JPH1155046A - High frequency amplifier - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high frequency amplifier whose occupancy area for an input/output matching circuit and a bias circuit is reduced, resulting in the reduction of a chip size, and which facilitates adjustment of matching conditions. SOLUTION: Sources of transistors M3-M6 for matching and bias supply are connected to the gates and drains of transistors M1 and M2 for amplification, and the drains of the transistors M2-M6 are connected to a power supply terminal B1. Further, by applying a fixed gate bias from resistors R5-R8 and R13-R16 to the transistors M3-M6, a reflection coefficient, seeing the source sides of the transistors M3-M6 for matching and bias supply from the gate and drain sides of the transistors M1 and M2 for amplification, is made inductive.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an amplifier used in a high frequency region such as a millimeter wave band, and more particularly to a high frequency amplifier suitable for MMIC.

[0002]

2. Description of the Related Art In designing a high-frequency amplifier for amplifying a high-frequency signal in a millimeter-wave band or the like, a signal input terminal of the amplifying element and a signal are used in order to maximize the characteristics of an amplifying element such as an FET (field effect transistor). Output end (for example,
In the case of a FET having a source grounded, it is necessary to add a matching circuit for converting the input / output impedance of the element into an impedance having a maximum gain characteristic or an impedance having a minimum noise characteristic. Such an input / output matching circuit is generally configured using a stub having an appropriate length branched from a signal line.

On the other hand, apart from this input / output matching circuit, a bias circuit for keeping the amplifier element under the optimum bias condition is required. Generally, in a high-frequency amplifier, this bias circuit is configured using an inductive transmission line that blocks a high-frequency signal component and allows only a direct current to pass.

An MMIC comprising such a high-frequency amplifier in which active elements and distributed constant lines are arranged on a semiconductor substrate.
(A monolithic microwave integrated circuit), wiring such as stubs and transmission lines on the board
It is designed based on a distributed constant line having a length of λ / 4 (where λ is the center wavelength used). For example, in a millimeter-wave band circuit, a stub or a transmission line having a length of about 1 mm needs to be connected to a signal input / output terminal of an amplification element in order to form an input / output matching circuit and a bias circuit. For this reason, the input / output matching circuit and the bias circuit occupy an extremely large area as compared with the amplifying element, and there arise problems such as an increase in manufacturing cost and a decrease in yield due to an increase in the chip size of the integrated circuit.

FIG. 10 shows a circuit diagram of a conventional high-frequency amplifier. This high-frequency amplifier has two amplifying transistors M
101 and M102 are two-stage amplifiers connected between an input terminal IN and an output terminal OUT via an interstage connection capacitor C101, and the input / output matching circuit is a transmission line ML1, ML.
2, ML5, ML6, ML7, ML10, ML11 and stubs ST1, ST2, ST3, ST4, ST5, ST
6, ST7, ST8, and the bias circuit includes transmission lines ML3, ML4, ML8, ML9, radial stubs RST1, RST2, RST3, RST4, resistors R101, R102, R103, R104, and capacitors C101, C102, C103, It is constituted by C104.

FIG. 11 shows an example of an IC chip layout of the high-frequency amplifier of FIG. As can be seen from the figure, the stubs ST1, ST2, ST3, ST4, ST5, ST6,
ST7, ST8 and transmission lines ML1, ML2, ML5, M
An input / output matching circuit and a bias circuit composed of L6, ML7, ML10, and ML11 are connected to the amplifying transistor M1.
01 and M102, and occupies a much larger area, and the chip size is increasing.

Further, stubs ST1, ST2, ST3, ST4, ST5, ST6, S
T7 and ST8 cannot be easily adjusted after the completion of the integrated circuit, and need to be trimmed by manual fine adjustment to a minimum noise condition or a maximum gain condition at a desired frequency, which also reduces the manufacturing cost. It contributes to the rise and the decline in mass productivity.

[0008]

As described above, in the conventional high-frequency amplifier for a millimeter wave band or the like, a matching circuit composed of a stub added to the input / output side of an amplification element and a transmission line. The area occupied by the bias circuit is larger than that of the amplifying element, and when integrated circuits are used, there are problems such as an increase in manufacturing cost and a decrease in yield due to an increase in chip size, and furthermore, it is not easy to adjust after completing the integrated circuit. However, this has also increased manufacturing costs and reduced mass productivity.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems. The present invention has been made to reduce the chip size by reducing the area occupied by the input / output matching circuit and the bias circuit, and to facilitate the adjustment of the matching conditions. It is an object of the present invention to provide an improved high-frequency amplifier.

