Electronic circuits and measuring devices

Abstract

To provide an analog switch capable of flowing a high current in a shorter on / off time while avoiding damage to a connection object.SOLUTION: An analog switch 10, 10A includes: a first transistor Q1 and a second transistor Q2; a first constant current source 11 connected between a first node N1 to which a control electrode of the first transistor Q1 and a control electrode of the second transistor Q2 are connected and a positive first power supply line Vccp; a voltage generation circuit 15 connected between a second node N2 to which a first main electrode of the first transistor Q1 and a first main electrode of the second transistor Q2 are connected and the first node N1, and generating a voltage according to a current flowing between the first node N1 and the second node N2; a second constant current source 12 connected between the second node N2 and a negative second power supply line Vccn; and a control part 16 for switching between outputting current by the first constant current source 11 and the second constant current source 12 and cutoff according to a control signal CNT1.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to an electronic circuit and a measuring device, and more particularly to an electronic circuit including an analog switch that controls the transmission of an analog signal, and a measuring device including the electronic circuit. [Background technology]

[0002] Many measurement devices, such as LCR meters, that measure the impedance of a device under test (DUT), have a contact check function that checks whether the device under test and the probe of the measurement device are electrically connected before or during measurement.

[0003] A contact check is a process in which a probe connected to the external terminal of a measuring device is brought into contact with the object to be measured, an analog signal is output from the measuring device via the probe, and the voltage, etc. detected from the probe at that time is measured to check whether the object to be measured and the probe are electrically connected.

[0004] A measuring device having a contact check function has an analog switch that controls the output of an analog signal from a circuit in the measuring device to an external terminal. The analog switch is a component that controls the transmission of an analog signal (see Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Utility Model Application Publication No. 61-187125 Summary of the Invention [Problem to be solved by the invention]

[0006] In developing a new measuring device, the inventors of the present application realized that an analog switch with a short on / off switching time and capable of passing a large current of several hundred mA or more was required.

[0007] Conventionally, measuring devices such as LCR meters and capacitance meters use analog switches consisting of relays such as reed relays and integrated circuits in which multiple transistors are integrated on a single semiconductor substrate. However, while a typical relay can pass a large current, it has the problem that it takes a long time to switch on and off. On the other hand, an analog switch consisting of a typical integrated circuit has a short on / off switching time but cannot pass a large current.

[0008] In order to solve the above problems, the inventors of the present application have considered designing a new analog switch using discrete components such as transistors.

[0009] FIG. 4 is a diagram showing a circuit configuration of an analog switch that the present inventors have examined prior to filing the present application.

[0010] An analog switch 90 shown in Fig. 4 is connected between an output terminal of a signal source 95 and an external terminal of the measuring device within the measuring device. The analog switch 90 employs power transistors that are discrete components as the transistors Mx1 and Mx2 for realizing the main function of the switch, and connects a constant current source 91 to the gate electrodes of the transistors Mx1 and Mx2. The constant current source 91 is turned on / off by a control signal CNT to control the on / off of the transistors Mx1 and Mx2. This makes it possible to realize an analog switch that has a shorter on / off switching time than a relay and is capable of passing a large current of several hundred mA.

[0011] However, the inventors' investigation revealed that the analog switch 90 shown in FIG. 4 has the following problems. In the analog switch 90, when the transistors Mx1 and Mx2 are turned off, the constant current source 91 is turned off by the control signal CNT. At this time, the transistor M3x connected between the node Nx to which the transistors Mx1 and Mx2 are commonly connected and the power supply line Vccn to which a negative power supply voltage (for example, -12V) is supplied is turned on, so that a current flows from the power supply line Vccn to the node Nx, and a negative voltage is generated at the node Nx. As a result, if a measurement object is connected to the external terminal P of the measurement device, a negative voltage is constantly applied to the measurement object, which may damage the measurement object.

[0012] The present invention has been made in consideration of the above-mentioned problems, and has an object to provide an analog switch that is capable of passing a large current with a shorter on / off time while preventing damage to an object to be connected. [Means for solving the problem]

[0013] An electronic circuit according to a representative embodiment of the present invention is characterized in that it comprises a first transistor and a second transistor, each having a first main electrode, a second main electrode, and a control electrode; a first constant current source connected between a first node to which the control electrode of the first transistor and the control electrode of the second transistor are connected and a first power supply line to which a positive power supply voltage is supplied, and outputs a current from the first power supply line to the first node; a voltage generating circuit connected between the first node and a second node to which the first main electrode of the first transistor and the first main electrode of the second transistor are connected, and the first node, and generates a voltage in response to a current flowing between the first node and the second node; a second constant current source connected between the second node and a second power supply line to which a negative power supply voltage is supplied, and a control unit that switches between outputting and blocking current by the first constant current source and the second constant current source in response to the control signal. Effect of the Invention

[0014] According to the electronic circuit of the present invention, it is possible to provide an analog switch that is capable of passing a large current with a short on / off time while preventing damage to an object to be connected. [Brief description of the drawings]

[0015] [Figure 1] FIG. 1 is a diagram showing a configuration of a measurement device according to a first embodiment. [Diagram 2] FIG. 2 is a diagram showing a circuit configuration of an analog switch according to the first embodiment. [Diagram 3] FIG. 11 is a diagram showing a circuit configuration of an analog switch according to a second embodiment. [Figure 4] FIG. 1 is a diagram showing a circuit configuration of an analog switch that the present inventors have examined prior to filing the present application. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] 1. Overview of the embodiment First, a typical embodiment of the invention disclosed in this application will be outlined. In the following description, as an example, reference numerals in the drawings corresponding to components of the invention are given in parentheses.

