JP2008182388A - Signal switching device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a signal switching apparatus capable of realizing lower distortion characteristics for a high output signal, even if a control signal voltage outputted from a baseband IC is set to a low voltage. <P>SOLUTION: A high-frequency switch 100 comprises field effect transistors FET1-FET3 and a resistor Rc, and a voltage-translating circuit 101b comprises field effect transistors FET1b-FET3b and constant-current sources 1-3. An antenna terminal ANT and high-frequency signal terminals RF1-RF3 are disposed at the high-frequency switch 100. Voltage higher than the one of control input terminals Vc1-Vc3 is impressed to a power source voltage terminal Vdd from a regulator etc. In this case, a voltage higher than the voltage of the control input terminals Vc1-Vc3 but lower than or equal to the voltage of the power source voltage terminal Vdd is impressed to a gate terminal of field effect transistors FET1-FET3; and thereby, lower distortion characteristics can be realized for a higher output signal, as compared with the case, when the voltage of the control input terminals Vc1-Vc3 is impressed directly. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a high-frequency signal switching device configured by a semiconductor integrated circuit and used in a communication terminal device such as a mobile phone or a radio communication device. This signal switching device is used, for example, for switching a signal path with respect to an antenna of a communication terminal device.

  FIG. 16 is a block diagram showing the prior art of the signal switching device. As shown in FIG. 16, this signal switching device is configured to include a high-frequency switch 100, and has input terminals I1 to In (n is a natural number), output terminals O1 to On, and control input terminals S1 to Sn. is doing. The connection relationship between the input terminals I1 to In and the output terminals O1 to On is switched according to the state (high level or low level) of the control input signal applied to the control input terminals S1 to Sn. The high-frequency switch 100 is directly supplied with control input signals input to the control input terminals S1 to Sn, and thereby the high-frequency switch 100 controls conduction and interruption of the internal switch device.

  A field effect transistor is often used as a switch device in a high-frequency switch. In order to use the field effect transistor as a switch device, the bias voltage applied to the gate terminal of the field effect transistor is controlled. In general, a field effect transistor has a threshold voltage. For example, when a voltage higher than the threshold voltage Vth is applied as a gate-source voltage Vgs, the field effect transistor is turned on with a low impedance. By applying a voltage lower than Vth, the field effect transistor is turned off with a high impedance.

  Thus, the function of the high frequency switch can be realized by changing the gate-source voltage Vgs of the field effect transistor to turn on / off the signal path.

  When a field effect transistor is used as a switch device, the maximum input power (Pmax) that can ideally obtain a distortion-free characteristic is expressed by the following equation.

Pmax = 2 | Vgs−Vth | ² / Z
However, Vgs: gate-source voltage, Vth: threshold voltage, and Z: load impedance.

That is, in order to increase the maximum input power, it is necessary to increase the difference between the gate-source voltage Vgs and the threshold voltage Vth.
JP-A-8-70245

  Today, the miniaturization of LSIs mounted on portable terminals is progressing, and accordingly, the output voltage of digital circuits such as baseband ICs is decreasing. Under such circumstances, the lowering of the control signal voltage for controlling the high-frequency switch similarly proceeds, and the control signal voltage of 3.0V to 2.8V has been 1.8V to 1.5V in recent years. Therefore, there has been a problem that a sufficient gate-source voltage Vgs cannot be obtained in order to realize low distortion.

  Therefore, an object of the present invention is to provide a signal switching device that can realize lower distortion even when a low control signal voltage of, for example, about 1.8 V to 1.5 V is input.

  In order to solve the above-described problems, a signal switching device according to the present invention receives a high-frequency switch and a control input signal supplied from outside to control conduction / cutoff of the high-frequency switch, and converts the control input signal to a voltage. And a voltage conversion circuit that outputs a control signal for controlling conduction / cutoff of the high frequency switch to the high frequency switch. The voltage conversion circuit includes a power supply voltage terminal, a control input terminal to which a control input signal is input, a control output terminal to which a control signal is output, and when the applied voltage is low, the resistance decreases and the applied voltage increases. A non-linear circuit having a non-linear characteristic with increased resistance and connected between the power supply voltage terminal and the control output terminal, and connected between the control output terminal and the control input terminal, depending on the potential of the control input signal And a DC switch that switches between conduction and interruption. As a result, the voltage conversion circuit applies a power supply voltage to the power supply voltage terminal from the outside, converts the power supply voltage into a predetermined voltage value within the range of the absolute value of the power supply voltage, and supplies a control signal to the high frequency switch. As a result, the potential difference between the high level signal potential and the low level signal potential of the control signal becomes larger than the potential difference between the high level signal potential and the low level signal potential of the control input signal. I am trying to convert it.

