Quality analysis device

Abstract

To provide an amplifier circuit that can be suppressed in heat generation and increases in size, and furthermore can materialize high frequency operation and high power.SOLUTION: An amplifier circuit 101 comprises a first current source circuit 113 that outputs a current having a predetermined amount of a current to a first wiring L1, a voltage amplifier circuit 110 that amplifies the voltage of an input signal, a first level shift circuit 111 that is connected between the first wiring L1 and the output of the voltage amplifier circuit 110 and shifts the voltage of the signal output from the voltage amplifier circuit 110, a first voltage follower 117 that is connected to the first wiring L1 and amplifies the signal in the first wiring L1, and a first capacitor 210 that is connected between the first wiring L1 and the output of the voltage amplifier circuit 110.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an amplifier circuit and a mass spectrometer including the same, and particularly to a technique for achieving both high-frequency operation and high power of the amplifier circuit and the mass spectrometer.

Background Art

[0002] A technique for achieving high-frequency operation of an amplifier circuit is described in, for example, Patent Document 1. That is, Patent Document 1 shows that an amplifier circuit is configured by cascading a plurality of amplifiers including a source-grounded transistor, a drain-grounded transistor, and a feedback resistor in order to achieve both high gain and wide bandwidth.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] As shown in Patent Document 1, when amplifiers are cascaded, there is a problem that the occupied area of the amplifier circuit (hereinafter, also simply referred to as size) increases. In addition, there is also a problem that an amplifier that achieves both high gain and wide bandwidth generally has high power consumption.

[0005] An object of the present invention is to provide an amplifier circuit capable of achieving both high-frequency operation and high power while suppressing heat generation and an increase in size, and a mass spectrometer including the amplifier circuit.

[0006] Other objects and novel features of the present invention will become apparent from the description of this specification and the accompanying drawings.

Means for Solving the Problems

[0007] A brief overview of some of the representative embodiments disclosed in this application is as follows.

[0008] In other words, an amplification circuit according to one embodiment includes a first current source circuit that outputs a predetermined amount of current to a first wiring, a voltage amplification circuit that amplifies the voltage of an input signal, a first level shift circuit connected between the first wiring and the output of the voltage amplification circuit that shifts the voltage of the signal output from the voltage amplification circuit, a first voltage follower connected to the first wiring that amplifies the signal in the first wiring, and a first capacitor connected between the first wiring and the output of the voltage amplification circuit.

[0009] In another embodiment, a mass spectrometer is provided. The mass spectrometer according to the other embodiment includes an amplification circuit having characteristics suitable for use therein. [Effects of the Invention]

[0010] To briefly explain the effects obtained by a representative embodiment of the invention disclosed in this application, it is possible to provide an amplification circuit that can achieve high-frequency operation and high power while suppressing heat generation and size increase, and a mass spectrometer equipped with the amplification circuit. [Brief explanation of the drawing]

[0011] [Figure 1] This is a circuit diagram showing the configuration of the amplification circuit according to Embodiment 1. [Figure 2] This is a circuit diagram showing the configuration of an amplifier circuit related to a comparative example. [Figure 3] (A) to (C) are waveform diagrams illustrating the operation of the amplifier circuit in the comparative example. [Figure 4] (A) to (D) are waveform diagrams illustrating the effect of the capacitor according to Embodiment 1. [Figure 5] (A) and (B) are waveform diagrams showing the output signals of the amplifier circuit according to Embodiment 1 and the amplifier circuit according to the comparative example. [Figure 6](A) and (B) are circuit diagrams illustrating the amplification circuit according to Embodiment 2. [Figure 7] This is a block diagram showing the configuration of a mass spectrometer according to Embodiment 3. [Figure 8] This is a circuit diagram showing the configuration of the RF signal generation unit according to Embodiment 3. [Figure 9] This figure shows the formula according to the embodiment. [Modes for carrying out the invention]

[0012] Embodiments will be described with reference to the drawings. It should be noted that the embodiments described below are not intended to limit the invention as defined in the claims, and not all of the elements and combinations thereof described in the embodiments are necessarily essential to the solution of the invention.

[0013] (Embodiment 1) <Overall configuration of the amplification circuit> Figure 1 is a circuit diagram showing the configuration of an amplifier circuit according to Embodiment 1. In Figure 1, 101 represents the amplifier circuit.

[0014] The amplification circuit 101 includes a voltage amplification circuit 110, a first level shift circuit 111, a first capacitor 210, a second level shift circuit 112, a second capacitor 220, a first current source circuit 113, a second current source circuit 114, a positive power supply 115, a negative power supply 116, a first voltage follower 117, and a second voltage follower 118.

[0015] The output terminal of the voltage amplification circuit 110 is connected to the first level shift circuit 111 and the second level shift circuit 112. The first current source circuit 113 is connected to the positive power supply 115, and the first current source circuit 113 and the first level shift circuit 111 are connected by the first wiring L1. Also, the second current source circuit 114 is connected to the negative power supply 116, and the second current source circuit 114 and the second level shift circuit 112 are connected by the second wiring L2. That is, between the output terminal of the voltage amplification circuit 110 and the positive power supply 115, the first current source circuit 113 and the first level shift circuit 111 are connected in series, and between the output terminal of the voltage amplification circuit 110 and the negative power supply 116, the second current source circuit 114 and the second level shift circuit 112 are connected in series.

