Current sensing circuit
AssigneeRCA Corporation
InventorAllen LeRoy Limberg
Life of this patent
Estimating the term…
Abstract
A current mirror amplifier (CMA) and another current amplifier are connected in a degenerative current feedback loop with a point therein which point exhibits a low a-c impedance with respect to a-c ground and provides for sensing signal current applied thereto from an impedance element. The CMA has an input terminal connected to this sensing point, a common terminal connected to a-c ground and an output terminal connected to a constant current source load. The other current amplifier has input and common terminals connected to the CMA output terminal and to the sensing point, respectively, and has an output terminal from which sensed signal current is available.
Claims8
In a current sensing circuit for sensing the flow of current through one of the terminals of an impedance, which circuit includes
- first and second terminals between which an operating potential may be applied;
- means for establishing a current through said impedance;
- a current mirror amplifier having input, output and common terminals, said common terminal being connected to said first terminal and said input terminal being connected to said one terminal of said impedance;
- amplifier means having input, output and common terminals, said amplifier means common terminal connected to said one terminal of said impedance;
- a constant current source for supplying a direct current, said source connected between said second terminal and an interconnection between the output terminal of said current mirror amplifier and the input terminal of said amplifier means;
- and
- load means including a direct current path connected between said second terminal and said amplifier means output terminal:
- an improvement for lowering the input impedance of said current sensing circuit without need for increasing the current through said load means comprising said current mirror amplifier exhibiting a current gain as between its input and output terminals that is substantially greater than unity.
A circuit for sensing the current in an impedance element without applying a potential thereacross which would in accordance with Ohm's Law give rise to spurious current flow therethrough, said circuit comprising, in combination:
- first and second terminals for connection to reference and operating potentials, respectively;
- third and fourth terminals between which said element is connected;
- a first current mirror amplifier having input, output and common terminals, said common terminal thereof being connected to said first terminal and said input terminal thereof being connected to said third terminal;
- first amplifier means having input, output and common terminals, said common terminal thereof being connected to said third terminal;
- a first constant current source for supplying a direct current, said source connected between said second terminal and an interconnection between the output terminal of said first current mirror amplifier and the input terminal of said first amplifier means;
- a direct current path between said second terminal and said first amplifier means output terminal;
- a second current mirror amplifier having input, output and common terminals, said second current mirror amplifier having its common terminal connected to said first terminal and its input terminal connected to said fourth terminal
- second amplifier means having input, output and common terminals, said second amplifier common terminal connected to said fourth terminal
- a second constant current source for supplying a direct current, said source connected between said second terminal and an interconnection between the output terminal of said second current mirror amplifier and the input terminal of said second amplifier means;
- and
- a direct current path between said second terminal and said second amplifier means output terminal;
- and
- load means being included in at least one of said direct current paths.
A circuit for establishing a low impedance between the respective ends of an impedance element and a point at a reference potential comprising, in combination:
- first and second current mirror amplifiers, each amplifier having input, output and common terminals, said common terminals connected to said point at a reference potential and said input terminals each connected to a respective end of said impedance;
- and
- first and second degenerative feedback means said first means connected between said first current mirror amplifier input and output terminals and said second means connected between said second current mirror amplifier input and output terminals.
A current sensing circuit for sensing the flow of current through one of the terminals of an impedance, said circuit comprising:
- first and second terminals between which an operating potential may be applied;
- means for establishing a current through said impedance;
- a first current mirror amplifier having an input terminal connected to said impedance to receive the current therethrough, having an output terminal, and having a common terminal connected to said first terminal;
- a second current mirror amplifier having an input terminal, having an output terminal, and having a common terminal connected to the input terminal of said first current mirror amplifier;
- a constant current source for supplying a direct current, said source connected between said second terminal and an interconnection between the output terminal of said first current mirror amplifier and the input terminal of said second current mirror amplifier;
- and
- load means including a direct current path connected between said second terminal and the output terminal of said second current mirror amplifier.
A method for providing short-circuit termination between first and second ends of a coil and for sensing current arising in said coil without applying appreciable potential across said coil as will undesirably give rise to spurious current flow in said coil, said method comprising the concurrent steps of:
- connecting the first end of said coil to the input terminal of a first current mirror amplifier;
- connecting the second end of said coil to the input terminal of a second current mirror amplifier similar to said first current mirror amplifier;
- applying a reference potential to an interconnection between the common terminals of said first and second current mirror amplifiers;
- supplying first and second currents of predetermined respective magnitudes;
- comparing said first current to the current demanded at the output terminal of said first current mirror amplifier to obtain a first error signal;
- comparing said second current to the current demanded at the output terminal of said second current mirror amplifier to obtain a second error signal;
- applying said first error signal to the input terminal of a further amplifier means having its common terminal connected to the input terminal of said first current mirror amplifier, for completing a direct-coupling feedback loop that reduces the impedance offered between the first end of said coil and said interconnection;
- applying said second error signal to the input terminal of a still further amplifier means having its common terminal connected to the input terminal of said second current mirror amplifier for completing a direct-coupled feedback loop that reduces the impedance offered between the second end of said coil and said interconnection;
- and
- utilizing the output current of said further amplifier means.
Dependencies are inferred from the claim text.