  According to this configuration, the high-frequency switch is controlled by applying the output voltage of another circuit such as a high regulator voltage as a power supply voltage to the power supply voltage terminal of the voltage conversion circuit compared to a low control signal voltage such as a baseband IC. Therefore, a low control signal voltage output from a baseband IC or the like can be converted into a high voltage. As a result, the high frequency switch can be operated with low distortion as compared with the conventional example shown in FIG.

  Further, since no oscillation circuit or the like is used for the voltage conversion circuit, spurious is basically not generated, and the voltage conversion circuit can be realized with a simpler circuit configuration.

  In addition, since the signal switching device uses a nonlinear circuit having a nonlinear characteristic in which the resistance increases as the applied voltage increases rather than the linear resistance as the load of the DC switch, the DC switch is off and the power supply voltage is supplied from the power supply voltage terminal. Is applied to the gate of the field-effect transistor constituting the high-frequency switch via a non-linear circuit, a gate leak occurs in the field-effect transistor constituting the high-frequency switch, and even if the gate terminal side impedance becomes a finite value, the nonlinearity The resistance of the circuit is small compared to the linear resistance, the voltage drop in the nonlinear circuit is small compared to the voltage drop in the case of the linear resistance, and the control output voltage output from the voltage conversion circuit uses the linear resistance. It can be higher than the case. Therefore, lower distortion can be realized with the same input power.

  In the signal switching device having the above configuration, the nonlinear circuit is preferably formed of a constant current source.

  The constant current source is, for example, a field effect transistor in which a gate terminal and a source terminal are directly connected. The drain terminal of the field effect transistor is one terminal of the constant current source, and the source terminal of the field effect transistor is constant. This is the other terminal of the current source.

  In addition to the above configuration, the constant current source includes a field effect transistor and a resistor having one end connected to the gate terminal of the field effect transistor and the other end connected to the source terminal of the field effect transistor. A configuration is also conceivable in which the drain terminal of the transistor is one terminal of the constant current source and the source terminal of the field effect transistor is the other terminal of the constant current source.

  In the signal switching device having the above configuration, the non-linear circuit exhibits a constant resistance R from 0 V to an arbitrary voltage region within the range of the power supply voltage, for example, and gradually increases as the voltage increases in a voltage region higher than that. It preferably has a non-linear characteristic indicating a resistance R ′ (R <R ′).

  The nonlinear circuit having nonlinear characteristics as described above includes, for example, a field effect transistor and a resistor having one end connected to the source terminal of the field effect transistor and the other end connected to the gate terminal of the field effect transistor. The drain terminal of the effect transistor is one terminal of the nonlinear circuit, and the other end of the resistor is the other terminal of the nonlinear circuit.

  The nonlinear circuit includes a field effect transistor, a first resistor having one end connected to the source terminal of the field effect transistor, and one end connected to the gate terminal of the field effect transistor and the other end to the other end of the first resistor. May be configured such that the drain terminal of the field effect transistor becomes one terminal of the nonlinear circuit and the other end of the first resistor becomes the other terminal of the nonlinear circuit.

  The signal switching device having the above configuration preferably employs a configuration in which the high-frequency switch and the voltage conversion circuit are integrated on the same semiconductor substrate to form a single chip.

  Further, the signal switching device having the above-described configuration may be configured such that the high-frequency switch and the voltage conversion circuit are manufactured using a plurality of semiconductor substrates and mounted in one package.

  The signal switching device according to the present invention has the above-described configuration, and can realize low distortion characteristics for a high output signal even in a situation where, for example, the control voltage output from the baseband IC is lowered. .

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Embodiment 1)
FIG. 1 is a block diagram showing the configuration of the signal switching apparatus according to the first embodiment of the present invention. As shown in FIG. 1, the signal switching device includes a high frequency switch 100 and a voltage conversion circuit 101b, and includes input terminals I1 to I1 (n is a natural number), output terminals O1 to On, and control input terminals. S1 to Sn.

  The high frequency switch 100 is composed of a plurality of switch devices, and their conduction / cutoff is controlled by a control signal from the voltage conversion circuit 101b, whereby the high frequency between the input terminals I1 to I1 and the output terminals O1 to On. The signal path is switched. Note that the input terminal and the output terminal are named as such for convenience. For example, in the case of a transmission / reception circuit, signals flow in both directions, so that both are input / output terminals.

  The voltage conversion circuit 101b receives a control input signal input from the outside to the control input terminals S1 to Sn in order to control conduction / cutoff of the high frequency switch 100, converts the control input signal into a voltage, and converts the control input signal to the high frequency switch 100. 100 is output as a control signal for controlling conduction / cutoff of 100. And according to the state of the control input signal applied to the control input terminals S1 to Sn, the high frequency switch 100 switches the connection relationship between the input terminals I1 to In and the output terminals O1 to On.