[0016] The first voltage follower 117 is connected between the positive power supply 115 and the output terminal of the amplification circuit 101, and the input terminal of the first voltage follower 117 is connected to the first wiring L1. Also, the second voltage follower 118 is connected between the negative power supply 116 and the output terminal of the amplification circuit 101, and the input terminal of the second voltage follower 118 is connected to the second wiring L2. That is, between the positive power supply 115 and the negative power supply 116, the first voltage follower 117 and the second voltage follower 118 are connected in series.

[0017] <Configuration of each circuit constituting the amplification circuit> Next, each circuit constituting the amplification circuit 101 will be described with reference to FIG. 1.

[0018] The voltage amplification circuit 110 amplifies the voltage amplitude of the input signal VIN supplied to the input terminal, and outputs an output signal Svg having the amplified voltage amplitude from the output terminal. <清

[0019] The first level shift circuit 111 comprises a load resistor 119 and an N-channel MOS (field-effect) transistor (hereinafter also referred to as an N-type transistor) Q1. The load resistor 119 is connected between the source of the N-type transistor Q1 and the output terminal of the voltage amplification circuit 110, and the drain and gate of the N-type transistor Q1 are connected to one end of the first wiring L1. The N-type transistor Q1 functions as a diode (voltage element) by connecting its drain and gate.

[0020] One terminal of the first capacitor 210 is connected to the source of the N-type transistor Q1, and the other terminal is connected to the drain and gate of the N-type transistor Q1.

[0021] The second level shift circuit 112 comprises a load resistor 120 and a P-channel MOS transistor (hereinafter also referred to as a P-type transistor) Q2. The load resistor 120 is connected between the source of the P-type transistor Q2 and the output terminal of the voltage amplification circuit 110, and the drain and gate of the P-type transistor Q2 are connected to one end of the second wiring L2. The P-type transistor Q2 also functions as a diode (voltage element) by connecting its drain and gate.

[0022] One terminal of the second capacitor 220 is connected to the source of the P-type transistor Q2, and the other terminal is connected to the drain and gate of the P-type transistor Q2.

[0023] The first level shift circuit 111 takes the output signal Svg from the voltage amplifier circuit 110 as input and outputs the positive-side level shift signal Shs to the first wiring L1. That is, the first level shift circuit 111 outputs a level shift signal Shs in which the output signal Svg is shifted towards the positive power supply 115 by the voltage amount defined by the diode formed by the N-type transistor Q1.

[0024] Furthermore, the second level shift circuit 112 takes the output signal Svg from the voltage amplification circuit 110 as input and outputs a negative-side level shift signal Sls to the second wiring L2. In other words, the second level shift circuit 112 outputs a level shift signal Sls in which the output signal Svg is shifted to the negative power supply 116 side by the voltage defined by the diode formed by the P-type transistor Q2.

[0025] The first and second capacitors 210 and 220 will be explained later, so we will omit their explanation here.

[0026] The first current source circuit 113 is connected to the other end of the first wiring L1 and outputs a predetermined value (current amount) of drive current Ihs to the first level shift circuit 111 via the first wiring L1. Similarly, the second current source circuit 114 is connected to the other end of the second wiring L2 and outputs a predetermined value of drive current Ils to the second level shift circuit 112 via the second wiring L2.

[0027] In Embodiment 1, the first voltage follower 117 is configured as a source follower circuit. Specifically, the first voltage follower 117 comprises a drain-grounded N-type transistor Q3 and a load resistor 121. The drain of the N-type transistor Q3 is connected to the positive power supply 115, the source is connected to the output terminal of the amplifier circuit 101 via the load resistor 121, and the gate is connected to the first wiring L1.

[0028] In Embodiment 1, the second voltage follower 118 is also configured as a source follower circuit. Specifically, the second voltage follower 118 comprises a drain-grounded P-type transistor Q4 and a load resistor 122. The drain of the P-type transistor Q4 is connected to the negative power supply 116, the source is connected to the output terminal of the amplifier circuit 101 via the load resistor 122, and the gate is connected to the second wiring L2.

[0029] The first voltage follower 117 takes the gate of the N-type transistor Q3 as its input terminal and receives the positive side level shift signal Shs in the first wiring L1 as its input terminal, and outputs a positive side output signal Shp corresponding to the positive side level shift signal Shs, using the source of the N-type transistor Q3 as its output terminal. In contrast, the second voltage follower 118 takes the gate of the P-type transistor Q4 as its input terminal and receives the negative side level shift signal Sls in the second wiring L2 as its input terminal, and outputs a negative side output signal Slp corresponding to the negative side level shift signal Sls, using the source of the P-type transistor Q4 as its output terminal.

