Drive circuit and attenuation device

Abstract

To easily output a plurality of drive signals having different voltage values.SOLUTION: A drive circuit comprises: a first amplifier circuit which amplifiers a first analog signal; a first clip circuit which outputs a signal clipped at a predetermined first voltage as a first drive signal when the output signal of the first amplifier circuit is included in a first voltage range; a second amplifier circuit which amplifies a first analog signal; and a second clip circuit which outputs a signal clipped at a predetermined second voltage as a second drive signal when the output signal of the second amplifier circuit is included within a second voltage range. The first clip circuit electrically connects a first reference voltage source which outputs the first voltage to the output of the first amplifier circuit when the voltage value of the output signal of the first amplifier circuit is smaller than the first voltage.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a drive circuit that outputs a plurality of drive signals and an attenuation device using the drive circuit.

Background Art

[0002] There is known a bias circuit that supplies a bias signal determined according to a control voltage applied from the outside to a high-frequency attenuator circuit and is configured to linearly change the attenuation amount of the high-frequency attenuator circuit in response to a linear change in the control voltage (see, for example, Patent Documents 1 and 2).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] Such an attenuator circuit includes a circuit that controls the attenuation amount with one input voltage and a circuit that controls the attenuation amount using two input voltages. And, among the attenuator circuits using two input voltages, there is a circuit having a characteristic of adjusting the attenuation amount by increasing one input voltage to a predetermined voltage value and then increasing the other input voltage. In this case, it is conceivable to prepare two systems of drive circuits that supply voltage to the attenuator circuit, but there has been a problem that it is costly and time-consuming.

[0005] Therefore, the present invention has been made in view of these points, and an object thereof is to be able to easily output a plurality of drive signals having different voltage values.

Means for Solving the Problems

[0006] In a first aspect of the present invention, there is provided a drive circuit that outputs a plurality of drive signals based on an input first analog signal, including a first amplification circuit that amplifies the first analog signal, and when the output signal of the first amplification circuit is included in a first voltage range, outputs a signal clipped to a predetermined first voltage as a first drive signal, and when the output signal of the first amplification circuit is not included in the first voltage range, outputs the output signal of the first amplification circuit as the first drive signal; a first clip circuit; a second amplification circuit that amplifies the first analog signal, and when the output signal of the second amplification circuit is included in a second voltage range, outputs a signal clipped to a predetermined second voltage as a second drive signal, and when the output signal of the second amplification circuit is not included in the second voltage range, outputs the output signal of the second amplification circuit as the second drive signal; a second clip circuit. The first clip circuit includes a first comparison circuit that compares the output signal of the first amplification circuit with the first voltage, and when the comparison result of the first comparison circuit indicates that the voltage value of the output signal of the first amplification circuit is smaller than the first voltage, a first reference voltage source that outputs the first voltage and a first switch circuit that electrically connects the output of the first amplification circuit. A drive circuit is provided.

[0007] The second clip circuit includes a second comparison circuit that compares the output signal of the second amplification circuit with the second voltage, and a second switch circuit that switches whether to electrically connect the second voltage and the output of the second amplification circuit according to the comparison result of the second comparison circuit. When the comparison result of the second comparison circuit indicates that the voltage value of the output signal of the second amplification circuit is greater than or equal to the second voltage, the second switch circuit electrically connects the second reference voltage source that outputs the second voltage and the output of the second amplification circuit. When the comparison result of the second comparison circuit indicates that the voltage value of the output signal of the second amplification circuit is smaller than the second voltage, the second switch circuit may electrically disconnect the second reference voltage source that outputs the second voltage and the output of the second amplification circuit.

[0008] When the first voltage is output in response to the predetermined first analog signal input by the first amplifier circuit, the second amplifier circuit may output the second voltage in response to the input predetermined first analog signal.

[0009] The first amplifier circuit and the second amplifier circuit may each be a differential amplifier circuit to which the first analog signal is input.

[0010] The voltage value of the reference voltage input to the differential amplifier circuit that is the first amplifier circuit and / or the resistance value of the voltage-dividing resistor connected to the reference voltage may be different from the voltage value of the reference voltage input to the differential amplifier circuit that is the second amplifier circuit and / or the resistance value of the voltage-dividing resistor connected to the reference voltage.