[0010]

In order to solve the above-mentioned problems, a high-frequency amplifier according to the present invention has at least one of a signal input terminal and a signal output terminal of an amplifying element viewed from the signal input terminal or the signal output terminal. An active element arranged such that the reflection coefficient is inductive is connected, and a bias is supplied to the amplifying element via the active element.

More specifically, a source or an emitter of a matching / bias supplying transistor is connected to at least one of a gate or a base and a drain or a collector of the amplifying transistor, and a drain or a collector of the matching / bias supplying transistor is connected. Is connected to a power supply terminal. It is desirable that the gate or base potential of this matching and bias supply transistor be kept substantially constant.

In the high-frequency amplifier of the present invention configured as described above, impedance conversion for input / output matching is performed while utilizing the output impedance characteristic of the matching and bias supply transistor as viewed from the source or emitter side. A stable bias is supplied to the amplification transistor.

The input / output impedance of the amplifying transistor varies in resistance component and reactance component depending on the frequency. For example, regarding the input impedance of this amplifying transistor, when the amplifying transistor has a gate or base as a signal input terminal and a source or an emitter is grounded, the impedance is high in a low-frequency region and is high in a high-frequency region. Indicates low capacitance. The input / output impedance greatly changes depending on the gate or base bias voltage of the amplifying transistor.

On the other hand, since the drain of the matching and bias supply transistor is grounded, the output impedance viewed from the source side or the emitter side is low in a low frequency region and high in a high frequency region. It is possible to show inducibility. This is an effect due to a decrease in current gain with an increase in frequency.

Therefore, the source or the emitter of the transistor for supplying the matching and bias of the common drain or the collector is connected to the gate or the base which is the signal input terminal of the amplifying transistor, and the matching or the bias is supplied from the gate or the base of the amplifying transistor. By configuring the bias supply transistor so that the reflection coefficient when viewed from the source or emitter side shows inductive properties, a transmission line having a length of λ / 4, a stub, and a bias, which is a major factor in increasing the chip size of an integrated circuit. Without using inductive feed lines,
It becomes possible to match the input impedance of the amplification transistor to the characteristic impedance of the system, for example, 50Ω.

Similarly, the source or the emitter of the matching / bias supply transistor is connected to the drain or collector, which is the signal output terminal of the amplification transistor, so that the matching / bias supply transistor is connected from the drain or collector of the amplification transistor. The output impedance of the amplifying transistor can be reduced without using a transmission line having a length of λ / 4 and a stub or an inductive line for bias supply by using a configuration in which the reflection coefficient as viewed from the source or emitter side shows inductive. It is possible to match the characteristic impedance of the system.

Therefore, according to the present invention, when the high-frequency amplifier is integrated, the area occupied by the input / output matching circuit and the bias circuit other than the amplification transistor can be reduced, and the chip size can be effectively reduced. Reduction in manufacturing cost and improvement in yield are achieved.

In the high-frequency amplifier of the present invention, when an element is connected between the power supply terminal and the gate or base of the matching and bias supply transistor, the impedance of the element appears in a high-frequency region. By changing the impedance of the element as, for example, a variable resistor, the input impedance of the matching and bias supply transistor can be adjusted. This eliminates the need for trimming of the conductor pattern, which was necessary when performing adjustment in the conventional method using a stub, so that adjustment for optimization can be easily performed. The time required is greatly reduced, and the manufacturing cost is reduced and the mass productivity is improved.

A constant current source composed of a transistor is connected to the gate or base of the amplifying transistor,
By changing the drain-gate capacitance or the collector-base capacitance of this constant current source transistor by adjusting the bias voltage applied between the drain or collector and the gate or base, the input / output impedance of the amplifying transistor can be further widened. Adjustment becomes possible, and adjustment for input / output matching becomes easier.

Further, by providing a Darlington connection transistor at the gate or base of the matching and bias supply transistor, the frequency characteristics of the matching and bias supply transistor can be improved, and the input / output matching conditions can be changed over a wider range. it can.

