JP2001237656A - System and method for compensating fluctuation in differential amplifier using field-effect transistor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To compensate fluctuation when producing a differential amplifier composed of GaAs depletion field-effect transistors(FET). SOLUTION: Concerning the fluctuation compensating system for the differential amplifier using GaAs depletion FET JP, JN, J1, J2, J3 and J4, this system is provided with a first fluctuation compensating current source 2A, which is the current source of the differential amplifier, for performing negative feedback control to the fluctuation at the time of production in the threshold voltage of a gate/source voltage to start the flow of a drain current and a second fluctuation compensating current source 2B for performing negative feedback control to the fluctuation at the time of production in the threshold voltage of the gate/source voltage by compensating the gain and band of the differential amplifier while fluctuating the current of the current source with the first fluctuation compensating current source corresponding to the fluctuation at the time of production in the gate length of the GaAs depletion FET comprising the differential amplifier.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a differential amplifier. In particular, the present invention relates to a fluctuation compensation system and method for a differential amplifier using a GaAs field transistor.

[0002]

2. Description of the Related Art In recent years, ultra-high-frequency devices are indispensable for realizing high-speed transmission in optical communication devices. However, with the increase in communication capacity, monolithic devices have been required to achieve higher speed, lower cost, and smaller devices. , IC (In
There is a growing demand for integrated circuits (chips).

[0003] Against this background, the degree of circuit integration has been greatly increased, but ultra-high frequency devices are generally:
Stability has not been established because of the use of advanced devices; the fluctuation factors due to the miniaturization of processes increase; and the trend of device performance does not match the trend of device performance, resulting in insufficient design margins. At the same time, there is a problem that high yield hinders cost reduction.

[0004] Most of the ultra-high frequency devices used in these apparatuses are silicon (Si) bipolar and compound semiconductors. Above all, since the mobility of GaAs electrons is higher than that of silicon (Si), devices using GaAs-based depletion field-effect transistors (FETs) have excellent high-frequency characteristics and are widely used in wireless systems. The most suitable device.

Next, there is a differential amplifier using a field effect transistor as disclosed in Japanese Patent Application Laid-Open No. Sho 62-160806. Do. FIG. 6 is a circuit diagram showing a schematic configuration of a differential amplifier which is a premise of the present invention. In addition,
The same components are denoted by the same reference numerals and numbers throughout the drawings and will be described.

As shown in FIG. 1, the differential amplifier is provided with field-effect transistors JP and JN. One of the resistors RP and RN is connected to the drain of each of the GaAs depletion field-effect transistors JP and JN. Connected. The other of each of the resistors RP and RN is connected to the power supply VDD. The sources of the GaAs depletion field effect transistors JP and JN are connected to each other,
It is connected to the power supply VSS via the system depletion field effect transistor J0.

The GaAs depletion field effect transistor J0 functions as a current source, and has a configuration in which a source is used as a constant voltage source for a gate. Input is performed from the gate sides of the GaAs depletion field effect transistors JP and JN, and output is performed from the drain sides of the GaAs depletion field effect transistors JP and JN. When the GaAs-based depletion field-effect transistor is used as the GaAs-based depletion field-effect transistor in the differential amplifier, the differential amplifier including the GaAs-based depletion field-effect transistor has a bipolar transistor and a bipolar transistor. By comparison, the transconductance (gm) is small,
Insufficient gain often increases the gain by multistage cascade connection.

However, there arises a problem that fluctuations in gain and band also increase due to variations in manufacturing. In addition, in a bipolar emitter-grounded amplifier, etc., by applying series feedback by adding an emitter resistor, the gain and band fluctuation caused by manufacturing variations can be stabilized. Therefore, since such a method cannot be taken, there arises a problem that the above-mentioned fluctuation becomes large.