  The voltage conversion circuit 101b applies a power supply voltage to the power supply voltage terminal Vdd from the outside, and converts a voltage obtained by converting the power supply voltage into a predetermined voltage value within the range of the absolute value of the power supply voltage. By setting the potential of the signal, the potential difference between the potential of the high level signal of the control signal and the potential of the low level signal is changed to the potential of the high level signal of the control input signal to the control input terminals S1 to Sn and the potential of the low level signal. It is converted into a state where the potential difference becomes larger.

  Hereinafter, a specific configuration of the signal switching device according to the first embodiment of the present invention will be described with reference to the drawings.

  FIG. 2 shows a circuit diagram of the signal switching device according to Embodiment 1 of the present invention. This is an example of an embodiment of an SP3T (Single Pole Three Throw) switch, and a signal switching device is configured using a gallium arsenide (GaAs) semiconductor substrate and a GaAs field effect transistor as a switch device.

  That is, the high frequency switch 100 includes field effect transistors FET1 to FET3 and a resistor Rc. The source terminals of the field effect transistors FET1 to FET3 are commonly connected to the antenna terminal ANT. The drain terminals of the field effect transistors FET1 to FET3 are individually connected to the high frequency signal terminals RF1, RF2, and RF3, respectively. The gate terminals of the field effect transistors FET1 to FET3 are individually connected to control output terminals Vco1, Vco2, and Vco3 of a voltage conversion circuit 101b described later.

  The resistor Rc has one end connected to the power supply voltage terminal Vdd and the other end connected in common to the source terminals of the field effect transistors FET1 to FET3. The voltage of the source terminals of the field effect transistors FET1 to FET3 is used as the power supply voltage. It fulfills the function of fixing. In the switching operation of the high-frequency switch 100, any one of the field effect transistors FET1 to FET3 is in a conductive state, and is consequently fixed to the potential of the high-frequency signal terminal connected to the conductive field effect transistor. Therefore, the resistor Rc can be omitted.

  The voltage conversion circuit 101b is composed of field effect transistors FET1b to FET3b which are DC switches and constant current sources 1 to 3 which are their loads. The constant current source 1 for flowing the current Id is connected between the power supply voltage terminal Vdd and the control output terminal Vco1. Similarly, the constant current source 2 is connected between the power supply voltage terminal Vdd and the control output terminal Vco2. Furthermore, the constant current source 3 is connected between the power supply voltage terminal Vdd and the control output terminal Vco3.

  The field effect transistor FET1b has a drain terminal connected to the control output terminal Vco1, a source terminal connected to the control input terminal Vc1, and a gate terminal grounded. The field effect transistor FET2b has a drain terminal connected to the control output terminal Vco2, a source terminal connected to the control input terminal Vc2, and a gate terminal grounded. The field effect transistor FET3b has a drain terminal connected to the control output terminal Vco3, a source terminal connected to the control input terminal Vc3, and a gate terminal grounded.

  All the field effect transistors FET1 to FET3 and FET1b to FET3b are depletion type field effect transistors, which are field effect transistors having a threshold voltage Vth of 0 V or less and are sometimes referred to as normally on type. The power supply voltage applied to the power supply voltage terminal Vdd (referred to as Vdd for convenience) is selected in a relationship of | Vth | <| Vdd |.

  As described above, the field effect transistors FET1 to FET3 are field effect transistors that pass and block high-frequency signals, and the resistor Rc is used to fix the source potential of the field effect transistors FET1 to FET3 to the power supply voltage (Vdd). It is a resistor arranged in The field effect transistors FET1b to FET3b play a role of voltage conversion, that is, switching between a high level and a low level of a control signal as a DC switch. The constant current sources 1 to 3 are respectively connected between the power supply voltage terminal Vdd and the field effect transistors FET1b to FET3b which are DC switches.

  The operation of the voltage conversion circuit 101b will be briefly described. Now, consider the blocks of the field effect transistors FET1 and FET1b.

  First, consider a case where a voltage of 0 V is applied to the control input terminal Vc1. Since the gate terminal of the field effect transistor FET1b is connected to the ground GND and the field effect transistor FET1b is a depletion type, the ON state of the resistance is low, and as a result, the voltage of 0V at the control input terminal Vc1 is applied to the field effect transistor FET1. It is also applied to the gate terminal. Since the field effect transistor FET1 is also a depletion type and the source potential is fixed to the power supply voltage (Vdd) by the resistor Rc, the field effect transistor FET1 is turned off from the relationship of Vth <Vdd when the source potential is used as a reference. The high frequency signal is blocked between the antenna terminal ANT and the high frequency signal terminal RF1.

  Next, consider a case where a voltage higher than the threshold voltage Vth is applied to the control input terminal Vc1. At this time, when the source potential is used as a reference, the gate potential of the field effect transistor FET1b is equal to or lower than the threshold voltage Vth, so that the resistance is turned off. As a result, the power supply voltage (Vdd) is applied to the field effect transistor FET1. The field effect transistor FET1 is also a depletion type, and since the source potential is fixed to the power supply voltage (Vdd) by the resistor Rc, the field effect transistor FET1 is turned on and a high frequency is generated between the antenna terminal ANT and the high frequency signal terminal RF1. Let the signal pass.