[0017] [1] An electronic circuit (10, 10A) according to a representative embodiment of the present invention includes a first transistor (Q1) and a second transistor (Q2), each having a first main electrode (source electrode), a second main electrode (drain electrode), and a control electrode (gate electrode), a first constant current source (11) connected between a first node (N1) to which the control electrode of the first transistor and the control electrode of the second transistor are connected and a first power supply line (Vccp) to which a positive power supply voltage (+12V) is supplied, and outputs a current from the first power supply line side to the first node side, and a first constant current source (11) connected between the first main electrode of the first transistor and the second main electrode of the second transistor. The power supply circuit is characterized by comprising: a voltage generating circuit (15) connected between the first node and a second node (N2) to which the first main electrode of the transistor is connected, and which generates a voltage according to a current flowing between the first node and the second node; a second constant current source (12) connected between the second node and a second power supply line (Vccn) to which a negative power supply voltage (-12V) is supplied, and which outputs a current from the second node side to the second power supply line side; and a control unit (13, 14, 16) which switches between outputting and blocking the current by the first constant current source and the second constant current source according to a control signal (CNT1).

[0018] [2] In the electronic circuit (10A) described in [1] above, the first constant current source includes a PNP transistor (Q1) having a collector electrode connected to the first node, a first resistor (R1) connected between an emitter electrode of the PNP transistor and the first power supply line, and a second resistor (R2) connected between a base electrode of the PNP transistor and the first power supply line, the second constant current source includes an NPN transistor (Q2) having a collector electrode connected to the second node, a third resistor (R3) connected between an emitter electrode of the NPN transistor and the second power supply line, and a fourth resistor (R4) connected between a base electrode of the NPN transistor and the second power supply line, and the control unit may include a control circuit (16) that switches between conduction and non-conduction between the base electrode of the PNP transistor and the base electrode of the NPN transistor in response to the control signal.

[0019] [3] In the electronic circuit (10A) described in [2] above, the control circuit (16) may include a switch (SWa) connected between a base electrode of the PNP transistor and a base electrode of the NPN transistor and turned on / off in response to the control signal, a fifth resistor (R5) connected between one end of the switch and the base electrode of the PNP transistor, and a sixth resistor (R6) connected between the other end of the switch and the base electrode of the NPN transistor.

[0020] [4] In the electronic circuit (10A) described in [3] above, the control circuit (16) may further include a first capacitance (C5) connected in parallel with the fifth resistor, and a second capacitance (C6) connected in parallel with the sixth resistor.

[0021] [5] In the electronic circuit (10) described in [1] above, the control unit has a first control circuit (13) that switches between outputting and cutting off a current by the first constant current source, and a second control circuit (14) that switches between outputting and cutting off a current by the second constant current source, the first constant current source includes a PNP transistor (Q1) having a collector electrode connected to the first node, a first resistor (R1) connected between an emitter electrode of the PNP transistor and the first power supply line, and a second resistor (R2) connected between a base electrode of the PNP transistor and the first power supply line, and the second constant current source includes an NPNP transistor (Q2) having a collector electrode connected to the second node, The circuit may include an N-type transistor (Q2), a third resistor (R3) connected between the emitter electrode of the NPN transistor and the second power supply line, and a fourth resistor (R4) connected between the base electrode of the NPN transistor and the second power supply line, wherein the first control circuit enables the first constant current source to output a current by making the voltage of the base electrode of the PNP transistor lower than the positive power supply voltage in response to the control signal, and the second control circuit enables the second constant current source to output a current by making the voltage of the base electrode of the NPN transistor higher than the negative power supply voltage in response to the control signal.

[0022] [6] In the electronic circuit (10) described in [5] above, the first control circuit (13) includes a fifth resistor (R5) having one end connected to a base electrode of the PNP transistor, and a first N-channel field effect transistor (M3) having a source electrode connected to a potential lower than the positive power supply voltage, a drain electrode connected to the other end of the fifth resistor, and a gate electrode to which the control signal is input, and the second control circuit (14) includes a sixth resistor (R6) having one end connected to the base electrode of the NPN transistor, and a second N-channel field effect transistor (M3) having one end connected to the other end of the sixth resistor and the other end connected to the second power supply line. a seventh resistor (R7) connected to the first end of the seventh resistor, a second P-channel field effect transistor (M4) having a source electrode connected to a potential (ground potential) higher than the negative power supply voltage and a drain electrode connected to one end of the seventh resistor, an eighth resistor (R8) having one end connected to a gate electrode of the second field effect transistor and the other end connected to the second power supply line, and a third P-channel field effect transistor (M5) having a source electrode connected to a potential corresponding to the high level of the control signal, a drain electrode connected to one end of the eighth resistor, and a gate electrode to which the control signal is input.

[0023] [7] In the electronic circuit (10) described in [5] or [6] above, a first signal (CNT1) which is a binary signal is input to the first control circuit as the control signal, and a second signal (CNT1a) which is a binary signal is input to the second control circuit as the control signal, and the second signal may have a phase lead over the first signal.

[0024] [8] A measuring device (100) according to a representative embodiment of the present invention is a measuring device for measuring electrical characteristics of a measuring object (20), and is characterized in that it comprises at least one electronic circuit (10, 10A) described in any one of [1] to [7] above, a plurality of external terminals (HP, HC, LP, LC) for connecting the measuring object, and an internal circuit (1-3, Rp1, Rp2, etc.), and the first transistor and the second transistor of the electronic circuit are connected between the internal circuit and at least one of the external terminals.

[0025] 2. Specific examples of embodiments DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific examples of embodiments of the present invention will be described with reference to the drawings. In the following description, components common to the respective embodiments are designated by the same reference numerals, and repeated description will be omitted.

[0026] First Embodiment FIG. 1 is a diagram showing a configuration of a measurement device 100 according to the first embodiment. 1 is a device that measures electrical characteristics of a device under test (DUT) 20. Examples of the measuring device 100 include an LCR meter and a capacitance meter that are capable of measuring impedance by a four-terminal method. In this embodiment, an example will be described in which the measuring device 100 is an LCR meter.

[0027] 1, the measuring device 100 includes a signal generating circuit 1, a voltage detecting circuit 2, a current detecting circuit 3, A / D converting circuits 4 and 5, a data processing control unit 6, a memory unit 7, an operation unit 8, and an output unit 9. The measuring device 100 also includes a plurality of external terminals HC, HP, LC, and LP, and a plurality of switches SW1 to SW4.

