JPH1022743A - Amplifier - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the amplifier in which the gain is easily controlled and nonlinear secondary distortion is reduced. SOLUTION: When a high frequency input signal is received by the amplifier, a capacitor C1 is used to cut off a DC component and the resulting signal is given to a gate of a field effect transistor(TR) Q1, the field effect TR Q1 amplifies the input signal and the amplified signal is outputted from a high frequency output terminal via a capacitor C2. The production of nonlinear secondary distortion in the field effect TR Q1 is suppressed by setting optionally the resistance of variable resistive elements R2, R3 and a voltage of a power supply VC.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an amplifier for amplifying a high frequency.

[0002]

2. Description of the Related Art Conventionally, as an amplifying device for amplifying such a high frequency, for example, a configuration shown in FIG. 3 is known.

In the amplifying device shown in FIG. 3, the gate of a field effect transistor Q11 as an amplifying element is connected to the input terminal of a high frequency input signal via a DC cut capacitor C11. The gate is connected to a power supply VG via a resistor R11. The drain of the field-effect transistor Q11 has a high-frequency output terminal formed via a DC cut capacitor C12, and has a high-frequency cut inductor L11 and a resistor R1.
2 is connected to the power supply VDD. The source of the field effect transistor Q11 is grounded.

Further, a feedback circuit 11 is formed between the drain and the gate of the field effect transistor Q11, and the feedback circuit 11 is formed by a series circuit of a variable resistance element R13 and a capacitor C13.

When a high frequency input signal is input,
The direct current is cut by the capacitor C11 and input to the gate of the field effect transistor Q11.
Q11 amplifies the input signal and outputs it from the high frequency output terminal via the capacitor C12.

If the resistance value of the variable resistance element R13 is arbitrarily set, the gain of the field effect transistor Q11 can be changed.

[0007]

However, the configuration shown in FIG. 3 has a problem that although the gain can be changed, the secondary distortion generated in the field effect transistor Q11 cannot be effectively removed.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide an amplifier capable of easily controlling gain and reducing nonlinear second-order distortion.

[0009]

According to a first aspect of the present invention, there is provided an amplifying device comprising: an amplifying element; a feedback circuit having a variable resistance element and a non-linear element for feeding back an output of the amplifying element; and a variable voltage applied to the amplifying element. A variable resistance element provided in the feedback circuit to reduce nonlinear second-order distortion by a nonlinear resistance element provided in the feedback circuit, and to vary a voltage applied to the variable resistance element and the amplification element provided in the feedback circuit. The gain is changed by changing the resistance value of the resistance element, and the nonlinear second-order distortion is reduced.

According to a second aspect of the present invention, in the amplifying apparatus according to the first aspect, the amplifying element is a field-effect transistor, and reduces nonlinear second-order distortion with a simple configuration.

According to a third aspect of the present invention, in the amplifying device according to the first or second aspect, the nonlinear element is one of a PIN diode and a PN junction diode. Reduce.

According to a fourth aspect of the present invention, there is provided the amplifying apparatus according to the third aspect, further comprising a variable resistance element connected in parallel to the nonlinear element, wherein the number of the amplifying elements is plural. By changing the characteristics, nonlinear second-order distortion is more reliably reduced.

According to a fifth aspect of the present invention, in the amplifying device according to the third or fourth aspect, the multi-stage amplifying element is formed of a plurality of field-effect transistors. Amplify.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of the amplifying device of the present invention will be described with reference to the drawings.

FIG. 1 is a circuit diagram showing an amplifying device according to an embodiment of the present invention. The gate of a field-effect transistor Q1 as an amplifying element is connected to an input terminal of a high-frequency input signal via a DC cut capacitor C1. At the same time, the gate of the field effect transistor Q1 is connected to the power supply VG via the resistor R1.
The drain of this field-effect transistor Q1 has a high-frequency output terminal formed through a DC cut capacitor C2, and a high-frequency cut inductor.
It is connected to power supply VDD via L1 and variable resistance element R2. The source of the field effect transistor Q1 is grounded.

Further, a feedback circuit 1 is formed between the drain and the gate of the field effect transistor Q1, and this feedback circuit 1 is formed by a series circuit of a PIN diode D1, a non-linear element, a variable resistance element R3 and a capacitor C3. The connection point between the PIN diode D1 and the variable resistance element R3 is connected to a power supply VC via a resistance R4.

Next, the operation of the above embodiment will be described.

First, when a high-frequency input signal is input, the direct current is cut by the capacitor C1 and the field-effect transistor Q1 is cut off.
The field effect transistor Q1 amplifies the input signal and outputs it from the high frequency output terminal via the capacitor C2.

