JPH02288409A - Resistance feedback type amplifier - Google Patents

Abstract

PURPOSE:To make unnecessary the need of detour of a feedback circuit for evading a source electrode to miniaturize the amplifier by dividing a drain electrode placed between gate electrodes divided into two, and placing a feedback resistance between its divided drain electrodes. CONSTITUTION:A drain electrode placed between divided gate electrodes G1, G2 is divided into D1 and D2, and between these divided drain electrodes, a feedback resistance 4 is placed. Also, ohmic electrodes 5, 6 are formed across this resistance 4, one electrode 5 is connected to a gate electrode leading-out conductor 8 through an air bridge 7, and the other electrode 6 is connected to a DC obstructing MIM(Metal-Insulator-Metal) capacitor 10 through an air bridge 9. This MIM capacitor 10 is formed on a drain electrode leading-out conductor 3. In such a way, detour of a feedback circuit for evading a source electrode and its leading-out part is made unnecessary and this amplifier can be miniaturized.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to improvement of MMIC (monolithic microwave integrated circuit), which is an integrated circuit mainly used in the microwave band. Furthermore.

Specifically, the present invention relates to an improvement of a feedback circuit composed of resistors in a resistive feedback amplifier.

(Prior art) MMIC is a general term for monolithic ICs used in the microwave band.1 Usually, a GaAs FET is mounted on a GaAs substrate.
(GaAs field effect transistor) and HEMT (formerly GH Electron #Iability Tra
It is made by integrating active elements such as high-frequency transistors such as n-sisters with passive elements such as resistors and capacitors. There are various types of MMICs, such as low-noise amplifiers, high-output amplifiers, switches, and phase shifters, and there are many applications for microwave amplifiers.

FIG. 3 shows an equivalent circuit of a wideband amplifier as an example of an MMIC. In the figure, T is a transistor such as a GaAsFET or HEMT, and G, D, and S are the gate electrodes of the transistor T.

A drain electrode and a source electrode are shown. C1 to C4 are capacitors, L+ to L7 are inductors, and R is a resistance.

As can be seen from Figure 3, the feature of this circuit is that feedback is applied by the series circuit of C3, Ls, and R that connects the drain electrode D (output terminal) and gate electrode G (input terminal) of the transistor T. This is due to the fact that By applying this feedback, wideband amplification characteristics can be realized. FIG. 4 shows the frequency characteristics of the gain obtained by simulation by optimizing each circuit constant shown in FIG. As you can see from this figure, from about 2GIIz to 18Gll
A flat gain can be obtained over a wide band up to z.

FIG. 5 shows the transistor 1 portion and the feedback circuits C3, L5, and R portions of the equivalent circuit of FIG. 3 as a pattern diagram of MMIC. In this diagram, transistor T
The gate electrode G is shown as having two branched electrode portions 68, G2.

The respective gate electrode portions G1 and G2 are, for example, gate electrodes)
JjO, 25ILm, and a unit gate width of 50 pm (total gate width as a transistor looJLm). In this case, only one drain electrode is required, or two source electrodes, sl and s2, are required as shown in FIG. Each source electrode S8, S2 must be grounded as shown in FIG.

Since MMICs are required to operate at an extremely high frequency of Gllz or higher, efforts are being made to minimize grounding inductance as much as possible. M
The ground electrode of the MIC is usually formed on the back surface of the substrate.

FIG. 6 shows an example of a method of grounding the source electrode, and shows a cross section taken along line BB' in FIG. In this figure, (1) is a GaAs substrate, (2) is a source electrode S,
The lead-out portion (20) is a ground electrode. (30) is a hole made in the substrate (1) and is called a via hole. As can be seen from this figure, the source electrodes S0 and S2 are directly connected to the ground electrode (20) on the back side of the substrate through the via hole (30) provided under the lead-out part (2), resulting in the minimum source inductance. It will come true.

The thickness of the substrate (1) is usually about 100 to 200 JLm, and the diameter of the via hole (30) needs to be larger than the thickness of the substrate (1). Therefore, the pattern size of the drawer part (2) is 2007mm square to 30mm square.
Approximately 0 pm square is required. As shown in FIG. 5, the feedback circuit section is composed of a series circuit of a capacitor C3 and a resistor, and is connected from the drain electrode to the gate electrode G so as to avoid the source electrode (S2) and its lead-out section (2). Connected.