[0028] The external terminals HC, HP, LP, and LC are terminals for connecting the object to be measured 20. For example, one terminal of the object to be measured 20 is commonly connected to the external terminals HC and HP as high-side terminals, and the other terminal of the object to be measured 20 is commonly connected to the external terminals LP and LC as low-side terminals.

[0029] The switches SW1 to SW4 are provided between the external terminals HC, HP, LP, and LC and the internal circuits of the measuring device 100, such as the signal generating circuit 1 and the current detecting circuit 3, and are electronic circuits that switch between electrical connection and disconnection between the external terminals HC, HP, LC, and LP and the internal circuits. The switches SW1 to SW4 will be described in detail later.

[0030] The measuring device 100, for example, applies an AC signal or the like from the external terminal HC to the object to be measured 20 connected between the external terminals HC, HP and the external terminals LP, LC, measures the voltage generated between the external terminals HP and LP at that time and the current flowing from the external terminal HC to the external terminal LC via the object to be measured 20, and measures the electrical characteristics (impedance) of the object to be measured 20 based on the measured voltage and current.

[0031] The signal generating circuit 1 is a circuit that generates an AC signal (for example, a sinusoidal AC signal) to be applied to the object to be measured 20 in order to measure the impedance of the object to be measured 20. An output terminal of the signal generating circuit 1 for outputting the AC signal is connected to an external terminal HC via a switch SW1.

[0032] The voltage detection circuit 2 is connected to the external terminal HP and the external terminal LP, respectively, and detects the voltage between the external terminal HP and the external terminal LP. The voltage detection circuit 2 has, for example, an operational amplifier, and amplifies the detected voltage between the external terminal HP and the external terminal LP by the operational amplifier, and outputs it as a voltage signal.

[0033] The A / D conversion circuit 4 samples the voltage signal output from the voltage detection circuit 2 at a predetermined sampling period (e.g., a period sufficiently shorter than the period of the AC signal output from the signal generation circuit 1) to convert the voltage signal into a digital signal and output it as voltage data.

[0034] The current detection circuit 3 is a circuit that is connected to the external terminal LC via a switch SW4 and detects a current flowing through the object to be measured 20. The current detection circuit 3 inputs, via the external terminal LC, a current flowing through the object to be measured 20 when an AC signal is applied from the signal generation circuit 1 to the object to be measured 20, for example, and converts the input current into a voltage to output as a current signal.

[0035] Similar to the A / D conversion circuit 4, the A / D conversion circuit 5 samples the current signal output from the current detection circuit 3 at a predetermined sampling period, thereby converting the current signal into a digital signal and outputting it as current data.

[0036] The operation unit 8 is an input interface for the user to operate the measuring device 100. Examples of the operation unit 8 include various buttons and a touch panel. For example, the user operates the operation unit 8 to set various measurement conditions for measuring the measurement target 20 in the measuring device 100, and to instruct the measuring device 100 to perform and stop the measurement.

[0037] The storage unit 7 is a functional unit for storing various programs for implementing the functions of the measuring device 100, various parameters used in calculations for measuring impedance, and data such as measurement results. The storage unit 7 is realized by a known storage device such as a ROM, a RAM, or a flash memory.

[0038] The data processing control unit 6 is a functional unit that comprehensively controls each functional unit in the measurement device 100. The data processing control unit 6 is configured to include a processor such as a CPU. The data processing control unit 6 is connected, for example, between an internal power supply line Vdd (e.g., 3.3 V) that is supplied with a power supply voltage lower than a positive power supply voltage (+12 V) described later and a ground potential GND (=0 V), and is operable by power supply from the internal power supply line Vdd.

[0039] The data processing control unit 6 controls each functional unit in the measuring device 100 by, for example, executing various calculations according to programs stored in the storage unit 7. The data processing control unit 6 also outputs control signals CNT1 to CNT4 to switch the switches SW1 to SW4 on / off.

[0040] Here, the control signals CNT1 to CNT4 are binary signals. For example, the high level of the control signal CNT1 is the power supply voltage (3.3 V) of the internal power supply line Vdd, and the low level of the control signal CNT1 is the ground potential (0 V).

[0041] The data processing control unit 6 also receives the voltage data and current data output from the A / D conversion circuits 4 and 5, and performs various data processing based on the received voltage data and current data to measure the electrical characteristics (impedance) of the object to be measured 20, and stores the measurement results in the memory unit 7. The data processing control unit 6 also performs a contact check based on the received voltage data to confirm the presence or absence of electrical connection between the external terminals HC, HP, LC, and LP and the object to be measured 20. The contact check will be described in detail later.

[0042] The output unit 9 is a functional unit for outputting various information such as the measurement conditions and measurement results in the measuring device 100. The output unit 9 is, for example, a display device equipped with an LCD (Liquid Crystal Display) or an organic EL. The output unit 9 may be a display device equipped with a touch panel that realizes some of the functions of the operation unit 8. The output unit 9 may also include a communication circuit or the like that outputs data such as the measurement results to the outside via a wired or wireless connection.

[0043] Next, the switches SW1 to SW4 will be described. The switch SW1 is connected between the output terminal of the signal generating circuit 1 and the external terminal HC. The switch SW2 is connected in series with a resistor Rp1 between a first power supply line Vccp to which a positive power supply voltage (e.g., +12V) of the measuring device 100 is supplied and the external terminal HP. The switch SW3 is connected in series with a resistor Rp2 between the first power supply line Vccp and the external terminal LP of the measuring device 100. The switch SW4 is connected between an input terminal of the current detecting circuit 3 and the external terminal LC.

[0044] As described above, the switches SW1 to SW4 switch between electrical continuity and non-conduction between each of the external terminals HC, HP, LP, and LC and the internal circuitry of the measurement device 100. The switches SW1 to SW4 are controlled to be turned on / off, for example, when measuring electrical characteristics of the measurement target 20 or when performing a contact check. For example, the on / off switching of the switches SW1 to SW4 is controlled by control signals CNT1 to CNT4 output from the data processing control unit 6 and corresponding to each of the switches SW1 to SW4.

