High voltage amplifier and mass spectrometry device comprising same
The high-voltage amplifier circuit stabilizes operation and improves switching speed by integrating an open-loop gain control circuit, addressing the instability and speed limitations of conventional designs, thereby enhancing mass spectrometer performance.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- HITACHI HIGH TECH CORP
- Filing Date
- 2025-07-01
- Publication Date
- 2026-07-02
Smart Images
Figure JP2025023682_02072026_PF_FP_ABST
Abstract
Description
High-voltage amplifier and mass spectrometer equipped with the same
[0001] The present invention relates to a high-voltage amplifier and a mass spectrometer equipped with the same.
[0002] Research is underway to apply a mass spectrometer, which is mainly used for identifying a measurement target substance based on the mass-to-charge ratio, to clinical examination applications. When using a mass spectrometer as a medical device, high throughput performance capable of processing a huge number of specimens is also emphasized.
[0003] In a mass spectrometer, a high voltage is applied to an ion generator called an ion source when ionizing a specimen, and to a mass analysis unit composed of multipole electrodes, etc. A high-voltage amplifier circuit that supplies a high voltage generally employs a multi-stage amplifier circuit, but the circuit operation may become unstable due to the multi-stage configuration. Therefore, in a conventional high-voltage amplifier circuit as described in Patent Document 1, a feedback circuit is provided to ensure circuit stability.
[0004] Japanese Patent Application Laid-Open No. 2007-96364
[0005] In a conventional high-voltage amplifier circuit, the circuit operation is stabilized by providing a feedback circuit, but in exchange for the stabilization, the response characteristics due to the feedback circuit may deteriorate, and there may be a delay in the operation speed of the circuit. On the other hand, in a mass spectrometer, a high voltage is applied to an ion generator called an ion source when ionizing a specimen, and to a mass analysis unit composed of multipole electrodes, etc. In that case, it is necessary to switch the high voltages of positive and negative polarities quickly and accurately according to the ionization voltage and polarity optimal for each component in the specimen, and a conventional high-voltage amplifier circuit provided with a feedback circuit is unsuitable (insufficient) for a mass spectrometer.
[0006] An object of the present invention is to provide a high-voltage amplifier that operates stably at high speed and a mass spectrometer equipped with the same.
[0007] The outline of typical ones among the inventions disclosed in the present application will be briefly described as follows.
[0008] A high-voltage amplifier comprising: an error amplification circuit that outputs a control signal based on an input signal and a feedback signal; a voltage conversion circuit that adjusts the potential of the control signal output from the error amplification circuit; a multi-stage transistor output circuit that outputs a supply high voltage based on the output of the voltage conversion circuit; a feedback circuit that outputs a feedback signal to be input to the error amplification circuit based on the supply high voltage; and an open-loop gain control circuit having a plurality of resistive elements and a capacitive element connected in parallel with at least one of the plurality of resistive elements to add poles and zeros to the open-loop gain, which generates a gain control signal that controls the voltage conversion circuit based on the supply high voltage output from the multi-stage transistor output circuit; and a mass spectrometer equipped therewith.
[0009] According to the present invention, it is possible to provide a high-voltage amplifier that operates stably at high speed, and a mass spectrometer equipped with the same.
[0010] Figure 56A shows the overall circuit block of the high-voltage amplifier circuit according to the embodiment. Figure 56A shows another example of the overall circuit block of the high-voltage amplifier circuit according to the embodiment. Figure 56A shows a diagram illustrating a conventional circuit with a phase compensation circuit added to the feedback circuit. Figure 56A shows a diagram illustrating the gain design specifications of the high-voltage amplifier circuit according to the embodiment. Figure 6A shows a diagram illustrating that conventional high-voltage designs cannot handle high speeds. Figure 700 shows a diagram illustrating an embodiment in which a voltage divider resistor Ro2 is added between Ro1 and Rg of the open-loop gain control circuit of the high-voltage amplifier circuit. Figure 800 shows a diagram illustrating that the noise level increase can be suppressed in the high-voltage amplifier circuit according to the embodiment. Figure 900 shows a diagram illustrating an embodiment in which an inductive load is driven using two high-voltage amplifier circuits. Figure 56A shows a diagram illustrating the details of the high-voltage amplifier circuit of the present invention applied to a mass spectrometer. Figure 900 shows a diagram illustrating that as Δm increases, the rise time of the ion signal slows down and the measurement sensitivity decreases. Figure 1000 shows a diagram illustrating that by using the high-voltage amplifier circuit of this embodiment, high-speed measurement is possible without causing a decrease in measurement sensitivity. Figure 1000 shows a diagram illustrating the overshoot seen in conventional high-voltage amplifier circuits.