[0030] The output signals Shp and Slp are combined (added) via load resistors 121 and 122 to form the output signal OUT (=Shp+Slp) of the amplifier circuit 101.

[0031] Functionally, the amplification circuit 101 can be broadly considered to consist of a voltage amplification stage, a level shift stage, and an output stage.

[0032] Here, the input stage corresponds to the section equipped with the voltage amplification circuit 110. The voltage amplification circuit 110 has a predetermined voltage amplification factor, for example, set during the design phase. The input stage amplifies the voltage of the input signal VIN according to this predetermined voltage amplification factor and outputs the amplified output signal Svg.

[0033] The level shift stage corresponds to the portion composed of a first level shift circuit 111 on the positive side, a first current source circuit 113, a second level shift circuit 112 on the negative side, and a second current source circuit 114.

[0034] The first level shift circuit 111 takes the output signal Svg obtained by amplification as input and outputs a positive-side level shift signal Shs. Here, the level shift signal Shs is the value obtained by level shifting the output signal Svg to the positive side by a voltage component determined by the current component of the drive current Ihs output from the first current source circuit 113 to the first wiring L1, which is the current component flowing through the N-type transistor Q1. In other words, as current flows through the diode formed by the N-type transistor Q1, the output signal Svg is leveled to the positive side by a voltage component generated in this diode.

[0035] Similarly, the second level shift circuit 112 takes the output signal Svg obtained by amplification as input and outputs a negative-side level shift signal Sls. Here, the level shift signal Sls is the output signal Svg level-shifted to the negative side by a voltage component determined by the current flowing through the P-type transistor Q2 from the drive current Ils output from the second current source circuit 114 to the second wiring L2. In other words, as current flows through the diode formed by the P-type transistor Q2, the output signal Svg is leveled to the negative side by a voltage component generated in this diode.

[0036] The first capacitor 210 and the second capacitor 220, connected to the first level shift circuit 111 and the second level shift circuit 112, have the role of charging the parasitic capacitances that are parasitic to the first wiring L1 and the second wiring L2. The capacitance parasitic to the first wiring L1 is, for example, the parasitic capacitance of the circuit connected to the second wiring, such as the input terminal of the first voltage follower 117. The parasitic capacitance of the input terminal of the first voltage follower 117 is, for example, the gate capacitance of the N-type transistor Q3. The capacitance parasitic to the second wiring L2 is similar to that of the first wiring L1, and is, for example, the parasitic capacitance of the circuit connected to the wiring L2, such as the input terminal of the second voltage follower 118. The parasitic capacitance of the input terminal of the second voltage follower 118 is, for example, the gate capacitance of the P-type transistor Q4.

[0037] In this specification, unless otherwise specified, capacity charging refers to both discharging and charging.

[0038] The output stage corresponds to the portion composed of a first voltage follower 117 on the positive side and a second voltage follower 118 on the negative side. Each voltage follower is equipped with a MOS transistor and a load resistor. The first voltage follower 117 takes the level shift signal Shs on the positive side as input and outputs an output signal Shp with a voltage drop equal to the threshold of the N-type transistor Q3. At this time, when the voltage of the level shift signal Shs on the positive side exceeds the threshold voltage of the N-type transistor Q3, the N-type transistor Q3 turns ON and allows current to flow on the positive side. In other words, a current corresponding to the voltage of the level shift signal Shs flows from the positive power supply 115 to the output terminal of the amplification circuit 101 via the N-type transistor Q3.

[0039] The second voltage follower 118 is the same as the first voltage follower 117. That is, the second voltage follower 118 takes the negative-side level shift signal Sls as input and outputs an output signal Slp with a voltage drop equal to the threshold value of the P-type transistor Q4. At this time, when the voltage of the level shift signal Sls exceeds the threshold voltage of the P-type transistor Q4, the P-type transistor Q4 turns ON and causes current to flow on the negative side. In other words, a current corresponding to the voltage of the level shift signal Sls flows from the negative power supply 116 to the output terminal of the amplification circuit 101 via the P-type transistor Q4.

[0040] The voltage of the input signal VIN changes alternately between the positive and negative terminals, for example, with respect to the ground voltage. This alternating current flow between the positive and negative terminals causes the output stage to achieve a push-pull operation.

[0041] Figure 1 illustrates the case where a source follower circuit is used as a voltage follower, but it is not limited to this. For example, when using bipolar transistors instead of MOS transistors, the first and second voltage followers 117 and 118 will be composed of emitter follower circuits.

[0042] <First and second capacitors> Next, we will explain the effects of the first capacitor 210 and the second capacitor 220 connected to the level shift circuits 111 and 112. Since the effect of the second capacitor 220 is similar to that of the first capacitor 210, we will only explain the first capacitor 210 here.

[0043] To facilitate understanding, we will first explain an amplifier circuit in which the first and second capacitors 210 and 220 are not connected to the first and second level shift circuits as a comparative example.