[0045] When measuring the impedance of the object to be measured 20, the data processing control unit 6 turns on the switches SW1 and SW4 and turns off the switches SW2 and SW3, for example, using the control signals CNT1 to CNT4. In this state, the data processing control unit 6 causes the signal generating circuit 1 to output an AC signal or the like, and measures the impedance of the object to be measured 20 by detecting the voltage across the object to be measured 20 and the current flowing through the object to be measured 20. When stopping the measurement of the impedance of the object to be measured 20, the data processing control unit 6 turns off, for example, the switches SW1 to SW4 using the control signals CNT1 to CNT4.

[0046] When performing a contact check on one terminal side (high side) of the measurement object 20, the data processing control unit 6 turns on the switches SW1 and SW2 and turns off the switches SW3 and SW4 by the control signals CNT1 to CNT4. In this state, the data processing control unit 6 determines whether one terminal of the measurement object 20 and the external terminals HP and HC are electrically connected based on the magnitude of the voltage of the external terminal HP when a current flows from the first power supply line Vccp to the output terminal of the signal generating circuit 1 via the resistor Rp1, the switch SW2, the external terminals HP and HC, and the switch SW1.

[0047] When a contact check is performed on the other terminal side (low side) of the measurement object 20, the data processing control unit 6 turns off the switches SW1 and SW2 and turns on the switches SW3 and SW4 by the control signals CNT1 to CNT4. In this state, the data processing control unit 6 determines whether or not the other terminal of the measurement object 20 and the external terminals LP and LC are electrically connected based on the magnitude of the voltage of the external terminal LP when a current flows from the first power supply line Vccp to the input terminal of the current detection circuit 3 via the resistor Rp2, the switch SW3, the external terminals LP and LC, and the switch SW4.

[0048] The switches SW1 to SW4 are, for example, analog switches that control the transmission of analog signals. A specific circuit configuration of the analog switch serving as the switch SW1 will be described below.

[0049] FIG. 2 is a diagram showing a circuit configuration of the analog switch 10 according to the first embodiment.

[0050] The analog switch 10 shown in Fig. 2 can be used as the switches SW1 to SW4 in the measuring device 100. In this embodiment, the description will be given assuming that the switch SW1 is realized by the analog switch 10 shown in Fig. 2, and the other switches SW2 to SW4 are realized by analog switches configured by known integrated circuits or the like.

[0051] The analog switch 10 (switch SW1) shown in FIG. 2 includes a first transistor M1, a second transistor M2, a first constant current source 11, a second constant current source 12, a voltage generating circuit 15, a first control circuit 13, and a second control circuit 14.

[0052] These circuits constituting the analog switch 10 are realized, for example, by fixing discrete components such as transistors and resistors by soldering them onto a printed circuit board and connecting the respective discrete components to each other by wiring patterns or lead wires made of metal formed on the surface or inside of the printed circuit board.

[0053] The first transistor M1 and the second transistor M2 are, for example, power transistors capable of passing a current of several hundred mA or more. Examples of the first transistor M1 and the second transistor M2 include a bipolar transistor, a field effect transistor, an IGBT, and the like. In this embodiment, a case where the first transistor M1 and the second transistor M2 are N-channel metal-oxide-semiconductor field-effect transistors (MOSFETs) will be described as an example.

[0054] The first transistor M1 and the second transistor M2 each have a source electrode as a first main electrode, a drain electrode as a second main electrode, and a gate electrode as a control electrode.

[0055] The first transistor M1 and the second transistor M2 are connected in series between the output terminal of the signal generating circuit 1 and the external terminal HC. Specifically, the drain electrode of the first transistor M1 is connected to the output terminal of the signal generating circuit 1, the source electrode of the first transistor M1 is connected to the source electrode of the second transistor M2, and the drain electrode of the second transistor M2 is connected to the external terminal HC. In addition, the gate electrode of the first transistor and the gate electrode of the second transistor are commonly connected.

[0056] The first constant current source 11 is a circuit that is connected between a first node N1, to which the gate electrode of the first transistor M1 and the gate electrode of the second transistor M2 are commonly connected, and a first power supply line Veep, to which a positive power supply voltage (e.g., +12V) is supplied, and outputs a current from the first power supply line Veep to the first node N1.

[0057] The first constant current source 11 includes, for example, a transistor Q1, a resistor R1, and a resistor R2. The transistor Q1 is, for example, a PNP transistor. The collector electrode of the transistor Q1 is connected to a first node N1. The resistor R1 is connected between the emitter electrode of the transistor Q1 and the first power supply line Vccp. The resistor R2 is connected between the base electrode of the transistor Q1 and the first power supply line Vccp.

[0058] The second constant current source 12 is a circuit connected between a second node N2, where the source electrode of the first transistor M1 and the source electrode of the second transistor M2 are connected, and a second power supply line Vccn, to which a negative power supply voltage (for example, -12V) is supplied, and outputs a current from the second node N2 side to the second power supply line Vccn side. For example, the second constant current source 12 is designed to pass a current of the same magnitude as that of the first constant current source 11.

[0059] The second constant current source 12 includes, for example, a transistor Q2, a resistor R3, and a resistor R4. The transistor Q2 is, for example, an NPN transistor. The collector electrode of the transistor Q2 is connected to the second node N2. The resistor R3 is connected between the emitter electrode of the transistor Q2 and the second power supply line Vccn. The resistor R4 is connected between the base electrode of the transistor Q2 and the second power supply line Vccn.

[0060] The circuit configurations of the first constant current source 11 and the second constant current source 12 are not limited to the one exemplified in FIG. 2, and various circuit configurations can be adopted.

[0061] The first control circuit 13 and the second control circuit 14 function as a control unit that switches between outputting and cutting off a current by the first constant current source 11 and the second constant current source 12 in response to the control signal CNT1. That is, the first control circuit 13 is a circuit that controls outputting and cutting off a current by the first constant current source 11, and the second control circuit 14 is a circuit that controls outputting and cutting off a current by the second constant current source 12.

[0062] In response to the control signal CNT1, the first control circuit 13 activates (starts up) the first constant current source 11 by lowering the voltage of the base electrode of the transistor Q1 that constitutes the first constant current source 11 below the power supply voltage (+12V) of the first power supply line Veep, thereby enabling the output of current from the first constant current source 11.

