JP2005311689A - High pressure resistant scode amplifier - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high frequency output circuit capable of securing high output power essential for a high frequency device by adopting transistors having different breakdown voltage. <P>SOLUTION: A cascode amplifier 1 includes a breakdown voltage MOS transistor 11 on the input side being provided corresponding to the small voltage amplitude of an output terminal (drain D), and a high breakdown voltage MOS transistor 12 on the output side. By means of the high breakdown voltage MOS transistor 12, load impedance can be set high so as to generate large output voltage amplitude, and the gain of the whole amplifier circuit can be increased. Further, by increasing the output voltage amplitude, current amplitude for obtaining desired output power can be suppressed low. Also, the efficiency of the amplifier circuit can be increased by hardly affected by a loss resulting from a parasitic resistance component included in a load 13. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a cascode amplifier circuit that exhibits a high-frequency amplification action, and may be used particularly in a high-frequency power amplifier circuit unit.

  In recent years, wireless communication has become popular in mobile devices such as mobile phones and PDAs. However, further downsizing of devices and longer operation with batteries are major issues. Under such circumstances, high gain and high efficiency are becoming very important for a high-frequency amplifier circuit as one of the essential circuits for wireless communication.

  Conventionally, as an amplifier circuit constituted by using two transistors 101 and 102, a cascode amplifier circuit 100 in which both transistors 101 and 102 are connected in series is used as shown in FIG. The gate of the lower transistor 101 is voltage-driven, and the gate of the upper transistor 102 is AC-shorted to GND. In a high frequency circuit, a stray capacitance called a mirror capacitance exists between a drain / gate (collector / base). There is a problem that the output decreases due to the feedback of the output signal of the high frequency circuit through such a mirror capacitor, and there is a problem that the signal interferes with the input signal, the output signal, and the signal propagation part in the middle. Further attention is required even when compared with a design in a normal IC circuit. In the cascode amplifier circuit 100 as shown in FIG. 5, since the source of the transistor 102 is connected as the drain load of the transistor 101, the change in the drain voltage of the transistor 101 is small, and in the high frequency region due to the mirror capacitance in the transistor 101. Gain attenuation can be suppressed. Further, even if the drain voltage of the transistor 102 changes, the change in the drain voltage of the transistor 101 is small, and therefore the change in the drain current of both transistors 101 and 102 is small. Therefore, the output impedance of the transistor 102 as viewed from the load side is extremely high. Become. In general, a cascode amplifier circuit is used when a gain at a high frequency is secured by utilizing such characteristics, or when an output impedance is designed to be high.

Since the cascode amplifier circuit 100 as shown in FIG. 5 generally has good high frequency characteristics, an inductive load circuit using an inductor is often connected as the high frequency amplifier circuit. When an inductive load circuit is connected, problems such as attenuation of gain due to mirror capacitance and generation of instantaneous peak voltage occur as problems specific to high frequencies that do not cause problems with normal frequencies and ICs. With respect to the peak voltage, the voltage at the output terminal (drain or collector) of the transistor 102 may instantaneously reach a level that is at least twice as high as the power supply voltage according to the amplitude of the input signal, and may exceed the breakdown voltage of the transistor 102. is there. In order to avoid these problems, in conventional circuit design, measures should be taken so that the level of the output signal does not cause a problem without changing the device configuration or taking measures against the process or circuit configuration. Has been done. That is, in the case of the cascode amplifier circuit 100 as shown in FIG. 5, the operating condition of the second-stage transistor 102 is changed with respect to the first-stage transistor 101 for signal input or connected to the output. For example, a design measure is adopted in which the output current amplitude is increased to reduce the output voltage amplitude by limiting the load itself, for example, by lowering the impedance when the load side is viewed from the output end of the transistor 102 (see FIG. Non-patent document 1).
Edited by Triqueps Planning Department, “Analog circuit design technology for CMOS conversion of portable wireless terminals”, Trikes, Inc., December 26, 1999, p. 182 “5.2 Cascode Amplification Circuit”, p. 208-209 "3.2 MOS conversion of PA"