[0044] <<Comparative Example>> Figure 2 is a circuit diagram showing the configuration of an amplifier circuit according to a comparative example. The amplifier circuit 301 shown in this figure is similar to the amplifier circuit 101 shown in Figure 1. The main difference is that the amplifier circuit 301 shown in Figure 2 does not have the first and second capacitors 210 and 220 shown in Figure 1. In Figure 2, Ihs represents a predetermined drive current output by the first current source circuit 113 to drive the N-type transistor Q1 of the first level shift circuit 111, and Vhh represents the level shift voltage by the first level shift circuit 111.

[0045] Figure 3 is a waveform diagram illustrating the operation of an amplifier circuit in a comparative example. Here, Figure 3(A) shows the current waveform of the input signal of the first voltage follower 117, Figure 3(B) shows the voltage waveform of the input signal of the first voltage follower 117, and Figure 3(C) shows the waveform of the output signal OUT of the amplifier circuit 301. In Figures 3(A) to (C), a dashed line extending horizontally and denoted by the sign 0 indicates the ground voltage (0V) or reference current (0A).

[0046] In interval tA, the input voltage of the first voltage follower 117 begins to rise from 0V, as shown in Figure 3(B). Then, as shown in Figure 3(A), an input current flows through the first voltage follower 117. When the input voltage of the first voltage follower 117 reaches its maximum value (when transitioning from interval tA to interval tB), that is, when the change in input voltage becomes 0, the input current flowing through the first voltage follower 117 becomes 0A.

[0047] In section tB, as shown in Figure 3(B), the input voltage begins to decrease from its maximum value. Then, as shown in Figure 3(A), a negative current begins to flow. The input current reaches its maximum value when the input voltage becomes 0V (when transitioning from section tB to section tC), that is, when the change in input voltage is at its maximum. When transitioning from section tB to section tC, the input voltage switches from a positive voltage to a negative voltage, as shown in Figure 3(B). At this time, the parasitic capacitance associated with the input terminal of the first voltage follower 117 discharges, and a transient large current Iht (Figure 2) flows, as indicated by the numeral 310. The transient large current Iht for discharging the parasitic capacitance is supplied from the first current source circuit 113.

[0048] However, since the first current source circuit 113 outputs a drive current Ihs to the first level shift circuit 111, a transient large current Iht flows through the first voltage follower 117, causing the value of the drive current flowing through the first level shift circuit 111 to fluctuate. As the supplied drive current fluctuates, the level shift voltage Vhh of the first level shift circuit 111 fluctuates.

[0049] The positive-side level shift signal Shs output by the first level shift circuit 111 corresponds to the signal obtained by level shifting the output signal Svg of the voltage amplifier circuit 110 by the level shift voltage Vhh. As a result, the level shift signal Shs will also fluctuate in a similar manner.

[0050] Since the level shift signal Shs is the input signal to the first voltage follower 117, this input signal also becomes a distorted signal due to the transient large current Iht, as indicated by the numeral 320 in Figure 3(B). Furthermore, since the waveform of the output signal of the first voltage follower 117 is obtained by voltage-dropping the input signal of the first voltage follower 117 by the threshold value of the N-type transistor Q3, the output signal OUT of the amplifier circuit 301 has a distorted waveform as indicated by the numeral 330 in Figure 3(C).

[0051] <<Effects of the first and second capacitors>> Next, we will explain the case where a first capacitor 210 and a second capacitor 220 are provided, as shown in Figure 1.

[0052] Figure 4 is a waveform diagram illustrating the effect of the capacitor according to Embodiment 1. The figure simply shows the current flowing through the first capacitor 210, the input voltage of the first voltage follower 117, and the input current of the first voltage follower 117. Here, Figure 4(A) shows the waveform of the input current of the first voltage follower 117, and Figure 4(B) shows the waveform of the current flowing through the first capacitor 210. Furthermore, Figure 4(C) shows the waveform of the input voltage of the first voltage follower 117, and Figure 4(D) shows the waveform of the output signal OUT of the amplifier circuit 101.

[0053] In Figures 4(A) to 4(D), the dashed lines extending horizontally and labeled with the symbol 0 indicate the ground voltage (0V) or the reference current 0A. In these figures, the area above the dashed line is the positive electrode side, and the area below it is the negative electrode side.

[0054] In the first voltage follower 117, which constitutes the output stage, the gate of the N-type transistor Q3 functions as an input terminal connected to the first wiring LI. Since the gate of the N-type transistor Q3 has a parasitic gate capacitance, the first wiring L1 has a parasitic capacitance, and the parasitic capacitance in the first wiring L1 is connected to the first capacitor 210.

[0055] In interval tA, as the input voltage of the first voltage follower 117 rises from 0V as shown in Figure 4(C), an input current flows through the first voltage follower 117 as shown in Figure 4(A). When transitioning from interval tA to interval tB, as shown in Figure 4(C), the input voltage of the first voltage follower 117 reaches its maximum value, the change in input voltage becomes 0, and the input current flowing through the first voltage follower 117 becomes 0A as shown in Figure 4(A).

