Current amplifier circuit
First Claim
1. A current amplifier circuit comprising:
- an operational amplifier which has a feedback loop between an input terminal and an output terminal, and receives a current signal input at said input terminal to amplify the current signal, the operational amplifier having at an output stage a signal detecting transistor through which a signal current flowing through said feedback loop flows;
a bias current adder circuit for allowing a bias current to flow steadily through the signal current detecting transistor of said operational amplifier;
a bias current subtracter circuit which has a further transistor through which a current flows of a magnitude equal to the sum current of the signal current flowing through said signal current detecting transistor and the bias current, and subtracts the bias current from the current flowing through the further transistor to output only the signal current; and
a reference bias generator circuit for determining a magnitude of said bias current.
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Accused Products
Abstract
In a current amplifier circuit having a feedback type operational amplifier, the operational amplifier has at an output stage a signal detecting transistor through which a signal current flowing through the feedback loop flows. The current amplifier circuit further comprises a bias current adder circuit, a bias current subtractor circuit, and a reference bias generator. The bias current adder circuit allows a bias current to flow steadily through the signal current detecting transistor of the operational amplifier. The bias current subtracter circuit has a further transistor through which a current flows of a magnitude equal to the sum current of the signal current flowing through the signal current detecting transistor and the bias current, and subtracts the bias current from the current flowing through the transistor to output only the signal current. The reference bias generator circuit determines a magnitude of the bias current.
13 Citations
17 Claims
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1. A current amplifier circuit comprising:
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an operational amplifier which has a feedback loop between an input terminal and an output terminal, and receives a current signal input at said input terminal to amplify the current signal, the operational amplifier having at an output stage a signal detecting transistor through which a signal current flowing through said feedback loop flows; a bias current adder circuit for allowing a bias current to flow steadily through the signal current detecting transistor of said operational amplifier; a bias current subtracter circuit which has a further transistor through which a current flows of a magnitude equal to the sum current of the signal current flowing through said signal current detecting transistor and the bias current, and subtracts the bias current from the current flowing through the further transistor to output only the signal current; and a reference bias generator circuit for determining a magnitude of said bias current. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. A current amplifier circuit comprising:
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a reference bias generating circuit for generating a reference bias; an operational amplifier for amplifying an input current, said operational amplifier including an input terminal for receiving the input current, an output terminal, a feedback loop between said input terminal and said output terminal, and a signal detector through which a signal current of said feedback loop flows; a bias current circuit responsive to the reference bias for providing a bias current which flows through said signal detector, whereby a sum current equal to said bias current and said signal current flows through said signal detector; and a bias current subtracting circuit having an input current equal to the current through said signal detector and subtracting a current equal to the bias current from the input current to output an output current signal equal to the signal current. - View Dependent Claims (16, 17)
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Specification