FIG. 7 is a diagram showing the relationship between the drain current (ID) and the gate-source voltage (VGS) of an N-channel GaAs-based depletion type field-effect transistor. As shown in this figure, in the GaAs-based depletion type field-effect transistor, the drain current flows at VGS = 0 V, and the voltage between the gate and the source at which the drain current starts flowing is the threshold voltage (VT).

| VT | is the threshold voltage of DFET1 having a large threshold voltage.
When GS = 0 V, the drain current is set to Iss1, and | VT |
Assuming that the drain current is Is2 when VGS = 0 V of DFET2 having a small threshold voltage, the drain current Iss2 becomes smaller than the drain current Iss1. During the manufacture of the differential amplifier of FIG. 6, if the threshold value | VT | fluctuates mainly due to the impurity concentration and the thickness of the channel layer, the current of the current source of the field effect transistor J0 depends on this fluctuation. Also fluctuates.

FIG. 8 is another circuit diagram showing a schematic configuration example of the differential amplifier in FIG. As shown in FIG.
Instead of the s-based depletion field-effect transistor J0, a GaAs-based depletion field-effect transistor J
Field effect transistor J between P, JN and power supply VSS
2 are provided. Further, a GaAs depletion field effect transistor J1 is provided, and the drain side of the GaAs depletion field effect transistor J1 is connected to a resistor R.
1 is connected to the power supply VDD, and the source side is connected to the power supply VS.
Connected to S.

The GaAs depletion field effect transistor J1 is of a gate-drain short type,
The gate of the As-based depletion field-effect transistor J1 is connected to the gate of the field-effect transistor J2.
Thus, a current mirror circuit is formed by the GaAs depletion field effect transistors J1 and J2 and the resistor R1.

As described above, in a current source circuit constituting a differential amplifier, a current mirror is used in many circuits.
For example, a highly accurate current mirror circuit is formed by using a reference voltage bias circuit based on a base-collector short circuit in a bipolar transistor and a gate-drain short circuit in an enhancement type field effect transistor.

However, since the GaAs field effect transistor operates in a linear region when the gate and drain are short-circuited, the drain current ID fluctuates depending on the fluctuation of the source-drain voltage VDS of the GaAs depletion field effect transistor J1. Problems arise. For this reason, in a current mirror circuit using a GaAs-based depletion field-effect transistor, it is difficult to realize a high-precision current mirror circuit, and there is a problem that the stability of the differential amplifier is degraded due to fluctuations in the current source circuit.

[0015]

SUMMARY OF THE INVENTION Accordingly, the present invention has been made in view of the above-mentioned problems, and has been developed in order to compensate for the above-mentioned fluctuations in manufacturing a differential amplifier composed of GaAs-based depletion field-effect transistors. It is an object of the present invention to provide a system and method for compensating fluctuation of a differential amplifier using a transistor.

[0016]

In order to solve the above-mentioned problems, the present invention provides a fluctuation compensation system for a differential amplifier using a GaAs depletion field effect transistor, wherein two GaAs depletion gates are connected to each other. The GaAs depletion field effect transistor forms a tail current of the differential amplifier, and the other GaAs depletion field effect transistor generates the same constant current as the tail current. Forming a current source of the differential amplifier and a drain / source of the other GaAs-based depletion field effect transistor in the current source in order to perform negative feedback control on a manufacturing variation of a threshold voltage of a gate-source voltage. Contact between gate and between gate and source Further comprising a resistor portion that is to provide a variation compensation system of the differential amplifier using a GaAs-based depletion field effect transistors, wherein.

By this means, GaAs constituting a current source is
Since the s-based depletion field effect transistor is set from the linear region to the saturated region, it is not affected by the fluctuation of the drain-source voltage, and furthermore, the threshold voltage of the gate-source voltage at which the drain current starts to flow is manufactured. Negative feedback control is applied to the GaAs depletion field-effect transistor constituting the current source by the resistance portion with respect to the time variation, so that the differential amplifier can be stabilized. As a result, the yield for ultra-high frequency operation and cost reduction are achieved.

Further, the present invention provides a fluctuation compensation system for a differential amplifier using a GaAs depletion field effect transistor, wherein the current source of the differential amplifier is:
A first fluctuation compensation current source for performing a negative feedback control on a manufacturing variation of a threshold voltage of a gate-source voltage; and a manufacturing variation of a gate length of a GaAs depletion field effect transistor constituting the differential amplifier. Variably vary the current of the current source by the first variation compensation current source to compensate for the gain and bandwidth of the differential amplifier and to reduce the manufacturing variation of the threshold voltage of the gate-source voltage. A second fluctuation compensation current source for performing feedback control.
A variation compensation system for a differential amplifier using an As-based field transistor is provided.