[0056] In interval tB, the input voltage of the first voltage follower 117 begins to decrease from its maximum value, as shown in Figure 4(C). As the input voltage begins to decrease, a negative (negative side) input current begins to flow through the first voltage follower 117, as shown in Figure 4(A). The value of this negative input current is maximum when the input voltage of the first voltage follower 117 reaches 0V, as shown in Figure 4(C), that is, when the change in input voltage is at its maximum.

[0057] When transitioning from section tB to section tC, the input voltage of the first voltage follower 117 switches from a positive (positive terminal side) voltage to a negative (negative terminal side) voltage, as shown in Figure 4(C). At this time, the parasitic capacitance associated with the input terminal of the first voltage follower 117 discharges, and a large current flows transiently, as indicated by the symbol 410 in Figure 4(A).

[0058] In Embodiment 1, this transient large current flows to the first capacitor 210, as shown in Figure 4(B), and the first capacitor 210 is charged. This prevents the value of the drive current Ihs flowing through the first level shift circuit 111 from fluctuating due to the transient large current, and makes it possible to maintain a constant value.

[0059] By keeping the current flowing through the level shift circuit 111 constant, it is possible to prevent fluctuations in the level shift voltage shifted by the level shift circuit 111, resulting in a stable output of the positive-side level shift signal Shs. As a result, as shown in Figure 4(D), the output signal OUT of the amplifier circuit 101 becomes a signal with reduced distortion.

[0060] From section tC to section tD, the positive and negative terminals are reversed, but the operation is the same as from section tA to section tB. From section tE onward, the operation is the same as from section tA to section tD. From section tC to section tD, the polarity is reversed compared to section tA to section tB, so as shown in Figure 4(A), when transitioning from section tD to section tE, the parasitic capacitance associated with the input terminal of the first voltage follower 117 is charged. At this time, the first capacitor 210 discharges to charge the parasitic capacitance, as shown in Figure 4(B).

[0061] These operations make it possible to produce a low-distortion signal OUT from the amplifier circuit 101 even when a transient large current flows to charge and discharge the parasitic capacitance associated with the first wiring L1. In Figure 4(D), the positive side of the output signal OUT is output from the first voltage follower 117, and the negative side is output from the second voltage follower 118.

[0062] Although the parasitic capacitance associated with the input terminal of the first voltage follower 117 was used as an example of the parasitic capacitance charged and discharged by the first capacitor 210, the parasitic capacitance charged and discharged by the first capacitor 210 is not limited to this. That is, the first capacitor 210 charges and discharges not only the parasitic capacitance associated with the input terminal of the first voltage follower 117, but also the parasitic capacitance associated with the first wiring L1, thereby stabilizing the current flowing through the first level shift circuit.

[0063] To reduce the transient large current generated by the parasitic capacitance associated with the first wiring L1, the first capacitor 210 performs a charge and discharge operation. The first capacitor 210 according to Embodiment 1 has the ability to supply current capable of charging (charging and discharging) the parasitic capacitance associated with the first wiring L1. Furthermore, since the first capacitor 210 is driven by the voltage amplification circuit 110, the voltage amplification circuit 110 has the ability to supply current capable of charging (charging and discharging) the first capacitor 210. As a result, in Embodiment 1, the transient large current can be offset by the charging and discharging of the first capacitor 210.

[0064] Figure 5 is a waveform diagram showing the output signals of the amplifier circuit according to Embodiment 1 and the amplifier circuit according to the comparative example. Here, Figure 5(A) shows the waveform of the output signal of the amplifier circuit according to the comparative example described in Figure 2, and Figure 5(B) shows the waveform of the output signal of the amplifier circuit according to Embodiment 1.

[0065] In Figure 5, 610 and 620 show the voltage waveforms of the input signal input to the amplification circuit, and 611 and 621 show the voltage waveforms of the output signal output from the amplification circuit.

[0066] As shown in Figure 5(A), distortion occurs in the amplifier circuit of the comparative example when the output signal reaches its maximum value. In contrast, in the amplifier circuit of Embodiment 1, the fluctuation of the current supplied to the level shift circuit is reduced by charging (charging and discharging) the capacitor connected to the level shift circuit, and as shown in Figure 5(B), distortion is eliminated even when the output signal reaches its maximum value. In other words, it becomes possible to obtain a large amplitude output signal by push-pull operation while reducing distortion of the signal waveform.

[0067] <Suppression of heat generation and size increase> The waveform distortion of the output signal caused by the transient large current described above can also be mitigated by the configuration of the first and second current source circuits 113 and 114 that supply the drive currents Ihs and Ils to the first and second level shift circuits. In other words, by configuring the first and second current source circuits with multiple multi-stage unit current source circuits and increasing the output impedance of the first and second current source circuits, it is possible to suppress the impact on the drive currents Ihs and Ils even when transient large currents occur.

[0068] However, in order to create a multi-stage system with multiple unit current source circuits, it is essential to increase the voltage (absolutely high voltage) of the positive power supply 115 and negative power supply 116 that supply power to the first and second current source circuits 113 and 114 that are formed by these circuits. Increasing the voltage of the positive power supply 115 and negative power supply 116 increases the heat generated in the first and second voltage followers 117 and 118, leading to a heat generation problem. Furthermore, since each of the first and second current source circuits is composed of multiple unit current source circuits, the number of semiconductor elements constituting the first and second current source circuits increases, increasing the size of the first and second current source circuits, and consequently the size of the amplifier circuit.