[0011] Embodiments of the present invention will now be described. Note that the embodiments described below are merely examples for realizing the present invention and do not limit the technical scope of the present invention. Problems, configurations, and effects other than those described above will be clarified by the following descriptions of the embodiments.
[0012] Furthermore, in the following embodiments, components having the same function are denoted by the same reference numerals, and repeated descriptions thereof are omitted unless particularly necessary.
[0013] Figure 1A shows the overall circuit block of the high-voltage amplification circuit (referred to as "high-voltage amplifier" when referring to the device) according to this embodiment. The high-voltage amplification circuit 1 of this embodiment consists of an error amplification circuit 2 (also referred to as "error amplifier") which compares the input signal with the feedback signal output from the feedback circuit 5 described later and outputs an error amplification signal, and a high-voltage circuit 7 which receives the error amplification signal from the error amplification circuit 2. The error amplification signal from the error amplification circuit 2 is input to a multi-stage voltage conversion circuit 3 (also simply referred to as "voltage conversion circuit") which adjusts the potential to a level that the subsequent multi-stage transistor output circuit 4 can handle and outputs it as a control signal.
[0014] The error amplification circuit 2 receives a low voltage of less than 300V, for example, a low voltage current of 5 to 12V, while the high-voltage amplification circuit 1 receives a high voltage of 300V or more, for example, a high voltage on the order of kV, which is applied to the multi-pole electrodes of the mass spectrometer (Figure 7) described later. If the high voltage of the high-voltage circuit 7 is applied to the error amplification circuit 2 due to some malfunction, there is a high possibility that the error amplification circuit 2 will be destroyed. To prevent this, the high-voltage amplifier may be configured with the high-voltage circuit 7 and the low-voltage circuit 8 on separate printed circuit boards (PCB boards).
[0015] Another example in which the high-voltage circuit 7 and the low-voltage circuit 8 are provided on separate printed circuit boards will be explained using Figure 1B. The feedback circuit 5 takes the supply high voltage as input and converts it into a low voltage output to the error amplification circuit 2 within the feedback circuit 5. In other words, even the same feedback circuit 5 can be divided into a high-voltage circuit and a low-voltage circuit. Therefore, as shown in Figure 1B, the high-voltage portion of the feedback circuit 5 may be provided on the high-voltage circuit 7 (which can be called a "high-voltage circuit board" as an item), and the low-voltage portion may be provided on the low-voltage circuit 8 (which can be called a "low-voltage circuit board" as an item), and they may be connected by electrical wiring.
[0016] Furthermore, in the multi-stage voltage conversion circuit 3, to prevent interference between the circuit that processes the signal (low voltage signal) from the error amplification circuit 2 and the control signal output to the subsequent multi-stage transistor output circuit 4, the circuit that processes the low voltage signal from the error amplification circuit 2 may be provided in the low-voltage circuit 8, and the circuit that generates the control signal output to the multi-stage transistor output circuit 4 may be provided in the high-voltage circuit 7. Similarly, in the open-loop gain control circuit 6, the circuit that generates the low voltage signal output to the multi-stage voltage conversion circuit may be provided in the low-voltage circuit 8, and the circuit that receives the supply high voltage as input may be provided in the high-voltage circuit 7.
[0017] Of course, if there is a limited space for installing the printed circuit board, it is possible to place all the circuits on a single printed circuit board by devising a circuit wiring arrangement that separates the high-voltage circuit 7 and the low-voltage circuit 8.
[0018] The multi-stage transistor output circuit 4 is a circuit block that outputs a supply high voltage based on the control signal which is the output of the multi-stage voltage conversion circuit.
[0019] The feedback circuit 5 is a circuit that outputs a feedback signal based on the supply high voltage, and also controls the overall gain of the high-voltage amplifier circuit 1.
[0020] The open-loop gain control circuit 6 is a core and important circuit block of the present invention. It generates an open-loop control signal based on the supply high voltage and a gain control signal to be input to the multi-stage voltage conversion circuit 3.
