Adaptive operational amplifier bias current
AssigneeMStar Semiconductor, Inc.
InventorLi-Wei Sheng
Life of this patent
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Abstract
An operation amplifier (op amp) having a bias current detection circuit that monitors the bias current flowing in an output stage of the op amp. When the bias current detection circuit detects that too much current is being wasted, e.g., sunk to ground, then the amount of bias current is reduced. Similarly, when the bias current detection circuit detects that insufficient bias current is being supplied to the output stage of the op amp, the amount of bias current is increased. In one implementation, the output of the bias current detection circuit may be signals indicative of, respectively, too much bias current and too little bias current, wherein those outputs are supplied to a state machine which is configured to control the amount of bias current being supplied in a stepwise fashion.
Claims19
An operational amplifier circuit, comprising:
- an input stage having at least one input node to receive an input signal;
- a bias current generator configured to generate a bias current;
- an output stage having at least one output node configured to output a signal responsive to the input signal input at the at least one input node and configured to receive the bias current from the bias current generator;
- and
- a bias current detection circuit configured to detect a comparison result of an amount of the bias current flowing in the output stage and a predetermined threshold and to control the bias current generator to generate the amount of bias current being supplied to the output stage in accordance to the comparison result.
A method of operating an operational amplifier, comprising:
- detecting bias current being sunk to ground in an output stage of an operational amplifier;
- comparing the detected bias current with predetermined low and high current thresholds;
- supplying control signals to a state machine wherein the control signals are generated based on whether the detected bias current is above or below each of the low and high predetermined low and high current thresholds;
- and
- controlling an amount of bias current being supplied to the output stage of the operational amplifier based on the control signals input to state machine to supply the same, more or less bias current.
Dependencies are inferred from the claim text.