[0011] In a second aspect of the present invention, an attenuator circuit having a first attenuator that reduces the signal strength of an input electrical signal in response to a first input signal, and a second attenuator that reduces the signal strength of the electrical signal output by the first attenuator in response to a second input signal, and a drive circuit according to the first aspect that supplies the first drive signal as the first input signal to the first attenuator and supplies the second drive signal as the second input signal to the second attenuator are provided.

Advantages of the Invention

[0012] According to the present invention, there is an effect that a plurality of drive signals having different voltage values can be easily output.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Mode for Carrying Out the Invention

[0014] <Configuration Example of Attenuation Device 10> FIG. 1 shows a configuration example of an attenuation device 10 according to this embodiment. The attenuation device 10 includes an attenuator circuit 20 and a drive circuit 30. The attenuation device 10 adjusts the attenuation amount of the attenuator circuit 20 according to a control voltage supplied from the outside.

[0015] The attenuator circuit 20 outputs, as an output signal, a signal obtained by attenuating an input input signal by an attenuation amount corresponding to a control voltage. The input signal is, for example, a high-frequency signal in a band from about several tens of MHz to about several tens of GHz. The attenuator circuit 20 includes a first attenuator 21 and a second attenuator 22.

[0016] The first attenuator 21 reduces the signal intensity of an input electrical signal according to a first input signal. The first input signal is a signal within a predetermined voltage range. For example, the first input signal is a signal in a voltage range from 0 [V] to V1 [V]. The first attenuator 21 reduces the signal intensity of the input electrical signal within an attenuation range from 0 [dB] to R1 [dB] according to the first input signal.

[0017] The second attenuator 22 reduces the signal intensity of the electrical signal output by the first attenuator 21 according to a second input signal. The second input signal is a signal within a predetermined voltage range. For example, the second input signal is a signal in a voltage range from V1 [V] to V2 [V]. The second attenuator 22 reduces the signal intensity of the input electrical signal within an attenuation range from 0 [dB] to R2 [dB] according to the second input signal.

[0018] Note that R1 and R2 may have the same value, or alternatively, may have different values. Also, V1 [V] and V2 [V] may be positive voltages, or alternatively, may be negative voltages. In this embodiment, an example where V1 [V] and V2 [V] are negative voltages will be described. The above-described attenuator circuit 20 reduces the signal strength of an electrical signal input within an attenuation range from 0 [dB] to R1+R2 [dB] according to the first input signal and the second input signal.

[0019] For example, when the first input signal is a signal of a constant voltage of V1 [V] and the second input signal is a signal of a constant voltage of 0 [V], the attenuation amount of the attenuator circuit 20 is R1 [dB]. Also, when the first input signal is a signal of a constant voltage of V1 [V] and the second input signal is a signal of a constant voltage of V2 [V], the attenuation amount of the attenuator circuit 20 is R1+R2 [dB].

[0020] As an example, by setting the second input signal to 0 [V], linearly changing the first input signal from 0 [V] to V1 [V], and then linearly changing the second input signal from 0 [V] to V2 [V] with the same slope after the first input signal reaches V1 [V], the attenuation amount of the attenuator circuit 20 can be linearly changed from 0 [dB] to R1+R2 [dB].

[0021] The drive circuit 30 supplies a plurality of drive signals to such an attenuator circuit 20 based on a control signal input from the outside. Here, the control signal is a first analog signal. The first analog signal is, for example, a signal that changes linearly. The first analog signal is, for example, the output voltage of an AD converter that converts an input digital signal into an analog signal. Thereby, based on the input digital signal, the drive circuit 30 can output a plurality of drive signals.

[0022] The drive circuit 30 generates a plurality of drive signals so that the attenuation amount of the attenuator circuit 20 changes linearly in response to the linear change in the voltage value of the first analog signal, and supplies the drive signals to the attenuator circuit 20. Before explaining the details of such a drive circuit 30, first, a conventional drive circuit 40 will be explained.

[0023] <Configuration example of the conventional drive circuit 40> FIG. 2 shows a configuration example of a conventional drive circuit 40. FIG. 3 shows an example of the result of simulating the output voltage characteristics of the conventional drive circuit 40 shown in FIG. 2. Note that the horizontal axis in FIG. 3 indicates the voltage value of the first analog signal input to the conventional drive circuit 40, and the vertical axis indicates the voltage value of the signal output by the conventional drive circuit 40. Note that the voltage value of the first analog signal is in the range of 0.8 [V] to 2.6 [V] as an example.