[0021] The open-loop gain control circuit 6 includes resistive elements Ro1 and Rg. As shown in Figure 1, the supply high voltage is divided by Ro1 and Rg to generate the open-loop gain control signal.
[0022] Furthermore, to add phase compensation characteristics to the open-loop gain control, capacitor Co1 is connected in parallel with Ro1 to create a circuit with phase characteristics that have poles and zeros. Note that there does not need to be one element each for Ro1, Co1, and Rg; equivalent functions can be achieved by combining multiple elements.
[0023] The poles and zeros generated by this open-loop gain control circuit 6 do not affect the overall gain of the high-voltage amplifier circuit 1 or the high-speed operation of the circuit directly connected to it. In other words, the addition of the open-loop gain control circuit 6 does not cause the high-voltage amplifier circuit to become slower in the desired operating bandwidth.
[0024] To explain the advantages of employing the high-voltage amplification circuit of this embodiment, we will describe them below in comparison with the disadvantages of a conventional multi-stage high-voltage amplification circuit, as shown in Figure 2.
[0025] As described in the [Background Technology] section, conventional high-voltage amplifier circuits include a feedback circuit to ensure circuit stability.
[0026] Figure 3A shows the frequency and gain characteristics of a high-voltage amplifier circuit. To stabilize the high-voltage amplifier circuit, it is desirable that the circuit gain be 0 dB or less at frequency 21, where the phase reaches 180° in the loop gain. This is because if the circuit gain is 0 dB or less at frequency 21, the circuit will be stably controlled without abnormal operation (abnormal oscillation). In Figure 3A, compared to the ideal gain characteristics shown by the solid line, a conventional high-voltage amplifier circuit with a feedback circuit as shown in Figure 2 performs phase compensation by reducing the gain as shown by the dashed line. However, with the level of gain reduction shown in "Conventional Countermeasure (1)", the gain at the frequency where the phase reaches 180° does not fall below 0 dB. Therefore, in conventional high-voltage amplifier circuits, as shown in "Conventional Countermeasure (2)" in Figure 3B, it is necessary to further reduce the circuit gain so that the gain at the frequency where the phase reaches 180° is 0 dB or less. However, this results in a significant decrease in the gain over the desired operating bandwidth, which has the disadvantage of leading to excessive slowdown of the circuit operation.
[0027] In contrast, by providing the open-loop gain control circuit 6 shown in Figures 1A and 1B, the circuit gain can be freely controlled near the frequency 21 where the phase reaches 180°. Therefore, as shown by the dashed line in Figure 3A, by setting the resistance values of the resistors Ro1 and Rg, and the capacitance of the capacitor Co1 connected in parallel with Ro1, the gain can be reduced sharply from outside the desired operating band 22 to near the frequency 21 where the phase reaches 180°, making it possible to reduce the gain to 0 before reaching frequency 21. In other words, by appropriately designing the open-loop gain control circuit, it is possible to achieve the gain change 23.
[0028] Furthermore, as shown in Figure 2, even when a phase compensation function is added to the error amplification circuit, the speed must be reduced in order to ensure stability, making it highly likely that it cannot handle high speeds. Moreover, in conventional circuits in which a phase compensation circuit is added to the feedback circuit, the feedback circuit is a high-voltage circuit, and the components used in the phase compensation circuit require high voltage resistance, so the usable component values are limited, and stable design can be difficult.
[0029] Example 2 of the present invention will be explained using Figure 4.
[0030] Figure 4 shows an embodiment in which a voltage divider resistor Ro2 is added between Ro1 and Rg in the open-loop gain control circuit 6 of the high-voltage amplifier circuit 1 shown in Figure 1. In the absence of Ro2, the potential of xb is equal to the potential of the xa contact.
[0031] Let's consider the case where Ro2 is absent (corresponding to the configurations in Figures 1A and 1B). In this case, Co1 and Rg form a differentiating circuit, so if the supply high voltage (high voltage output) changes abruptly due to the operation of the high-voltage amplifier circuit (see Figure 5(a)), spike noise may be generated at contact xa due to the differentiating circuit (see Figure 5(b)).
[0032] Depending on the design guidelines and circuit configuration of the multi-stage voltage conversion circuit 3, the overall noise of the high-voltage amplification circuit may increase due to the influence of spike noise generated at the xa contact.