  The same operation is performed for the paths of the other field effect transistors FET2, FET2b, and FET3, FET3b.

  FIG. 3 shows a circuit diagram of a first comparative example of the signal switching device compared with the signal switching device according to the first embodiment of the present invention. This signal switching device uses a resistor Rd having the same resistance value instead of the constant current sources 1, 2, and 3 in the voltage conversion circuit 101b, and other configurations are the same as those in FIG.

  Differences in operation between the voltage conversion circuit 101b in the first embodiment and the voltage conversion circuit 101a in the signal switching device of the comparative example are considered for the blocks of the field effect transistors FET1, FET1b, and the resistor Rd, and the operation points are illustrated in FIG. This will be described with reference to FIG. The common conditions in both signal switching devices are as follows. The gate terminal side impedance of the field effect transistor FET1 is RL, and the gate terminal voltage of the field effect transistor FET1 is Vg1.

  The gate terminal of the field effect transistor is usually high impedance, and the gate terminal side impedance RL is ideally ∞. However, when the voltage applied to the field effect transistor FET1 actually exceeds the source withstand voltage / drain withstand voltage, such as when a large signal is input, a leak current flows and the gate terminal side impedance RL has a finite value. To drop.

  First, with respect to the voltage conversion circuit 101b of the first embodiment, the operating point when a low level (for example, 0V) is applied to the control input terminal Vc1 and when a high level (for example, the threshold voltage Vth or higher, for example, the power supply voltage (Vdd)) is applied. This will be described with reference to FIG.

  First, consider the case where the gate terminal side impedance RL is ∞. A Vds-Ids characteristic curve of the field effect transistor FET1b when a low level signal is applied to the control input terminal Vc1 is denoted by reference numeral 111 in FIG. Further, a Vds-Ids characteristic curve of the field effect transistor FET1b when a high level signal is applied to the control input terminal Vc1 is denoted by reference numeral 112 in FIG. Further, a characteristic curve of the constant current source 1 is denoted by reference numeral 121 in FIG.

  The operating point when a high level signal is applied to the control input terminal Vc1 (when FET1 is on) is obtained at the intersection of the curve indicated by reference numeral 112 and the curve indicated by reference numeral 121, and is indicated by reference numeral 202.

  The operating point when a low level signal is applied to the control input terminal Vc1 (when FET1 is OFF) is obtained at the intersection of the curve indicated by reference numeral 111 and the curve indicated by reference numeral 121, and is indicated by reference numeral 201.

  Next, consider the case where the gate terminal side impedance RL is a finite value. Since the impedance of the gate terminal side impedance RL decreases, this load line is set to 131. In FIG. 4, the operating point at the time of OFF (when a low level signal is applied to the control input terminal Vc1) does not change, but the operating point at the time of ON (when a high level signal is applied to the control input terminal Vc1) is the load denoted by reference numeral 131. It moves to the intersection 203 of the line and the curve indicated by reference numeral 121.

  Next, regarding the voltage conversion circuit 101a of the first comparative example, the operating points when a low level (for example, 0 V) is applied to the control input terminal Vc1 and when a high level (for example, a power supply voltage (Vdd) or higher) is applied to the control input terminal Vc1 5 will be described.

  First, consider the case where the gate terminal side impedance RL is ∞. Now, the Vds-Ids characteristic curve 111 of the field effect transistor FET1b when a low level signal is applied to the control input terminal Vc1, and the Vds-Ids characteristic of the field effect transistor FET1b when a high level signal is applied to the control input terminal Vc1. The curve 112 is the same as described above.

  In the case of the first comparative example, the constant current source in FIG. 2 is replaced with the resistor Rd as shown in FIG. Therefore, the operating point when FET 1 is on (when a high level signal is applied to the control input terminal Vc 1) is obtained at the intersection of the curve indicated by reference numeral 112 and the load line indicated by reference numeral 122, and is represented by reference numeral 212.

  The operating point when FET 1 is off (when a low level signal is applied to the control input terminal Vc 1) is obtained at the intersection of the curve indicated by reference numeral 111 and the load line indicated by reference numeral 122, and is indicated by reference numeral 211.

  Next, consider the case where the gate terminal side impedance RL is a finite value. The load line of the gate terminal side impedance RL is the same as that of FIG. In FIG. 5, there is no change in the operating point when FET1 is off (when a low level signal is applied to the control input terminal Vc1), but the operating point when FET1 is on (when a high level signal is applied to the control input terminal Vc1) is The load line indicated by reference numeral 131 and the load line indicated by reference numeral 122 move to the intersection 213.

  4 is compared with the operating point 213 of the first comparative example in FIG. 5, the voltage value of the operating point 203 is higher than the voltage value of the operating point 213. I understand.