[0063] Specifically, the first control circuit 13 includes a resistor R5 and a transistor M3. One end of the resistor R5 is connected to the base electrode of the transistor Q1. The transistor M3 is, for example, an N-channel type field effect transistor (MOSFET). The source electrode of the transistor M3 is connected to a potential lower than the voltage of the first power supply line Vccp (for example, the ground potential GND (=0V)). The drain electrode of the transistor M3 is connected to the other end of the resistor R5. A control signal CNT1 is input to the gate electrode of the transistor M3.

[0064] In response to the control signal CNT1, the second control circuit 14 makes the voltage of the base electrode of the transistor Q2 that constitutes the second constant current source 12 higher than the power supply voltage (-12V) of the second power supply line Vccn, thereby enabling the second constant current source 12 to output a current.

[0065] Specifically, the second control circuit 14 includes resistors R6, R7, and R8 and transistors M4 and M5. One end of the resistor R6 is connected to the base electrode of the transistor Q2 that constitutes the second constant current source 12. One end of the resistor R7 is connected to the other end of the resistor R6, and the other end of the resistor R7 is connected to the second power supply line Vccn.

[0066] The transistors M4 and M5 are, for example, P-channel field effect transistors (MOSFETs). The source electrode of the transistor M4 is connected to a potential (for example, ground potential GND) higher than the power supply voltage (-12V) of the second power supply line. The drain electrode of the transistor M4 is connected to one end of a resistor R7. One end of the resistor R8 is connected to the gate electrode of the transistor M4, and the other end of the resistor R8 is connected to the second power supply line Vccn.

[0067] A source electrode of the transistor M5 is connected to a potential corresponding to the high level of the control signal CNT1, i.e., the internal power supply line Vdd (+3.3 V). A drain electrode of the transistor M5 is connected to one end of the resistor R8. The control signal CNT1 is input to the gate electrode of the transistor M5.

[0068] Here, the operation of the analog switch 10 serving as the switch SW1 will be described.

[0069] First, consider the case where the control signal CNT1 is at a low level (0 V). In this case, the first control circuit 13 puts the first constant current source 11 into an inactive state (current cut-off state) in which current output is disabled. Specifically, when the control signal CNT1 is at a low level, the transistor M3 of the first control circuit 13 is turned off. As a result, the base electrode of the transistor Q1 of the first constant current source 11 is pulled up to the voltage (+12V) of the first power supply line Vccp by the resistor R2, so that the transistor Q1 is turned off and the output of current from the first constant current source 11 is stopped.

[0070] Moreover, when the control signal CNT1 is at a low level, the second control circuit 14 puts the second constant current source 12 in an inactive state in which current output is disabled. Specifically, when the control signal CNT1 is at a low level, the transistor M5 of the second control circuit 14 is turned on. As a result, the gate electrode of the transistor M4 rises to near the power supply voltage (=3.3V) of the internal power supply line Vdd, and the transistor M4 is turned off. As a result, the base electrode of the transistor Q2 of the first constant current source 11 is pulled down to the voltage (-12V) of the second power supply line Vccn by the resistors R6 and R7, and the transistor Q2 is turned off, and the output of current from the second constant current source 12 is stopped.

[0071] As described above, when the control signal CNT1 is at a low level, the current output from the first constant current source 11 and the second constant current source 12 stops. This causes the gate-source voltage of the transistors M1 and M2 to become 0V by the voltage generating circuit 15 (Zener diode ZD and resistor R8), so that the transistors M1 and M2 are turned off. As a result, a non-conductive state is established between the output terminal of the signal generating circuit 1 and the external terminal HC. At this time, since not only the first constant current source 11 but also the second constant current source 12 are stopped as described above, no negative voltage is generated at the second node N2.

[0072] Next, consider the case where the control signal CNT1 is at a high level (3.3 V). In this case, the first control circuit 13 puts the first constant current source 11 into an active state in which current output is possible. Specifically, when the control signal CNT1 is at a high level, the transistor M3 of the first control circuit 13 is turned on. As a result, the resistors R5 and R2 are connected between the power supply voltage (+12V) of the first power supply line Vccp and the ground potential (0V), so that a voltage according to the voltage division ratio of the resistors R5 and R2 is applied to the base electrode of the transistor Q1 of the first constant current source 11. As a result, the transistor Q1 is turned on, and a current is output from the first constant current source 11.

[0073] Also, when the control signal CNT1 is at a high level (3.3V), the second control circuit 14 puts the second constant current source 12 into an active state in which current output is possible. Specifically, when the control signal CNT1 is at a high level, the transistor M5 of the second control circuit 14 is turned off. As a result, the gate electrode of the transistor M4 is pulled down to the power supply voltage (-12V) of the second power supply line Vccn, and the transistor M4 is turned on. As a result, the resistors R7 and R6 are connected between the ground potential (0V) and the power supply voltage (-12V) of the second power supply line Vccn, and a voltage according to the voltage division ratio of the resistors R7 and R6 is applied to the base electrode of the transistor Q1 of the second constant current source 12. As a result, the transistor Q2 is turned on, and a current is output from the second constant current source 12.

[0074] When the first constant current source 11 and the second constant current source 12 output currents, the current output from the first constant current source 11 mainly flows into the second constant current source 12 via the Zener diode ZD and resistor R8 as the voltage generating circuit 15. As a result, the voltage generating circuit 15 generates a voltage between the gate and source of the transistors M1 and M2 that is greater than the threshold voltages of the transistors M1 and M2. As a result, the transistors M1 and M2 are turned on, and the external terminal HC and the output terminal of the signal generating circuit 1 are brought into a conductive state. At this time, if the currents of the first constant current source 11 and the second constant current source 12 are equal, the voltage of the second node N2 becomes an intermediate voltage (e.g., 0V) between the positive power supply voltage (+12V) and the negative power supply voltage (-12V).

