JPH0250644B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a high frequency amplification device using an integrated circuit that can be used in a television tuner circuit, an indoor unit for satellite broadcasting, and the like.

Conventional configurations and their problems In recent years, the frequency of integrated circuits using silicon bipolar has been increasing, and it has become possible to integrate circuits up to 1 GHz.

A conventional high frequency amplification device will be described below with reference to the drawings. FIG. 1 shows a conventional high frequency amplification device using an integrated circuit. The figure shows an integrated circuit chip, a package, and bonding wires connecting the chip and the package. The IC in the figure has a 7-pin configuration,
A wire inductance made of bonding wire is formed between each pin and the terminal of the package. In the figure, this is expressed as an equivalent circuit by _L1 to _L7 . Wire inductance usually shows a value of about 2.5nH to 5nH, although it depends on the thinness of the wire and the distance. The input signal is given from the input terminal IN, and the coupling capacitance C ₁
It is supplied to the terminal through wire inductance L ₁ and then to the base of amplification transistor Q ₁ in the integrated circuit. The emitter of transistor _Q1 is connected to the ground inside the chip,
The internal chip ground is connected to the terminal via wire inductance L ₂ and then to the external ground. The collector of transistor Q ₁ is also connected to the stabilizing voltage V _cpost line in the chip via a load resistor R ₁ . The amplified signal is supplied from the collector of the transistor Q ₁ to the terminal via the wire inductance L ₃ through the external filter circuit 11, and is then supplied to the base of the amplification transistor Q ₂ via the wire inductance L ₄ . Ru. Between the collector of transistor Q ₁ and the base of transistor Q ₂ is a high resistance R ₂ (usually
1KΩ or more) and are connected in a direct current manner. The collector of the transistor Q ₂ is connected to the stabilizing voltage V _cpost line via a load resistor R ₆ and is also supplied to the outside via a wire inductance L ₆ from the terminal via a coupling capacitor C ₃ . transistor
The emitter of Q ₂ is divided into three directions, one side is connected to the terminal via wire inductance L ₅ , and the other is grounded to external earth via resonant capacitance C ₂ and damping resistor R ₈ . Furthermore, the above emitter is connected to the ground within the chip via a resistor _R3 , and in the third direction, the divided potential of resistors _R4 and _R5 is connected to a transistor _Q1.
The transistors Q ₁ and Q ₂ are configured to provide direct current negative feedback. The regulated voltage V _cpost in the chip is
The current is amplified and supplied by the emitter follower consisting of transistor Q ₃ and resistors R ₉ and R ₈ , and the stabilized voltage is supplied by the emitter follower of transistor Q ₄ .
It is obtained by using the Zener characteristics of the base. Transistors _Q5 to _Q7 are used as diodes. Therefore, from the Zener potential of transistor _Q4 ,
A potential higher than 3 diodes has a low resistance R ₈ (200Ω
(before and after) is supplied to the base of transistor _Q3 . The power supply voltage V _cc (approximately 12V) is connected to the resistor R ₈ from the terminal through the wire inductance L ₇ ,
_R7 is supplied. A specific example of the filter circuit 11 is shown in FIG. In the figure, a high-pass filter is configured by capacitors C ₁₁ and C ₁₂ and inductance L ₁₁ , but this may be a low-pass filter or a band-pass filter.

With this configuration, between the input terminal IN and the output terminal OUT, the frequency of 17
Gain of ~20dB is obtained. By the way, if you want to further improve the gain by, say, 10 dB in the configuration shown in Figure 1, it is not possible just by changing the constants of each element in Figure 1, and you will have to increase the chip area (number of elements) and current. There was a problem in that it was difficult to improve the gain under the restriction of not allowing the

Purpose of the invention The present invention solves the above-mentioned conventional problems.
This provides a means to improve gain without increasing current or number of elements.

Composition of the Invention A high frequency amplifier according to the present invention connects a first amplifier circuit and a second amplifier circuit of a grounded emitter type so that they can share a direct current. A filter is connected to the connection point to make this connection point low impedance, and a DC bias potential is supplied from a stabilized voltage source to the base of the second amplifier circuit to suppress voltage fluctuations due to fluctuations in the power supply voltage. The present invention is characterized in that the output terminal of the first amplifier circuit and the input terminal of the second amplifier circuit are coupled via a filter circuit that allows a desired frequency to pass through. By using a transistor that acts as an emitter follower as the second amplifier circuit, the gain can be improved without increasing the number of elements or the current.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. 3 to 5. FIG. 3 is a block diagram of a high frequency amplification device in one embodiment of the present invention. In the figure, 1 is a first amplifier circuit, which amplifies a high frequency signal input from an input terminal IN. 2 is the second
This amplifier circuit further amplifies the signal of a desired frequency input from the output terminal of the first amplifier circuit 1 via the filter circuit 3, and in FIG. 1, the transistor acts as an emitter follower for impedance conversion. _Q3 is commonly used for amplification, and together with the first amplifier circuit 1, a necessary gain is obtained. and second amplifier circuit 2
A high frequency output signal is obtained from the output end of the . Also, at this time, in order to lower the impedance of the emitter of the second amplifier circuit 2 and prevent feedback from occurring,
A filter circuit 5 is connected to the emitter. A stabilized voltage source 4 supplies a bias voltage to the second amplifier circuit 2, so that the operation is stabilized regardless of fluctuations in the power supply voltage.

FIG. 4 shows a configuration of the configuration shown in FIG. 3 using a concrete circuit.

