CURRENT MEASUREMENT CIRCUIT

• US 20160154032A1
• Filed: 10/28/2015
• Published: 06/02/2016
• Est. Priority Date: 11/28/2014
• Status: Active Grant

• Current Assignee: Advantest Corporation
• Original Assignee: Advantest Corporation
• Inventors: Kuramochi, Yasuhide
• Granted Patent: US 9,869,702 B2
• Time in Patent Office: Days
• CPC Class Codes: B82Y 15/00 Nanotechnology for interacting, sensing or actuating, e.g. quantum dots as markers in protein assays or molecular motors
• CPC Class Codes: C12Q 1/6869 Methods for sequencing
• CPC Class Codes: G01N 33/48721 Investigating individual macromolecules, e.g. by translocation through nanopores Coulter counters in general G01N15/12; fabrication methods for nanoscale apertures B81B1/00; sequencing of nucleic acids C12Q1/68
• CPC Class Codes: G01R 19/0023 Measuring currents or voltages from sources with high internal resistance by means of measuring circuits with high input impedance, e.g. OP-amplifiers electrostatic instruments G01R5/28; measuring electrostatic potential G01R15/165; measuring electrostatic fields G01R29/12; amplifiers per se H03F
• CPC Class Codes: G01R 19/0092 measuring current only all subgroups of G01R19/00 take precedence
• CPC Class Codes: G05F 1/561 Voltage to current converters amplifiers H03F
• CPC Class Codes: H03F 1/34 Negative-feedback-circuit arrangements with or without positive feedback H03F1/02 - H03F1/30, H03F1/38 - H03F1/50, H03F3/50 take precedence ; for rejection of common mode signals H03F3/45479
• CPC Class Codes: H03F 2200/261 Amplifier which being suitable for instrumentation applications
• CPC Class Codes: H03F 2200/462 the current being sensed
• CPC Class Codes: H03F 2203/45138 Two or more differential amplifiers in IC-block form are combined, e.g. measuring amplifiers
• CPC Class Codes: H03F 2203/45156 At least one capacitor being added at the input of a dif amp
• CPC Class Codes: H03F 3/45475 using IC blocks as the active amplifying circuit

Abstract

A current measurement circuit converts a current signal I_IN into a voltage signal V_OUT. The current signal I_IN is transmitted via a signal line. A shield line is arranged in the vicinity of at least a part of the signal line. A non-inverting amplifier includes an operational amplifier, and the current signal I_IN is input to its non-inverting input terminal. The output signal of the non-inverting amplifier is input to its inverting input terminal as a feedback signal. An inverting amplifier amplifies the output signal of the non-inverting amplifier with inversion so as to generate a voltage signal V_OUT. An impedance circuit includes a feedback resistor R_F between the output terminal of the inverting amplifier and the non-inverting input terminal of the operational amplifier. A guard amplifier receives the electric potential at the inverting input terminal of the operational amplifier, and applies the electric potential to the shield line.

Claims

1. A current measurement circuit that converts a current signal into a voltage signal, the current measurement circuit comprising:

a signal line via which the current signal is transmitted;

a shield line arranged in the vicinity of at least a part of the signal line;

a non-inverting amplifier comprising an operational amplifier having its non-inverting input terminal supplied with the current signal the signal line and its inverting input terminal supplied with its output signal as a feedback signal;

an inverting amplifier that amplifies the output signal of the non-inverting amplifier with inversion so as to generate the voltage signal;

an impedance circuit comprising a feedback resistor arranged between an output terminal of the inverting amplifier and the non-inverting input terminal of the operational amplifier; and

a guard amplifier that receives an electric potential at the inverting input terminal of the operational amplifier, and that applies the electric potential to the shield line.

2. The current measurement circuit according to claim 1, further comprising a correction amplifier that corrects frequency characteristics of an output signal of the inverting amplifier.

3. The current measurement circuit according to claim 1, further comprising a shield that covers at least a part of the feedback resistor,

wherein an output of the guard amplifier is connected to the shield.

4. The current measurement circuit according to claim 3, wherein the shield covers one electrode, which is arranged on an input terminal side of the non-inverting amplifier, of the feedback resistor having two electrodes.

5. The current measurement circuit according to claim 1, further comprising a protection element arranged between the signal line and the shield line.

6. The current measurement circuit according to claim 1, wherein the signal line and the shield line are configured as a cable having a hollow coaxial cable structure or otherwise a low-capacitance coaxial cable structure.

7. The current measurement circuit according to claim 1, wherein the current measurement circuit is integrated on a semiconductor substrate together with a part of a device under test that generates the current signal,

and wherein the signal line and the shield line are formed on the semiconductor substrate.

8. The current measurement circuit according to claim 1, wherein the impedance circuit further comprises a feedback capacitor arranged in parallel with the feedback resistor between an output terminal of the inverting amplifier and the non-inverting input terminal of the non-inverting amplifier.

9. A base sequence analyzing apparatus comprising:

an electrode pair;

a position control apparatus that controls a base sequence having a linear structure such that it passes through the electrode pair;

the current measurement circuit according to claim 1, that detects a current that flows between a gap of the electrode pair; and

a data processing apparatus that analyzes an output of the current measurement circuit.