[0024] The conventional drive circuit 40 includes a first differential amplifier circuit 41, a second differential amplifier circuit 42, a first diode circuit 43, a second diode circuit 44, a first output resistor 56 with a resistance value of R9, and a second output resistor 66 with a resistance value of R 10 Note that the signal output by the first differential amplifier circuit 41 and the signal output by the second differential amplifier circuit 42 are used as the drive signals output by the conventional drive circuit 40.

[0025] The first differential amplifier circuit 41 differentially amplifies the first analog signal input to the conventional drive circuit 40. The first differential amplifier circuit 41 includes, for example, a first resistor 51 with a resistance value of R1, a second resistor 52 with a resistance value of R2, a third resistor 53 with a resistance value of R3, a fourth resistor 54 with a resistance value of R4, and a first operational amplifier 55. When the first analog signal input to the minus-side input of the first operational amplifier 55 is V IN- and the reference voltage input to the plus-side input is V IN+ , the output voltage V OUT of the first differential amplifier circuit 41 is calculated as follows.

Equation

[0026] In FIG. 3, an example of the output voltage of the first differential amplifier circuit 41 is shown as VC1. The voltage value V of the first analog signal IN- is in the range of about 0.8 [V] to 1.7 [V]. As shown by equation (1), it can be seen that the output voltage of the first differential amplifier circuit 41 attenuates linearly. In the simulation, R1 = 2.2 kΩ, R2 = 1 kΩ, R3 = 5.1 kΩ, R4 = 1 kΩ, R9 = 1 kΩ, V IN+ = 3.3 [V] was set.

[0027] The first diode circuit 43 includes a plurality of diodes (D1 to D4 in FIG. 2) connected in the reverse direction to the first differential amplifier circuit 41. When a voltage equal to or lower than a predetermined reverse bias is applied to the first diode circuit 43, current flows through the plurality of diodes, so that the output voltage of the first differential amplifier circuit 41 is clipped. In other words, the first diode circuit 43 is a circuit for clipping the signal amplified by the first differential amplifier circuit 41 to a predetermined first clip voltage. In FIG. 3, when the voltage value V of the first analog signal IN- is about 1.7 [V] or more, it can be seen that the output voltage of the first differential amplifier circuit 41 is gradually clipped to a first clip voltage of about -2.4 [V].

[0028] The second differential amplifier circuit 42 differentially amplifies the input first analog signal in the same manner as the first differential amplifier circuit 41. The second differential amplifier circuit 42 includes, for example, a fifth resistor 61 having a resistance value of R5, a sixth resistor 62 having a resistance value of R6, a seventh resistor 63 having a resistance value of R7, an eighth resistor 64 having a resistance value of R8, and a second operational amplifier 65.

[0029] The resistance values of the voltage dividing resistors connected to the reference voltage input to the second differential amplifier circuit 42 are different from the resistance values of the voltage dividing resistors connected to the reference voltage input to the first differential amplifier circuit 41. For example, the resistance values of the seventh resistor 63 and / or the eighth resistor 64 connected to the positive side input of the second operational amplifier 65 of the second differential amplifier circuit 42 are different from the resistance values of the third resistor 53 and / or the fourth resistor 54 connected to the positive side input of the first operational amplifier 55 of the first differential amplifier circuit 41.

[0030] Instead, the voltage value of the reference voltage V of the second differential amplification circuit 42 IN+ may be different from the voltage value of the reference voltage V of the first differential amplification circuit 41 IN+ . Thus, the voltage value of the first analog signal at which the second differential amplification circuit 42 performs the clip operation can be made different from the voltage value of the first analog signal at which the first differential amplification circuit 41 performs the clip operation.

[0031] In FIG. 3, an example of the output voltage of the second differential amplification circuit 42 is shown as VC2. It can be seen that the output voltage of the second differential amplification circuit 42 linearly decays in the range where the voltage value V of the first analog signal IN- is about 1.7 [V] or more. In the simulation, R5 = 2.2 kΩ, R6 = 1 kΩ, R7 = 5.1 kΩ, R8 = 1 kΩ, R 10 = 1 kΩ, and V IN+ = 3.3 [V].

