JPH0693576B2 - Bypass capacitor structure, field effect transistor circuit using the same, and transistor circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention is designed to insulate a high frequency signal such as a microwave in a direct current manner and to short-circuit the high frequency signal with a substantially extremely low impedance. The present invention relates to a bypass capacitor structure, a field effect transistor circuit using the same, and a transistor circuit.

(Prior Art) FIG. 5 is a circuit diagram of an example of a conventional amplifier circuit using field effect transistors. In recent years, low-noise gallium arsenide field-effect transistors have become available at low cost, and the use of devices for receiving high-frequency signals such as microwaves in RF amplifiers is becoming common. In FIG. 5, a reception signal received by a horn antenna (not shown) is given to the gate of the first-stage field effect transistor FET ₁ via the first strip line 1, and the signal appearing at its drain is the second signal.
Is applied to the gate of the field effect transistor FET ₂ of the next stage via the strip line 2 of Furthermore, the signal appearing at the drain of the field-effect transistor FET _{2 in} the next stage is transmitted through the third strip line to the field-effect transistor in the final stage.
A signal given to the gate of FET ₃ and appearing at its drain is led to the fourth strip line 4 as an amplified output. The drains of the first, second and final stage field effect transistors FET _{1 to} FET ₃ are connected to the positive power source + V _CC via the high frequency blocking choke coils 5, 5, 5 respectively, and the sources are All grounded, choke coil gate
6, 6 and 6 are connected to the negative power supply −V _EE via each.

In such a circuit configuration, two power sources having different polarities, that is, a positive power source + V _CC and a negative power source −V _EE are required, which complicates the configuration of the power source circuit. Therefore, a self-bias type amplification circuit that can operate only with a positive power supply + V _CC has been proposed. FIG. 6 shows a circuit diagram of an example of a conventional self-bias type amplifier circuit using this field effect transistor.
In FIG. 6, the same circuit members as those in FIG. 5 are designated by the same reference numerals to omit redundant description.

6 is different from FIG. 5 in that the sources of the first-stage, second-stage and final-stage field effect transistors FET _{1 to} FET ₃ are grounded via a bypass capacitor 7 and a choke for high frequency blocking is provided. Coil 8 and bias resistor 9
And to be grounded in series.

In such a circuit configuration, the field effect transistor FET ₁
The source of the FET ₃ is grounded at a high frequency by the bypass capacitor 7, but has a certain positive potential in terms of direct current due to the voltage drop generated in the bias resistor 9 by the drain current. The gate of the field effect transistor FET ₁ ~FET ₃ is because it is DC grounded, the gate becomes lower than the source potential. Therefore, only the positive power supply + V _{CC provides the} negative bias voltage.

(Problems to be Solved by the Invention) By the way, as shown in FIG.
If a lumped-constant type element is used as this, there is a problem that a high-frequency signal such as a microwave is not grounded with a sufficiently low impedance, and the amplification gain is reduced by, for example, about 4 dB as compared with the circuit of FIG. It is considered that this is due to the inductance component of the bypass capacitor 7 itself or the inductance component of the wiring for connection.

An object of the present invention is to solve the above-mentioned problems of the conventional bypass capacitor structure and to provide a bypass capacitor structure capable of being short-circuited at high frequency with a substantially extremely low impedance, and further by using this bias capacitor structure. An object of the present invention is to provide a field effect transistor circuit having improved high frequency characteristics and a transistor circuit.

(Means for Solving the Problems) In order to achieve the above object, the bypass capacitor structure of the present invention is a metal that covers one end of a high frequency active element disposed on a printed wiring board and covers the back surface of the printed wiring board. Along with connecting the films, this printed wiring board is arranged in a metal housing with a thin insulating film interposed, and one end of the high-frequency active element is galvanically isolated from the metal housing and at the same time high-frequency. It is configured to short circuit.

Further, in the field-effect transistor circuit of the present invention, the source of the field-effect transistor arranged on the printed wiring board is connected to a metal film covering the back surface of the printed wiring board, and the printed wiring board is provided with a thin insulating film. It is disposed in a metal case with the interposition interposed, and either one of the source of the field effect transistor and the metal film is connected to the metal case via a bias resistor, and the gate of the field effect transistor is DC-directed. The circuit is configured by a self-bias method by short-circuiting to the metal case.