[0021]

Embodiments of the present invention will be described below with reference to the drawings. (First Embodiment) FIG. 1 shows a circuit diagram of a high-frequency amplifier according to a first embodiment of the present invention. This high-frequency amplifier is a two-stage amplifier using an FET (hereinafter simply referred to as a transistor), and is mainly composed of two amplifying transistors M1 and M2 whose sources are grounded. That is, the gate that is the signal input terminal of the first amplifying transistor M1 is connected to the input terminal IN. The source of the first amplifying transistor M1 is grounded, and the drain, which is the signal output terminal, is connected to the gate, which is the signal input terminal of the second amplifying transistor M2, via the interstage connection capacitor C1. The source of the second amplifying transistor M2 is grounded, and the drain as the signal output terminal is connected to the output terminal OU.
Connected to T.

In this embodiment, input / output matching and bias supply of the amplification transistors M1 and M2 are performed by the matching and bias supply transistors M3, M4, M5 and M6. The resistors R1, R2, R3 and R4 are transistors M
3, M4, M5, and M6. Resistance R
5 and R13, R6 and R14, R7 and R15, R8 and R1
Reference numeral 6 denotes voltage dividing resistors for generating gate bias potentials of the transistors M3, M4, M5, and M6. The gate potentials of the transistors M1 and M2 are kept constant by these voltage dividing resistors. Be kept constant.

That is, the source of the transistor M3 is connected to the gate of the first amplifying transistor M1 and grounded via the resistor R1, the drain is connected to the power supply terminal B1, and the gate is connected between the power supply terminal B1 and ground. It is connected to the connection point of the connected voltage dividing resistors R5 and R13. The source of the transistor M4 is the first amplifying transistor M1.
And the ground is connected via a resistor R2, the drain is connected to a power supply terminal B1, and the gate is connected to a connection point between voltage dividing resistors R6 and R14 connected between the power supply terminal B1 and the ground.

Similarly, the source of the transistor M5 is the second
, And grounded via a resistor R3, a drain is connected to a power supply terminal B1, and a gate is a connection point between voltage dividing resistors R7 and R15 connected between the power supply terminal B1 and the ground. Connected to. The source of the transistor M5 is connected to the drain of the second amplifying transistor M2 and grounded via the resistor R4, the drain is connected to the power supply terminal B1, and the gate is connected between the power supply terminal B1 and ground. It is connected to the connection point of the voltage dividing resistors R8 and R16.

Next, the operation of the high-frequency amplifier of this embodiment will be described. The high-frequency signal input from the input terminal IN is
First, after being amplified by the first amplifying transistor M1, it is supplied to the second amplifying transistor M2 via the interstage connecting capacitor C1, and the second amplifying transistor M2
The high frequency signal amplified in 2 is output from the output terminal OUT to, for example, the outside of the integrated circuit.

At this time, the amplification transistors M1 and M2
Input reflection coefficient (transistor M
The reflection coefficient of M1 and M2 viewed from the gate side greatly changes depending on the gate-source voltage Vgs of the transistors M1 and M2, but is generally capacitive in an operation region used.

The input reflection coefficients of the amplification transistors M1 and M2 are shown in the Smith chart of FIG. In FIG. 2, the gate-source voltage V of the amplification transistors M1 and M2 is
gs as Vgs = Vgs1, Vgs2, Vgs3 (Vgs1>Vgs2>
Vgs3) when the input reflection coefficient is changed. Each input reflection coefficient is capacitive, but it can be seen that the higher the gate-source voltage Vgs, the lower the impedance.

On the other hand, the output reflection coefficients of the matching and bias supply transistors M3, M4, M5 and M6 (the reflection coefficients of the transistors M3, M4, M5 and M6 as viewed from the source side).
Is shown in the Smith chart of FIG. In FIG. 3, the gate-source voltage of the amplification transistors M1 and M2 is Vgs = V
gs2, resistances R5 to R8, R13 to R
Rb = Rb1, Rb2, Rb3 (Rb1
<Rb2 <Rb3) shows the output reflection coefficient.

