JPH02173574A - Current detector - Google Patents

Abstract

PURPOSE:To detect and amplify a minute signal current which is an original signal, without a frequency separation, by providing a circuit shifting a high voltage level down to a low voltage level near the earth voltage and a transmission circuit. CONSTITUTION:When an electron is incident to an MCP (microchannel plate) 1, the signal i0 is made to flow to the anode A and to be a signal current i1 of the collector current for an FET Q1. Most collector current fro the FET Q1 is made to be an emitter current for an FET Q2. The emitter current for an FET Q3 is approximately expressed as I3 = I2X(R2/R1), i3 = i2X(R2/R1). The emitter current for the FET Q3 is almost equal to its collector current which is made to be the emitter current for an FET Q4. The emitter current for the FET Q4 is almost equal to its collector current which is made to be the emitter current for an FET Q5. The high voltage of a power supply EB is divided by resistors R6, R7 after the voltage is somewhat decreased by a zener diode D1. As the result, a current which is almost equal to a signal current I5 in the low voltage level is made to flow into the terminal of a resistor R4. An output signal voltage VO is made to be VO = -i5XR5 accordingly.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is applicable to microelectronic devices at high voltage levels, such as the output of continuous dynode electron multiplier tubes (channeltrons) and microchannel plates (hereinafter abbreviated as MCP). The present invention relates to a current detection device that amplifies a current signal.

[Conventional technology]

As a conventional device of this kind, the Japanese Patent Publication No. 62-22114
There is an electron beam detection device described in the above publication.

In a device using a continuous dynode electron multiplier having an AC coupling detection means for detecting a signal by AC coupling from a high potential end that collects multiplied electrons, the continuous dynode electron multiplier is DC coupling detection means for detecting a signal by DC coupling from the low potential side end where signal electrons are incident; means for adding the outputs of the DC coupling detection means and the AC coupling detection means; and a signal from the re-detection means. This is an electron beam detection device characterized by being provided with a filter circuit for flattening the frequency characteristics of the circuit until addition.

[Problem that the invention seeks to solve]

In the conventional technology described above, a filter circuit for band adjustment is required in order to flatten the frequency characteristics of signal amplification from DC to high frequency bands, and the characteristics of the filter circuit must be adjusted for each device. The problem is that it is complicated, and even if the filter is adjusted, it is difficult to obtain a straightforward frequency response.

The present invention has been made in view of these conventional problems, and makes it possible to detect and amplify the minute signal current, which is the original signal, without dividing it into a low frequency region and a high frequency region. The aim is to obtain completely flat frequency characteristics up to high frequency bands.

[Means for solving problems]

In order to solve the above problems, the present invention uses a high-speed, high-voltage transistor in a current detection device that detects a minute signal current at a high voltage level, such as the output signal of a continuous dynode electron multiplier tube or MCP. a transmission circuit for forming a shift-down circuit for shifting a high voltage level to a low voltage level in the vicinity of the ground voltage, and for causing a current corresponding to the minute signal current to flow into the shift-down circuit. shall be.

[For production]

In the present invention, since it is possible to detect and amplify a small signal current at a high voltage level, which is the original signal, without separating it into a low frequency band and a high frequency band as in the conventional case, it is possible to easily obtain flat frequency characteristics from direct current to high frequency band. be able to.

(Embodiment) The figure is a circuit diagram showing an embodiment of the present invention, in which the emitter of a transistor Q and the collector of a transistor Q are connected to an anode A of the MCPI.

Transistor Q is a transistor for passing a bias current, and its emitter is connected to a constant current source 2 (DC current: 8°) for supplying the bias current.

The base of the transistor Q1 is connected to the power supply Ea (for example +IK
It is connected to the connection point between the Zener diode D+ and the resistor Rh of a series connection circuit consisting of the Zener diode DI and the resistors R, , R, connected between the Zener diode D+ and the common terminal (ground).

This Zener diode D is for applying a bias voltage to a current mirror circuit to be described later.

The collector of transistor Q is connected to the collector and base of transistor Q and to the base of transistor Q, respectively.

The thick transmitter of transistor Q2 is connected to power supply E via resistor R.
The emitters of transistor Q and transistor Q are connected to a power source E6 via a resistor R2.

The collector of transistor Q is connected to the emitter of transistor Q4 via resistor R1, and the base of transistor Q4 is connected to Zener diode D.

and the connection point between the resistor R4 and the resistor R4. Here, transistors Qz, Qs, resistors R,, R,, R.

constitutes a current mirror circuit, and approximately (Q,
Emitter current) - (Q, emitter current) x (Rt/R+) can be made to hold.