  That is, when the gate terminal side impedance RL is a finite value, the voltage conversion circuit 101b of the first embodiment keeps the output voltage of the voltage conversion circuit higher than that of the voltage conversion circuit 101a of the first comparative example. be able to. As described above, in order to increase the maximum input power, it is necessary to increase the difference between the voltage (Vgs) between the gate terminal and the source terminal and the threshold voltage (Vth), and the higher the output voltage of the voltage conversion circuit, If this condition is satisfied and the input power is the same, it means that lower distortion can be realized.

  As described above, according to this embodiment, the output voltage of another circuit such as a high regulator voltage is applied to the power supply voltage terminal of the voltage conversion circuit as a power supply voltage compared to a low control signal voltage such as a baseband IC. Thus, a low control signal voltage output from a baseband IC or the like for controlling the high frequency switch can be converted to a high voltage. As a result, the high frequency switch can be operated with low distortion as compared with the conventional example shown in FIG.

  Further, since no oscillation circuit or the like is used for the voltage conversion circuit, spurious is basically not generated, and the voltage conversion circuit can be realized with a simpler circuit configuration.

  In addition, since the signal switching device uses the constant current source 1 which is a non-linear circuit having a non-linear characteristic in which the resistance increases as the applied voltage increases instead of the linear resistance, the field effect transistor FET1b which is a DC switch is turned off. When the power supply voltage is applied from the power supply voltage terminal Vdd to the gate of the field effect transistor FET1 constituting the high frequency switch via the constant current source 1, a gate leak occurs in the field effect transistor FET1 constituting the high frequency switch, and the gate Even when the terminal-side impedance RL becomes a finite value, the resistance of the nonlinear circuit is smaller than the linear resistance, and the voltage drop in the nonlinear circuit is smaller than that of the linear resistance, and the voltage conversion circuit 101b. The control output voltage output from is higher than when a linear resistor is used. It is possible. Therefore, lower distortion can be realized with the same input power.

  6A and 6B show an example of a constant current source in the signal switching device according to Embodiment 1 of the present invention. FIG. 6A shows a configuration in which the gate terminal and the source terminal of the field effect transistor FET1c are directly connected. The drain terminal of the field effect transistor FET1c is one terminal of the constant current source, and the source terminal of the field effect transistor FET1c is the other terminal of the constant current source.

  FIG. 6B shows a configuration in which one end of the resistor Rg1 is connected to the gate terminal of the field effect transistor FET1c, the other end of the resistor Rg1 is connected to the source terminal, and the resistor Rg1 is arranged between the gate terminal and the source terminal. Show.

  The drain terminal of the field effect transistor FET1c is one terminal of the constant current source, and the source terminal of the field effect transistor FET1c is the other terminal of the constant current source. In general, a field effect transistor can realize a constant current characteristic by setting a gate terminal and a source terminal to the same potential.

  FIG. 7 shows a simulation result of Vds-Id characteristics of the constant current source of FIG. The simulation was performed under the condition that the threshold voltage Vth of the field effect transistor FET1c was about −1.2 V, the gate width Wg was 200 μm, and the resistance Rg1 was 50 kΩ.

  The range where the drain-source voltage Vds is from 0 V to about 1 V is a non-saturated region of the field effect transistor, and the drain-source voltage Vds and the drain current Id increase linearly, but the drain-source voltage Vds. When the voltage is 1 V or higher, a constant current characteristic of 65 mA to 68 mA is realized.

  Incidentally, since almost no current flows to the gate terminal of the field effect transistor, there is substantially no difference in circuit operation between the constant current source of FIG. 6A and the constant current source of FIG. The simulation results are also the same.

  FIG. 8 shows a specific circuit example of the signal switching apparatus according to Embodiment 1 of the present invention. This signal switching device is an example of an SP3T (Single Pole Three Throw) switch, and voltage conversion using the constant current sources of the field effect transistors shown in FIG. 6A as the constant current sources 1 to 3 in FIG. Circuit 101c is shown.

  From the Vds-Ids characteristic simulation result of FIG. 7, the same effect can be obtained even when the constant current source of the field effect transistor shown in FIG. 6B is used as the constant current source of the first embodiment. Needless to say.

  The constant current source is not limited to the above configuration, and any constant current source may be used as long as the above constant current characteristics can be obtained, such as a constant current source using a bipolar transistor.

(Embodiment 2)
FIGS. 9A and 9B show nonlinear circuits in the signal switching device according to Embodiment 2 of the present invention. This nonlinear circuit is used in place of the constant current source in the first embodiment, and has a nonlinear characteristic that the resistance increases as the applied voltage increases. Specifically, a constant resistance R is shown from 0 V to an arbitrary voltage range within the range of the power supply voltage, and a resistance R ′ (R <R ′) that gradually increases as the voltage increases in a voltage range higher than that. It exhibits nonlinear characteristics.

