JPS61190971A - high frequency transistor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a high frequency transistor, and particularly to the structure of a small and high output transistor.

High-frequency, high-output transistors formed on silicon substrates require large-area emitters in order to obtain large outputs, which increases the emitter junction area and collector junction area, resulting in large input and output capacitances. As a result, the values of input impedance and output impedance are extremely reduced, and the feedback capacitance from the collector to the base also becomes large.

Normally, it is desirable that the matching impedance with the load be about 50 ohms, but the impedance is usually much lower than this value.

For these reasons, high frequency output transistors have poor matching with external circuits, resulting in a reduction in power gain, making circuit design to maintain performance complex and difficult.

For these reasons, there is a demand for an appropriate configuration of high frequency transistors that can achieve impedance matching with the load.

[Conventional technology]

FIG. 3 shows an equivalent circuit of a high-frequency transistor that has been put into practical use for conventional impedance matching.

A base terminal 2 and a collector terminal 3 of the transistor 1,
There is an emitter terminal 4, and a low frequency filter consisting of a capacitor 5 (MOS-C) and an inductance 6 (formed with bonding wire) is connected to the input side between the base terminal and the emitter terminal. On the other hand, a shunt inductance 7 and a DC blocking capacitor 8 are connected in series between the emitter terminal and the collector terminal on the output side, and the impedance is matched with the 50 ohm of the external circuit by incorporating it into the transistor. Internally matched high frequency, high output transistors are widely used.

However, since transistors configured in this manner are assembled using individual circuit elements, variations in the constants of those elements cause variations in product characteristics41b. There are disadvantages such as difficulty in design and design, and a narrow frequency bandwidth as a characteristic of the product.

[Problem that the invention seeks to solve]

When the above-mentioned high-frequency transistor has a large output, the junction area of the emitter and collector increases and the capacitance increases, which lowers the impedance between the input and output sides of the transistor, making it difficult to match the constant load impedance. The problem is that even if measures are taken to match the impedance in a circuit, the frequency band is narrow and circuit design becomes difficult.

[Means to solve the problem]

The present invention provides a high-frequency transistor that solves the above-mentioned problems, and its means include first and second transistor elements provided on the surface of the same semiconductor chip;
and the second transistor element are connected to the collector external terminal with their respective collectors in common, the emitter of the first transistor is connected to the base of the second transistor, and the connection between the connection part and the emitter of the second transistor is connected to the collector external terminal. This can be achieved by high-frequency transistors connected within the same package with inductance between them.

[Effect]

The present invention uses two high-frequency transistors, the input terminal is the base side of the first transistor, the output terminal is the collector of the second transistor, and the collectors of the two transistors are connected in common. Further, the emitter of the second transistor is a ground terminal, and the emitter of the first transistor is directly connected to the base of the second transistor, so that its input impedance is set to a predetermined value higher than the input impedance of the second transistor. This is achieved by using sophisticated high-frequency power amplifier circuit technology and semiconductor monolithic integrated circuit technology to provide a technology for increasing the impedance on the input side of high-frequency transistors.

〔Example〕

FIG. 1 shows a main part of a transistor circuit showing one embodiment of the present invention.

The base 12 and collector 13 of the first transistor 11,
If there is an emitter 14, and a base 16, a collector 17, and an emitter 18 of a second transistor 15, the input terminal B is the base 12 of the transistor 11, and the output terminal C is the first
The collectors of two transistors, the transistor 11 and the second transistor, are connected in common.

The ground terminal E is grounded at the emitter 18 of the second transistor 15, but the emitter of the first transistor is directly connected to the base 16 of the second transistor, and a predetermined value (second It is grounded via an inductance 19 having a value higher than the input impedance of the transistor.

To explain the circuit operation of the high frequency transistor according to the present invention, the emitter DC current in the first transistor flows through the inductance 19 and does not flow into the second transistor, so there is no reduction in collector efficiency. , the high frequency current does not flow through the inductance 19, but flows into the second transistor and is amplified.

That is, the second transistor performs class C operation with high efficiency, and performs optimal operation for high frequency and high output amplification.

Since the power handled by the first transistor is reduced by the power gain of the second transistor, a shorter emitter perimeter is sufficient, resulting in a transistor with high input impedance.

Therefore, the input impedance of the transistor of the present invention is mainly the input impedance of the first transistor, and has higher input impedance characteristics than the second transistor alone.

Furthermore, as a feature of the present invention, the power gain is the product of the power gains of the first transistor and the second transistor, making it possible to obtain high gain and high output.

Regarding the manufacture of this transistor chip, its pattern is only slightly different from that of conventional transistors, and there are no major manufacturing or design variations.

That is, the inductance connected between the emitters of the first transistor and the second transistor is built into the transistor package using a bonding wire or a strip line, or by adding a new external connection terminal to the transistor package. Of course, a predetermined inductance can be connected to the outside of the package by providing a predetermined inductance and connecting it to the emitter of the first transistor.

By using an external connection type as described above, various arbitrary inductances can be connected, and resistance and capacitance can be combined, which expands the range of applications.

FIG. 2 shows a main cross-sectional view of an npn transistor chip according to the invention.

On the n+ semiconductor substrate 21, there is an n-type epitaxial collector layer 22, a p-type base diffusion layer 23, 24, and an n+ emitter diffusion layer 25, 26. The insulation of silicon oxide 1IiI
27, and necessary wiring 28 is provided.

The inductance 19, which is the main point of the present invention, is connected as shown in the figure, and is connected to terminals B and C shown in FIG.

E is the corresponding sign.

〔Effect of the invention〕

As described above in detail, the high-frequency transistor of the present invention has great effects in that it has good impedance matching and can provide high-frequency characteristics with a small size and large gain.

[Brief explanation of drawings]

FIG. 1 is an equivalent circuit diagram of a high-frequency transistor showing an embodiment of the present invention. FIG. 2 is a sectional view of a high-frequency transistor showing an embodiment of the present invention. FIG. 3 is an equivalent circuit diagram of a conventional high-frequency transistor. In the circuit diagram, 11 is the first transistor, 12 is the base, 13 is the collector, 14 is the emitter, 15 is the second transistor, 16 is the base, 17 is the collector,
18 is an emitter, 19 is an inductance, 21 is an n+ semiconductor substrate, 22 is an n-type epitaxial collector layer, 23.24 is a p-type base diffusion layer, 25.26 is an n+ emitter diffusion layer, 27 is a silicon oxide film , 28 indicate wiring, respectively. Figure 2 Figure 3

Claims (1)

[Claims] First and second transistor elements are provided on the surface of the same semiconductor chip, the respective collectors of the first and second transistor elements are connected to a common collector external terminal, and the emitter of the first transistor is connected to a common collector external terminal. is connected to the base of a second transistor, and the connecting portion and the emitter of the second transistor are connected by an inductance within the same package.