[0032] The second diode circuit 44 includes a plurality of diodes (D5 to D8 in FIG. 2) connected in the reverse direction to the second differential amplification circuit 42. Similar to the first diode circuit 43, when a voltage equal to or lower than a predetermined reverse bias is applied to the second diode circuit 44, current flows through the plurality of diodes, so that the output voltage of the second differential amplification circuit 42 is clipped to a predetermined second clip voltage. The second clip voltage is, for example, the same voltage as the first clip voltage.

[0033] Note that FIG. 3 shows an example in which the second clip voltage is the same voltage as the first clip voltage (-2.4 [V]). After the voltage value V of the first analog signal IN- exceeds 2.6 [V], the output voltage of the second differential amplification circuit 42 is clipped, so that the state in which the output voltage is clipped cannot be seen.

[0034] Since the second diode circuit 44 further includes a diode D9 connected in the forward direction to the second differential amplifier circuit 42, a current flows when a voltage equal to or higher than a predetermined voltage is applied. As a result, the second diode circuit 44 clips the output voltage of the second differential amplifier circuit 42 to a predetermined third clip voltage. In FIG. 3, it can be seen that the output voltage of the second differential amplifier circuit 42 is clipped to about 0.5 [V] when the voltage value V IN- of the first analog signal is in the range of about 0.8 [V] to 1.5 [V].

[0035] The above-described conventional drive circuit 40 can clip the output voltage between the first clip voltage (= second clip voltage) and the third clip voltage. However, in the process of clipping the output voltage, the output voltage of the conventional drive circuit 40 gradually varies. Therefore, the difference between the output voltage characteristics of the conventional drive circuit 40 and the ideal output voltage characteristics shown by the dotted line in FIG. 3 becomes large.

[0036] When such an output voltage VC1 is supplied as the first input signal of the attenuator circuit 20 and the output voltage VC2 is supplied as the second input signal of the attenuator circuit 20, a region where the attenuation amount of the attenuator circuit 20 gradually varies is generated, and the linearity deteriorates. In addition, since the diodes may have large variations in the input-output characteristics and temperature characteristics of the elements, in this case, the linearity of the attenuation characteristics of the attenuator circuit 20 further deteriorates.

[0037] Therefore, the drive circuit 30 according to the present embodiment clips the output voltage without using a diode, thereby improving the linearity of the attenuation characteristics of the attenuator circuit 20. Such a drive circuit 30 will be described next.

[0038] <Configuration Example of Drive Circuit 30> FIG. 4 shows a configuration example of the drive circuit 30 according to the present embodiment. FIG. 5 shows an example of the result of simulating the output voltage characteristics of the drive circuit 30 according to the present embodiment shown in FIG. 4. In FIG. 5, the horizontal axis represents the voltage value of the first analog signal input to the drive circuit 30, and the vertical axis represents the voltage value of the signal output by the drive circuit 30.

[0039] Based on the input first analog signal, the drive circuit 30 outputs a first drive signal and a second drive signal. The drive circuit 30 includes a first amplifier circuit 31, a first clip circuit 32, a second amplifier circuit 33, a second clip circuit 34, a first output resistor 56, a second output resistor 66, a third output resistor 69, and a fourth output resistor 70.

[0040] The first amplifier circuit 31 amplifies the input first analog signal. The first amplifier circuit 31 is, for example, an amplifier circuit that amplifies the first analog signal at a predetermined amplification factor and outputs a signal obtained by adding a predetermined offset voltage to the amplified signal. The first amplifier circuit 31 may be a differential amplifier circuit. FIG. 4 shows an example in which the first amplifier circuit 31 is the first differential amplifier circuit 41 described in FIG. 2.

[0041] When the output signal of the first amplifier circuit 31 is not included in the first voltage range, the first clip circuit 32 outputs the output signal of the first amplifier circuit 31 as the first drive signal. In the example of FIG. 5, the first voltage range is a voltage range less than -2 [V], and the first voltage is -2 [V]. The first clip circuit 32 includes a first comparison circuit 35, a first switch circuit 36, and a ninth resistor 67.

