Patent ID: 7161415

Claim:
A current modulation filter electrically interposed between a power source and a load circuit, comprising: a biasing circuit having a first voltage reference node and a current reference node, said biasing circuit electrically coupled in parallel connection to the power source; a load voltage measurement circuit having a second voltage reference node, said load voltage measurement circuit electrically coupled in parallel connection to the load circuit; a current sensing circuit series connected between the power source and the load circuit; and a current controller electrically coupled at a first input terminal thereof to said first voltage reference node, at a second input terminal thereof to said second voltage reference node, at a first output terminal thereof to the load circuit and at a second output terminal thereof to said current reference node, said current controller supplying electrical current to, or sinking electrical current from, the load circuit responsive to a voltage difference between said first input terminal thereof and said second input terminal thereof such that said current through said current sensing circuit remains substantially constant over a range of load current variations, said current controller including: (a) a difference amplifier having a first input terminal thereof connected as said first input terminal of said current control circuit and a second input terminal thereof connected as said second input terminal of said current control circuit; and (b) a current control circuit electrically coupled at a control terminal thereof to an output terminal of said difference amplifier and having a first output terminal thereof connected as said first output terminal of said current control circuit and a second output terminal thereof connected as said second output terminal of said current control circuit.