Further, preferably, the first fluctuation compensation current source has two GaAs gates connected to each other.
A GaAs depletion field effect transistor forms the tail current of the differential amplifier, and the other GaAs depletion field effect transistor has the same constant current as the tail current. In order to perform negative feedback control on the current source of the differential amplifier that forms a current and the manufacturing fluctuation of the threshold voltage of the gate-source voltage,
A resistance portion connected between a drain and a gate and between a gate and a source of the other GaAs-based depletion field effect transistor in the current source.

Still preferably, the second fluctuation compensating current source is constituted by a current mirror circuit having two GaAs-based depletion field effect transistors whose gates are connected to each other. The gate length of the GaAs-based depletion field-effect transistor is made larger than the gate length of the other GaAs-based depletion field-effect transistor, and the gate voltage is kept constant with respect to the change in the gate length.
Varying the drain current of the system depletion field effect transistor varies the current of the current source.

By this means, in addition to the above-described invention, the tail current of the differential amplifier fluctuates with respect to the fluctuation of the gate length during manufacturing, so that the gain and band of the differential amplifier can be stabilized. Can be As a result, the yield for ultra-high frequency operation and cost reduction are achieved. Further, in the present invention, in a fluctuation compensation system for a differential amplifier using a field effect transistor, the current source of the differential amplifier and the gate length of the field effect transistor constituting the differential amplifier vary according to manufacturing variations. A fluctuation compensating system for a differential amplifier using an electric field transistor, comprising: a fluctuation compensating current source that fluctuates a current of a current source to compensate a gain and a band of the differential amplifier.

Still preferably, the fluctuation compensating current source comprises a current mirror circuit having two field-effect transistors whose gates are connected to each other, and the gate of one of the field-effect transistors whose drain and gate are short-circuited. The current of the current source is varied by making the length longer than the gate length of the other field-effect transistor, keeping the gate voltage constant with respect to the variation of the gate length, and varying the drain current of the other field-effect transistor. .

Still preferably, the field effect transistor is a GaAs enhancement field effect transistor or a silicon field effect transistor. By this means, the tail current of the differential amplifier is changed with respect to the change of the gate length at the time of manufacturing for the GaAs-based enhancement field-effect transistor or the silicon-based field-effect transistor. And stabilization of the band.

Further, the present invention relates to a method for compensating a fluctuation of a differential amplifier using a GaAs-based depletion field effect transistor, wherein the current source of the differential amplifier is adapted to prevent a fluctuation in a threshold voltage of a gate-source voltage during manufacturing. Performing negative feedback control, and GaAs constituting the differential amplifier.
The current of the current source is varied in accordance with the manufacturing variation of the gate length of the system depletion field-effect transistor to compensate for the gain and band of the differential amplifier, and the manufacturing variation of the threshold voltage of the gate-source voltage. And a step of performing negative feedback control on the differential amplifier using a GaAs-based field-effect transistor.

By this means, similarly to the above-described invention, the current source is constituted by the resistance portion against the variation in the threshold voltage of the gate-source voltage at which the drain current starts to flow at the time of manufacturing.
Negative feedback control has been applied to the As-based depletion field-effect transistor, and the tail current of the differential amplifier has been changed with respect to the change in the gate length during manufacturing.
The gain and band of the differential amplifier are stabilized. As a result, the yield for ultra-high frequency operation and cost reduction are achieved.

[0026]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a schematic configuration for explaining a fluctuation compensation system for a differential amplifier according to the present invention. As shown in the figure, the differential amplifier has a differential amplifier 1
Are provided, and the differential amplifying unit 1 has an input and an output, and amplifies the differential input.

The differential amplifier 1 is provided with a fluctuation compensating current source 2 for reducing the fluctuation of the tail current of the differential amplifier 1 and compensating for the fluctuation of the gain and band generated in the differential amplifier 1. FIG.
FIG. 2 is a circuit diagram showing a schematic configuration of a differential amplifier in FIG. The differential amplifier shown in this figure is, for example, a common source type differential amplifier, and a differential amplifier 1 and a fluctuation compensation current source 2 of the differential amplifier are GaAs depletion type field effect suitable for high-speed operation. Transistors JP, JN, J1, J
It consists of two.