[0069] In the amplification circuit according to Embodiment 1, the waveform distortion of the output signal can be reduced by the first and second capacitors. Therefore, even if the first and second current source circuits 113 and 114 are configured as a multi-stage unit current source circuit in addition to the first and second capacitors, the number of stages of the multi-stage unit current source circuit can be reduced. Although the size increases due to the inclusion of the first and second capacitors, the increase in size can be suppressed because the number of stages of the unit current source circuit can be reduced. Furthermore, because the number of stages can be reduced, it is possible to suppress the high voltage of the positive power supply 115 and the negative power supply 116, thereby suppressing heat generation.

[0070] Furthermore, in Embodiment 1, the first and second level shift circuits are composed of MOS transistors connected in series and a load resistor, so they can be constructed with a small number of elements, and an increase in size can be suppressed.

[0071] (Embodiment 2) Figure 6 is a circuit diagram illustrating the amplifier circuit according to Embodiment 2. Here, Figure 6(A) is a circuit diagram showing the configuration of the amplifier circuit according to Embodiment 2. Figure 6(B) is a circuit diagram showing the configuration of a comparison circuit illustrating the amplifier circuit according to Embodiment 2.

[0072] Figure 6(A) shows only the portion corresponding to a part of the amplifier circuit shown in Figure 1 (the positive side). That is, Figure 6(A) shows only the parts corresponding to the first level shift circuit 111, the first current source circuit 113, and the first voltage follower 117 shown in Figure 1, and the other parts are omitted. However, the configuration on the negative side is the same as in Figure 6(A), except that the transistor is replaced with a P-type transistor.

[0073] In Embodiment 2, the first current source circuit 113 is composed of one unit current source circuit UVI. In Figure 6(A), the voltage drop across this unit current source circuit UVI is indicated by the symbol Vi.

[0074] Similar to Embodiment 1, the first capacitor 210 is connected to the first level shift circuit 111. As described above, even if a transient large current flows, the first capacitor 210 charges and discharges, thereby reducing waveform distortion of the output signal. In other words, the transient large current is canceled out by the first capacitor 210.

[0075] Therefore, even if the output impedance of the first current source circuit 113 is relatively low, it is possible to prevent the drive current supplied to the first level shift circuit 111 from fluctuating due to transient large currents.

[0076] The comparative example shown in Figure 6(B) is similar to that in Figure 6(A). The differences are that in Figure 6(B), the first capacitor is not provided, and the first current source circuit 113 has a multi-stage configuration of two unit current source circuits UVI.

[0077] The unit current source circuit UVI shown in Figure 6(B) is the same as the one shown in Figure 6(A). In Figure 6(B), by increasing the number of stages in the unit current source circuit UVI, the drive current Ihs supplied to the first level shift circuit 111 is the same as the drive current Ihs in Figure 6(A), but the output impedance of the first current source circuit 113 can be increased. As a result, even in the comparative example shown in Figure 6(B), it is possible to suppress fluctuations in the drive current supplied to the first level shift circuit and suppress waveform distortion of the output signal, even if a large current flows transiently.

[0078] However, in order for the voltage of the signal Shp output by the first voltage follower 117 to be the same in Figures 6(A) and (B), the voltage of the positive power supply 115 must be different in Figures 6(A) and (B).

[0079] In other words, in Figure 6(A), the positive voltage of the positive power supply 115 is VHj, and in order to make the signal Shp a predetermined voltage value, a voltage Vqc is applied between the source and drain of the N-type transistor Q3 that constitutes the first voltage follower 117.

[0080] In contrast, in the configuration of Figure 6(B), in order to obtain the same predetermined voltage value signal Shp, the first current source circuit 113 is composed of two stages of unit current source circuits UVI. Therefore, the voltage drop across the first current source circuit 113 becomes twice the voltage drop Vi, and the positive voltage VHk of the positive power supply in Figure 6(B) is the value expressed by equation (1) shown in Figure 9. Consequently, in the configuration of Figure 6(B), the voltage Vqi obtained by equation (2) shown in Figure 9 is applied between the source and drain of the N-type transistor Q3 that constitutes the first voltage follower 117. In other words, when the first current source circuit 113 is composed of multiple stages of unit current source circuits, it becomes necessary to operate the amplification circuit at a high voltage, the voltage applied to the first voltage follower 117 becomes larger, power consumption increases, and the circuit heats up due to the increased power consumption.

[0081] Because heat generation can cause the temperature of a semiconductor element to exceed its rated specifications, heat sinks and cooling fans are sometimes used to suppress heat generation. However, the inclusion of such cooling mechanisms is undesirable because it directly leads to an increase in circuit size and manufacturing costs.

[0082] According to Embodiment 2, waveform distortion of the output signal can be suppressed by a single unit current source circuit and first and second capacitors, and an increase in size and heat generation can be suppressed.

