JP2007281930A - Bias circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a stable bias circuit to a reference voltage or variation of temperature without complicating circuit configuration. <P>SOLUTION: A first circuit region is provide with at least one resistance R1, and one terminal of resistance R1 is connected to a control terminal. When a reference voltage Vref is impressed to the control terminal, a reference current Iref flows into the resistance R1. The voltage drop occurs by flowing the current Iref into the resistance R1. When the amount of voltage drop is set to ΔV, the voltage V1 of a second terminal of the resistance R1 is represented by Vref-ΔV. A part of the current Iref is consumed in the first circuit region, the remaining current is output to the second terminal of the first circuit region as a current I1. A part of the current I1 flows into a second circuit region as a current I2, the remaining current is output from an output terminal as idle current Iout and flows into a transistor. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a transistor bias circuit, and more particularly to a bias circuit used in a base bias circuit of a bipolar transistor for high frequency power amplification.

  A base bias circuit used for a grounded-emitter bipolar transistor is required to have current supply capability, temperature stability, and the like. In addition to these requirements, battery-driven terminals such as cellular phones are increasingly required to have low voltage and stability against voltage fluctuations.

  A configuration of a conventional base bias circuit used during low-voltage driving will be described with reference to the drawings. FIG. 2 is a configuration diagram of a conventional bias circuit based on resistance division. The bias circuit by resistance division is composed of two resistors R1 and R2. One terminal of the resistor R1 is connected to the control terminal, the other terminal is connected to one terminal of the resistor R2, the other terminal of the resistor R2 is grounded, and a connection point between the two resistors is connected to the output terminal. .

  The output terminal is connected to the base of the transistor TR1 and supplied with a base voltage and a base current. When the reference voltage Vref is applied to the control terminal, the current Iref is input from the control terminal and passes through the resistor R1. Part of Iref flows through the resistor R2, and the rest is input to the transistor TR1 as the output current Iout.

However, in the above configuration, the operating current of the transistor TR1 easily varies due to the variation of the reference voltage Vref. Further, when the temperature fluctuates and the on-voltage of the transistor TR1 changes, the operating current of the transistor TR1 greatly fluctuates.

  In order to improve the problem in resistance division, a bias circuit using resistance-diode division is used. FIG. 3 is a configuration diagram of a conventional bias circuit using resistance-diode division. A conventional base bias circuit using resistance-diode division includes a resistor R1 and a diode D1. One terminal of the resistor R1 is connected to the control terminal, the other is connected to the anode of the diode D1, and the cathode of the diode D1 is grounded. A connection point between the resistor R1 and the diode D1 is connected to the output terminal.

  When a reference voltage is applied to the control terminal, a current Iref is input from the control terminal and passes through the resistor R1. Part of Iref flows through diode D1, and the rest is input to transistor TR1 as output current Iout.

  According to the above configuration, even if the reference voltage Vref is increased, the output voltage Vout is clipped to the on-voltage of the first diode D1, so that fluctuations in the operating current of the transistor TR1 with respect to fluctuations in the reference voltage Vref are suppressed. The

  FIG. 4 shows a simulation result of the idle current Icq of the transistor TR1 with respect to the reference voltage Vref when the bias circuit using resistance division and the bias circuit using resistance-diode division are used. Here, the idle current Icq is a DC operating current of the transistor TR1.

  Compared with the bias circuit using resistance division, the bias circuit using resistance-diode division has a smaller fluctuation of the idle current with respect to the fluctuation of the control voltage. However, in both circuits, the idle current tends to monotonously increase as the control voltage Vref increases, and a circuit that stabilizes the reference voltage Vref is required to make the idle current constant.

  FIG. 5 shows a simulation result of the idle current Icq of the transistor TR1 with respect to the temperature when the conventional bias circuit is used. During high temperature operation, the on-voltage of the transistor TR1 is shifted to the low voltage side. At this time, the idle current is greatly increased in the bias circuit based on resistance division.