That is, in the differential amplifying section 1, the drain side of each of the GaAs depletion field effect transistors JP and JN is connected to the power supply VDD via the resistors RP and RN, and the source side is connected to each other. An input is made to the gate sides of the GaAs depletion field effect transistors JP and JN, and an output is made from the drain sides of the GaAs depletion field effect transistors JP and JN.

Next, the fluctuation compensating current source 2 is provided with a fluctuation compensating current source 2A.
The drain side of the depletion field effect transistor J2 is connected to the source side of the GaAs depletion field effect transistors JP and JN, and the source side is the power supply V.
Connected to SS. Further, the drain side of the GaAs depletion field-effect transistor J1 is connected to the power supply VDD via the resistor R1, and the source side is connected to the power supply VSS.

The voltage dividing resistors R2 and R3 are connected to both ends of the GaAs depletion field effect transistor J1, and the gates of the GaAs depletion field effect transistors J1 and J2 are connected to the connection point of the voltage dividing resistors R2 and R3. And the gate sides are also directly connected. GaAs
s-based depletion field effect transistors J1, J2
Are formed with the same gate length.

By setting the constants of the resistance values of the resistors R1, R2, R3, an arbitrary voltage is set on the gate sides of the GaAs depletion field effect transistors J1, J2.
As a result, the GaAs depletion field effect transistors J1 and J2 are set from their linear region to their saturated region by raising their gate voltages, and the drain-source voltage V
It is not affected by DS fluctuation.

Further, negative feedback control by the resistor R2 acts on the GaAs depletion field effect transistor J1. During the manufacture of the differential amplifier, in the GaAs-based depletion field effect transistor constituting the differential amplifier, the fluctuation of the threshold value | VT | is mainly caused by the uniform variation in the impurity concentration and the thickness of the channel layer. , The gate length fluctuates, and the drain current ID fluctuates as shown in FIG.

If there is no negative feedback control, for example,
Considering a state where | VT | (VT <0) becomes small, the drain current ID of the GaAs-based depletion field-effect transistor J1 decreases, and at the same time, the GaAs-based depletion field-effect transistor J1
Drain current ID also decreases. The negative feedback control has an effect of suppressing the fluctuation of the drain current ID as described below.

In the fluctuation compensation current source 2A, the drain voltage of the GaAs depletion field effect transistor J1 controlled by the resistor R1 and the drain current ID of the GaAs depletion field effect transistor J1 rises depending on the decrease of the drain current. Further, the resistors R2 and R3 serve to increase the gate voltage of the GaAs depletion field effect transistor J1.

As described above, the fluctuation compensation current source 2A performs the negative feedback control to suppress the fluctuation of the drain current of the GaAs depletion field effect transistor J1 which depends on the fluctuation of | VT | Compensate for fluctuations in drain current for the GaAs depletion field effect transistor J2. Next, at the time of manufacturing the differential amplifier circuit, in the GaAs depletion field effect transistors JP and JN constituting the differential amplifier unit 1, the gain and the bandwidth of the differential amplifier caused by the uniform variation of the gate length are generated. The suppression of the fluctuation will be described.

FIG. 3 is a diagram showing a modified example of the differential amplifier in FIG. As shown in the figure, as compared with FIG. 2, the fluctuation compensation current source 2 is provided with a fluctuation compensation current source 2B, and the fluctuation compensation current source 2B is connected in parallel to the fluctuation compensation current source 2A. It serves to reduce the current of source 2A. The fluctuation compensating current source 2A corrects the current value of the fluctuation compensating current source 2B depending on the fluctuation of the gate length caused in the differential amplifying unit 1 at the time of manufacturing, and adjusts the gain of the differential amplifying unit 1 and the band. Bias adjustment is performed so as to cancel the fluctuation.