[0042] The first comparison circuit 35 compares the output signal of the first amplifier circuit 31 with the first voltage. The first comparison circuit 35 determines, for example, whether the voltage value of the output signal of the first amplifier circuit 31 is smaller than the first voltage. The first comparison circuit 35 is, as an example, a comparator. In this case, the output of the first amplifier circuit 31 is connected to one input of the comparator, and a first reference voltage source or the like that outputs the first voltage is connected to the other input different from the one input via the ninth resistor 67. The resistance value of the ninth resistor 67 is, as an example, 1 kΩ.

[0043] The first switch circuit 36 switches whether to electrically connect the first voltage and the output of the first amplifier circuit 31 according to the comparison result of the first comparison circuit. The first switch circuit 36 is, for example, an N-channel FET. For example, when the comparison result of the first comparison circuit 35 indicates that the voltage value of the output signal of the first amplifier circuit 31 is equal to or higher than the first voltage, the first switch circuit 36 electrically disconnects the first reference voltage source that outputs the first voltage and the output of the first amplifier circuit 31. As a result, the drive circuit 30 can output the output signal of the first amplifier circuit 31 as the first drive signal via the first output resistor 56 in the range where the output of the first amplifier circuit 31 is -2 [V] or higher.

[0044] In FIG. 5, an example of the first drive signal is shown as VC1. When the voltage value V of the first analog signal is about 0.8 [V] to 1.7 [V], the output voltage of the first amplifier circuit 31 becomes -2 [V] or higher, so the output signal of the first amplifier circuit 31 becomes the first drive signal. In other words, when the voltage value V of the first analog signal is about 0.8 [V] to 1.7 [V], as shown in Equation (1), the output voltage of the first amplifier circuit 31 that linearly decays becomes the first drive signal. Note that the values of the resistors included in the first amplifier circuit 31 and the voltage value of the reference voltage are the same as the values of the resistors included in the first differential amplifier circuit 41 and the voltage value of the reference voltage described with reference to FIG. 3. IN- When the voltage value V of the first analog signal is about 0.8 [V] to 1.7 [V], the output voltage of the first amplifier circuit 31 becomes -2 [V] or higher, so the output signal of the first amplifier circuit 31 becomes the first drive signal. In other words, when the voltage value V of the first analog signal is about 0.8 [V] to 1.7 [V], as shown in Equation (1), the output voltage of the first amplifier circuit 31 that linearly decays becomes the first drive signal. Note that the values of the resistors included in the first amplifier circuit 31 and the voltage value of the reference voltage are the same as the values of the resistors included in the first differential amplifier circuit 41 and the voltage value of the reference voltage described with reference to FIG. 3. IN- When the voltage value V of the first analog signal is about 0.8 [V] to 1.7 [V], as shown in Equation (1), the output voltage of the first amplifier circuit 31 that linearly decays becomes the first drive signal. Note that the values of the resistors included in the first amplifier circuit 31 and the voltage value of the reference voltage are the same as the values of the resistors included in the first differential amplifier circuit 41 and the voltage value of the reference voltage described with reference to FIG. 3.

[0045] Also, when the output signal of the first amplifier circuit 31 is included in the first voltage range, the first clip circuit 32 outputs, as the first drive signal, a signal clipped to a predetermined first voltage. When the comparison result of the first comparison circuit 35 indicates that the voltage value of the output signal of the first amplifier circuit 31 is smaller than the first voltage, the first switch circuit 36 electrically connects the first reference voltage source that outputs the first voltage and the output of the first amplifier circuit. As a result, when the output of the first amplifier circuit 31 is in the range less than -2 [V] of the first voltage range, the first clip circuit 32 can output, as the first drive signal, a signal clipped to -2 [V], which is the first voltage, via the third output resistor 69.

[0046] Here, the voltage drops across the first output resistor 56 and the third output resistor 69 are equal to the potential difference between the first amplifier circuit 31 and the first voltage. Therefore, the resistance value of the first output resistor 56 is made larger than the resistance value of the third output resistor 69. In other words, the first output resistor 56 functions to limit the output current of the first amplifier circuit 31, and since it can maintain a stable potential, when the first clip circuit 32 is clipped, the FET of the first clip circuit 32 can be surely turned on. As an example, the resistance value of the first output resistor 56 is 1 kΩ, and the resistance value of the third output resistor 69 is 10 Ω.