The figure shows a case where the integrated circuit is configured with eight terminals. Wire inductances L ₁ to L ₈ made of bonding wires are inserted between the package terminals and the chip, each having an inductance value of 2.5 to 5 nH. are doing. The input signal is supplied from the input terminal IN to the terminal via the coupling capacitor _C1 , and is supplied via the wire inductance _L1 to the base of the first transistor _Q1 of the common emitter type that constitutes the first amplifier. . transistor
The emitter of Q ₁ is connected to the chip's internal ground, which is connected to the terminal via the wire inductance L ₂ and then to the external ground. The collector of transistor Q ₁ is a load resistor
Transistor supplying constant voltage power through _R1
Connected to the emitter of _Q3 . Also, the collector of transistor _Q1 is connected to the second amplification transistor.
Connected to the base of _Q2 . The collector of transistor Q ₂ is connected to the above transistor through load resistor R ₂ .
Connected to the emitter of _Q3 . transistor
The emitter of Q ₂ is divided into three directions, one is the resistance
Transistor divide potential with resistor _R5 through _R4
It is supplied to the base of _Q1 , and negative DC feedback is applied.
The second direction of the emitter of transistor Q ₂ is connected to ground within the chip via a resistor R ₃ . The third direction of the emitter of transistor Q ₂ is
Resonant capacitance C ₂ through wire inductance L ₃
and is grounded to external earth via damping resistor _R8 . The output signal amplified by the first amplifier 1 is passed from the collector of the transistor Q ₂ to the terminal via the wire inductance L ₄ , passes through an external filter circuit 3 for extracting the desired signal, and then passes from the terminal to the wire inductance L 4 .
It is connected via _L5 to the base of transistor _Q3 , which constitutes the second amplifier. A constant voltage is applied to the base of the transistor _Q3 via a high resistance _R6 .

Also, the collector of transistor Q ₃ is the load resistor R ₇
It is connected to the power supply V _cc (approximately +12V) line via. By fixing the base of transistor _Q3 at a constant DC potential, the transistor
The emitter of Q ₃ is fixed at a constant potential using direct current.
The emitter of transistor Q ₃ is connected to the first amplifier 1
are connected to the load resistances R ₁ and R _{2 of}
By being grounded via a filter circuit 5 set externally from the terminal via a wire inductance _L7 , the emitter of the transistor _Q3 is set to have a low impedance for a desired frequency. Other examples of the filter circuit 5 are shown in FIGS. 5A and 5B. transistor
The constant voltage applied to the base of Q ₃ is provided by a stabilized voltage source 4 consisting of a resistor R ₅ and transistors Q ₄ to Q ₇ .
Using the Zener voltage between the emitter and base of transistor _Q4 , this potential is increased by three transistors _Q5 to _Q7 , whose collectors and bases are connected and used as diodes. At least it is added to the base of transistor _Q3 . Bias is applied from the power supply V _CC through resistor _R5 . This stabilizing potential is connected to a high resistance _R6
It is supplied to the base of transistor _Q3 via. The output signal is output from the collector of the transistor Q ₃ via the wire inductance L ₈ and from the terminal via the external coupling capacitor C ₃ .

Compared to the conventional example shown in Fig. 1, the amplifier circuit configured in this way has a higher value than the sum of the currents flowing through the transistors Q ₁ and Q ₂ in Fig. 1, that is, the sum of the currents I ₃ and I ₄ .
With respect to I ₁ , the total value of currents I ₃ and I ₄ flowing through transistors Q ₁ and Q ₂ in FIG. 4 can be set to be less than the total value of I ₃ +I ₄ in FIG. 1. In this case, the transistor Q ₃ used for amplification has I ₃ + I ₄ ≒ I ₁
Since a current flows through this transistor _Q3 ,
It is extremely easy to secure a gain of 10 dB or more, and when combined with the gain of the first amplifier circuit 1, a sufficient gain can be obtained compared to conventional devices.

In this way, it is possible to improve the gain of the constructed circuit without increasing the current or the number of elements compared to the conventional example, and to improve the distortion characteristics by increasing the current of the third transistor _Q3 .

Effects of the Invention As described above, according to the present invention, gain and distortion characteristics can be improved without increasing current and the number of elements by sharing an emitter follower transistor in a conventional circuit with an amplification transistor. It is something.

[Brief explanation of drawings]

Figure 1 is a circuit diagram of a conventional high frequency amplifier, Figure 2 is a circuit diagram of a conventional high frequency amplification device.
The figure is a specific circuit diagram of the filter circuit in Figure 1, and
The figure is a block diagram of a high frequency amplification device according to an embodiment of the present invention, FIG. 4 is a specific circuit diagram of FIG. 3, and FIG.
The figure is a circuit diagram showing another specific example of the filter circuit 5. 1... First amplifier circuit, 2... Second amplifier circuit, 3, 5... Filter circuit, 4... Stabilized power supply.

Claims (1)

[Claims] 1. Connect the first and second amplifier circuits composed of grounded-emitter transistors so that they can share the current, and connect the DC intersection of the first and second amplifier circuits to the ground for a desired frequency. In addition to inserting a filter that provides low impedance, the first
The collector output of the amplifier circuit and the base of the second amplifier circuit are coupled via a filter circuit that allows a desired frequency to pass through in an alternating current manner, thereby passing only the alternating current signal, and forming the second amplifier circuit. A high frequency amplification device characterized in that a constant voltage is supplied to the base of a transistor from a constant voltage circuit via a resistor.