Next, the basic concept of forming the fluctuation compensation current source 2B will be described. The gain of the common source type differential amplifier is as follows: When the mutual conductance of the GaAs depletion field effect transistors JP and JN is gm, the resistance values of the drain load resistances RP and RN are RL, and the drain output resistance is infinite, and ignored, It can be represented by gm · RL.

Further, gm can be represented by the following equation (1). gm = (2K (W / L) ID) ^1/2 (1) W is gate width, L is gate length, ID is drain current,

K is a constant. Therefore, gm is (I
D / L) Since it is proportional to ^1/2 , by using the current source of the drain current ID proportional to the variation of the gate length L,
It is possible to suppress the gain fluctuation of the differential amplifier and the band fluctuation in which the cutoff frequency ft is proportional to gm.

Based on the above concept, the fluctuation compensation current source 2B
Are formed as follows as a current source of the drain current ID proportional to the variation of the gate length L. FIG. 4 is a diagram showing a configuration of the fluctuation compensation current source 2B in FIG. As shown in the figure, the fluctuation compensation current source 2B is provided with GaAs-based depletion field effect transistors J3 and J4.

The drain side of the GaAs depletion field effect transistor J3 is connected to the drain side of the GaAs depletion field effect transistor J1,
The source side is connected to the power supply VSS. The drain side of the GaAs depletion field effect transistor J4 is connected to the power supply VDD via the resistor 4, and the source side is the power supply V.
Connected to SS.

Voltage dividing resistors R5 and R6 are connected to both ends of a GaAs depletion field effect transistor J4,
The gates of the GaAs depletion field effect transistors J3 and J4 are connected to the connection point of the voltage dividing resistors R5 and R6, and the gates are also directly connected to each other. The GaAs depletion field effect transistors J3 and J4 are formed with different gate lengths.

The gate length of the GaAs depletion field-effect transistor J4 is longer than the gate length of the GaAs depletion field-effect transistor J3, for example, about 10 times longer. That is, since the drain current is inversely proportional to the gate length, the drain current flowing through the GaAs depletion field effect transistor J3 is G
It becomes about ten times larger than the drain current flowing through the aAs-based depletion field-effect transistor J4. That is, the mirror ratio is set to about 10.

More specifically, GaAs-based depletion field-effect transistors J1, J2, J3, JP, J
When the minimum gate length of each N is 0.5 μm, Ga
The gate length of the As-based depletion field effect transistor J4 is 5 μm. At the time of manufacturing, GaAs-based depletion field effect transistors J1, J2, J3, J
0.05 for each 0.5 μm gate length of P and JN
In a process in which a variation of μm (10%) occurs, GaAs
5μm of depletion field effect transistor J4
The fluctuation of 0.05 μm with respect to the gate length is suppressed to 1%.

Since the drain current (ID) is inversely proportional to the gate length, the influence on the drain current of the GaAs-based depletion field-effect transistor J4 due to the gate length fluctuation at the time of manufacturing is the GaAs-based depletion field-effect transistor J1 having a short gate length. , J2, J3, JP, JN
Will be stronger than In this case, the GaAs depletion field effect transistors J3 and J4 follow the threshold voltage (VT) fluctuation of the gate-source voltage because the resistor R5 performs the negative feedback control as described above. The current is constant. That is, the characteristics of the differential amplifier are not affected.

Next, as shown in FIG. 4, GaAs-based depletion field-effect transistors J1, J2, J3,
The drain current flowing through the resistor R1 is represented by I1, I2, I3, I3
Assuming that I1 = 4, I1 = I2 due to the nature of the current mirror.

I1 = I4-I3. If the gate length becomes longer when the gate length changes,
The drain current of the GaAs depletion field effect transistor J4, which is not affected by the gate length, does not change.
Therefore, the gate voltage of the GaAs depletion field effect transistor J3 is constant.

The GaAs depletion field effect transistor J3 having a constant gate voltage is affected by the gate length, and the drain current I3 of the GaAs depletion field effect transistor J3 decreases. At this time,
The drain current I1 (= I) flowing through the GaAs depletion field effect transistor J1 of the fluctuation compensation current source 2A
4-I3) increases, and the current mirror structure
The drain current I2 flowing through the As-based depletion field-effect transistor J2 increases, so that the tail current of the differential amplifier increases.