  However, such design measures such as changing the operating conditions and connection load not only reduce the gain of the amplifier circuit, but also require a large current to flow through the transistor. By flowing through the inductor, power loss is large due to the parasitic resistance component of the inductor, and it is difficult to ensure high output power (power) that is essential for high-frequency devices. This shortage of output becomes a serious problem particularly in the case of an MMIC (Monolithic Microwave Integrated Circuit) in which an inductor is built on an integrated circuit chip. In addition, it has been conventionally performed to use a transistor with a high withstand voltage for both the transistor 101 and the transistor 102. However, generally, when the withstand voltage of the transistor is increased, the transconductance gm decreases in proportion to the drain current, and the gain of the amplifier circuit is increased. In this case, the performance as an amplifier has to be sacrificed to some extent.

  Therefore, in a high-frequency output circuit consisting of a cascode amplifier circuit connected in series with two transistors, by adopting a transistor with a different withstand voltage as the type of each transistor, a measure to overcome the change in the above operating conditions and connection load is intended. There are issues to be solved.

  An object of the present invention is to provide a high-frequency output circuit that makes it possible to ensure high output power that is essential for a high-frequency device by adopting transistors having different breakdown voltages as the types of transistors.

  In order to solve the above problems, a high-frequency output circuit according to the present invention is a high-frequency output circuit comprising a cascode amplifier circuit in which two transistors are connected in series, wherein the transistor connected to the load on the output side is replaced with the transistor on the input side. It is characterized by a high breakdown voltage type.

  According to this high frequency output circuit, the transistor connected to the load on the output side has a higher withstand voltage than the transistor on the input side, so that a high voltage is applied to the transistor on the output side according to the signal fluctuation on the input side. But it can withstand this. As a result, the output voltage amplitude can be increased by adjusting the load connected to the output side, and the output current amplitude can be decreased accordingly. Therefore, the current that should be passed to obtain the same level of power as in the past, that is, the current that flows in the load inductor can be suppressed compared to the conventional one, and the power loss due to the parasitic resistance component of the inductor is reduced. The required high output power can be ensured, and at the same time, the gain can be increased because the power loss is small.

  In the high-frequency output circuit, the input-side transistor can be a normal voltage MOS transistor, and the output-side transistor can be a high voltage MOS transistor. That is, this high-frequency output circuit is a combination in which MOS transistors of the same type are employed as a combination of the input side and output side transistors, the input side is a normal withstand voltage type, and the output side is a high withstand voltage.

  In this high-frequency output circuit, the input-side transistor can be a normal breakdown voltage bipolar transistor, and the output-side transistor can be a high breakdown voltage bipolar transistor. That is, this high-frequency output circuit is a combination in which bipolar transistors of the same type are employed as a combination of transistors on the input side and the output side, the input side is a normal withstand voltage type, and the output side is a high withstand voltage.

  In this high-frequency output circuit, the transistor on the input side can be a normal voltage MOS transistor, and the transistor on the output side can be a high voltage bipolar transistor. That is, this high frequency output circuit employs different types of MOS transistors and bipolar transistors on the input side and output side, respectively, as a combination of transistors on the input side and output side, and the input side is a normal withstand voltage type and the output side is It is a combination with high pressure resistance.

  In this high-frequency output circuit, the transistor on the input side can be a normal voltage bipolar transistor, and the transistor on the output side can be a high voltage MOS transistor. That is, this high frequency output circuit employs different types of bipolar transistors and MOS transistors on the input side and the output side in the combination of the input side and output side transistors, respectively, and the input side is a normal withstand voltage type and the output side is It is a combination with high pressure resistance.

