KR100937039B1 - A Bias Circuit having Compensation Capability for Threshold Voltage and Temperature Variations and Amplifier using the same - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bias circuit capable of applying a stable voltage to a transistor under conditions of temperature change and change of threshold voltage, and conditions of supply power supply, and an amplifier using the same. A bias circuit for compensating gain characteristics for a change in a power supply, comprising: a second transistor connected in parallel to a source terminal of a first transistor of an active gate bias circuit to which a first feedback resistor is connected, and to which a second feedback resistor is connected; It includes.

Bias, circuit, amplifier, transistor, compensation, temperature, change, voltage

Description

A Bias Circuit having Compensation Capability for Threshold Voltage and Temperature Variations and Amplifier using the same}

The present invention relates to a bias circuit of a transistor capable of compensating for temperature and threshold voltage changes and an amplifier using the same. More particularly, the present invention relates to a temperature change and a threshold voltage in a field effect transistor (FET) series bias circuit. The present invention relates to a bias circuit capable of applying a stable voltage to a transistor under conditions of a change in voltage and a change in supply power, and an amplifier using the same.

The present invention is derived from a study conducted as part of the IT new growth engine core technology development project of the Ministry of Information and Communication and the Ministry of Information and Communication Research and Development. [Task Management No .: 2007-S-301-01, Title: Satellite Navigation and Land Station System and Search] Development of rescue terminal technology].

In general, the transistor performance changes depending on the temperature characteristics. That is, the transistor has a characteristic that the gain characteristics (gain of the amplifier) are deteriorated because the transconductance (Gm) and the drain (Drain) current become small under the same bias condition at a high temperature. Therefore, there is a need for a bias circuit that can increase the gate voltage of the transistor as the temperature increases.

As a compensation technique for temperature change, Kazuhisa Yamauchi implemented a temperature change compensation circuit using the characteristic that the threshold voltage of the diode decreases as the temperature increases. However, such a temperature change compensation circuit has a disadvantage in that it is difficult to expect a compensation effect against a change in threshold voltage and power supply.

In general, when transistors of field effect transistor (FET) series are manufactured, the threshold voltages have different values depending on the position of the wafer. Therefore, in order to operate transistors manufactured in all wafers under the same conditions, different gate voltages must be applied. For this reason, conventionally, the bias circuit of the transistor was not embedded in the MMIC (Microwave Monolithic Integrated Circuit) circuit, but the external device was used to apply a desired gate bias voltage to each transistor. As a result, additional processes and parts are required, which limits the cost of manufacturing parts.

To compensate for temperature and threshold voltage changes, Koji Yamanaka implemented a temperature and threshold voltage change compensation circuit using transistors and diodes. However, such a temperature and threshold voltage change compensation circuit has a disadvantage in that it is difficult to expect a compensation effect on a change in the power supply.

MMICs in real radio frequency (RF) systems require a bias circuit that allows the transistor to operate stably with changes in threshold voltage, temperature, and supply. If the bias circuit can be embedded in the MMIC with a small area, the manufacturing cost is reduced by that much. Therefore, there is a need for a bias circuit capable of compensating for the threshold voltage and temperature of a simple structure that can be integrated on-chip, and the change of power supply.

Accordingly, the present invention has been proposed to solve the above problems of the prior art, and in the active gate bias circuit to which the feedback resistor is connected, a compensation transistor is added in parallel to the source terminal of the active bias transistor to change the threshold voltage and temperature. It is an object of the present invention to provide a bias circuit capable of supplying a stable bias against a change in the power supply while supplying a stable bias with respect to the power supply, and an amplifier using the same.

Other objects and advantages of the present invention can be understood by the following description, and will be more clearly understood by the embodiments of the present invention. Also, it will be readily appreciated that the objects and advantages of the present invention may be realized by the means and combinations thereof indicated in the claims.

A bias circuit according to the present invention for achieving the above object is a bias circuit for compensating for gain characteristics against a change in a threshold voltage and a temperature of a transistor and a power supply, wherein a bias circuit of the active gate bias circuit is connected to a first feedback resistor. And a second transistor connected in parallel to the source terminal of the first transistor and connected to the second feedback resistor.