[0047] In FIG. 5, for example, when the voltage value V of the first analog signal IN- exceeds 1.7 [V], the output voltage of the first amplifier circuit 31 becomes less than -2 [V], so the first voltage becomes the first drive signal. The drive circuit 30 according to the present embodiment switches from the output voltage of the first amplifier circuit 31 to a predetermined first voltage using a switch without using a diode, so that the first drive signal can be quickly switched from a signal that linearly attenuates to a clip voltage. Therefore, the drive circuit 30 can make the output voltage characteristic of the first drive signal approach the ideal output voltage characteristic shown by the dotted line in FIG. 3.

[0048] The second amplifier circuit 33 amplifies the input first analog signal. The second amplifier circuit 33 is, for example, an amplifier circuit that amplifies the first analog signal at a predetermined amplification factor and outputs a signal obtained by adding a predetermined offset voltage to the amplified signal. The second amplifier circuit 33 may be a differential amplifier circuit. FIG. 4 shows an example in which the second amplifier circuit 33 is the second differential amplifier circuit 42 described with reference to FIG. 2.

[0049] When the output signal of the second amplification circuit 33 is included in the second voltage range, the second clip circuit 34 outputs, as a second drive signal, a signal clipped to a predetermined second voltage. In the example of FIG. 5, the second voltage range is a voltage range of 0 [V] or more, and the second voltage is 0 [V]. The second clip circuit 34 includes a second comparison circuit 37, a second switch circuit 38, and a tenth resistor 68.

[0050] The second comparison circuit 37 compares the output signal of the second amplification circuit 33 with the second voltage. The second comparison circuit 37 determines, for example, whether or not the voltage value of the output signal of the second amplification circuit 33 is smaller than the second voltage. The second comparison circuit 37 is, as an example, a comparator. In this case, the output of the second amplification circuit 33 is connected to one input of the comparator, and a second reference voltage source or the like that outputs the second voltage is connected to the other input different from the one input via the tenth resistor 68. The resistance value of the tenth resistor 68 is, as an example, 1 kΩ.

[0051] The second switch circuit 38 switches whether or not to electrically connect the second voltage and the output of the second amplification circuit 33 according to the comparison result of the second comparison circuit 37. The second switch circuit 38 is, as an example, a P-channel FET. The second switch circuit 38 electrically connects, for example, the second reference voltage source that outputs the second voltage and the output of the second amplification circuit 33 when the comparison result of the second comparison circuit 37 indicates that the voltage value of the output signal of the second amplification circuit 33 is equal to or higher than the second voltage.

[0052] Thereby, when the output of the second amplification circuit 33 is in the range of 0 [V] or more of the second voltage range, the second clip circuit 34 can output, as a second drive signal, a signal clipped to 0 [V] which is the second voltage via the fourth output resistor 70. In FIG. 5, an example of the second drive signal is shown as VC2.

[0053] Here, the voltage drops across the second output resistor 66 and the fourth output resistor 70 are equal to the potential difference between the second amplifier circuit 33 and the second voltage. Therefore, the resistance value of the second output resistor 66 is made larger than the resistance value of the fourth output resistor 70. In other words, the second output resistor 66 functions to limit the output current of the second amplifier circuit 33, and since it can maintain a stable potential, when the second clip circuit 34 is clipped, the FET of the second clip circuit 34 can be surely turned on. As an example, the resistance value of the second output resistor 66 is 1 kΩ, and the resistance value of the fourth output resistor 70 is 10 Ω.

[0054] Since the second voltage is 0 [V], the second reference voltage source may be the ground potential (GND). In FIG. 5, for example, when the voltage value V IN- of the first analog signal is about 0.8 [V] to 1.7 [V], the output voltage of the second amplifier circuit 33 is 0 [V] or more, so the signal clipped to the second voltage becomes the second drive signal.

[0055] Also, when the output signal of the second amplifier circuit 33 is not included in the second voltage range, the second clip circuit 34 outputs the output signal of the second amplifier circuit 33 as the second drive signal. In this case, when the comparison result of the second comparison circuit 37 indicates that the voltage value of the output signal of the second amplifier circuit 33 is smaller than the second voltage, the second switch circuit 38 electrically disconnects the second voltage and the output of the second amplifier circuit. Thereby, the drive circuit 30 can output the output signal of the second amplifier circuit 33 as the second drive signal via the second output resistor 66 in the range where the output of the second amplifier circuit 33 is less than 0 [V].