  Since the present invention is configured as described above, in a high-frequency output circuit such as a cascode amplifier circuit, an output-side transistor can withstand a high voltage that can be applied. The power loss due to the parasitic resistance component of the inductor can be reduced, and high output power (power) can be ensured, and higher gain and higher efficiency of the circuit can be obtained. As a result, restrictions such as changing the operating conditions and limiting the load are reduced, the degree of freedom in design as a high-frequency device is improved, and as a result, the output power can be increased and the device characteristics are also improved. Can be improved. Furthermore, in wireless communication of mobile devices, it is possible to meet the needs of the times such as downsizing of devices and long-time operation by batteries by increasing the gain and efficiency of high-frequency amplifier circuits. Especially in communication equipment with a transmission output power exceeding 10 mW, the ratio of current consumption in the high-frequency power amplifier circuit for transmission is large with respect to the current consumption of the entire equipment. It is very effective.

  Hereinafter, embodiments of a high-frequency output circuit according to the present invention will be described with reference to the accompanying drawings. FIG. 1 is a circuit diagram showing an embodiment of a high frequency output circuit according to the present invention. The high frequency output circuit is configured as a cascode amplifier circuit.

  A cascode amplifier circuit 1 as a high-frequency output circuit shown in FIG. 1 is an example in which two transistors are realized by MOS transistors 11 and 12 of the same type. In the cascode amplifier circuit 1, the MOS transistor on the input side is the normal withstand voltage MOS transistor 11, the input voltage Vin is applied to the gate G, and the source S is grounded. Further, the source S of the high voltage MOS transistor 12 on the output side is connected to the drain D of the MOS transistor 11. A fixed potential is applied to the gate G of the high voltage MOS transistor 12, and a load 13 is connected to the drain D of the high voltage MOS transistor 12.

  The gain in the cascode amplifier circuit 1 is substantially determined by the transconductance gm of the transistor and the load impedance. However, since the voltage amplitude of the output terminal (drain D) of the transistor 11 on the input side is small, the withstand voltage of the transistor 11 is small. Can be used. Therefore, as the transistor 11, a normal voltage MOS transistor having a high transconductance gm can be used. On the other hand, as the output side transistor 12, the transconductance gm hardly contributes to the amplification factor of the entire amplifier circuit, so that only the transistor 12 is a high voltage MOS transistor so that a large output voltage amplitude can be generated. The impedance can be set high, so that the gain of the entire amplifier circuit can be increased. In addition, by increasing the output voltage amplitude, the current amplitude for obtaining the desired output power can be kept small, and at the same time, the drain D current for obtaining the desired linearity can be kept small. This suppresses not only the effect of suppressing the current consumption of the power supply, but also suppresses the current flowing through the load 13, thereby making it less susceptible to the loss due to the parasitic resistance component included in the load 13 and increasing the efficiency of the amplifier circuit.

  FIG. 2 is a circuit diagram showing another embodiment of the high-frequency output circuit according to the present invention. The cascode amplifier circuit 2 as a high-frequency output circuit shown in FIG. 2 is configured such that an input-side transistor is a normal breakdown voltage bipolar transistor 21 and an output-side transistor is a high breakdown voltage bipolar transistor 22. In the normal breakdown voltage bipolar transistor 21, as in the case of the cascode amplifier circuit 1 shown in FIG. 1, the input voltage Vin is applied to the base B, the emitter E is grounded, and the emitter E of the high breakdown voltage bipolar transistor 22 is connected to the collector C. Is connected. In the high breakdown voltage bipolar transistor 22, the base B is set to a fixed potential, the collector C is used as an output, and a load 23 is connected. The operation of the cascode amplifier circuit 2 is equivalent to that of the cascode amplifier circuit 1 shown in FIG.