In addition, the amplifier according to the present invention, an amplifier transistor; Active gate bias means connected to the amplifying transistor and having a first feedback resistor connected thereto; And a second transistor connected in parallel to the source terminal of the first transistor of the active gate bias means, and having a second feedback resistor connected thereto.

Preferably the amplifier according to the invention further comprises a third resistor connected between the amplifying transistor and the active gate bias means to prevent leakage of radio frequency signals from the amplifying transistor to the active gate bias means.

Preferably, the amplifier according to the present invention further comprises an inductor connected between the amplifying transistor and the active gate bias means to prevent leakage of radio frequency signals from the amplifying transistor to the active gate bias means.

Preferably, the second feedback resistor is configured as a basic resistor when the amplification transistor increases in gain when the gate voltage decreases.

Preferably, the second feedback resistor is composed of a thermistor in the form of a negative temperature coefficient (NTC) to increase the compensation effect when the gain increases when the gate voltage decreases.

Preferably, the second feedback resistor is configured as a thermistor of PTC (Positive Temperature Coefficient) type, in which the resistance value increases when the temperature increases when the gain increases when the gate voltage increases.

As described above, in order to supply a constant bias against a change in the threshold voltage generated during transistor fabrication, the present invention is compensated by adding a transistor including feedback in parallel to a source terminal of an active bias transistor including a feedback resistor. Provide a bias.

In addition, the present invention can provide a compensated gate bias regardless of where the gate bias voltage of the amplifying transistor is selected under conditions of temperature change, as well as provide a stable voltage at which the gate voltage is hardly changed even with a changed supply of negative power. have.

The above objects, features and advantages will become more apparent from the following detailed description taken in conjunction with the accompanying drawings, whereby those skilled in the art may easily implement the technical idea of the present invention. There will be. In addition, in describing the present invention, when it is determined that the detailed description of the known technology related to the present invention may unnecessarily obscure the gist of the present invention, the detailed description thereof will be omitted. Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

First, prior to explaining the present invention, the operating principle of a general active gate bias circuit will be described.

In the general active gate bias circuit illustrated in FIG. 1, assuming that the transistor has a linearized IV curve as shown in FIG. 2, the current I _D and the bias voltage V _B as shown in Equations 1 and 2 are as follows. Is displayed.

At this time, when the threshold voltage V _T changes, the condition in which the change amount of the bias voltage V _B is kept constant is a condition in which g _m1 R1 represented by the ratio of the change amount of the threshold voltage and the bias voltage of Equation 3 becomes 1.

However, g _m1 is a value determined because V _GS1 is fixed at 0 V, and R1 is also a value determined by the bias voltage (V _B ) with respect to the current of transistor Q1 and thus cannot be perfectly compensated.

3 illustrates an active gate bias circuit to which a general feedback resistor is connected, and the operating principle of the active gate bias circuit to which the feedback resistor shown in FIG. 3 is connected is as follows.

Assuming that the transistor has a linearized IV curve as in the general active gate bias circuit shown in FIG. 1, the current I _D and the bias voltage V _{B as} shown in Equations 4 and 5 are shown.

At this time, the condition that the change amount of the bias voltage V _B is kept constant when the threshold voltage V _T changes is g _m1 R1 / (1+ g _m1 R2 expressed as the ratio of the change amount of the threshold voltage and the bias voltage of Equation 6 ) Is a condition of 1.

However, the bias voltage (V _B ) and the threshold voltage (V _T ) may not have the same value and thus may not be perfectly compensated. In general, the bias voltage V _B has a value closer to 0 V than the threshold voltage V _T.

Next, an improved bias circuit and an amplifier using the improved bias circuit according to the present invention will be described in detail with reference to FIGS. 4 and 5.

As shown in FIG. 4, the bias circuit according to the present invention includes a transistor Q2 connected in parallel to the source terminal of the transistor Q1 of the active gate bias circuit to which the feedback resistor R2 is connected and including the feedback resistor R3. The operation principle of the threshold voltage and temperature change compensation bias circuit is as follows.

Assuming that the transistor has a linearized IV curve and disregards the gate current, the current I _D1 and the bias voltage V _{B as} shown in Equations 7 and 8 are shown.

In this case, in order to change the bias voltage V _B in the same manner when the threshold voltage V _T changes, the ratio of the threshold voltage and the change amount of the bias voltage in Equation 9 is designed by determining appropriate operating points of three resistors and transistors. do.