  In the bias circuit by resistance-diode division, the on-voltage of the diode D1 is also shifted to the low voltage side as in the transistor. Since the output voltage Vout is clipped to the on-voltage of the diode D1, the output voltage Vout decreases during high temperature operation, canceling the shift of the on-voltage of the transistor TR1 and suppressing the increase in the idle current Icq.

  Conversely, the on-voltage of the transistor shifts to the high voltage side during the low temperature operation, but in the bias circuit based on resistance-diode division, the on-voltage of the diode D1 also shifts to the high voltage side. The shift of the ON voltage of TR1 is canceled, and the decrease in the idle current Icq is suppressed.

Normally, the diode D1 has a smaller device size than the transistor TR1, and therefore the on-voltage shift amount does not completely match, or an inductor or resistor for high-frequency signal separation is inserted between the bias circuit and the transistor TR1. As a result, a voltage drop occurs between the bias circuit and the transistor TR1, and the temperature dependence of the idle current remains.

In order to improve this, a configuration has been proposed in which a resistor is inserted in series with a temperature compensation diode, and a diode made of a material different from a Schottky diode or a transistor is used as the temperature compensation diode (for example, Patent Document 1). reference).
JP-A-11-68469

  As described above, in the configuration of the conventional bias circuit, as the reference voltage increases, the idle current of the transistor increases. For this reason, when setting the idle current constant, a circuit for stabilizing the reference voltage is required.

  Further, the conventional bias circuit configuration has a problem that the idle current fluctuates depending on the temperature. In order to improve the temperature dependence of the idle current, the process is complicated, such as making the diode a special configuration different from the transistor, which is disadvantageous in terms of cost.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a bias circuit that is stable against fluctuations in the reference voltage and temperature without complicating the circuit configuration.

  The bias circuit of the present invention is a bias circuit having a control terminal and an output terminal, and is connected between the control terminal and the output terminal, and has a first circuit region having at least one resistor, and the control terminal And a second circuit region connected between the output terminal and the output terminal, and having a function of changing a current flowing through the resistance of the first circuit region by a voltage applied to the control terminal.

  According to the above configuration, by appropriately setting the voltage (ON voltage) at which the second circuit region operates, the current flowing through the resistor in the first circuit region can be controlled, and the voltage drop of this resistor can be controlled. The output current can be controlled. Therefore, a stable bias circuit can be realized with a wide range of reference voltages.

  The bias circuit of the present invention is a bias circuit including a control terminal and an output terminal, and is connected between the control terminal and the output terminal, and has a first circuit region having at least one resistor, And a second circuit region connected between the control terminal and the output terminal and having a function of changing a current flowing through the resistor of the first circuit region depending on temperature.

  According to the above configuration, by appropriately setting the ON voltage of the second circuit region according to the temperature, the current flowing through the resistor of the first circuit region can be controlled, and the voltage drop of this resistor can be controlled. The output current can be controlled. Therefore, it is possible to realize a bias circuit that is stable against temperature fluctuations.

  In the bias circuit of the present invention, the resistance of the first circuit region is connected between the control terminal and the output terminal, and the first circuit region is connected at one end to the output terminal. It further has a resistor whose end is grounded.

  In the bias circuit of the present invention, the resistance of the first circuit region is connected between the control terminal and the output terminal, and the first circuit region is connected at one end to the output terminal. It has a diode whose end is grounded.

  In the bias circuit of the present invention, the second circuit region includes a diode whose anode is connected to the control terminal, a base connected to the cathode of the diode, a collector connected to the output terminal, and an emitter. And a transistor to be grounded.

  Furthermore, in the bias circuit of the present invention, the diode is a Schottky diode.

  According to the above configuration, the on-voltage can be freely set by selecting the metal of the Schottky diode. Therefore, by using the Schottky diode that has an on-voltage lower than the on-voltage of the transistor to be used, 2 circuit areas can be operated, and fluctuations in the output current can be suppressed to a lower voltage.