  FIG. 3 is a circuit diagram showing still another embodiment of the high-frequency output circuit according to the present invention. The cascode amplifier circuit 3 as the high frequency output circuit shown in FIG. 3 uses different types of transistors on the input side and the output side. The input side transistor is a normal withstand voltage MOS transistor 31 and the output side transistor is the same. A high voltage bipolar transistor 32 is provided. In the normal voltage MOS transistor 31 on the input side, the input voltage Vin is applied to the gate G and the source S is grounded, as in the case of the cascode amplifier circuit 1 shown in FIG. The drain D of the normal breakdown voltage MOS transistor 31 is connected to the emitter E of the high breakdown voltage bipolar transistor 32 on the output side. As in the case of the cascode amplifier circuit 2 shown in FIG. 2, the high voltage bipolar transistor 32 has a base B set at a fixed potential, a collector C as an output, and a load 33 connected thereto. The operation of the cascode amplifier circuit 3 is equivalent to that of the cascode amplifier circuit 1 shown in FIG.

  FIG. 4 is a circuit diagram showing another embodiment of the high-frequency output circuit according to the present invention. The cascode amplifier circuit 4 as the high frequency output circuit shown in FIG. 4 uses different types of transistors on the input side and the output side. The input side transistor is a normal withstand voltage bipolar transistor 41, and the output side transistor is the same. The high voltage MOS transistor 42 is used. In the normal withstand voltage bipolar transistor 41 on the input side, the input voltage Vin is applied to the base B and the emitter E is grounded, as in the case of the cascode amplifier circuit 1 shown in FIG. The collector C of the normal breakdown voltage bipolar transistor 41 is connected to the source S of the high breakdown voltage MOS transistor 42 on the output side. In the high voltage MOS transistor 42, as in the case of the cascode amplifier circuit 1 shown in FIG. 1, the gate G is set to a fixed potential, the drain D is output, and the load 43 is connected. The operation of the cascode amplifier circuit 4 is the same as that of the cascode amplifier circuit 1 shown in FIG.

  Although the MOS transistor and the bipolar transistor have been described as the transistors used in the high-frequency output circuit according to the present invention, the structure according to the present invention is an effective technique for standard CMOS, bipolar, and BiSCMOS transistors.

The circuit diagram which shows one Example of the high frequency output circuit by this invention. The circuit diagram which shows another Example of the high frequency output circuit by this invention. The circuit diagram which shows another Example of the high frequency output circuit by this invention. The circuit diagram which shows the other Example of the high frequency output circuit by this invention. The circuit diagram which shows an example of the conventional cascode type | mold amplifier circuit.

Explanation of symbols

1, 2, 3, 4 Cascode amplifier circuit 11 Normal breakdown voltage MOS transistor 12 High breakdown voltage MOS transistor 21 Normal breakdown voltage bipolar transistor 22 High breakdown voltage bipolar transistor 31 Normal breakdown voltage MOS transistor 32 High breakdown voltage bipolar transistor 41 Normal breakdown voltage bipolar transistor 42 High breakdown voltage MOS Transistor 13, 23, 33, 43 Load G Gate B Base S Source E Emitter D Drain C Collector Vin Input voltage

Claims (5)

  A high-frequency output circuit comprising a cascode amplifier circuit in which two transistors are connected in series, wherein the transistor connected to an output-side load is of a higher withstand voltage than the input-side transistor.   2. The high-frequency output circuit according to claim 1, wherein the transistor on the input side is a normal voltage MOS transistor, and the transistor on the output side is a high voltage MOS transistor.   2. The high frequency output circuit according to claim 1, wherein the transistor on the input side is a normal withstand voltage bipolar transistor, and the transistor on the output side is a high withstand voltage bipolar transistor.   2. The high frequency output circuit according to claim 1, wherein the transistor on the input side is a normal voltage MOS transistor and the transistor on the output side is a high voltage bipolar transistor.   2. The high frequency output circuit according to claim 1, wherein the transistor on the input side is a normal withstand voltage bipolar transistor, and the transistor on the output side is a high withstand voltage MOS transistor.

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