  FIGS. 9A and 9B show examples of nonlinear circuits. FIG. 9A shows a configuration in which one end of the resistor Rd1 is connected to the source terminal of the field effect transistor FET1c and the other end of the resistor Rd1 is connected to the gate terminal. In this nonlinear circuit, the drain terminal of the field effect transistor FET1c is one terminal of the nonlinear circuit, and the other end of the resistor Rd1 is the other terminal of the nonlinear circuit.

  FIG. 9B shows a configuration in which one end of the resistor Rd1 is connected to the source terminal of the field effect transistor FET1c, one end of another resistor Rg1 is connected to the gate terminal, and the other ends of Rd1 and Rg1 are connected to each other. Show. In this nonlinear circuit, the drain terminal of the field effect transistor FET1c is one terminal of the nonlinear circuit, and the other end of the resistor Rd1 is the other terminal of the nonlinear circuit.

  FIG. 10 shows a simulation result of Vds-Id characteristics of the nonlinear circuit of FIG. The simulation was performed under the condition that the threshold voltage Vth of the field effect transistor FET1c was about −1.2 V, the gate width Wg was 200 μm, the resistance Rd1 was 400 kΩ, and the resistance Rg1 was 50 kΩ.

  The range where the drain-source voltage Vds is from 0 V to about 1.5 V is a non-saturated region of the field effect transistor, and the drain-source voltage Vds and the drain current Id increase linearly, and the resistance value is about A constant current characteristic of 3.4 μA to 3.6 μA is realized at a voltage of 400 kΩ or higher, and the resistance value is about 30 MΩ, and the resistance is higher at 1.5 V or higher. .

The basis for calculating the resistance value of about 30 MΩ is as follows. The resistance value is calculated from the slope of the straight line in the region where the voltage Vds of FIG. Since it is 3.566 μA when Vds = 5.0 V and 3.464 μA when Vds = 2.0 V,
R = (5V-2V) / (3.566 μA-3.464 μA)
= 29.4 MΩ
≒ 30MΩ
It becomes.

  Incidentally, since almost no current flows to the gate terminal of the field effect transistor, there is substantially no difference in circuit operation between FIG. 9A and FIG. 9B, and the simulation results are the same.

  The resistor Rd1 is arranged to suppress the constant current value to a small value. Compared with the constant current value of the constant current source of the first embodiment in which the resistor Rd1 is not arranged is 65 mA to 68 mA, the current value is greatly increased. It can be seen that there is a merit that is suppressed.

  As shown in FIG. 10, the non-linear circuit has a Vds-Id characteristic in which, when the voltage Vds is increased, the transition from the constant resistance region to the constant current region does not need to be performed rapidly, and the voltage Vds is increased. It is also possible to have a characteristic such that when it is made to move gradually from the constant resistance region to the constant current region.

  FIG. 11 shows a signal switching apparatus according to Embodiment 2 of the present invention. This is an example of an SP3T (Single Pole Three Throw) switch, in which the constant current source of the first embodiment is replaced with a non-linear circuit shown in FIG. 9B. It will be described below that the same effects as those of the first embodiment can be obtained by this circuit configuration.

  FIG. 12 shows a circuit diagram of a second comparative example of the signal switching device compared with the signal switching device according to the second embodiment of the present invention. This signal switching device uses a voltage conversion circuit 101e in which a nonlinear circuit is replaced with a resistor Rd. The voltage conversion circuit 101d of FIG. 11 and the voltage conversion circuit 101e of FIG. 12 were simulated by considering the difference in operation of the blocks of the field effect transistors FET1 and FET1b.

  In the second embodiment of FIG. 11 and the second comparative example of FIG. 12, a resistor Rg is arranged at the gate terminals of the field effect transistors FET1 to FET3 and the field effect transistors FET1b to FET3b. The resistor Rg is arranged to reduce the leakage current from the source terminal or drain terminal of the field effect transistor to the gate terminal during large signal operation.

  The threshold voltages Vth of the field effect transistors are all about −1.2 V, the gate width Wg of the field effect transistors FET1b to FET3b is 400 μm, the gate width Wg of the field effect transistors FET1c to FET3c is 200 μm, the resistance Rd1 is 400 kΩ, and the resistance Rd is 800 kΩ. The resistance Rg1 and the resistance Rg were simulated under the condition of 50 kΩ.

  Assuming a leak current to the field effect transistor at the time of a large signal, the field effect transistor FET1 has a gate terminal side impedance RL and the field effect transistor FET1 has a gate terminal voltage Vg1 as in the case of the first embodiment. The effect was confirmed by simulating the gate terminal voltage Vg1 of the field effect transistor FET1 when the impedance RL and power supply voltage (Vdd) of the gate terminal of the transistor FET1 were varied.