As shown in FIG. 3, the output reflection coefficients of the matching and bias supply transistors M3, M4, M5 and M6 vary depending on the respective bias conditions, but all show inductive properties. This is the output impedance Z
out is approximately expressed as Zout = Zb / (1 + β) (1) Here, Zb is the impedance of the matching and bias supply transistors M3, M4, M5, M6 as viewed from the gate side, and β is the transistor M3,
These are the current gains of M4, M5, and M6.

The current gain β has a frequency dependency represented by the following equation. β = βo / (1 + jωτ) (2) where βo is the current gain at DC, ω is the angular frequency, and τ is the charge accumulation time of the transistors M3, M4, M5, and M6.

From equations (1) and (2), it can be seen that the matching and bias supply transistors M3, M4, M5 and M6 have a low output impedance at low frequencies and an output impedance of Zb at high frequencies. This behaves like an inductor.

Next, the high-frequency amplifier of FIG.
FIG. 4 shows the input reflection coefficient as viewed from the side. here,
The gate-source voltage Vgs of the amplification transistors M1 and M2 is fixed at Vgs2, and the combined resistance values of the resistors R5 and R13 that determine the bias condition of the matching and bias supply transistor M3 are Rb = Rb1, Rb2, Rb3 (Rb1 <Rb2 <Rb
The input reflection coefficient when the gate input impedance of the transistor M3 is changed instead of 3) is shown.

As shown in FIG. 4, the input reflection coefficient is determined by the inductive input reflection coefficient of the amplifying transistor M1 shown in FIG. 2 and the capacitive reflection of the matching and bias supply transistor M3 shown in FIG. In this example, if the resistance value Rb is selected to be an appropriate value between Rb1 and Rb2, impedance matching can be achieved at a desired frequency.

On the other hand, the gain frequency characteristic of the amplifying transistor M1 when the input matching condition is changed by changing the resistance value Rb is as shown in FIG. 5, and is constant at 20 dB or more regardless of the input matching condition. Gain has been obtained.

FIG. 6 shows the high-frequency amplifier of FIG.
1 shows an example of an IC chip layout in the case of a monolithic microwave integrated circuit. 6, the elements corresponding to those in FIG. 1 are denoted by the same reference numerals. Matching and bias supply transistors M3, M4, M5, M6
Are arranged in a region at a distance of λ / 4 or less from signal input / output terminals (gate and drain) of the amplification transistors M1 and M2.

As described above, the high-frequency amplifier of this embodiment is
Matching and bias supply transistors M3, M4, M5
Since the input / output matching and bias supply of the amplification transistors M1 and M2 are performed by M6, a stub or a transmission line having a length of λ / 4 is not required for input / output matching and bias supply, and the circuit is configured to be very small. be able to. In the case of FIG. 6, the chip size can be reduced to a size limited by pads such as the input terminal IN, the output terminal OUT, the power supply B1, and the ground GND on the IC.

(Second Embodiment) FIG. 7 shows a second embodiment of the present invention.
FIG. 3 is a circuit diagram of the high-frequency amplifier according to the embodiment. In this embodiment, the current drain resistors R1 and R1 shown in FIG.
2, R3, and R4 are transistors M7, M8, and M, respectively.
9 and M10.

These constant current source transistors M7, M
When the voltage between the drain and the gate of M8, M9 and M10 is changed by the bias voltage source B2, the capacitance between the drain and the gate changes.
The input / output impedance of M2 can be adjusted over a wide range, and adjustment for input / output matching can be performed more easily.

(Third Embodiment) FIG. 8 shows a third embodiment of the present invention.
1 shows a circuit diagram of a high-frequency amplifier according to an embodiment. In this embodiment, of the voltage dividing resistors for generating the gate bias potential of the matching and bias supply transistors M3, M4, M5, M6 in FIG.
The resistors R5, R6, R7, and R8 connected between the gates of the gates M5 and M6 and the power supply terminal B1 are variable resistors, and are connected between the resistors R5, R6, R7, and R8 and the power supply terminal B1. Variable voltage sources Vb1, Vb2, Vb3, Vb4 are inserted respectively.

According to the present embodiment, the resistors R5, R6, R
7, R8 and variable voltage sources Vb1, Vb2, Vb3, V
By adjusting b4, the transistors M3, M
4, M5, M6 output impedance changes,
The combined impedance of the input / output impedance of each of the amplification transistors M1 and M2 at the desired frequency and the impedance of the bias circuit can be easily changed after the completion of the IC chip. Therefore, the trimming operation becomes unnecessary, and the period for IC evaluation can be significantly reduced.