And, the transistor circuit of the present invention, while connecting the emitter of the transistor arranged on the printed wiring board to the metal film covering the back surface of the printed wiring board,
This printed wiring board is arranged in a metal housing with a thin insulating film interposed, and either the emitter of the transistor or the metal film is connected to the metal housing via an emitter resistor. .

(Operation) In the bypass capacitor structure configured as described above, a capacitor having a large capacitance is formed between the metal film covering the back surface of the printed board and the metal housing. Moreover, by connecting one end of the high-frequency active element to the metal film with an appropriately short wiring, the inductance component due to the wiring for connection is extremely small. Therefore, the impedance is extremely low with respect to high frequency signals such as microwaves, and one end of the high frequency active element is reliably short-circuited to the metal housing in terms of high frequency.

Further, in the field effect transistor circuit, the field effect transistor is self-biased, and the source is short-circuited to the metal case with a very low impedance at high frequencies.

The transistor circuit is temperature-compensated by the current feedback action of the emitter resistance, and the emitter is short-circuited to the metal casing with a very low impedance in terms of high frequency.

(Embodiment) An embodiment of the present invention will be described below with reference to FIGS. 1 and 2. FIG. 1 is a circuit diagram of an embodiment of a field effect transistor amplifier circuit using the bypass capacitor structure of the present invention, and FIG. 2 is a partially cutaway perspective view of the bypass capacitor structure used in FIG. Is. In FIG. 1 and FIG. 2, the same circuit members as those in FIG. 6 are designated by the same reference numerals, and a duplicate description will be omitted.

In FIGS. 1 and 2, the sources of the field effect transistors FET _{1 to} FET ₃ arranged on the printed wiring board 20 are metal films 22 that cover the entire back surface of the printed wiring board 20 by, for example, through holes 21. Connected to.
Then, this printed wiring board 20 is arranged on the metal casing 24 with an insulating film 23 such as a thin mica or plastic film interposed. Also a field effect transistor FET ₁
~ One end of a series connection body of the choke coil 8 formed in a pattern on the printed wiring board 20 and the bias resistor 9 as a chip component is connected to the source of the FET ₃ , and the other end of the series connection body is connected to the lead wire 25. Is connected to the metal housing 24 by. Then, to the gate of the field effect transistor FET ₁ ~FET _3, one end of the choke coil 6 which is formed in a pattern it is connected on the printed wiring board 20, the choke coil 6
The other end of is connected to the metal housing 24 by a lead wire 26.

In such a circuit configuration, the drain current flowing to the bias resistor 9, the field effect transistor FET ₁ ~FET ₃ are self-biased, can be operated by a single positive power supply + V _CC. Moreover, the metal film 22 covering the entire back surface of the printed wiring board 20 and the metal housing 24 form a large-capacity capacitor, and the wiring connecting this capacitor to the field effect transistors FET _{1 to} FET ₃ is a through hole.
It can be made extremely short by 21 etc., and the inductance component is extremely small. Therefore, the impedance becomes extremely low with respect to a high frequency signal such as a microwave, and the sources of the field effect transistors FET _{1 to} FET ₃ are short-circuited to the metal casing 24 in a high frequency manner. As a result, the self-biasing method uses one positive power source + V _CC , but does not lower the amplification gain as in the conventional case. Moreover, the amplified signal is not distorted.

FIG. 3 is a circuit diagram showing an embodiment of a transistor amplifier circuit using the bypass capacitor structure of the present invention, and FIG. 4 is a vertical sectional view of the bypass capacitor structure used in FIG.

In FIGS. 3 and 4, the emitters of the transistors Tr _{1 to} Tr ₃ arranged on the printed wiring board 30 are connected to the metal film 31 covering the entire back surface of the printed wiring board 30 through through holes or the like. To be done. Then, the printed wiring board 30 is arranged on the metal casing 33 with the thin insulating film 32 interposed. Further, the metal film 31 is connected to the metal housing 33 via the choke coil 34 and the emitter resistor 35 in series.