According to the bias circuit of the present invention, it is possible to realize a bias circuit that is stable against changes in the reference voltage and temperature.

(First embodiment)
FIG. 1 is a configuration diagram of a bias circuit according to a first embodiment of the present invention. The bias circuit of the present invention includes a control terminal and an output terminal, and is composed of a first circuit region and a second circuit region. The first terminal of the first circuit region is connected to the control terminal, and the second terminal is electrically connected to the output terminal.

  The first terminal of the second circuit area is connected to the control terminal, and the second terminal is connected to the output terminal. The first circuit region includes at least one resistor R1, and one terminal of the resistor R1 is connected to the control terminal.

  When the reference voltage Vref is applied to the control terminal, the reference current Iref flows into the resistor R1. A voltage drop is caused by the current Iref flowing through the resistor R1. When this voltage drop amount is ΔV, the voltage V1 of the second terminal of the resistor R1 is expressed by Vref−ΔV.

  A part of the current Iref is consumed in the first circuit area, and the rest is output as the current I1 to the second terminal of the first circuit area. Part of the current I1 flows into the second circuit region as the current I2, and the remaining current is output from the output terminal as the idle current Iout and flows into the transistor.

  The second circuit region is set to turn on when the reference voltage Vref becomes larger than a certain value, and the current I2 changes according to the value of the reference voltage Vref. Since the current I2 is supplied from the current Iref, the current Iref flowing through the resistor R1 can be changed by operating the second circuit region. If the current Iref can be controlled, the voltage drop ΔV and the voltage V1 due to the resistor R1, and thus the output voltage Vout and the idle current Iout can also be controlled.

  By appropriately setting the voltage at which the second circuit region is turned on, fluctuations in the idle current of the transistor can be improved over a wide range of reference voltages. Further, the voltage at which the second circuit region is turned on is set so as to vary with temperature, and the temperature dependence of the idle current can be improved.

  As a specific method for realizing the bias circuit, the first circuit area is a conventional resistor-diode bias bias circuit, and the second circuit area is composed of a diode and a transistor. The description will be made in comparison with a bias circuit using diode division. It is assumed that all transistors are InGaP / GaAs heterojunction bipolar transistors, and diodes are short-circuited from the base-collector of the InGaP / GaAs heterojunction bipolar transistors.

  FIG. 6 shows one configuration example of the bias circuit according to the first embodiment of the present invention. The bias circuit shown in FIG. 6 includes a first circuit region and a second circuit region. The first circuit region includes a resistor R1 and a diode D1, and one terminal of the resistor R1 is connected to the control terminal, the other terminal is connected to the anode of the diode D1, and the cathode of the diode D1 is grounded. A connection point between the resistor R1 and the diode D1 is connected to the output terminal.

  The second circuit region includes a diode D2 and a transistor TR2. The anode of the diode D2 is connected to the control terminal, and the cathode of the diode D2 is connected to the base of the transistor TR2. The emitter of the transistor TR2 is grounded, and the collector of the transistor TR2 is connected to the output terminal of the circuit area.

  When the reference voltage Vref is applied to the control terminal, the reference current Iref is input to the circuit constituting the first circuit region via the resistor R1. A voltage drop is caused by the current Iref flowing through the resistor R1. When this voltage drop amount is ΔV, the output voltage Vout is expressed by Vref−ΔV. Part of the current Iref flows into the diode D1, and the rest is output to the output terminal as the current I1. A part of the current I1 flows into the second circuit region as the current I2, and the remaining current flows into the transistor as the idle current Iout.

  When the reference voltage Vref applied to the control terminal becomes larger than the sum of the on-voltage of the diode D2 and the on-voltage of the transistor TR2, the diode D2 and the transistor T2 are turned on, and the collector of the transistor TR2 is turned on from the output terminal of the bias circuit. Current I2 flows through

  Since the current I2 is supplied from the current Iref, the current Iref increases and the voltage drop ΔV due to the resistor R1 increases. Since the output voltage Vout is expressed by Vref−ΔV, when the reference voltage Vref is higher than the voltage at which the second circuit region is turned on, ΔV also increases as the voltage Vref increases, and the voltages Vref and ΔV Cancel each other, and the fluctuation of the output voltage Vout is suppressed.