(Fourth Embodiment) FIG. 9 shows a fourth embodiment of the present invention.
1 shows a circuit diagram of a high-frequency amplifier according to an embodiment. In this embodiment, the gates of the matching and bias supply transistors M3, M4, M5, M6 in FIG. 1 and the voltage dividing resistors R5 and R13 for generating the gate bias potential, R6 and R14, R7.
And the transistors M11, M12, M13, M connected in Darlington between the voltage dividing points of R15, R8 and R16.
14 has been added.

With such a configuration, the frequency characteristics of the matching and bias supply transistors M3, M4, M5, and M6 can exhibit greater inductive properties, and the matching conditions can be changed over a wide range.

In the above embodiment, a high-frequency amplifier using FETs has been described. However, it goes without saying that a similar amplifier can be formed using bipolar transistors. When a bipolar transistor is used, F
The gate, drain and source of ET may be replaced with the base, collector and emitter of the bipolar transistor.

[0044]

As described above, in the high-frequency amplifier of the present invention, the input / output matching and bias supply of the amplifying element are arranged such that the reflection coefficient viewed from the signal input / output end of the amplifying element is inductive. By using active elements,
The occupied area of the input / output matching circuit and bias circuit is reduced to reduce the chip size when integrated circuits are used, thereby reducing the manufacturing cost and improving the yield, and adjusting the matching conditions with complicated trimming. This can be easily performed without the necessity, and has an advantage of excellent mass productivity.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a high-frequency amplifier according to a first embodiment of the present invention.

FIG. 2 is a diagram showing an input reflection coefficient of a single amplification transistor according to the first embodiment;

FIG. 3 is a diagram showing an output reflection coefficient as viewed from the source side of the matching and bias supply transistor according to the first embodiment;

FIG. 4 is a diagram showing an input reflection coefficient of the high-frequency amplifier according to the embodiment;

FIG. 5 is a diagram showing gain frequency characteristics of the amplifying transistor according to the first embodiment;

FIG. 6 is a diagram showing an example of an IC chip layout of the high-frequency amplifier according to the embodiment;

FIG. 7 is a circuit diagram of a high-frequency amplifier according to a second embodiment of the present invention.

FIG. 8 is a circuit diagram of a high-frequency amplifier according to a third embodiment of the present invention.

FIG. 9 is a circuit diagram of a high-frequency amplifier according to a fourth embodiment of the present invention.

FIG. 10 is a circuit diagram of a conventional high-frequency amplifier.

FIG. 11 is a diagram showing an example of an IC chip layout of a conventional high-frequency amplifier.

[Explanation of symbols]

IN: input terminal OUT: output terminal M1, M2: amplifying transistor C1: interstage connection transistor M3, M4, M5, M6: matching and bias supply transistor R1, R2, R3, R4: current drain resistor R5 R6, R7, R8, R13, R14, R15, R
16: Voltage dividing resistor for generating gate bias potential B1: Power supply terminal M7, M8, M9, M10: Transistor for constant current source B2: Bias voltage source Vb1, Vb2, Vb3, Vb4: Variable voltage source M11, M12, M13, M14 ... Darlington connection transistor

Claims (5)

[Claims] An amplifying element is connected to at least one of a signal input end and a signal output end thereof with an active element arranged such that a reflection coefficient seen from the signal input end or the signal output end is inductive. A high-frequency amplifier, wherein a bias is supplied to the amplification element via an active element. 2. A source and an emitter of a matching and bias supplying transistor are connected to at least one of a gate or a base and a drain or a collector of the amplifying transistor, and a drain or a collector of the matching and bias supplying transistor is connected to a power supply terminal. A high frequency amplifier characterized by being connected. 3. The high-frequency amplifier according to claim 2, further comprising means for keeping the potential of the gate or base of the matching and bias supply transistor substantially constant. 4. The high-frequency amplifier according to claim 2, wherein a variable resistor is connected between a gate or base of said matching and bias supply transistor and a power supply terminal. 5. The high-frequency amplifier according to claim 2, further comprising a transistor connected in Darlington connection to a gate or a base of the matching / bias supply transistor.