The threshold voltage V _T has a negative value in the case of a depletion mode transistor. When the threshold voltage V _T increases in the direction of 0 V, the current decreases when the gate-source bias voltage V _GS of the transistor is constant. In this case, the drain current of the transistor Q2 shown in FIG. 4 decreases, and the voltage applied to the feedback resistor R3 decreases, thereby increasing the current of the transistor Q2 again. As a result, the drain current of the transistor Q2 is fixed in a slightly reduced form, and the gate voltage of the transistor Q2 decreases.

Since the gate of transistor Q2 and the source terminal of transistor Q1 of the active gate bias circuit having feedback resistor R2 are directly connected to each other, the reduced gate voltage of transistor Q2 increases the gate-source voltage of transistor Q1, thereby providing a threshold voltage. (V _T ) will compensate for the increased effect.

The drain current of the final transistor Q1 is determined to be less than the reference value. The drain current of the transistor Q1 determined here increases the bias voltage V _B through the resistor R1, so that the bias voltage of the transistor to be driven can be increased to operate at the same current value when the threshold voltage is increased.

5 is an embodiment of an amplifier having a threshold voltage and temperature change compensation bias circuit according to the present invention.

Transistors Q1 and Q2 used 2F75 (2 fingers, gate width = 75㎛), which is a small area for bias transistors, and amplified transistor Q3 used 8F150 (8 fingers, gate width = 150㎛), which had a larger area. . The resistor RB is a bias resistor to prevent leakage of the RF signal toward the bias circuit when the amplifying transistor Q3 operates at a high frequency, so that the difference in the gate bias of the amplifying transistor Q3 can be ignored. Meanwhile, the resistor RB may be replaced with an inductor, and the inductor is used to prevent leakage of the RF signal.

FIG. 6 illustrates a case in which an 8F150 amplifier transistor is connected as shown in FIG. 5 by using an active gate bias circuit shown in FIG. 1 and an active gate bias circuit connected to a feedback resistor shown in FIG. The operating point current I _{Q is} shown. In FIG. 6, 101 is a case using the active gate bias circuit shown in FIG. 1, 102 is a case using the bias circuit shown in FIG. 3, and 103 is a case where the gate bias is directly applied. The representative value of the threshold voltage is -1.52V, and the threshold voltage varies from -1.82 to -1.22V as a result of the process.

As shown in FIG. 6, the operating point current of the amplifying transistor when the direct gate bias is applied without the bias circuit shows a current difference of about 70.7 mA. In general, the active gate bias circuit exhibits a very good compensation characteristic when the direct bias is applied with a total change of 26.2 mA against the 0.6 V change of the threshold voltage. The active gate bias circuit with the feedback resistor is about 18.3 mA. The operating point current changes.

FIG. 7 is a graph illustrating an operating point current of an amplifying transistor using a threshold voltage and temperature change compensation bias circuit according to the present invention shown in FIG. 5.

The change of 1.1mA against the 0.6V change of the threshold voltage kept constant with almost no change in operating point current. Therefore, if the compensation bias circuit is used for the variation of the threshold voltage generated during the fabrication of the transistor, the operating point current of the amplifier can be expected to be very stable device characteristics with a variation of less than 1%.

Transistors are temperature sensitive. In fact, the temperature at which transistor components are used is used in the range of more than 100 degrees. Therefore, there is a need for a bias circuit capable of a stable operation of the transistor against temperature changes. The operation of the threshold voltage and temperature change compensation bias circuit when the operating temperature changes is as follows.

Suppose that the temperature rises while operating at room temperature in the circuit shown in FIG. As the temperature increases, the drain current decreases. Therefore, the drain current of the transistor Q2 decreases, so that the voltage applied to the feedback resistor R3 decreases. Ideally, the gate voltage of the transistor Q2 is kept constant, but in reality, the gate voltage of the transistor Q2 decreases minutely. The reduced gate voltage of transistor Q2 increases the gate-source voltage of transistor Q1 so that the drain current of transistor Q1 also increases slightly to reduce the bias voltage (V _B ).

8 shows gain characteristics with respect to the gate voltage of the amplifying transistor.