  FIG. 13 shows a first simulation result when the impedance RL is changed in the voltage conversion circuit 101d according to the second embodiment of the present invention and the voltage conversion circuit 101e according to the second comparative example. Common simulation conditions were power supply voltage: Vdd = 2.8V, Vc1 = 1.8V, and the impedance RL was changed to examine the variation of the gate terminal voltage Vg1. From FIG. 13, in the range of RL> 0.4 MΩ, the voltage conversion circuit 101d has a higher value as the gate terminal Vg1 of the field effect transistor FET1 than the voltage conversion circuit 101e for the same impedance RL. Has been obtained. This means that the voltage conversion circuit 101d has a higher voltage applied between the gate terminal and the source terminal of the field effect transistor, and can realize low distortion for a larger input power.

  14 and 15 show the second simulation result when the power supply voltage (Vdd) is changed in the voltage conversion circuit 101d according to the second embodiment of the present invention and the voltage conversion circuit 101e according to the second comparative example. Is shown. The common simulation condition is Vc1 = 1.8V in FIG. 14, Vc1 = 0V in FIG. 15, the inflow current to the control terminal Vc1 is Ic1, and the fluctuations in Vg1 and Ic1 when the power supply voltage Vdd is changed are examined. It was.

  14A, the voltage conversion circuit 101d has a higher value of the gate terminal Vg1 of the field effect transistor FET1 than the voltage conversion circuit 101a with respect to the same power supply voltage Vdd. On the other hand, it means that low distortion can be realized.

  14B, the voltage conversion circuit 101d has a flatter inflow current Ic1 to the control input terminal Vc1 with respect to fluctuations in the power supply voltage Vdd, and the voltage conversion circuit 101d has a power supply. It can be seen that even if the voltage Vdd is changed, there is a merit that the fluctuation of the inflow current Ic to the control input terminal is small.

  The inflow current Ic1 preferably has a small absolute value, and when determining this specification, it is necessary to determine it from the worst value including the power supply voltage fluctuation. For example, when the power supply voltage maximum value is 4.2 V, the absolute value of the inflow current Ic1 is about 5.2 μA in the conventional voltage conversion circuit 101a, as shown in FIG. 15, whereas the voltage conversion circuit 101d of the present invention. In FIG. 5, the absolute value of the inflow current Ic1 is about 3.5 μA, and it can be seen that the inflow current Ic1 can be reduced in the present invention.

  From the Vds-Ids characteristic simulation result of FIG. 10, the same effect can be obtained even if the constant current source of the first embodiment is replaced with the constant current source of the field effect transistor shown in FIG. Needless to say.

  According to the signal switching device of this embodiment, the gate terminal control voltage can be increased as compared with the case where the control input terminal voltage is directly applied to the gate terminals of the field effect transistors FET1 to FET3 for the high frequency switch. As a result, the potential difference between the gate of the field effect transistor that allows the signal to pass through and the gate of the field effect transistor that blocks the signal can be increased. Therefore, a signal switching device with higher output and lower distortion can be realized. Further, by using a DC regulator voltage of a set (for example, a mobile phone), it is not necessary to configure a booster circuit, and a small signal switching device with a simple circuit configuration can be realized. The other effects are the same as those of the mobile phone 1 of the embodiment.

  In the signal switching device of this embodiment, the high frequency switch 100 and the voltage conversion circuit 101d are formed on the same semiconductor substrate to form a single chip, but the high frequency switch 100 and the voltage conversion circuit 101d are formed on a plurality of semiconductor substrates. It may be configured to be formed and mounted in one package.

  It goes without saying that a similar circuit can be realized when an enhancement type field effect transistor is used as the high frequency switch, or when a MOS field effect transistor or bipolar transistor is used as the DC switch of the voltage conversion circuit.

  Further, as a high frequency switch, a Si semiconductor MOSFET may be used instead of the GaAs field effect transistor.

  The signal switching device according to the present invention can increase the gate terminal control voltage of the high-frequency switch FET as compared with the case where the control input signal voltage is applied as it is to the gate terminal of the high-frequency switch FET, thereby allowing the high-frequency signal to pass through the signal. Since the potential difference between the gate of the switch FET and the gate of the high-frequency switch FET that cuts off the signal can be increased, distortion at the time of high output can be reduced, and since the booster circuit is not used, the circuit configuration is simple and the device And is useful as a signal switching device used in a communication terminal device such as a mobile phone or a wireless device. It is possible to provide a low-distortion signal switching device that can reduce the output voltage of a digital circuit such as a baseband IC.