  FIG. 7 is a diagram comparing the simulation result of the transistor idle current Icq with respect to the reference voltage Vref when the conventional bias circuit and the bias circuit of this embodiment are used. All transistors and diodes were simulated using InGaP / GaAs heterojunction bipolar transistors. Compared to the conventional bias circuit using resistance division or resistance-diode division, the bias circuit of the present embodiment has an idle current with respect to the reference voltage Vref at the reference voltage Vref> 2.2 V at which the second circuit region is turned on. The fluctuation has improved.

  Next, the fluctuation of the idle current with respect to the temperature will be described. During high temperature operation, the on-voltage of the transistor TR1 shifts to the low voltage side. The output voltage Vout of the bias circuit is clipped to the ON voltage of the diode D1. During the high temperature operation, the on-voltage of the diode D1 also shifts to the low voltage side. However, since the diode D1 is usually smaller in device size than the transistor TR1, the on-voltage shift amount with respect to the temperature is different from that of the transistor TR1, Dependence cannot be removed. In FIG. 5, the idle current increases as the temperature rises.

In the bias circuit of this embodiment, the on-voltage of the diode D2 and the on-voltage of the transistor TR2 shift to the low voltage side during high temperature operation. At this time, since the current flowing through the diode D2 and the transistor TR2 increases, the current I2 flowing into the collector of the transistor TR2 also increases. Since the current I2 is supplied from the current Iref, the current Iref increases and the voltage drop ΔV due to the resistor R1 increases. Since the output voltage Vout is expressed by Vref−ΔV, Vout becomes small at high temperatures, and an increase in idle current can be suppressed.

  FIG. 8 is a diagram comparing the simulation results of the transistor idle current Icq with respect to the temperature when the conventional bias circuit and the bias circuit of this embodiment are used. Compared to the conventional bias circuit using resistance division or resistance-diode division, the bias circuit of this embodiment suppresses an increase in idle current with respect to temperature and improves fluctuations in idle current with respect to temperature on the high temperature side. .

(Second embodiment)
The bias circuit of the present embodiment uses a Schottky diode as the diode in the second circuit region. In a diode using a pn junction, the on-voltage is determined by the band structure of the p-layer and n-layer semiconductors. Therefore, the on-voltage cannot be changed unless the semiconductor material is changed. On the other hand, the Schottky diode uses a metal-semiconductor Schottky junction, and the on-voltage can be freely set by selecting a metal.

By using a Schottky diode having an on-voltage lower than the on-voltage of the transistor to be used, the second circuit region can be turned on with a lower voltage. According to this embodiment, fluctuations in the idle current can be suppressed to a lower voltage.

In the above embodiments, the transistors are all assumed to be InGaP / GaAs heterojunction bipolar transistors and the diodes are short-circuited from the base-collector of the InGaP / GaAs heterojunction bipolar transistors. Alternatively, a bipolar transistor using any of SiC, GaN, and InP or a heterojunction bipolar transistor that can be formed by combining them may be used.

  In the above embodiment, the operation has been described in the case where the first circuit area is a bias circuit by resistance-diode division as an example. However, as shown in FIG. 9A, the first circuit area is resistance division of resistors R1 and R2. Also good. Further, as shown in FIGS. 9b and 9c, the resistor R2 may be connected in parallel or in series to the diode D1 in the first circuit region. Further, as shown in FIG. 9d, a resistor R3 may be connected between the anode of the diode D2 and the output terminal. Although the temperature characteristics and the Vref value can be adjusted by inserting resistors as shown in FIGS. 9b to 9d, the basic operation is the same as the configuration described in the first embodiment.

