Current sensing probe incorporating a current-to-voltage conversion circuit
First Claim
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1. A current sensing probe comprising:
- an inductive current sensing element; and
a current-to-voltage conversion circuit connected to the inductive current sensing element, the current-to-voltage conversion circuit comprising;
an operational amplifier;
a coupling capacitor disposed between the inductive current sensing element and a negative input terminal of the operational amplifier;
a first resistor coupled between the negative input terminal of the operational amplifier and an output node of the operational amplifier, the first resistor providing stability to the operational amplifier when the coupling capacitor blocks a first signal frequency that is below a threshold frequency; and
a second resistor coupled between a junction node, located between the inductive current sensing element and the coupling capacitor, and the output node of the operational amplifier, the second resistor operating in parallel with the first resistor to provide a transimpedance gain to a second signal frequency that is above the threshold frequency.
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Abstract
Generally, in accordance with the various illustrative embodiments disclosed herein, a current sensing probe includes a current-to-voltage conversion circuit that not only presents a desirable impedance into an inductive current sensing element of the current sensing probe, but also remains operationally stable over a wide range of frequencies when measuring a current flowing through a device-under-test. The wide frequency range can extend down to some low frequencies that can prove challenging to conventional current sensing probe circuits.
16 Citations
17 Claims
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1. A current sensing probe comprising:
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an inductive current sensing element; and a current-to-voltage conversion circuit connected to the inductive current sensing element, the current-to-voltage conversion circuit comprising; an operational amplifier; a coupling capacitor disposed between the inductive current sensing element and a negative input terminal of the operational amplifier; a first resistor coupled between the negative input terminal of the operational amplifier and an output node of the operational amplifier, the first resistor providing stability to the operational amplifier when the coupling capacitor blocks a first signal frequency that is below a threshold frequency; and a second resistor coupled between a junction node, located between the inductive current sensing element and the coupling capacitor, and the output node of the operational amplifier, the second resistor operating in parallel with the first resistor to provide a transimpedance gain to a second signal frequency that is above the threshold frequency. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A current sensing probe comprising:
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an inductive current sensing element; and a current-to-voltage conversion circuit connected to the inductive current sensing element, the current-to-voltage conversion circuit comprising; an operational amplifier; a coupling capacitor disposed between the inductive current sensing element and a negative input terminal of the operational amplifier; a first resistor coupled between the negative input terminal of the operational amplifier and an output node of the operational amplifier, the first resistor providing stability to the operational amplifier when no current is coupled into the inductive current sensing element; and a second resistor connected at one end between the inductive current sensing element and coupling capacitor, and coupled to the output node of the operational amplifier, the second resistor operating in parallel with the first resistor when impedance presented by the coupling capacitor is low in response to an AC current having a signal frequency above a threshold frequency being coupled into the inductive current sensing element. - View Dependent Claims (11)
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12. A current sensing probe comprising:
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an inductive current sensing element; and a current-to-voltage conversion circuit connected to the inductive current sensing element, the current-to-voltage conversion circuit comprising; an operational amplifier; and a current buffer circuit disposed between the inductive current sensing element and an input terminal of the operational amplifier, the current buffer circuit configured to couple into the operational amplifier an AC current sensed by the inductive current sensing element, the current buffer circuit comprising; a transistor arranged in a common-base configuration, wherein an emitter of the transistor is AC-coupled to the inductive current sensing element and a collector of the transistor is connected to the input terminal of the operational amplifier; a biasing resistor, connected between the emitter of the transistor and a negative biasing voltage, configured to provide a bias that places the transistor in a linear mode of operation; and a resistor connected between the base of the transistor and ground. - View Dependent Claims (13, 14, 15, 16, 17)
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Specification