[0033] Here, by adding Ro2 for voltage division between Ro1 and Rg, even if spike noise occurs at contact xa, it can be reduced by voltage division. Ultimately, since the noise level of the open-loop control signal also depends on the noise at contact xb, the reduced spike noise is transmitted (see Figure 5(c)), thus reducing the impact on the multi-stage voltage conversion circuit 3 and suppressing the rise in the overall noise level of the high-voltage amplification circuit. Note that if the allowable noise voltage level of the multi-stage voltage conversion circuit 3 is Vn, the voltage division ratio of the voltage division circuit formed by Ro1, Ro2, and Rg must be such that the voltage level of xb is ≤Vn. The same design guidelines must be observed even when Ro3 is added in Embodiment 3 described later.
[0034] Embodiment 3 of the present invention will be explained using Figures 6A and 6B.
[0035] Figure 6A shows an embodiment in which an inductive load is driven using two high-voltage amplifier circuits 1 as shown in Figures 1A and 1B. That is, it is an example in which the high-voltage amplifier circuits 1 are connected to both ends of the inductive load, driving the inductive load on both the positive and negative sides.
[0036] The positive and negative circuits operate in opposite phases and supply power to the inductive load.
[0037] In devices or applications that supply high voltage using the high-voltage amplification circuit 1, parasitic capacitance components may be generated from the medium through which the supplied high voltage is transmitted. Furthermore, depending on the circuit implementation, the parasitic capacitance components generated on the positive and negative sides may not be the same, resulting in a characteristic imbalance between the positive and negative sides.
[0038] When this characteristic imbalance occurs, the charging and discharging current of the parasitic capacitance component may cause spike noise or characteristic deviations in the high-voltage amplification circuit. To counter this, in this embodiment, as shown in Figure 6A, a damping resistor Ro3 is added between Ro1 and the supply high voltage in the open-loop gain control circuit 6. By adding Ro3 near Co1 and between Co1 and the supply high voltage, the charging and discharging current from the parasitic capacitance component is reduced, and the influence of current flowing into the open-loop gain control circuit is suppressed, thereby suppressing the occurrence of characteristic deviations and spike noise.
[0039] An embodiment 4 in which the high-voltage amplification circuit of the present invention is applied to a mass spectrometer will be described with reference to Figure 7.
[0040] The mass spectrometer of this embodiment includes an ion source 121 that ionizes the sample to be mass analyzed, an ion filter unit 126 that filters the ionized sample so that only ion molecules with the mass of the target to be analyzed are allowed to pass through, an ion control unit 128 that controls the orbits of ion molecules and causes them to collide with a conversion dynode 122 to obtain electrons, a scintillator 123 that converts the obtained electrons into photons, a photodetector (not shown) that acquires an electrical signal from the converted photons, an information processing unit 129 that calculates the mass from the obtained electrical signal, a first high-voltage amplification circuit 130 that applies voltage to the ion source 121, a second high-voltage amplification circuit 131 that applies voltage to the ion filter unit 126, a third high-voltage amplification circuit 132 that applies voltage to the conversion dynode 122, a fourth high-voltage amplification circuit 133 that applies voltage to the scintillator 123, and a mass spectrometer control unit 134 that controls the high-voltage amplification circuits.
[0041] The first to fourth high-voltage amplification circuits 130 to 133 are constituted by the high-voltage amplification circuits described in the first embodiment. The mass spectrometer control unit 134 supplies the input signal in FIG. 1A to the corresponding first to fourth high-voltage amplification circuits 130 to 133, and each high-voltage amplification circuit outputs a supply high voltage according to the supplied input signal.
[0042] The input signal is a low-voltage signal of less than 300 V, and the supply high voltage is a high voltage of 300 V or more suitable for controlling ionization and ion trajectories. Therefore, in each high-voltage amplification circuit, the maximum voltage handled by the low-voltage circuit 8 (FIG. 1) is less than 300 V, and the maximum voltage handled by the high-voltage circuit 7 (FIG. 1) is 300 V or more.