[Problem to be solved by the invention]

A problem in providing the feedback circuit section as described above is that the via hole section for grounding the source electrode occupies a relatively large area. That is, the detour distance of the feedback circuit that avoids the source electrode and its lead portion becomes longer. Inductor L5 in Fig. 3 represents the inductance of the same number of lines necessary for detouring the feedback circuit, but as the detour distance increases, the inductance of inductor L5 increases, so MM
It becomes impossible to improve the performance of the IC. In other words, even if good performance is obtained through simulation, it may not be possible to realize it based on the pattern diagram. Further, as the detour distance of the feedback circuit increases, a problem arises in that the area occupied by the feedback circuit increases.

The present invention was made to solve the above-mentioned problems, and it is an object of the present invention to provide a resistive feedback amplifier that does not require a detour of the feedback circuit.

(Means for Solving Problem W#) A resistive feedback amplifier according to the present invention divides a drain electrode arranged between at least two divided gate electrodes, and divides a drain electrode between the divided drain electrodes. It's like placing a resistor.

(Function) The resistive feedback amplifier according to the present invention divides the drain electrode placed between the divided gate electrodes, places a feedback resistor between the divided drain electrodes, and uses the feedback resistor to connect the drain electrode to the gate electrode. Since it is connected to the electrode, there is no need to detour the feedback circuit to avoid the source electrode.

(Embodiment) FIG. 1 shows an embodiment of this invention. In this figure, (3) indicates the drain electrode and the lead conductor of D2. As can be seen from this figure, the structural difference from the conventional transistor shown in Fig. 5 is the drain electrode.
and D2. A feedback resistor (4) is placed between the divided drain electrodes. In this example, the resistor (4) is formed of a semiconductor layer. In addition, ohmic electrodes (5) are connected to both ends of this resistor (4).
(5) is formed, and one electrode (5) is formed with an air bridge (
7) is connected to the gate electrode lead conductor (8),
The other electrode (6) is connected to a DC blocking MI M (Metal-Insulator) via an air bridge (9).
-Metal) connected to the capacitor (lO). This MIM capacitor (lO) is formed on the drain electrode lead conductor (3). Figure 2 is line A in Figure 1.
-A”. As can be seen from this figure, the M!M capacitor (!0) has a metal film (3).
This is a flat plate capacitor with a three-layer structure of - dielectric film (101) - metal film (102), and in this embodiment, it also serves as the base electrode of the drain electrode lead-out conductor (3) or the MIM capacitor (10). ing. The upper electrode of the MIM:7 capacitor (10), that is, the metal film (102) is connected to the air bridge (
9).

In the above embodiment, a semiconductor layer was used as the feedback resistor (4), but a metal resistor may also be used.
) and the gate electrode lead conductor (8) and MIM capacitor (lO) are connected by air bridges (7) and (9).
was used, but normal wiring may also be used. Further, the MIM capacitor (10) may be formed on the drain electrode lead-out conductor (3) or may be formed on the substrate (1). Furthermore, M
The IM capacitor (lO) is the gate electrode lead conductor (8)
Needless to say, it may be placed on the substrate (1) on the gate electrode side. Furthermore, the transistor is 2
Although the present invention is taken as an example of a transistor having bifurcated gate electrode portions G, . Rather, the effects of the present invention are more pronounced in transistors having a large number of gate electrodes. That is, a high-output transistor usually has several tens of gate electrodes, and as the transistor size increases, the inductance of the feedback circuit increases in the conventional method shown in Figure 5, making it difficult to configure the feedback circuit. Although it would be impossible to do so, it is easily possible with this invention.

〔Effect of the invention〕

As described above, according to the present invention, the feedback circuit can be formed compactly, so the pattern layout becomes extremely easy, and the amplifier can be made high-performance and compact.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an embodiment of the present invention, FIG. 2 is a partial cross-sectional view of FIG. 1, FIG. 3 is a diagram showing an example of a monolithic microwave integrated circuit, and FIG. 3, FIG. 5 is a diagram showing the pattern of the main part of FIG. 3, and FIG. 6 is a diagram showing a partial cross section of FIG. 5. In the figure, (3) is the drain electrode lead conductor, (4) is the feedback resistor, (8) is the gate electrode lead conductor, (10) is the DC blocking capacitor, (61) and (G2) are the gate electrode, (DI ), (D2) is a drain electrode. Note that the same reference numerals in each figure indicate the same or corresponding parts. 1st Figure 8) r-1t xylo 18 elm O:MIM con dry size ol, oz:t'shikun t41M 21! All Fig. 3 Fig. 4 Lay down (Gl-1z) Fig. 5

Claims (1)

[Claims] (1) A resistive feedback amplifier in which feedback is applied from the drain electrode to the gate electrode of a field effect transistor by a resistor, in which the drain electrode arranged between at least two divided gate electrodes is divided, A resistive feedback amplifier in which a feedback resistor is placed between the divided drain electrodes.