JP3147597B2 - Monolithic integrated circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor integrated circuit, and more particularly to a monolithic integrated circuit for forming a feedback type wideband variable gain amplifier including a variable attenuator.

[0002]

2. Description of the Related Art Referring to FIG. 7, which shows a block diagram of a conventional feedback type wideband variable gain amplifier 1b including a variable attenuation circuit of this type, a junction type field effect transistor (FET) 11, an FET 12, and an attenuation circuit 13 are shown. And a resistance element 14. The source electrode of the FET 11 is connected to the lower power supply side, and one of the drain electrodes is connected to the FE via the variable resistance component 131 and the variable phase component 132 of the attenuation circuit 13.
FET 12 is connected to the gate electrode of T12, and the other of the drain electrodes is
It is connected so as to feed back to eleven gate electrodes.

A wide-band variable gain amplifier 1b having this configuration
Has a configuration in which a feedback path for widening the amplification stage and the variable attenuation circuit 13 are completely separated.

[0004]

In the feedback type wideband variable gain amplifier 1b including the above-described conventional variable attenuation circuit 13, when the gain is changed, the frequency characteristic of the variable attenuation circuit 13 is directly changed to the output characteristic. In addition, the dynamic range of the gain cannot be increased at a high frequency because of the gate-source capacitance (Cgs) of the FET built in the variable attenuation circuit 13.

Also, in the feedback path of the broadband amplification stage, since the feedback is performed from the drain electrode of the FET 11 to the gate electrode of the FET 11 via the resistance element 14, a capacitance element 15 for blocking DC current is required. In the case of operation, the capacitance becomes large, and a large chip layout area is required for disposing the capacitive element 15. Therefore, there is a disadvantage that the chip size of the entire monolithic integrated circuit also increases.

SUMMARY OF THE INVENTION It is an object of the present invention to increase the dynamic range at a high frequency in a feedback wideband variable gain amplifier having a variable attenuation circuit.

[0007]

SUMMARY OF THE INVENTION A monolithic integrated circuit of the present invention includes a first junction field effect transistor for amplifying a radio frequency signal, and an attenuating voltage level of the radio frequency signal amplified by the transistor. Second
A variable attenuator using a junction field effect transistor or a diode, a third junction field effect transistor receiving an output of the variable attenuator, and a feedback resistor for attenuating the radio frequency signal attenuated by the variable attenuator. A feedback circuit that feeds back to the gate electrode of the first junction field effect transistor via an element is formed on the same semiconductor substrate, and a passing phase of the variable attenuator is set to a maximum amount of attenuation of the variable attenuator. In such a case, the phase difference between the fed-back signal and the radio frequency signal is set to be 180 °, and a variable gain wideband amplifier is configured to increase the gain variable amount of the whole amplifier. I do. The variable attenuator has a first capacitive element, a fourth junction field-effect transistor, and a second capacitive element connected in series between an input terminal and an output terminal thereof. A series circuit composed of first and second resistance elements is connected in parallel with the fourth junction field effect transistor, and a series connection point of the first and second resistance elements is connected to a lower power supply side. And a fifth junction field-effect transistor inserted between them, and the gate electrodes of the fourth and fifth junction field-effect transistors are respectively connected to predetermined control means. Further, the variable attenuator has first and second capacitance elements connected in series between its own input terminal and output terminal, and a drain electrode of a fourth junction field effect transistor connected to the series connection point. The source electrode may be connected to the lower power supply, and the gate electrode may be connected to predetermined control means. Still further, the variable attenuator has a first capacitive element, a fourth junction field effect transistor, and a second capacitive element between the input terminal and the output terminal of the variable attenuator. The fourth junction field-effect transistor may be connected in series with the gate of the fourth junction-type field-effect transistor.