[0043] In each voltage supply source of the ion source 121, the ion filter unit 126, the conversion dynode 122, and the scintillator 123, the voltage values of the high voltages suitable for each are different. Therefore, a corresponding high-voltage amplification circuit is mounted for each voltage supply source. That is, the first high-voltage amplification circuit 130 outputs a supply high voltage according to the input signal to the ion source 121, and the second high-voltage amplification circuit 131 outputs a supply high voltage according to the input signal to the filter electrode 127 in the ion filter unit 126. Further, the third high-voltage amplification circuit 132 outputs a supply high voltage according to the input signal to the conversion dynode 122, and the fourth high-voltage amplification circuit 133 outputs a supply high voltage according to the input signal to the scintillator 123.
[0044] In FIG. 7, an example of supplying a high voltage from the high-voltage amplifier described in the first embodiment to the ion source 121, the ion filter unit 126, the conversion dynode 122, and the scintillator 123 has been described, but a high voltage may be supplied from the high-voltage amplifier described in the first embodiment to at least one of these.
[0045] When a high voltage with an equivalent voltage value may be applied to each of the ion source 121, the ion filter unit 126, the conversion dynode 122, and the scintillator 123, one common high-voltage amplifier may be mounted.
[0046] In a mass spectrometer, particularly a mass spectrometer used in medical equipment, it is necessary to measure a huge amount of specimens for different analysis items, that is, different measurement target substances. Therefore, it is necessary to quickly switch the voltage applied to the multipole electrodes of the mass analysis unit according to the mass-to-charge ratio (m / z) of each measurement target substance.
[0047] The left diagram in Fig. 8 is a diagram plotting the m / z of the ions to be measured on the vertical axis and time on the horizontal axis. When measuring different measurement target substances m1, m2, m3, and m4, particularly when switching the measurement target substance from m3 to m4, Δm becomes the largest. When Δm becomes large, as shown in the right diagram of Fig. 8, the rise of the ion signal becomes slow, and there is a risk of a decrease in measurement sensitivity. When using a conventional high-voltage amplification circuit, in order to ensure sensitivity, it is necessary to wait until the relative value of the ion amount increases to around 1, that is, it is necessary to delay the measurement start time. However, doing so has the problem of a decrease in the analysis throughput of the device.
[0048] When using the high-voltage amplification circuit according to this embodiment, the rise of the supplied high voltage becomes fast, and as shown in Fig. 9, the rise of the measured ion amount becomes fast, enabling high-speed measurement without causing a decrease in measurement sensitivity. Specifically, when starting the measurement at the measurement start time shown in the right diagram of Fig. 8 during ion analysis, while a signal loss of 20% or more occurred in the conventional technology, the signal loss in the mass spectrometer using the high-voltage amplification circuit of this embodiment could be made 10% or less.
[0049] Further, as another effect of the present invention, it is possible to improve the waveform distortion when switching the supplied high voltage. As shown in Fig. 10, when switching the supplied high voltage using a conventional high-voltage amplification circuit, an overshoot occurs. When using the high-voltage amplification circuit of this embodiment, no waveform distortion is observed, and an improvement in the voltage switching speed (the time t1 until the output voltage reaches half of the predetermined voltage is reduced by 20%) and a shortening of the time until voltage stabilization (the time t2 until the output voltage stabilizes at the predetermined voltage is reduced by 50%) can be realized.
[0050] The high-voltage power supply module installed in the mass spectrometer of this embodiment includes at least one high-voltage amplification circuit as described in Figures 1 to 5. This enables the supply of high-speed high voltage to various parts of a medical mass spectrometer where throughput is important, thereby providing a mass spectrometer capable of high-speed analysis. Furthermore, the detection sensitivity of a mass spectrometer is greatly influenced by the amount of noise in the high-voltage amplification circuit. Therefore, by incorporating a high-voltage amplification circuit with noise reduction means as described in Figures 2 and 5, a highly sensitive mass spectrometer can be provided.
[0051] Although various embodiments of the present invention have been described above, the present invention is not limited to the embodiments described above and includes various modifications. Furthermore, the embodiments described above are described in detail for the purpose of explaining the present invention in an easy-to-understand manner and are not necessarily limited to those having all the configurations described. In addition, it is possible to replace a part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. All of these fall within the scope of the present invention. Moreover, the numerical values and names included in the text and figures are merely examples, and using different ones will not impair the effects of the present invention.
[0052] Furthermore, it is possible to add, delete, or replace some of the configurations in each embodiment with other configurations. In addition, some or all of the above configurations, functions, circuits, etc., may be realized by designing them, for example, as integrated circuits or programmable semiconductor chips.