The collector of transistor Q4 is connected to the emitter of transistor Q5, and the base of transistor Q5 is connected to resistor R1.
and the connection point between the resistor R1 and the resistor R1.

The collector of the transistor Q is connected to the inverting input terminal of the operational amplifier ICI via a resistor R4, and is also connected to a constant current source 3 (DC current 2, .) for supplying bias current. The non-inverting input terminal of the operational amplifier ICI is connected to a common terminal, and the inverting input terminal is connected to a resistor R1 as a feedback resistor.

Because of this configuration, the anode A of MCPI is
The potential is maintained at a high potential obtained by subtracting the voltage drop between the base and emitter of the Zener diode D, . Therefore, when electrons are incident on the MCPI, they collide with the side wall and generate secondary electrons, reaching the anode A, and the anode A receives a signal current of 10
flows. The minute signal current 1. outputted from MCPI in this way. becomes the signal current 11 of the collector current (Il+il) of the common base transistor Q1. (Approximately 1t-1t., i, -i.).

The collector current of transistor Q (+, +i.

) are mostly transistors Q! emitter current (1*
+i,), (approximately 1.=1.,i,=i,)
.

Then, as a current mirror effect, transistor Q
, the emitter current (13+j,) is approximately 13-1.
x (R□/R8), i, +mi! ×(Rg/R1)
That is, by appropriately selecting the values of the resistors R, , RgO, the signal current can be amplified to an appropriate magnification.

The emitter current (Is+i*) of the transistor Q3 is approximately equal to its collector current, which becomes the emitter current ([, ++4) of the common-base transistor Q.

The emitter current (14+ia) of the transistor Q4 is approximately equal to its collector current, which becomes the emitter current (1,+i,) of the common base transistor Qs.

Following, approximately ls −1m −Is , Is −+
4-1. becomes.

By the way, the high voltage of the electric current fIXE* is slightly reduced by the Zener diode D1, and then divided by the resistors R6, R,1. Therefore, in this embodiment, R and -R7 are used, transistors Q, and Q are high-speed transistors that have a high withstand voltage of about 600 mm and respond to high frequencies, and have a constant DC current of 'a3! ,. By setting almost equal to the bias current I flowing through the transistor Q, the collector voltage of the transistor Q is reduced to approximately the voltage of the common terminal (earth voltage).

the result,. At the terminal of the resistor R4 connected to the collector of the transistor Q, there is a signal current ■, which is at a low voltage level.
A current approximately equal to that flows in. Therefore, the resistance R,, Rs
, the output signal voltage VO of the current-voltage conversion circuit constituted by the operational amplifier ICI becomes VO--isxRs.

In this way, the small signal current I0 at a high voltage level, which is the output of the MCPI, is converted into the small signal current i5 at a low potential without frequency separation, so the gain is flat from DC to high frequency band. A circuit with these characteristics can be easily obtained.

Further, in the above embodiment, while shifting the voltage level of the minute signal current I0 at the high voltage level to near the ground voltage, the current mirror circuits (Qz, Qs, Ri,
Rt-R1), which is extremely efficient.

Of course, in the above embodiment, two high-speed, high-voltage transistors Q, Q, and Qs are used, but the number of these transistors may be one or three or more.
This is determined by circuit design considerations, such as the voltage value of It can be replaced with another structure in which the signal flows into a high-speed, high-voltage transistor serving as a shift-down circuit that shifts the level down to near the ground level.

〔Effect of the invention〕

As described above, according to the present invention, since the signal current is detected without frequency separation, there is an advantage that the frequency characteristic can easily be flat from the direct current to the high frequency band.

[Brief explanation of the drawing]

The figure is a circuit diagram of an embodiment of the present invention. [Explanation of symbols of main parts] 1...MCP. Q□%Q! ...High speed transistor, Ri, Rz, Rs...Resistor, Q, , Qs...High speed high voltage transistor, 10...
- Signal current at high voltage level, i, . . . signal current shifted down to low voltage level.

Claims (1)

[Claims] In a current detection device that detects a minute signal current at a high voltage level, a shift-down circuit for shifting the high voltage level to a low voltage level near the ground voltage is formed using a high-speed, high-voltage transistor, and the minute signal current is A current detection device comprising a transmission circuit that causes a current corresponding to the current to flow into the shift down circuit.