[0075] As described above, the analog switch (electronic circuit) 10 as the switch SW1 included in the measuring device 100 according to the first embodiment includes the transistors M1 and M2, a first constant current source 11 that is connected between a first node N1 to which the control electrode (gate electrode) of the transistor M1 and the control electrode of the transistor M2 are connected and a first power supply line Veep to which a positive power supply voltage (for example, +12 V) is supplied and outputs a current from the first power supply line Veep to the first node N1, and a second constant current source 12 that is connected between a first main electrode (source electrode) of the transistor M1 and a first main electrode of the transistor M2. The device is equipped with a voltage generating circuit 15 connected between the node N2 and a first node N1 for generating a voltage according to a current flowing between the first node N1 and the second node N2, a second constant current source 12 connected between the second node N2 and a second power supply line Vccn to which a negative power supply voltage (e.g., -12V) is supplied for outputting a current from the second node N2 side to the second power supply line Vccn side, and a first control circuit 13 and a second control circuit 14 as a control unit for switching between outputting and cutting off the current by the first constant current source 11 and the second constant current source 12 according to a control signal CNT1.

[0076] According to the analog switch 10 having the above configuration, as described above, the transistors M1 and M2 can be turned on by activating the first constant current source 11 and the second constant current source 12 with the control signal CNT1. Here, by using power transistors as the transistors M1 and M2, it is possible to pass a large current of several hundred mA or more through the transistors M1 and M2, and the on / off switching time can be made shorter than that of a relay.

[0077] Furthermore, with the analog switch 10 having the above configuration, when the transistors M1 and M2 are turned off by the control signal CNT1, as described above, not only the first constant current source 11 but also the second constant current source 12 are in an inactive state (current cut-off state), so that no negative voltage is generated at the second node N2. As a result, during the period when the analog switch 10 (switch SW1) is off, a negative voltage is not constantly applied to the measurement object 20 via the external terminal HC, so that damage to the measurement object 20 can be prevented.

[0078] Therefore, the analog switch 10 according to the first embodiment makes it possible to pass a large current with a shorter on / off time while preventing damage to the object to be measured 20 as the object to be connected.

[0079] In the analog switch 10 according to the first embodiment, the first constant current source 11 includes a transistor Q1 (PNP transistor) whose collector electrode is connected to a first node N1, a resistor R1 connected between the emitter electrode of the transistor Q1 and a first power supply line Vccp (+12V), and a resistor R2 connected between the base electrode of the transistor Q1 and the first power supply line Vccp. The second constant current source 12 includes a transistor Q2 (NPN transistor) whose collector electrode is connected to a second node N2, a resistor R3 connected between the emitter electrode of the transistor Q2 and a second power supply line Vccn, and a resistor R4 connected between the base electrode of the transistor Q2 and the second power supply line Vccn. By employing the above circuit configuration for the first constant current source 11 and the second constant current source 12, it is possible to easily realize a constant current source that is switchable between outputting and cutting off a current.

[0080] In the above embodiment, the first control circuit 13 and the second control circuit 14 operate in response to one control signal CNT1, but this is not limiting. The first control circuit 13 and the second control circuit 14 may operate in response to different control signals. This will be described in detail below.

[0081] The first control circuit 13 and the second control circuit 14 differ in the number and type of transistors constituting them. Therefore, the timing at which the first constant current source 11 and the second constant current source 12 switch between the active state and the inactive state in response to the control signal CNT1 differs, and there are cases in which the difference in the switching timing cannot be tolerated.

[0082] For example, the second control circuit 14 uses P-channel MOSFETs for the transistors M4 and M5, which generally have a slower response speed than N-channel MOSFETs, and must switch two transistors M4 and M5 on and off to switch the active / inactive state of the second constant current source 12. This means that the response speed may be slower than that of the first control circuit 13, which switches the active / inactive state of the first constant current source 11 using a single N-channel MOSFET (transistor M3).

[0083] If the second control circuit 14 has a slower response speed than the first control circuit 13, it is considered that the voltage at the second node N2 changes as follows.

[0084] For example, when the transistors M1 and M2 are turned on, the first constant current source 11 starts up earlier than the second constant current source 12. Therefore, the voltage of the second node N2 momentarily becomes a voltage higher than the intermediate voltage (e.g., 0 V), and then, in response to the start-up of the second constant current source 12, the voltage of the second node N2 settles down to the intermediate voltage.

[0085] On the other hand, when the transistors M1 and M2 are turned off, the first constant current source 11 stops before the second constant current source 12. Therefore, the voltage of the second node N2 momentarily becomes a voltage lower than the intermediate voltage (for example, 0 V), and then, in response to the stopping of the second constant current source 12, the voltage of the second node N2 settles to the intermediate voltage.

[0086] In this way, if the timing at which the first constant current source 11 and the second constant current source 12 switch between the active state and the inactive state differs, there is a possibility that the voltage at the second node N2 will fluctuate instantaneously.

[0087] Therefore, in order to reduce the difference in timing between the active / inactive states of the first constant current source 11 and the second constant current source 12, it is preferable to make the control signals controlling the first control circuit 13 and the second control circuit 14 different from each other.

[0088] For example, the first control circuit 13 receives a control signal CNT1 (first signal) which is a binary signal as a control signal, and the second control circuit 14 receives a control signal CNT1a (second signal) which is a binary signal as a control signal, and it is preferable that the control signal CNT1a has a phase leading that of the control signal CNT1. That is, it is preferable that the control signal CNT1a for controlling the second control circuit 14 is a signal which becomes high level before the control signal CNT1 and becomes low level before the control signal CNT1. This makes it possible to reduce the difference in timing at which the first constant current source 11 and the second constant current source 12 switch between the active state and the inactive state.

[0089] Second Embodiment FIG. 3 is a diagram showing a circuit configuration of an analog switch 10A according to the second embodiment. The analog switch 10A shown in FIG. 3 can be used as the switch SW1 in the measurement device 100, similar to the analog switch 10 according to the first embodiment.

[0090] The analog switch 10A of the second embodiment differs from the analog switch 10 of the first embodiment in that the first constant current source 11 and the second constant current source 12 are controlled by one control circuit instead of two control circuits, but is similar to the analog switch 10 of the first embodiment in other respects.

[0091] 3, the analog switch 10A has a control circuit 16 instead of the first control circuit 13 and the second control circuit 14. The control circuit 16 switches between conduction and non-conduction between the base electrode of a transistor Q1 (a PNP transistor) and the base electrode of a transistor Q2 (an NPN transistor) in response to a control signal CNT1.