  Also for the second circuit region, as shown in FIG. 10, all of the resistance R4 between the control terminal and the anode of the diode, the resistance R5 between the emitter and ground of the transistor, and the resistance R6 between the output terminal of the bias circuit and the collector of the transistor, Alternatively, the current I2 can be adjusted by inserting a resistor in part, but the basic operation is the same as the configuration described in the first embodiment. 11 is obtained by replacing the diode D2 (with the base and collector of the bipolar transistor short-circuited) in FIG.

  As described above, according to the bias circuit of the present embodiment, the second circuit region is turned on when the reference voltage Vref becomes larger than a certain value, and the current I2 is changed according to the value of the reference voltage Vref. Since the second circuit region operates, the current Iref flowing through the resistor R1 can be changed, and the voltage drop ΔV and the voltage V1 due to the resistor R1, and thus the output voltage can be changed. Vout and idle current Iout can be controlled. Accordingly, it is possible to provide a bias circuit in which fluctuations in the idle current of the transistor are improved over a wide range of reference voltages and temperatures.

  The bias circuit according to the present invention has an effect of providing a stable bias circuit with respect to variations in the reference voltage and temperature without complicating the circuit configuration, and is useful for a transistor bias circuit and the like.

Configuration of bias circuit according to the first embodiment of the present invention (1) Bias circuit configuration diagram by conventional resistance division Configuration diagram of bias circuit using conventional resistor-diode division The figure which shows the simulation result of the idle current Icq of the transistor with respect to the reference voltage at the time of using the conventional bias circuit The figure which shows the simulation result of the idle current of the transistor with respect to the temperature when using the conventional bias circuit Configuration of bias circuit according to the first embodiment of the present invention (2) The figure which shows the simulation result of the idle current Icq of the transistor with respect to the reference voltage Vref at the time of use of the conventional bias circuit and the bias circuit according to the first embodiment of the present invention The figure which shows the simulation result of the idle current Icq of the transistor with respect to the temperature at the time of use of the conventional bias circuit and the bias circuit according to the first embodiment of the present invention Configuration of bias circuit according to second embodiment of the present invention (1) Configuration of bias circuit according to second embodiment of the present invention (2) Configuration of bias circuit according to second embodiment of the present invention (3) Configuration of bias circuit according to second embodiment of the present invention (4) Configuration of bias circuit according to second embodiment of the present invention (5) Configuration of bias circuit according to second embodiment of the present invention (6)

Explanation of symbols

R1 to R6 Resistance D1 to D2 Diode D3 Schottky diode TR1 to TR2 Transistor Iref Current flowing through R1 I1 Current output from the first circuit area I2 Current flowing into the second circuit area Iout Bias circuit output current ΔV R1 voltage Drop Vout Bias output voltage Vref Reference voltage

Claims (6)

A bias circuit comprising a control terminal and an output terminal,
A first circuit region connected between the control terminal and the output terminal and having at least one resistor;
A second circuit region connected between the control terminal and the output terminal and having a function of changing a current flowing through a resistor of the first circuit region by a voltage applied to the control terminal;
A bias circuit comprising: A bias circuit comprising a control terminal and an output terminal,
A first circuit region connected between the control terminal and the output terminal and having at least one resistor;
A second circuit region connected between the control terminal and the output terminal and having a function of changing a current flowing through the resistor of the first circuit region according to a temperature;
A bias circuit comprising: The resistance of the first circuit region is connected between the control terminal and the output terminal,
The bias circuit according to claim 1, wherein the first circuit region further includes a resistor having one end connected to the output terminal and the other end grounded. The resistance of the first circuit region is connected between the control terminal and the output terminal,
The bias circuit according to claim 1, wherein the first circuit region has a diode having one end connected to the output terminal and the other end grounded.   The second circuit region has a diode whose anode is connected to the control terminal, and a transistor whose base is connected to the cathode of the diode, whose collector is connected to the output terminal, and whose emitter is grounded. The bias circuit according to claim 1 or 2.   The bias circuit according to claim 5, wherein the diode is a Schottky diode.

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