It is a block diagram which shows the structure of the signal switching apparatus of Embodiment 1 of this invention. It is a circuit diagram which shows the specific structure of the signal switching apparatus of Embodiment 1 of this invention. It is a circuit diagram which shows the specific structure of the signal switching apparatus used as the 1st comparative example. FIG. 3 is a diagram illustrating an operating point of the voltage conversion circuit 101b according to the first embodiment. It is a figure which shows the operating point of the voltage conversion circuit 101a of a 1st comparative example. (A), (b) is a figure which shows the example of the constant current source in the signal switching apparatus of Embodiment 1 of this invention, respectively. It is a figure which shows the Vds-Id characteristic simulation result of the constant current source in the signal switching apparatus of Embodiment 1. It is a circuit diagram which shows the specific structure of the signal switching apparatus of Embodiment 1 of this invention. (A), (b) is a figure which shows the example of the nonlinear circuit in the signal switching apparatus of Embodiment 2 of this invention, respectively. It is a figure which shows the Vds-Id characteristic simulation result of the nonlinear circuit in the signal switching apparatus of Embodiment 2 of this invention. It is a circuit diagram which shows the specific structure of the signal switching apparatus of Embodiment 2 of this invention. It is a circuit diagram which shows the specific structure of the signal switching apparatus used as the 2nd comparative example. It is a figure which shows the 1st simulation result of the voltage converter circuit of Embodiment 2 of this invention. It is a figure which shows the 2nd simulation result of the voltage converter circuit of Embodiment 2 of this invention. It is a figure which shows the 3rd simulation result of the voltage converter circuit of Embodiment 2 of this invention. It is a block diagram which shows the structure of the conventional signal switching apparatus.

Explanation of symbols

100 High-frequency switches 101a, 101b, 101c, 101d Voltage conversion circuits FET1 to FET3 Field effect transistors FET1b to FET3b Field effect transistors FET1c to FET3c Field effect transistors Vc1 to Vc3 Control input terminal Vdd Power supply voltage terminal ANT Output terminals RF1 to RF3 Input terminal Rc , Rd, Rg1, Rd1, Rg resistance

Claims (9)

A high frequency switch,
A control input signal given to control conduction / cut-off of the high-frequency switch from outside is input, and the control input signal is converted into a voltage and output to the high-frequency switch as a control signal for controlling conduction / cut-off of the high-frequency switch. And a voltage conversion circuit that
The voltage conversion circuit includes a power supply voltage terminal, a control input terminal to which the control input signal is input, a control output terminal to which the control signal is output, and when the applied voltage is low, the resistance is small and the applied voltage is high. A non-linear circuit connected between the power supply voltage terminal and the control output terminal with a non-linear characteristic in which the resistance increases, and the control input connected between the control output terminal and the control input terminal And a DC switch that switches between conduction and interruption according to the signal potential,
The voltage conversion circuit applies a power supply voltage to the power supply voltage terminal from the outside, and converts a voltage obtained by converting the power supply voltage into a predetermined voltage value within a range of an absolute value of the power supply voltage to the high frequency switch. By supplying as the control signal, the potential difference between the high-level signal potential and the low-level signal potential of the control signal is compared with the potential difference between the high-level signal potential and the low-level signal potential of the control input signal. And a signal switching device that converts it to a larger state.   The signal switching device according to claim 1, wherein the nonlinear circuit includes a constant current source.   The constant current source includes a field effect transistor in which a gate terminal and a source terminal are directly connected, a drain terminal of the field effect transistor is one terminal of the constant current source, and a source terminal of the field effect transistor is the constant current source. The signal switching device according to claim 2, which becomes the other terminal of the current source.   The constant current source includes a field effect transistor and a resistor having one end connected to the gate terminal of the field effect transistor and the other end connected to the source terminal of the field effect transistor, and the drain terminal of the field effect transistor 3. The signal switching device according to claim 2, wherein the signal switching device is one terminal of the constant current source, and a source terminal of the field effect transistor is the other terminal of the constant current source.   The nonlinear circuit exhibits a constant resistance R from 0 V to an arbitrary voltage range within the range of the power supply voltage, and a resistance R ′ (R <R ′) that gradually increases as the voltage increases in a voltage range beyond that. The signal switching device according to claim 1, having the characteristics shown.   The nonlinear circuit includes a field effect transistor and a resistor having one end connected to the source terminal of the field effect transistor and the other end connected to the gate terminal of the field effect transistor, and the drain terminal of the field effect transistor The signal switching device according to claim 1, wherein the signal switching device is one terminal of the nonlinear circuit, and the other end of the resistor is the other terminal of the nonlinear circuit.   The nonlinear circuit includes a field effect transistor, a first resistor having one end connected to the source terminal of the field effect transistor, and one end connected to the gate terminal of the field effect transistor and the other end of the first resistor. A second resistor connected to the other end, the drain terminal of the field effect transistor serving as one terminal of the nonlinear circuit, and the other end of the first resistor serving as the other terminal of the nonlinear circuit. Item 1. The signal switching device according to Item 1.   2. The signal switching device according to claim 1, wherein the high-frequency switch and the voltage conversion circuit are integrated on the same semiconductor substrate to form a single chip.   The signal switching device according to claim 1, wherein the high-frequency switch and the voltage conversion circuit are manufactured using a plurality of semiconductor substrates and mounted in one package.

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