[0092] The control circuit 16 includes, for example, a switch SWa and resistors R5 and R6. The switch SWa is connected between the base electrode of the transistor Q1 and the base electrode of the transistor Q2, and is an element that is switched on / off according to a control signal CNT1. For example, when the control signal CNT1 is at a high level (3.3 V), the switch SWa is turned on, and when the control signal CNT1 is at a low level (0 V), the switch SWa is turned off. As the switch SWa, for example, an analog switch or a relay made of a general integrated circuit can be used.

[0093] The resistor R5 is connected between one end of the switch SWa and the base electrode of the transistor Q1, and the resistor R6 is connected between the other end of the switch SWa and the base electrode of the transistor Q2.

[0094] When the control signal CNT1 is at a low level (0V), the switch SWa is turned off in the control circuit 16, so that the terminal of the resistor R5 on the switch SWa side and the terminal of the resistor R6 on the switch SWa side are both open. As a result, the base electrode of the transistor Q1 is pulled up to the first power supply line Vccp by the resistor R2, so that the transistor Q1 is turned off. Also, the base electrode of the transistor Q2 is pulled down to the second power supply line Vccn by the resistor R4, so that the transistor Q2 is turned off. As a result, the first constant current source 11 and the second constant current source 12 are in an inactive state (current cut-off state), and the transistors M1 and M2 are turned off.

[0095] On the other hand, when the control signal CNT1 is at a high level (3.3V), the switch SWa in the control circuit 16 is turned on, so that the resistors R5 and R6 are connected via the switch SWa. This causes a current to flow from the first power supply line Vccp (+12V) to the second power supply line Vccn (-12V) via the resistor R2, resistor R5, switch SWa, resistor R6, and resistor R4. This causes a voltage to be generated between the base and emitter of each of the transistors Q1 and Q2, turning both the transistors Q1 and Q2 on. As a result, the first constant current source 11 and the second constant current source 12 are activated, turning the transistors M1 and M2 on.

[0096] As shown in FIG. 3, a capacitor C5 may be connected in parallel to the resistor R5, and a capacitor C6 may be connected in parallel to the resistor R6. According to this, immediately after the switch SWa is turned on, a current flows through the capacitors C5 and C6, so that the first constant current source 11 and the second constant current source 12 can be started up more quickly, and the difference in the timing of start-up between the first constant current source 11 and the second constant current source 12 can be reduced.

[0097] As described above, according to the analog switch 10A of the second embodiment, like the switch SW1 of the first embodiment, it is possible to pass a large current with a shorter on / off time while preventing damage to the object to be measured 20.

[0098] Furthermore, the analog switch 10A of embodiment 2 switches the active / inactive states of the first constant current source 11 and the second constant current source 12 using a single control circuit 16 that switches between conduction and non-conduction between the base electrode of transistor Q1 and the base electrode of transistor Q2 in response to a control signal CNT1, making it possible to further reduce the lag in the timing of switching between the active / inactive states between the first constant current source 11 and the second constant current source 12.

[0099] Specifically, the control circuit 16 has a switch SWa connected between the base electrode of transistor Q1 and the base electrode of transistor Q2 and turned on / off in response to a control signal CNT1, a resistor R5 connected between one end of the switch SWa and the base electrode of transistor Q1, and a resistor R6 connected between the other end of the switch SWa and the base electrode of transistor Q2.

[0100] According to this, when the switch SWa is turned on, a voltage can be generated almost simultaneously between the base and emitter of the transistor Q1 constituting the first constant current source 11 and between the base and emitter of the transistor Q2 constituting the second constant current source 12, so that the difference in the start timing of the first constant current source 11 and the second constant current source 12 can be further reduced. On the other hand, when the switch SWa is turned off, the base electrode of the transistor Q1 is quickly pulled up to the first power supply line Vccp and the base electrode of the transistor Q2 is quickly pulled down to the second power supply line Vccn, so that the difference in the stop timing of the first constant current source 11 and the second constant current source 12 can be further reduced.

[0101] Furthermore, by connecting the capacitors C5 and C6 in parallel with the resistors R5 and R6, the difference in start-up timing between the first constant current source 11 and the second constant current source 12 can be further reduced, as described above.

[0102] Since the operations of the first constant current source 11 and the second constant current source 12 are controlled by a single control circuit 16, the circuit scale of the analog switch 10A can be reduced, thereby making it possible to reduce the manufacturing cost of the measurement device 100.

[0103] <<Extension of the embodiment>> The invention made by the inventors of the present application has been specifically described above based on an embodiment, but it goes without saying that the present invention is not limited thereto and can be modified in various ways without departing from the spirit of the invention.

[0104] For example, the analog switches 10 and 10A according to the above-described embodiments can be mounted not only in measuring devices such as LCR meters, but also in various electric devices and the like.

[0105] In the above embodiment, the switch SW1 is realized by the analog switches 10 and 10A. However, the present invention is not limited to this. The switches SW2 to SW4 other than the switch SW1 may also be realized by the analog switches 10 and 10A.

[0106] Furthermore, the above-described switches SW1 to SW4 are representative of some of the analog switches included in measurement device 100, and measurement device 100 may include analog switches other than switches SW1 to SW4. In this case, the analog switches other than switches SW1 to SW4 may have the same circuit configuration as analog switches 10 and 10A.

[0107] Furthermore, the circuit configurations shown in FIGS. 2 and 3 are merely examples, and various circuit elements may be added as appropriate to the above-described circuit configurations as long as the basic operation of an analog switch can be performed.

[0108] Further, although an example has been given in which N-channel MOSFETs are used as the transistors M1 and M2, P-channel MOSFETs may also be used.

