode, 5A...
・Busbar, 5B...Finger. Figure 1 Figure 2

Claims (1)

[Claims] In a microwave field effect transistor having a comb-shaped gate electrode and a drain electrode formed on an active layer, from a gate pad connected to the gate electrode, each finger constituting the gate electrode and an end of the active layer The distances from the drain pad connected to the drain electrode to the intersections of the fingers constituting the drain electrode and the ends of the active layer are equal. A microwave field effect transistor featuring: