Compensation circuit for offset voltage in a measurement amplifier and/or for DC-signal component in a measurement signal

Patent metadata

Field	Value
Publication number	US-9667233-B2
Application number	US-201615059295-A
Country	US
Kind code	B2
Filing date	Mar 2, 2016
Priority date	Mar 2, 2015
Publication date	May 30, 2017
Grant date	May 30, 2017

Abstract

A circuit for the compensation of an offset voltage in a measurement amplifier and/or of a DC-signal component contained in a measurement signal is provided. The circuit comprises a measurement-signal terminal for the measurement signal. The non-inverting input of the measurement amplifier serves for the feeding in of an AC-signal component of the measurement signal via a first capacitor. Additionally, the circuit contains a second amplifier for the addition of the DC-signal component in the measurement signal and of a signal corresponding to the negative offset voltage and to the negative DC-signal component, and a unit arranged at the input end or output end of the measurement amplifier for subtraction of an output signal of the second amplifier from the AC-signal component of the measurement signal.

First claim

What is claimed is:

1. A device for compensation of one or more of an offset voltage of a measurement amplifier and a DC-signal component of a measurement signal input to the measurement amplifier, the device comprising:
a signal terminal configured to receive the measurement signal;
a second amplifier configured to add the DC-signal component of the measurement signal with a signal corresponding to a negative offset voltage and to a negative of the DC-signal component; and
a subtractor device, arranged at one of an input terminal or an output terminal of the measurement amplifier, configured to subtract an output signal of the second amplifier from an AC-signal component of the measurement signal; and
wherein the measurement amplifier is configured to receive the AC-signal component of the input measurement signal at a non-inverting input terminal.

2. The device according to claim 1 , wherein the AC-signal component of the measurement signal is supplied via a first capacitor of a respective capacitance arranged between the signal terminal and the non-inverting input terminal of the measurement amplifier, and wherein a bandwidth of the second amplifier corresponds to a threshold frequency resulting from the respective capacitance of the first capacitor and an input impedance of the measurement amplifier.

3. The device according to claim 1 , wherein the signal corresponding to the negative offset voltage and to the negative of the DC-signal component is generated via a voltage source having a voltage level that is adjustable.

4. The device according to claim 3 , wherein the voltage source is arranged with a first terminal connected via a first resistor to an inverting input terminal of the second amplifier, and with a second terminal connected to ground.

5. The device according to claim 4 , wherein the voltage level of the voltage source is at a higher potential at the second terminal relative to the first terminal.

6. The device according to claim 1 , wherein the signal corresponding to the negative offset voltage and to the negative of the DC-signal component is generated via a current source having a current level that is adjustable.

7. The device according to claim 6 , wherein the current source is arranged with a first terminal connected to an inverting input terminal of the second amplifier, and with a second terminal connected to ground.

8. The device according to claim 7 , wherein the current source is configured to generate a current that flows in a direction towards the second terminal connected to ground.

9. The device according to claim 1 , wherein the DC-signal component of the measurement signal is connected via a second resistor to an inverting input terminal of the second amplifier.

10. The device according to claim 1 , wherein the non-inverting input terminal of the measurement amplifier is connected to ground via a third resistor, which corresponds to the desired input impedance of the measurement amplifier.

11. The device according to claim 1 , wherein the subtractor device is integrated in the measurement amplifier in that an output terminal of the second amplifier is connected to an inverting input terminal of the measurement amplifier.

12. The device according to claim 1 , wherein the subtractor device is a first subtraction circuit, which is arranged whereby an output terminal of the measurement amplifier is connected via a first analog-to-digital (A/D) converter to a non-inverting input terminal of the first subtraction circuit, and an output terminal of the second amplifier is connected via a second analog-to-digital (A/D) converter to an inverting input terminal of the first subtraction circuit.

13. The device according to claim 12 , wherein an accuracy of the second A/D converter is higher relative to an accuracy of the first A/D converter.

14. The device according to claim 12 , wherein a circuit configured to remove an average value from an output signal of the first A/D converter is connected between the first A/D converter and the first subtraction circuit.

15. The device according to claim 14 , wherein the circuit configured to remove an average value from the output signal of the first A/D converter comprises a digital averaging filter and a second subtraction circuit.

16. The device according to claim 12 , wherein an inverting input terminal of the measurement amplifier is connected to ground.

17. A measuring device comprising at least one input terminal, wherein each input terminal is connected to a signal terminal of a measurement circuit configured to compensate for one or more of an offset voltage of a measurement amplifier and a DC-signal component of a measurement signal input to the measurement amplifier, wherein the measurement circuit comprises:
a second amplifier configured to add the DC-signal component of the measurement signal with a signal corresponding to a negative offset voltage and to a negative of the DC-signal component; and
a device, arranged at one of an input terminal or an output terminal of the measurement amplifier, configured to subtract an output signal of the second amplifier from an AC-signal component of the measurement signal; and
wherein the measurement amplifier is configured to receive the AC-signal component of the input measurement signal at a non-inverting input terminal.

18. A measurement sensor comprising a measurement probe, wherein the measurement probe is connected to a signal terminal of a measurement circuit configured to compensate for one or more of an offset voltage of a measurement amplifier and a DC-signal component of a measurement signal input to the measurement amplifier, wherein the measurement circuit comprises:
a second amplifier configured to add the DC-signal component of the measurement signal with a signal corresponding to a negative offset voltage and to a negative of the DC-signal component; and
a device, arranged at one of an input terminal or an output terminal of the measurement amplifier, configured to subtract an output signal of the second amplifier from an AC-signal component of the measurement signal; and
wherein the measurement amplifier is configured to receive the AC-signal component of the input measurement signal at a non-inverting input terminal.

Assignees

• Rohde & Schwarz

Inventors

• Peschke Martin

Classifications

• H03F2203/45138

  Two or more differential amplifiers in IC-block form are combined, e.g. measuring amplifiers · CPC title

• H03F2200/411

  the output amplifying stage of an amplifier comprising two power stages · CPC title

• H03F2200/375

  Circuitry to compensate the offset being present in an amplifier · CPC title

• H03F3/45968

  by offset reduction · CPC title

• H03K5/003 Primary

  Changing the DC level (reinsertion of DC component of a television signal H04N5/16) · CPC title