[0083] (Embodiment 3) Embodiment 3 describes a mass spectrometer equipped with the amplification circuit described in Embodiment 1. Figure 7 is a block diagram showing the configuration of the mass spectrometer according to Embodiment 3. In Figure 7, 701 indicates the mass spectrometer.

[0084] The mass spectrometer 701 includes a measurement unit 702 which comprises an ion source 710 that ionizes the sample to be analyzed delivered from a pre-processing unit, a focusing unit 711 that focuses the ionized analytical sample 728, a separation unit 712 that filters the focused ions according to the mass-to-charge ratio, allowing only the ionized sample to be detected to pass through, and a detection unit 713 that collides the ionized sample that has passed through with a conversion dynode 714, converting the ionized sample into electrons 715, and then injects these electrons into a scintillator 716 to output photons corresponding to the amount of electrons. Furthermore, the mass spectrometer 701 includes a detector 717 that outputs an electrical signal corresponding to the photons output from the detection unit 713, an analysis result processing unit 718 that processes the electrical signal output from the detector 717, a driver 719 that drives the measurement unit 702, a monitor 720 that monitors the measurement unit 702, a power supply 721 that supplies power to each part, and a control unit 722 that controls the mass analysis.

[0085] The control unit 722 includes an RF signal generation unit 723 that generates AC signals, a DC signal generation unit 724 that generates DC signals, an oscillation unit 725 that boosts the input signal using a resonant circuit and outputs it, and a pre-processing unit 726 that processes the signal input from the oscillation unit 725 and outputs it to the MS filter 727 included in the separation unit 712.

[0086] Next, the process by which the ionized analytical sample 728 reaches the detection unit 713 will be explained using Figure 7.

[0087] The MS filter 727 included in the separation unit 712 consists of four electrodes, and a voltage is applied to it which is the sum of a DC voltage U and an AC voltage Vcos(ωt), with the polarity of the opposing electrodes being the same. The value of this applied voltage is expressed by equation (3) shown in Figure 9. The MS filter 727 forms an electric field corresponding to the voltage expressed by equation (3). In equation (3), ω = 2πf, where f is the frequency of the AC voltage and V is the maximum value of the AC voltage.

[0088] When the ionized analytical sample 728 is incident on the electric field formed by the MS filter 727 of the separation unit 712, it vibrates up, down, left, and right as it moves towards the detection unit 713. At this time, only ions with a specific mass spectrometry ratio m / z pass through the MS filter 727 with a stable amplitude motion relative to the voltage value applied to the MS filter 727 and reach the detection unit 713. On the other hand, ions with other mass spectrometry ratios m / z have large amplitudes and diverge, colliding with the electrodes. As a result, only ions with the target mass spectrometry ratio m / z reach the detection unit 713.

[0089] The mass spectrometry ratio m / z of ions measured by the mass spectrometer 701 is set by the magnitude V of the AC voltage applied to the MS filter 727, its frequency ω, and the distance 2ro between the electrodes of the MS filter 727. The mass spectrometry ratio m / z is expressed by equation (4) shown in Figure 9. In equation (4), ^2 represents squaring.

[0090] From equation (4) for the mass spectrometry ratio m / z, it can be considered that to analyze ions with larger masses, the AC voltage V should be increased and the distance ro and frequency ω should be decreased. However, due to the structure of the actual mass spectrometer 701, the distance ro cannot be reduced to a few millimeters or less, and if the frequency ω is reduced too much, the ions will not be able to vibrate sufficiently. Therefore, expanding the measurement range of ions and analyzing ions with larger masses is possible by increasing the AC voltage V. Furthermore, the resolution of the mass spectrometer 701 depends on the assembly precision of the electrodes of the MS filter 727, the processing precision of the electrode surface, the stability of the DC voltage U and AC voltage V, and the frequency ω of the AC voltage. The frequency ω determines the number of vibrations when ions pass through the MS filter 727, and a higher number of vibrations results in higher resolution. Therefore, a higher frequency ω and longer electrodes of the MS filter 727 result in a higher resolution device. From these factors, expanding the measurement range and improving the resolution of the mass spectrometer 701 requires a high voltage and high frequency applied to the MS filter 727.

[0091] As shown in Figure 7, the AC signal output from the RF signal generation unit 723 is boosted by the oscillation unit 725, then passed through the pre-processing unit 726 and applied to the MS filter 727. Since high frequency stability is essential for the signal applied to the MS filter 727, the oscillation unit 725 uses an LC circuit that achieves a high Q value. However, in order to achieve both high voltage and high frequency with this LC circuit, it is essential to increase the drive current from the RF signal generation unit 723.

[0092] Figure 8 is a circuit diagram showing the configuration of the RF signal generation unit according to Embodiment 3. Figure 8 shows a specific example of the RF signal generation unit 723 shown in Figure 7, and an oscillation unit 725 to which the signal from the RF signal generation unit 723 is supplied.