[0056] In FIG. 5, for example, when the voltage value V IN- of the first analog signal exceeds 1.7 [V], the output voltage of the second amplifier circuit 33 becomes less than 0 [V], so the output signal of the second amplifier circuit 33 becomes the second drive signal. In other words, the voltage value V IN-When it exceeds 1.7 [V], as shown in Equation (1), the output voltage of the second amplification circuit 33 that linearly decays becomes the second drive signal. Note that the resistance value included in the second amplification circuit 33 and the voltage value of the reference voltage are the same as the resistance value and the voltage value of the reference voltage included in the second differential amplification circuit 42 described in FIG. 3.

[0057] As described above, the drive circuit 30 according to the present embodiment switches from a predetermined second voltage to the output voltage of the second amplification circuit 33 without using a diode, so that the second drive signal can be quickly switched to a signal that linearly decays from the clip voltage. Therefore, the drive circuit 30 can make the output voltage characteristic of the second drive signal approach the ideal output voltage characteristic shown by the dotted line in FIG. 3.

[0058] For example, as the first analog signal increases, the first drive signal linearly decays from the initial voltage to the first voltage and maintains the first voltage when it reaches the first voltage. Also, as the analog signal increases, the second drive signal maintains the second voltage of the initial voltage and linearly decays from the second voltage to the first voltage when the first drive signal reaches the first voltage.

[0059] Here, it is desirable that the voltage value of the first analog signal when the first drive signal reaches the first voltage and the voltage value of the first analog signal when the second drive signal starts to decay from the second voltage are the same voltage. In other words, when the first amplification circuit 31 outputs the first voltage input in response to the first analog signal of a predetermined voltage, the second amplification circuit 33 outputs the second voltage in response to the first analog signal of the input predetermined voltage. The parameters of the circuit elements of the first amplification circuit 31 and the second amplification circuit 33 are designed.

[0060] As described above, the drive circuit 30 can output two drive signals having different voltage values and different input / output characteristics in response to the input of one analog signal. Then, as the input analog signal increases linearly, after linearly changing the first drive signal from the initial value to the first voltage, the first drive signal can be linearly changed from the first voltage to the second voltage with the same slope.

[0061] Note that, in this embodiment, an example in which the drive circuit 30 outputs two drive signals has been described, but the present invention is not limited thereto. By increasing the combination of the amplifier circuit and the clip circuit, the drive circuit 30 can easily output a plurality of drive signals having different voltage values and different input / output characteristics.

[0062] Such a drive circuit 30 can linearly change the attenuation amount of the attenuator circuit 20 from 0 [dB] to R1 + R2 [dB], for example, by supplying the first drive signal as the first input signal to the first attenuator 21 of the attenuator circuit 20 and supplying the second drive signal as the second input signal to the second attenuator 22.

[0063] In the above embodiment, an example in which the drive circuit 30 generates a drive signal that decreases from the initial value to a negative-side voltage has been described, but the present invention is not limited thereto. The drive circuit 30 may generate a drive signal that increases from the initial value to a positive-side voltage. In this case, an inverting amplifier circuit may be added to the above-described drive circuit 30, or alternatively, the inputs of the differential amplifier circuit may be interchanged and circuit parameters or the like may be adjusted.

[0064] For example, when the comparison result of the first comparison circuit 35 indicates that the voltage value of the output signal of the first amplifier circuit 31 is greater than the first voltage, the first switch circuit 36 of the first clip circuit 32 electrically connects the first reference voltage source that outputs the first voltage and the output of the first amplifier circuit 31. Also, for example, when the comparison result of the second comparison circuit 37 indicates that the output signal of the second amplifier circuit 33 is greater than the second voltage, the second switch circuit 38 of the second clip circuit 34 electrically disconnects the second voltage and the output of the second amplifier circuit 33.

[0065] In the above-described embodiment, an example in which the drive circuit 30 supplies a plurality of drive signals to the attenuator circuit 20 has been described, but the present invention is not limited thereto. The drive circuit 30 can generate and supply a plurality of drive signals corresponding to the circuit device as long as the circuit device operates based on the plurality of drive signals. The circuit device is, for example, an amplifier, an oscillator, a synthesizer, a variable filter, or the like.