[0008]

Embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing one embodiment of the present invention. Referring to the figure, the source electrode of the FET 11 that inputs a radio frequency (RF) signal to the gate electrode is connected to the lower power supply side, and the drain electrode is connected to the FE via the variable resistance component 131 and the variable phase component 132 of the attenuation circuit 13a.
Gate electrode of T12 and feedback resistor 1
4 is connected to one end, and the other end is connected to the gate electrode of FET1.

After the RF signal is amplified by the FET 11, the variable resistance component 131 and the variable phase component 13 of the attenuation circuit 13a are amplified.
2 and the signal is fed back to the gate electrode of the FET 11 by the feedback resistance element 14. Referring to FIG. 2 showing a circuit diagram in which the variable attenuating circuit 13a is configured as a constant impedance type, and FIG. 4 showing the frequency characteristic of the passing phase thereof,
a is between the input terminal and the output terminal of the capacitive element 133 and F
The ET 137 and the capacitance element 134 are connected in series, and a series circuit of resistance elements 135 and 136 is connected in parallel with the FET 138 between the respective series connection points. The series connection point of the resistance elements 135 and 136 is connected to the lower power supply side. The FET 138 is inserted between the two. The gate electrodes of the FETs 137 and 138 are each connected to a control circuit (not shown) for setting.

Referring to FIG. 3, this variable attenuation circuit 13
According to the maximum and minimum characteristics of attenuation with respect to the frequency, the phase difference increases as the attenuation increases,
It is also evident that the higher the frequency, the greater the phase difference. In this case, the phase difference changes by about 50 ° at 9 GHz.

Therefore, in FIG.
When the attenuation of 3a is minimized, for example, the phase of the RF signal fed back to the gate electrode of the FET 11 is
The frequency characteristics of the entire wideband variable gain amplifier 1a are designed by setting 180 ° -50 ° = 130 ° at 9 GHz. In this case, assuming that the attenuation of the variable attenuation circuit 13a is maximized,
180 ° phase difference between feedback signal and RF signal
And the gain variable amount of the wideband variable gain amplifier 1a can be made larger than that of the amplifier of the conventional example shown in FIG.

The present invention in which the amplifier and the variable attenuator 13a are connected in five stages and the conventional feedback type wideband gain amplifier 1a in which the variable attenuator 13 is connected in five stages.
Referring to FIG. 4 which compares the characteristics of the amplifiers, it can be seen that the dynamic range of the gain can be increased by 5 dB or more in the amplifier according to the configuration of the present invention.

Further, the dynamic range of the gain was improved even at a low frequency. Here, the fact that the phase difference between the minimum and the maximum of the amount of attenuation at the high frequency in the variable attenuation circuit 13a is larger than the phase difference at the low frequency (about 20 ° at 3 GHz and 9 GHz) is used. Then, if the phase is set with high precision so that the amount of attenuation becomes maximum at a high frequency, the frequency characteristic at the maximum amount of attenuation increases the amount of attenuation at a high frequency.

Further, the feedback type wide band variable gain amplifier 1a of the present invention is capable of forming a feedback loop at the same potential between the gate electrodes of the FET 11 and the FET 12, and thus requires a direct current cut-off capacitive element 15 required in the conventional example. And the chip size of the monolithic integrated circuit can be reduced. The variable attenuation circuit 13
For a, it is also possible to use the configuration of FIG. 5 showing the shunt type attenuation circuit 13b and the configuration of FIG. 6 showing the series type attenuation circuit 13c.

The shunt type attenuator 13b has a configuration in which capacitive elements 133 and 134 are connected in series between an input terminal and an output terminal, and an FET 1 is connected between the series connection point and a lower power supply.
39, and the gate electrode is connected to a control circuit (not shown). The series-type attenuator 13c has a configuration in which a capacitor 133, an FET 139, and a capacitor 134 are connected in series between an input terminal and an output terminal, and a gate electrode is connected to a control circuit (not shown). The RF signal phase of the feedback system can be adjusted by adjusting and setting the feedback line length to a predetermined length.