[0093] The RF signal generation unit 723 comprises a generation unit 730 that generates RF signals and an amplification circuit. In Figure 8, the amplification circuit 101 shown in Figure 1 is used as the amplification circuit.

[0094] The configuration and operation of the amplification circuit 101 have already been described in Embodiment 1, so a detailed explanation will be omitted. The generation unit 730 generates an AC signal whose voltage changes periodically. This AC signal is input to the amplification circuit 101 as the input signal VIN. The output terminal of the amplification circuit 101 is connected to the LC circuit that constitutes the oscillation unit 725. As a result, the AC signal, which is the output signal output from the amplification circuit 101, is supplied to the LC circuit, then supplied to the pre-processing unit 726 via the LC circuit, and further supplied to the electrodes of the separation unit 712.

[0095] As can be seen from Figure 8, the first capacitor 210 and the load resistor 119 are connected in series between the first wiring L1 and the output terminal of the voltage amplification circuit 110. Therefore, the first capacitor 210 and the load resistor 119 can be considered to constitute a filter (hereinafter also referred to as the first filter). Similarly, the second capacitor 220 and the load resistor 120 can be considered to constitute a filter (hereinafter also referred to as the second filter).

[0096] In Embodiment 3, the values ​​of the first capacitor 210, the second capacitor 220, and the load resistors 119 and 120 are set so that the cutoff frequencies of the first and second filters are higher than the resonant frequency of the separation unit 712. More specifically, the values ​​of the capacitors and load resistors are set so that the cutoff frequencies of the first and second filters are higher than the resonant frequency of the MS filter 727 of the separation unit 712 (Figure 7).

[0097] This makes it possible to supply the AC signal, which has been amplified by the amplification circuit 101 and has a high drive current, to the oscillation unit 725 while suppressing an increase in size and heat generation. By making the AC signal supplied to the oscillation unit 725 a high drive current, it is possible to increase the voltage applied to the MS filter 727. In addition, waveform distortion can be suppressed in the amplification circuit 101, and since the cutoff frequencies of the first and second filters are higher than the resonant frequency of the MS filter, the output signal from the voltage amplification circuit 110 can be transmitted to the MS filter 727 without distortion.

[0098] In other words, it is possible to increase the voltage and frequency applied to the MS filter 727, thereby expanding the measurement range and improving the resolution of the mass spectrometer 701 without increasing the size of the mass spectrometer or increasing heat generation.

[0099] The amplification circuit 101 described in Embodiments 1 to 3 may be formed on a single semiconductor chip, or it may be constructed by combining multiple discrete semiconductor elements.

[0100] Although embodiments 1 to 3 used a voltage follower as an example, the invention is not limited to a voltage follower. In other words, a current amplifier circuit that amplifies current may be used instead of a voltage follower.

[0101] Although the present invention has been specifically described above based on embodiments, it goes without saying that the present invention is not limited to the above embodiments and can be modified in various ways without departing from its essence. [Explanation of Symbols]

[0102] 101, 301 Amplifier Circuit 119, 120, 121, 122 Load resistance L1 First Wiring L2 Second Wiring Q1, Q3 N-type transistors Q2, Q4 P-type transistors UVI Unit Current Source Circuit

Claims

1. A mass spectrometer equipped with an amplification circuit that outputs an output signal corresponding to an input signal, The mass spectrometer is equipped with a separation unit that allows only the ionized sample to be detected to pass through, The aforementioned amplification circuit is A first current source circuit that outputs a predetermined amount of current to the first wiring, A voltage amplification circuit for amplifying the voltage of the input signal, A first level shift circuit comprising a first resistive element and a first voltage element connected in series between the first wiring and the output of the voltage amplification circuit, which shifts the voltage of the signal output from the voltage amplification circuit, A first voltage follower connected to the first wiring and which amplifies the signal in the first wiring, A first capacitor connected in parallel with the first voltage element, Equipped with, The capacitance value of the first capacitor is set such that the cutoff frequency defined by the first resistive element and the first capacitor is higher than the resonant frequency of the isolation unit. Mass spectrometer.

2. In the mass spectrometer described in claim 1, The aforementioned amplification circuit further, A second current source circuit that outputs a predetermined amount of current to a second wiring different from the first wiring, A second level shift circuit is provided, comprising a second resistive element and a second voltage element connected in series between the second wiring and the output of the voltage amplification circuit, which shifts the voltage of the signal output from the voltage amplification circuit. A second voltage follower connected to the second wiring and which amplifies the signal in the second wiring, A second capacitor connected in parallel with the second voltage element, Equipped with, The capacitance value of the second capacitor is set such that the cutoff frequency defined by the second resistive element and the second capacitor is higher than the resonant frequency of the isolation unit. The output of the first voltage follower and the output of the second voltage follower are combined and output as the output signal. Mass spectrometer.

3. In the mass spectrometer according to Claim 2, The separation unit includes an MS filter that forms an electric field into which the sample is incident. An AC signal is supplied to the amplification circuit as the input signal, and a signal based on the output signal of the amplification circuit is supplied to the MS filter. Mass spectrometer.

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