[0066] As described above, the present invention has been described using embodiments, but the technical scope of the present invention is not limited to the scope described in the above embodiments, and various modifications and changes are possible within the scope of the gist thereof. For example, all or part of the device can be configured by functionally or physically dispersing and integrating it in any unit. Also, new embodiments resulting from an arbitrary combination of a plurality of embodiments are included in the embodiments of the present invention. The effects of the new embodiments resulting from the combination have the effects of the original embodiments combined.

Explanation of Reference Numerals

[0067] 10 Attenuation device 20 Attenuator circuit 21 First attenuator 22 Second attenuator 30 Drive circuit 31 First amplifier circuit 32 First clip circuit 33 Second amplifier circuit 34 Second clip circuit 35 First comparison circuit 36 First Switch Circuit 37 Second Comparison Circuit 38 Second Switch Circuit 40 Conventional Drive Circuit 41 First Differential Amplifier Circuit 42 Second Differential Amplifier Circuit 43 First Diode Circuit 44 Second Diode Circuit 51 First Resistor 52 Second Resistor 53 Third Resistor 54 Fourth Resistor 55 First Op-Amp 56 First Output Resistor 61 Fifth Resistor 62 Sixth Resistor 63 Seventh Resistor 64 Eighth Resistor 65 Second Op-Amp 66 Second Output Resistor 67 Ninth Resistor 68 Tenth Resistor 69 Third Output Resistor 70 Fourth Output Resistor

Claims

1. A drive circuit that outputs a plurality of drive signals based on an input first analog signal, comprising: a first amplifier circuit that amplifies the first analog signal; when the output signal of the first amplifier circuit is within a first voltage range, a first clip circuit that outputs, as a first drive signal, a signal clipped to a predetermined first voltage, and when the output signal of the first amplifier circuit is not within the first voltage range, outputs the output signal of the first amplifier circuit as the first drive signal; a second amplifier circuit that amplifies the first analog signal; when the output signal of the second amplifier circuit is within a second voltage range, a second clip circuit that outputs, as a second drive signal, a signal clipped to a predetermined second voltage, and when the output signal of the second amplifier circuit is not within the second voltage range, outputs the output signal of the second amplifier circuit as the second drive signal; and comprising: the first clip circuit comprises: a first comparison circuit that compares the output signal of the first amplifier circuit with the first voltage; a first switch circuit that electrically connects the first reference voltage source that outputs the first voltage and the output of the first amplifier circuit when the comparison result of the first comparison circuit indicates that the voltage value of the output signal of the first amplifier circuit is smaller than the first voltage; A drive circuit having the above.

2. The second clip circuit comprises: a second comparison circuit that compares the output signal of the second amplifier circuit with a second voltage; a second switch circuit that switches whether to electrically connect the second voltage and the output of the second amplifier circuit according to the comparison result of the second comparison circuit; and having: the second switch circuit: when the comparison result of the second comparison circuit indicates that the voltage value of the output signal of the second amplifier circuit is greater than or equal to the second voltage, electrically connects the second reference voltage source that outputs the second voltage and the output of the second amplifier circuit; when the comparison result of the second comparison circuit indicates that the voltage value of the output signal of the second amplifier circuit is smaller than the second voltage, electrically disconnects the second reference voltage source that outputs the second voltage and the output of the second amplifier circuit; The drive circuit according to Claim 1.

3. When the first voltage is output according to a predetermined first analog signal input by the first amplifier circuit, the second amplifier circuit outputs the second voltage according to the input predetermined first analog signal. The drive circuit according to Claim 1.

4. The first amplification circuit and the second amplification circuit are differential amplification circuits into which the first analog signal is input, respectively. The drive circuit according to claim 1.

5. The voltage value of the reference voltage input to the differential amplification circuit that is the first amplification circuit and / or the resistance value of the voltage dividing resistor connected to the reference voltage are different from the voltage value of the reference voltage input to the differential amplification circuit that is the second amplification circuit and / or the resistance value of the voltage dividing resistor connected to the reference voltage. The drive circuit according to claim 4.

6. An attenuator circuit having a first attenuator that reduces the signal strength of an electrical signal input in response to a first input signal, and a second attenuator that reduces the signal strength of the electrical signal output by the first attenuator in response to a second input signal. The drive circuit according to any one of claims 1 to 5, which supplies the first drive signal as the first input signal to the first attenuator and supplies the second drive signal as the second input signal to the second attenuator. An attenuation device comprising the same.

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