Thus, the GaAs shown in the above equation (2)
s-based depletion field-effect transistors JP, JN
, The increase in the gate length L can be canceled. That is, it is possible to suppress the gain fluctuation and the band fluctuation with respect to the manufacturing fluctuation of the differential amplifier, to establish the stability of the circuit operation, and to expect the improvement of the yield and the cost reduction.

In the manufacturing variation of the differential amplifier, the variation in the gate length occurs not only in the GaAs-based depletion field-effect transistor but also in the GaAs-based enhancement field-effect transistor and the silicon-based field-effect transistor. In this case, it is not necessary to consider the threshold voltage (VT) fluctuation of the gate-source voltage unlike the GaAs depletion field-effect transistor, so that the circuit can be simplified as described below. is there.

FIG. 5 is a modification of FIG. 4, and shows an example in which a GaAs enhancement field effect transistor and a silicon field effect transistor are used. As shown in the figure, a GaAs-based enhancement field-effect transistor, a silicon-based enhancement field-effect transistor J1P, J1N, J11,
When J12, J13, and J14 are used, the function of the negative feedback control is set by comparing the resistance of the fluctuation compensation current source 2A and the fluctuation compensation current source 2B with R2 = R5 = 0 and R3 = R6∞, as compared with FIG. Is removed.

As described above, when the gate length is increased when the gate length is changed, GaAs which is not affected by the gate length is used.
The drain current of a system-based enhancement field-effect transistor or a silicon-based field-effect transistor J4 is:
As described above, there is no change, so that the gate voltage of the GaAs depletion field effect transistor J3 is constant.

Even in the case of a differential amplifier composed of a GaAs enhancement field effect transistor or a silicon field effect transistor, it is possible to suppress a gain fluctuation and a band fluctuation with respect to a manufacturing fluctuation, and to perform a circuit operation. Stability can be established, and improvement in yield and cost reduction can be expected.

[0054]

As described above, according to the present invention,
Since the negative feedback control is performed on the current source of the differential amplifier, the threshold voltage (V) of the gate-source voltage at which the drain current of the depletion type field effect transistor starts to flow.
T) Allows the tail current of the differential amplifier to be stabilized against fluctuations.

Further, by varying the drain current depending on the variation of the gate length, it is possible to suppress the gain variation and the bandwidth variation of the differential amplifier. Therefore, the stability of the circuit operation with respect to manufacturing fluctuations can be established, and it is possible to expect an improvement in yield and a reduction in cost.

[Brief description of the drawings]

FIG. 1 is a diagram showing a schematic configuration for explaining a fluctuation compensation system for a differential amplifier according to the present invention.

FIG. 2 is a circuit diagram showing a schematic configuration of a differential amplifier in FIG.

FIG. 3 is a diagram illustrating a modified example of the differential amplifier in FIG. 2;

4 is a diagram showing a configuration of a fluctuation compensation current source 2B in FIG.

FIG. 5 is a modified example of FIG. 4, showing an example in which a GaAs-based enhancement field-effect transistor and a silicon-based field-effect transistor are used.

FIG. 6 is a circuit diagram showing a schematic configuration of a differential amplifier which is a premise of the present invention.

FIG. 7 is a diagram showing a relationship between a drain current (ID) and a gate-source voltage (VGS) of an N-channel GaAs-based depletion-type electric field transistor.

FIG. 8 is another circuit diagram illustrating a schematic configuration example of the differential amplifier in FIG. 6;

[Explanation of symbols]

Reference Signs List 1 ... Differential amplification unit 2, 2A, 2B ... Variation compensation current source J1, J2, J3, J4, JP, JN ... GaAs depletion field effect transistor RP, RN, R1, R2, R3, R4, R5, R6 ... Resistance VDD, VSS ... Power supply J11, J12, J13, J14, J1P, J1N ... G
aAs-based or silicon-based enhancement field-effect transistor

Claims (8)