[0053] 1: High-voltage amplifier circuit 2: Error amplifier circuit 3: Multi-stage voltage conversion circuit 4: Multi-stage transistor output circuit 5: Feedback circuit 6: Open-loop gain control circuit 7: High-voltage circuit 21: Frequency 22: Operating bandwidth 23: Gain change 121: Ion source 122: Conversion dynode 123: Scintillator 126: Ion filter section 128: Ion control section 129: Information processing unit 130: First high-voltage power supply module 131: Second high-voltage power supply module 132: Third high-voltage power supply module 133: Fourth high-voltage power supply module 134: Mass spectrometer control unit
Claims
1. A high-voltage amplifier comprising: an error amplification circuit that outputs a control signal based on an input signal and a feedback signal; a voltage conversion circuit that adjusts the potential of the control signal output from the error amplification circuit; a multi-stage transistor output circuit that outputs a supply high voltage based on the output of the voltage conversion circuit; a feedback circuit that outputs the feedback signal to be input to the error amplification circuit based on the supply high voltage; and an open-loop gain control circuit that has a plurality of resistive elements and a capacitive element connected in parallel with at least one of the plurality of resistive elements and that imparts a phase characteristic having poles and zeros to the open-loop gain, and generates a gain control signal that controls the voltage conversion circuit based on the supply high voltage output from the multi-stage transistor output circuit.
2. A high-voltage amplifier according to claim 1, characterized in that the open-loop gain control circuit is configured such that the gain is sharply reduced from outside the desired operating band to near the frequency where the phase is 180°, and the resistance values of the plurality of resistive elements and the capacitance of the capacitive elements are determined so that the gain becomes 0 or less before reaching the aforementioned frequency.
3. A high-voltage amplifier according to claim 1, characterized in that the supply high voltage is 300V or more.
4. A high-voltage amplifier according to claim 1, characterized in that a high-voltage circuit operating at a high voltage of 300V or more and a low-voltage circuit operating at a low voltage of less than 300V are provided in different areas on the same printed circuit board, or are provided on separate printed circuit boards.
5. A high-voltage amplifier according to claim 4, wherein the high-voltage circuit includes the multi-stage transistor output circuit, a part of the voltage conversion circuit, and a part of the open-loop gain control circuit, and the low-voltage circuit includes the error amplification circuit, a part of the voltage conversion circuit, and a part of the open-loop gain control circuit.
6. The high-voltage amplifier according to claim 1, characterized in that, among the resistive elements of the open-loop gain control circuit, a resistive element Ro2 is provided between the feedback resistive element Ro1 that determines the open-loop gain and the ground resistive element Rg, for dividing and reducing the noise signal.
7. A high-voltage amplifier comprising two high-voltage amplifiers as described in claim 1, wherein each high-voltage amplifier is configured to drive the same inductive load with an inverse phase voltage, and a damping resistor Ro3 is provided between the output terminal of the supply high voltage output from each of the two high-voltage amplifiers and the feedback resistor Ro1 of the open-loop gain control circuit.
8. A mass spectrometer comprising an ion source for ionizing a sample, an ion filter for filtering ions, and a detector for detecting ions, wherein the high-voltage amplifier that supplies a high voltage to at least one of the ion source, the ion filter, and the detector includes an error amplification circuit that outputs a control signal based on an input signal and a feedback signal, a voltage conversion circuit that adjusts the potential of the control signal output from the error amplification circuit, a multi-stage transistor output circuit that outputs a supply high voltage based on the output of the voltage conversion circuit, a feedback circuit that outputs the feedback signal to be input to the error amplification circuit based on the supply high voltage, and an open-loop gain control circuit that has a plurality of resistive elements and a capacitive element connected in parallel with at least one of the plurality of resistive elements and that imparts a phase characteristic having poles and zeros to the open-loop gain, and generates a gain control signal that controls the voltage conversion circuit based on the supply high voltage output from the multi-stage transistor output circuit.
9. A mass spectrometer according to claim 8, wherein the mass spectrometer comprises a high-voltage amplifier corresponding to the ion source, the ion filter, and the detector, respectively.
10. A mass spectrometer according to claim 8, characterized in that the high-voltage amplifier has at least two substrates: a high-voltage circuit board having a maximum voltage of 300V or more and a low-voltage circuit board having a maximum voltage of less than 300V.