In such a circuit configuration, the temperature compensation of the collector current of the transistor Tr ₁ to Tr ₃ is made by a current feedback function of the emitter resistor 35. Moreover, the emitters of the transistors Tr _{1 to} Tr ₃ are short-circuited to the metal casing 33 at high frequency by the large-capacity capacitor between the metal film 32 and the metal casing 33, and the gain is not reduced.

In the above embodiments, the amplifier circuit using the bypass capacitor structure of the present invention has been described, but it may be used to short-circuit one end of a high frequency active element forming an oscillation circuit or the like at high frequency. Of course. The bias resistor 9 and the emitter resistor 35 are connected to the metal films 22 and 31 and the metal housing 2.
Source and emitter of the high frequency active element and the metal casing arranged between the printed circuit board 20 and 30 or between the printed circuit board 20 and 30.
Between 24 and 33, it suffices if it is interposed on either side.

(Effects of the Invention) Since the bypass capacitor structure of the present invention, and the field effect transistor circuit and the transistor circuit using the same are configured as described above, the following effects are achieved.

With the bypass capacitor structure of the present invention, a capacitor having a large capacity and an extremely small inductance component of the wiring for connection can be formed, so that the impedance is extremely low for high frequency signals such as microwaves, and one end of the high frequency active element Can surely be short-circuited to the metal housing at high frequencies.

In addition, in the field effect transistor circuit, the bypass capacitor structure and the bias resistor are interposed in parallel between the source and the metal casing, and the bypass capacitor structure and the bias resistor are connected by a self-biasing method.
The circuit can be operated with two positive power supplies, and the amplification gain is not reduced and the amplified signal is not distorted.

Even in the transistor circuit, the temperature of the transistor can be compensated by the current feedback effect of the emitter resistance, and the amplification gain is not reduced and the amplified signal is not distorted.

[Brief description of drawings]

FIG. 1 is a circuit diagram of an embodiment of a field effect transistor amplifier circuit using the bypass capacitor structure of the present invention, and FIG. 2 is a partially cutaway perspective view of the bypass capacitor structure used in FIG. FIG. 3 is a circuit diagram showing an embodiment of a transistor amplifier circuit using the bypass capacitor structure of the present invention, and FIG. 4 is a vertical sectional view of the bypass capacitor structure used in FIG. Yes, Fig. 5 shows
FIG. 6 is a circuit diagram of an example of a conventional amplifier circuit using field effect transistors, and FIG. 6 is a circuit diagram of an example of a conventional self-bias type amplifier circuit using field effect transistors. 9: Bias resistance, 20, 30: Printed circuit board wiring, 22, 31: Metal film, 23, 32: Insulator, 24, 33: Metal housing, 35: Emitter resistance, FET _{1 to} FET ₃ : Field effect transistor, Tr _{1 to} Tr ₃ : Transistors.

Claims (3)

[Claims] 1. A metal casing that connects one end of a high-frequency active element disposed on a printed wiring board to a metal film that covers the back surface of the printed wiring board, and interposes this printed wiring board with a thin insulating film. A bypass capacitor structure, wherein the bypass capacitor structure is arranged in a body, and one end of the high frequency active element is insulated from the metal casing in a direct current manner and short-circuited in a high frequency manner. 2. A metal housing which connects a source of a field effect transistor arranged on a printed wiring board to a metal film which covers a back surface of the printed wiring board, and which interposes a thin insulating film on the printed wiring board. And connecting either the source of the field effect transistor or the metal film to the metal housing via a bias resistor,
A field-effect transistor circuit, characterized in that the gate of the field-effect transistor is short-circuited to the metal casing in a direct current manner to form a circuit by a self-bias method. 3. An emitter of a transistor arranged on a printed wiring board is connected to a metal film covering a back surface of the printed wiring board, and the printed wiring board is arranged in a metal housing with a thin insulating film interposed. A transistor circuit, wherein either the emitter of the transistor or the metal film is connected to the metal housing via an emitter resistor.