[0109] In addition, in the above embodiment, the analog switches 10 and 10A are realized by discrete components, but this is not limited to this, and some or all of the analog switches may be realized by integrated circuits depending on the specifications and applications required for the analog switches. [Explanation of symbols]

[0110] 1...signal generating circuit, 2...voltage detection circuit, 3...current detection circuit, 4,5...A / D conversion circuit, 6...data processing control unit, 7...memory unit, 8...operation unit, 9...output unit, 10,10A...analog switch, 11...first constant current source, 12...second constant current source, 13...first control circuit, 14...second control circuit, 15...voltage generating circuit, 16...control circuit, 20...measurement object, 100...measuring device, HC,HP,LC,LP...external terminal, SW1 to SW4,SWa...switch, CNT1 to CNT4...control signal, Vccp...first power supply line, Vccn...second power supply line, Vdd...internal power supply line, Q1...transistor (PNP transistor), Q2...transistor (PNP transistor), M1,M2,M3...transistor (N-channel MOSFET), M4,M5...transistor (P-channel MOSFET), R1 to R8...resistor, C5,C6...capacitor.

Claims

1. a first field effect transistor and a second field effect transistor each having a first main electrode, a second main electrode, and a control electrode; a first constant current source connected between a first node, to which a control electrode of the first field effect transistor and a control electrode of the second field effect transistor are connected, and a first power supply line to which a positive power supply voltage is supplied, and which outputs a current from the first power supply line side to the first node side; a voltage generating circuit connected between the first node and a second node to which the first main electrode of the first field effect transistor and the first main electrode of the second field effect transistor are connected, the voltage generating circuit generating a voltage in response to a current flowing between the first node and the second node; a second constant current source connected between the second node and a second power supply line to which a negative power supply voltage is supplied, and outputting a current from the second node side to the second power supply line side; a control unit that switches between outputting and cutting off current from the first constant current source and the second constant current source in response to a control signal; the first constant current source includes a PNP transistor having a collector electrode connected to the first node, a first resistor connected between an emitter electrode of the PNP transistor and the first power supply line, and a second resistor connected between a base electrode of the PNP transistor and the first power supply line; the second constant current source includes an NPN transistor having a collector electrode connected to the second node, a third resistor connected between an emitter electrode of the NPN transistor and the second power supply line, and a fourth resistor connected between a base electrode of the NPN transistor and the second power supply line, The control unit includes a control circuit that switches between conduction and non-conduction between the base electrode of the PNP transistor and the base electrode of the NPN transistor in response to the control signal. electronic circuit.

2. 2. The electronic circuit of claim 1, The control circuit includes: a switch connected between a base electrode of the PNP transistor and a base electrode of the NPN transistor, the switch being switched on / off in response to the control signal; a fifth resistor connected between one end of the switch and the base electrode of the PNP transistor; a sixth resistor connected between the other end of the switch and the base electrode of the NPN transistor. electronic circuit.

3. 3. The electronic circuit of claim 2, The control circuit includes: a first capacitance connected in parallel with the fifth resistor; and a second capacitance connected in parallel with the sixth resistor. electronic circuit.

4. A first field effect transistor and a second field effect transistor each having a first main electrode, a second main electrode, and a control electrode; a first constant current source connected between a first node, to which a control electrode of the first field effect transistor and a control electrode of the second field effect transistor are connected, and a first power supply line to which a positive power supply voltage is supplied, and which outputs a current from the first power supply line side to the first node side; a voltage generating circuit connected between the first node and a second node to which the first main electrode of the first field effect transistor and the first main electrode of the second field effect transistor are connected, the voltage generating circuit generating a voltage in response to a current flowing between the first node and the second node; a second constant current source connected between the second node and a second power supply line to which a negative power supply voltage is supplied, and outputting a current from the second node side to the second power supply line side; a control unit that switches between outputting and cutting off current from the first constant current source and the second constant current source in response to a control signal; The control unit is a first control circuit including a third field effect transistor, which switches between outputting and blocking a current from the first constant current source; a second control circuit including a fourth field effect transistor, which switches between outputting and blocking a current from the second constant current source; the first constant current source includes a PNP transistor, a first resistor connected between an emitter electrode of the PNP transistor and the first power supply line, and a second resistor connected between a base electrode of the PNP transistor and the first power supply line; the second constant current source includes an NPN transistor, a third resistor connected between an emitter electrode of the NPN transistor and the second power supply line, and a fourth resistor connected between a base electrode of the NPN transistor and the second power supply line; the first control circuit turns on the third field effect transistor in response to the control signal to make a voltage of a base electrode of the PNP transistor lower than the positive power supply voltage, thereby enabling a current to be output by the first constant current source; The second control circuit turns on the fourth field effect transistor in response to the control signal to make the voltage of the base electrode of the NPN transistor higher than the negative power supply voltage, thereby enabling the second constant current source to output a current. electronic circuit.

5. 5. The electronic circuit according to claim 4, The first control circuit is a fifth resistor having one end connected to the base electrode of the PNP transistor; the third field effect transistor of an N-channel type having a source electrode connected to a potential lower than the positive power supply voltage, a drain electrode connected to the other end of the fifth resistor, and a gate electrode to which the control signal is input; The second control circuit is a sixth resistor having one end connected to the base electrode of the NPN transistor; a seventh resistor having one end connected to the other end of the sixth resistor and the other end connected to the second power supply line; the fourth field effect transistor of a P-channel type having a source electrode connected to a potential higher than the negative power supply voltage and a drain electrode connected to one end of the seventh resistor; an eighth resistor, one end of which is connected to the gate electrode of the fourth field effect transistor and the other end of which is connected to the second power supply line; a fifth field effect transistor of a P-channel type having a source electrode connected to a potential corresponding to a high level of the control signal, a drain electrode connected to one end of the eighth resistor, and a gate electrode to which the control signal is input; electronic circuit.

6. 6. The electronic circuit according to claim 4, a first signal, which is a binary signal, is input to the first control circuit as the control signal; a second signal, which is a binary signal, is input to the second control circuit as the control signal; The second signal has a phase lead over the first signal.

1. An electronic circuit comprising:

7. A measuring device for measuring an electrical characteristic of a measurement object, comprising: At least one electronic circuit according to any one of claims 1 to 6; A plurality of external terminals for connecting the object to be measured; An internal circuit, The first field effect transistor and the second field effect transistor of the electronic circuit are connected between the internal circuit and at least one of the external terminals. Measuring equipment.

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