[Claims] 1. A fluctuation compensating system for a differential amplifier using a GaAs depletion field effect transistor, comprising a current mirror circuit having two GaAs depletion field effect transistors whose gates are connected to each other. A current source of the differential amplifier, wherein a depletion field effect transistor forms a tail current of the differential amplifier, and the other GaAs-based depletion field effect transistor forms the same constant current as the tail current; and a gate-source voltage. In order to perform negative feedback control on the manufacturing fluctuation of the threshold voltage of the other GaAs-based depletion field effect transistor in the current source, a resistor connected between the drain and the gate and between the gate and the source of the other GaAs-based depletion field-effect transistor. GaAs system characterized by comprising Variation compensation system of the differential amplifier using repression field transistor. 2. A fluctuation compensation system for a differential amplifier using a GaAs-based depletion field-effect transistor, wherein the current source of the differential amplifier is negative feedback control with respect to a fluctuation in the threshold voltage of a gate-source voltage during manufacturing. A variation-compensating current source that performs the following operation; and varying the current of the current source by the first variation-compensating current source in accordance with the manufacturing variation of the gate length of the GaAs-based depletion field-effect transistor that forms the differential amplifier. A second fluctuation compensation current source that compensates for the gain and band of the differential amplifier and that performs negative feedback control on the manufacturing fluctuation of the threshold voltage of the gate-source voltage. Compensation system for a differential amplifier using a GaAs-based field transistor. 3. The first fluctuation compensating current source comprises a current mirror circuit having two GaAs-based depletion field-effect transistors whose gates are connected to each other, and one of the GaAs-based depletion field-effect transistors is connected to the difference mirror. A current source of the differential amplifier, which forms a tail current of the dynamic amplifier, and the other GaAs-based depletion field-effect transistor forms the same constant current as the tail current; and a manufacturing variation of a threshold voltage of a gate-source voltage. In order to perform negative feedback control on the current source, the current source further includes a resistor connected between a drain and a gate of the other GaAs-based depletion field-effect transistor and between a gate and a source. A fluctuation compensation of a differential amplifier using the GaAs field transistor according to claim 2. Stem. 4. The second fluctuation compensating current source comprises a current mirror circuit having two GaAs-based depletion field-effect transistors whose gates are connected to each other, and one of the GaAs-based circuits whose drain and gate are short-circuited. The gate length of the depletion field-effect transistor is made longer than the gate length of the other GaAs-based depletion field-effect transistor, the gate voltage is kept constant with respect to the change in gate length, and the drain current of the other GaAs-based depletion field-effect transistor is changed. 3. The method according to claim 2, wherein the current of the current source is varied, and a resistor is connected between the drain and the gate and between the gate and the source of the other GaAs-based depletion field-effect transistor. Ga
A fluctuation compensation system for a differential amplifier using an As-based field transistor. 5. A fluctuation compensating system for a differential amplifier using a field effect transistor, wherein the current source is supplied to the differential amplifier according to a manufacturing variation of a gate length of a field effect transistor constituting the differential amplifier. A fluctuation compensation current source for fluctuating the current of the source and compensating the gain and the band of the differential amplifier. 6. The fluctuation compensating current source is constituted by a current mirror circuit having two field-effect transistors whose gates are connected to each other, and the gate length of one field-effect transistor whose drain / gate is short-circuited is set to the other. The current of the current source is varied by making the gate voltage larger than the gate length of the field effect transistor, keeping the gate voltage constant with respect to the variation of the gate length, and varying the drain current of the other field effect transistor. And
A fluctuation compensation system for a differential amplifier using the electric field transistor according to claim 5. 7. The fluctuation compensation system for a differential amplifier using a field transistor according to claim 5, wherein the field effect transistor is a GaAs-based enhancement field-effect transistor or a silicon-based field-effect transistor. 8. A method for compensating fluctuation of a differential amplifier using a GaAs-based depletion field-effect transistor, wherein the current source of the differential amplifier is a negative feedback control with respect to a fluctuation in a threshold voltage of a gate-source voltage during manufacturing. And changing the current of the current source in accordance with the manufacturing variation of the gate length of the GaAs-based depletion field-effect transistor that constitutes the differential amplifier, compensates for the gain and band of the differential amplifier, and And performing a negative feedback control on the manufacturing variation of the threshold voltage of the gate-source voltage. A method for compensating a variation of a differential amplifier using a GaAs field transistor.