[0017]

As described above, the monolithic integrated circuit of the present invention comprises an FET for amplifying an RF signal, a variable attenuating circuit composed of an FET or a diode for attenuating an RF signal, and an RF attenuator from the variable attenuating circuit. A signal output is fed back to the gate electrode of the amplifying FET via a feedback resistor, and a feedback circuit is used in combination. Therefore, when the attenuation is maximized by using the change in the phase with respect to the attenuation of the variable attenuation circuit, the phase of the RF signal fed back to the gate electrode of the amplification FET is set to be 180 ° different from the main RF signal. This has the effect that the dynamic range of the variable attenuation of the feedback amplifier can be increased.

Further, by utilizing the difference in the amount of phase change with respect to the frequency of the variable attenuator, the frequency characteristics of the feedback amplifier can be improved when the amount of attenuation is maximized. Furthermore, the need for the capacitive element for blocking direct current required by the conventional feedback circuit is eliminated, so that the chip size of the monolithic integrated circuit can be reduced.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention.

FIG. 2 is a circuit diagram of an impedance type attenuation circuit showing an attenuation circuit in an embodiment.

FIG. 3 is a diagram illustrating frequency characteristics of a passing phase of the attenuation circuit illustrated in FIG. 2;

FIG. 4 is a diagram comparing the frequency characteristics of a feedback-type wideband gain amplifier when the variable attenuation circuit shown in FIG.

FIG. 5 is another configuration diagram of the variable attenuation circuit shown in FIG. 2;

FIG. 6 is a diagram showing still another configuration of the variable attenuation circuit shown in FIG. 2;

FIG. 7 is a block diagram of a conventional variable gain wideband amplifier.

[Explanation of symbols]

 11, 12, 137, 138, 139 FET 13a Variable attenuation circuit 14, 135, 136 Resistance element 15, 133, 134 Capacitance element for DC cutoff 131 Variable resistance component 132 Variable capacitance element

Claims (4)

(57) [Claims] 1. A first junction field effect transistor for amplifying a radio frequency signal, and a second junction field for attenuating a voltage level of the radio frequency signal amplified by the transistor. A variable attenuator using an effect transistor or a diode, and a variable attenuator receiving the output of the variable attenuator.
3. The junction type field effect transistor and the variable attenuator
Feedback resistor for attenuating the radio frequency signal
The first junction field effect transistor through the element
A feedback circuit for feeding back to the gate electrode is formed on the same semiconductor substrate, and a pass path of the variable attenuator is formed.
When the attenuation of the variable attenuator is maximized,
Position between the feedback signal and the radio frequency signal
Set so that the phase difference is 180 °, and
A monolithic integrated circuit having a configuration of a variable gain wideband amplifier for increasing a variable amount . 2. The variable attenuator has a first capacitive element, a fourth junction field-effect transistor, and a second capacitive element connected in series between an input terminal and an output terminal thereof, and each of the variable attenuators is connected in series. A series circuit composed of first and second resistance elements is connected in parallel with the fourth junction type field effect transistor between a connection point and a series connection point of the first and second resistance elements. A fifth junction field-effect transistor is inserted and connected between the low-order power source and a gate electrode of each of the fourth and fifth junction field-effect transistors is connected to predetermined control means. 2. The monolithic integrated circuit according to 1. 3. The variable attenuator has first and second capacitive elements connected in series between an input terminal and an output terminal of the variable attenuator, and a drain electrode of a fourth junction field effect transistor is connected to the serial connection point. 2. The monolithic integrated circuit according to claim 1, wherein the source electrode is connected to a lower power supply, and the gate electrode is connected to predetermined control means. 4. The variable attenuator has a first capacitive element, a fourth junction field effect transistor, and a second capacitive element between an input terminal and an output terminal of the variable attenuator. Connected in series with the capacitor element side,
2. The monolithic integrated circuit according to claim 1, wherein the gate electrode of said junction field effect transistor is connected to predetermined control means.