If the resistance values of the variable resistance elements R2 and R3 and the voltage value of the power supply VC are arbitrarily set, the current consumption of the field effect transistor Q1 and the change of the gain can be suppressed, while the change of the field effect transistor Q1 can be suppressed. Generation of non-linear second-order distortion can be suppressed.

Note that, instead of the PIN diode D1, a PN
Similar effects can be obtained by using a junction diode.

Next, an amplifier according to another embodiment will be described with reference to FIG.

FIG. 2 is a circuit diagram showing an amplifying apparatus according to another embodiment. The amplifying apparatus according to the embodiment shown in FIG.
In the amplifying device according to the embodiment shown in FIG. 1, the gate of the field-effect transistor Q3, which is the first-stage amplifying element, is connected to the connection point between the capacitor C1 and the resistor R1, and the drain of the field-effect transistor Q3 is connected to the source follower as the last stage. Connected to the gate of field effect transistor Q1. An output terminal is formed at the source of the field-effect transistor Q1 via a DC cut capacitor C3, and is grounded via a resistor R5. In addition, field effect transistors
The drain of Q1 is connected to power supply VDD. Also, the variable resistance element R6 is connected to the drain load circuit of the field effect transistor Q3.
And a series circuit of a PIN diode D2 as a non-linear element, and a variable resistance element R7 is connected in parallel to the PIN diode D2.

The basic operation is similar to that of the amplifying device of the embodiment shown in FIG. 1, except that a non-linear circuit is arranged not in the feedback section but in the load section. If the resistance value is set arbitrarily, the nonlinear characteristic of the PIN diode D2 also changes, and it is possible to suppress the generation of nonlinear secondary distortion of the field effect transistor Q1 while suppressing the current consumption and the gain of the field effect transistor Q1. it can.

In this case, instead of the PIN diode D2,
The same operation is performed for a PN junction diode.

In any case, as the field effect transistor of the amplifying element, for example, JFET, GaAs
FETs and MOSFETs can be used.

The amplifying device according to any of the above embodiments can be effectively used in a sensor amplifier used in a quasi-microwave band or in a digital communication field.

[0027]

According to the amplifying device of the first aspect, the nonlinear secondary distortion can be reduced by the nonlinear resistance element provided in the feedback circuit, and is applied to the variable resistance element and the amplification element provided in the feedback circuit. The gain can be changed by changing the resistance value of the variable resistance element that changes the voltage, and the nonlinear secondary distortion can be reduced.

According to the amplifying device of the second aspect, in addition to the amplifying device of the first aspect, since the amplifying element is a field-effect transistor, the secondary distortion can be reduced with a simple configuration.

According to the amplifier of the third aspect, the first aspect
Or in addition to the amplifying device described in 2, the non-linear element is a PIN
It is either a diode or a PN junction diode, and can reduce nonlinear secondary distortion with a simple configuration.

According to the amplifier of the fourth aspect, in addition to the amplifier of the third aspect, the variable resistance element connected in parallel to the nonlinear element is provided, so that the characteristics of the nonlinear element are changed. Nonlinear second-order distortion can be reduced more reliably.

According to the amplifying device of the fifth aspect, in addition to the amplifying device of the third or fourth aspect, since the multi-stage amplifying element is formed by the multi-stage field effect transistor,
It can be amplified in multiple stages with a simple configuration.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing one embodiment of an amplifying device of the present invention.

FIG. 2 is a circuit diagram showing an amplifier according to another embodiment of the present invention;

FIG. 3 is a circuit diagram showing a conventional amplifying device according to the first embodiment;

[Explanation of symbols]

 1 Feedback circuits D1, D2 PIN diodes Q1, Q3 as non-linear elements Field-effect transistors R2, R3, R6, R7 as amplifying elements Variable resistance elements

Claims (5)

[Claims] Amplifying element; a feedback circuit having a variable resistive element and a non-linear element for feeding back the output of the amplifying element; and a variable resistive element for varying a voltage applied to the amplifying element. Amplifying device. 2. The amplifying device according to claim 1, wherein the amplifying element is a field effect transistor. 3. The amplifying device according to claim 1, wherein the nonlinear element is one of a PIN diode and a PN junction diode. 4. The amplifying device according to claim 3, further comprising a variable resistance element connected in parallel to the nonlinear element, wherein a plurality of amplifying elements are provided. 5. The amplifying device according to claim 3, wherein the multi-stage amplifying element is formed by a multi-stage field effect transistor.