Current control circuit
First Claim
1. A current control circuit comprising current mirror means having first and second transistor devices, one of said transistor devices being operative to receive a controllable current and the other of said transistor devices being operative to conduct a current whose value is determined by and changeable with the current received by said one transistor device, said other transistor device being adapted to be connected to a load such that the current in said load is equal to the current conducted by said other transistor device, means coupled to said one transistor device for supplying said controllable current thereto;
- constant current generating means for generating a substantially constant current, said means for supplying said controllable current being coupled to said constant current generating means and being operative to establish the level of said controllable current in accordance with the constant current applied thereto; and
variable current conducting means coupled to said constant current generating means for conducting a selectively variable amount of said constant current such that said level of said controllable current is established in accordance with the difference between said constant current and the amount of said constant current conducted by said variable current conducting means, and said controllable current varies substantially linearly with said difference.
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Abstract
A current control circuit for a muting circuit including a current mirror circuit formed of first and second transistor devices, one of which being operative to receive a controllable current and the other being operative to conduct a current whose value is determined by and changeable with the controllable current, such other transistor device being adapted to be connected to a load. A constant current generator generates a substantially constant current and is connected to a current-responsive circuit which, in turn, supplies the controllable current to the first-mentioned transistor device included in the current mirror circuit. A variable conducting circuit is coupled to the constant current generator for conducting a selectively variable amount of the constant current such that the level of the controllable current which is supplied to the first-mentioned transistor device is established in accordance with the difference between the constant current and the current conducted by the variable conducting circuit. Thus, the current through the current mirror circuit, and thus the load current, is determined by the conductivity of the variable conducting circuit.
13 Citations
11 Claims
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1. A current control circuit comprising current mirror means having first and second transistor devices, one of said transistor devices being operative to receive a controllable current and the other of said transistor devices being operative to conduct a current whose value is determined by and changeable with the current received by said one transistor device, said other transistor device being adapted to be connected to a load such that the current in said load is equal to the current conducted by said other transistor device, means coupled to said one transistor device for supplying said controllable current thereto;
- constant current generating means for generating a substantially constant current, said means for supplying said controllable current being coupled to said constant current generating means and being operative to establish the level of said controllable current in accordance with the constant current applied thereto; and
variable current conducting means coupled to said constant current generating means for conducting a selectively variable amount of said constant current such that said level of said controllable current is established in accordance with the difference between said constant current and the amount of said constant current conducted by said variable current conducting means, and said controllable current varies substantially linearly with said difference. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
- constant current generating means for generating a substantially constant current, said means for supplying said controllable current being coupled to said constant current generating means and being operative to establish the level of said controllable current in accordance with the constant current applied thereto; and
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11. A current control circuit comprising a first current mirror circuit including first and second transistors of substantially identical characteristics having their base electrodes connected to each other and their emitter electrodes respectively coupled to a source of reference potential, the base electrode of said first transistor being connected to the collector electrode thereof and the collector electrode of said second transistor being adapted to be connected to a load;
- a third transistor having its collector-emitter circuit connected in series with the collector-emitter circuit of said first transistor to supply a controllable current to said first transistor;
a constant current generator for supplying at an output thereof a substantially constant current;
means for connecting the base electrode of said third transistor to said constant current generator output;
a second current mirror circuit including fourth and fifth transistors of substantially identical characteristics having their base electrodes connected to each other and their emitter electrodes respectively coupled to said source of reference potential, the base electrode of said fourth transistor being connected to the collector electrode thereof and the collector electrode of said fifth transistor being connected to said constant current generator output such that the current supplied to the base electrode of said third transistor is proportional to the difference between said constant current and the current conducted by said fifth transistor;
control means coupled to said fourth transistor for controlling the currents conducted by said fourth and fifth transistors, respectively; and
means for linearly increasing the current supplied to said collector electrode of said first transistor when said control means renders said fourth and fifth transistors non-conductive.
- a third transistor having its collector-emitter circuit connected in series with the collector-emitter circuit of said first transistor to supply a controllable current to said first transistor;
Specification