Transistors are characterized by a decrease in gain as the temperature increases. Therefore, when the gate bias is selected in FIG. 8, the characteristics of the temperature of the bias circuit should be reversed when the bias A and the bias B are selected. As described above, the bias voltage V _B slightly decreases as the temperature increases. Therefore, when bias A is selected as the operating gate voltage, the gain characteristic of the amplifying transistor can be compensated for with temperature change.

On the contrary, when bias B is set as the operation gate voltage and the amplifying transistor is driven, the temperature change characteristic can be compensated by the following method. In FIG. 5, when using a PTC (Positive Temperature Coefficient) type thermistor whose resistance value increases as the temperature increases, the following operation is performed. Increasing the temperature increases the value of resistor R3 using a PTC thermistor. Thus, the gate-source voltage of transistor Q1 is reduced and the drain current of transistor Q1 is also reduced. Therefore, the bias voltage V _B , which is determined by the current flowing through the resistor R1 and the current value, becomes large to compensate for the gain characteristic of the amplifying transistor that decreases with increasing temperature.

Likewise, in FIG. 8, to compensate more temperature characteristics when selecting bias A, a thermistor in the form of a negative temperature coefficient (NTC) may be used as the resistor R3.

The bias voltage Vs of FIG. 5 has a negative voltage. This external supply voltage Vs should not be continuously supplied at a constant value, but should operate stably even if it is supplied at a changed value.

FIG. 9 shows a gate bias voltage V _B variation curve when the negative bias voltage Vs varies from −6 to −4 V with a variation of ± 20% at −5 V. FIG. For a negative supply change of ± 20%, the gate bias voltage (V _B ) is stable, showing only a change of less than 1.5%.

The present invention described above is capable of various substitutions, modifications, and changes without departing from the technical spirit of the present invention for those skilled in the art to which the present invention pertains. It is not limited by the drawings.

1 is a block diagram of a general active gate bias circuit,

2 shows a linearized I-V curve,

3 is a configuration diagram of an active gate bias circuit connected with a general feedback resistor;

4 is a configuration diagram of a threshold voltage and temperature change compensation bias circuit according to the present invention;

5 is a configuration diagram of an amplifier having a threshold voltage and temperature change compensation bias circuit according to the present invention;

6 is a view for explaining an operating point current of an amplifying transistor;

7 is a view illustrating an operating point current of an amplifying transistor using a threshold voltage and temperature change compensation bias circuit according to the present invention;

8 is a diagram illustrating a gain according to a gate voltage of an amplifying transistor;

9 is a view illustrating a change in the gate bias voltage V _B according to the negative bias voltage Vs.

Claims (10)

A first transistor electrically connected between a gate terminal and an input terminal and electrically connected with a drain terminal and an output terminal, a first resistor disposed between the source terminal and the input terminal of the first transistor, and a drain terminal of the first transistor An active gate bias circuit comprising a second resistor disposed between ground and ground, A second transistor electrically connected with a gate terminal and a source terminal of the first transistor; A third resistor disposed between the source terminal of the second transistor and the gate terminal of the second transistor Comprising a bias circuit. delete The method of claim 1, wherein the third resistor, A bias circuit that is a negative temperature coefficient (NTC) thermistor. The method of claim 1, wherein the third resistor, A bias circuit that is a PTC (Positive Temperature Coefficient) thermistor. A first transistor electrically connected between a gate terminal and an input terminal and electrically connected with a drain terminal and an output terminal, a first resistor disposed between the source terminal and the input terminal of the first transistor, and a drain terminal of the first transistor An amplifier comprising a second resistor disposed between ground and ground, A second transistor electrically connected with a gate terminal and a source terminal of the first transistor; A third resistor disposed between the source terminal of the second transistor and the gate terminal of the second transistor; Amplifying transistor for amplifying the input voltage according to the voltage level of the output terminal Including, an amplifier. The method of claim 5, wherein And a fourth resistor disposed between the output terminal and the amplifying transistor. The method of claim 5, wherein And an inductor disposed between the output terminal and the amplifying transistor. delete The method of claim 5, wherein the third resistor, An amplifier that is a negative temperature coefficient (NTC) thermistor. The method of claim 5, wherein the third resistor, An amplifier that is a PTC (Positive Temperature Coefficient) thermistor.

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