Method and apparatus for compensating amplifier output for temperature and process variations
First Claim
1. A method for calibrating an output of an amplifier comprising the steps of:
- providing an amplifier, the amplifier including a transistor, the transistor having a channel with a digitally controllable channel resistance, the channel resistance changing as a function of a calibration parameter;
generating a calibration word to control a characteristic of a digitally controllable circuit element such that the characteristic remains at a desired level, the circuit element being configured such that the characteristic changes as a function of the calibration parameter in an amount proportional to an amount by which the resistance of the transistor changes as a function of the calibration parameter; and
controlling the channel width of the transistor based on the calibration word such that the resistance of the transistor is calibrated for variations in the calibration parameter.
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Abstract
An amplifier circuit includes a calibration circuit with a controllable circuit element such as a digital resistor. One or more properties of the controllable circuit element (e.g., the resistance in a digital resistor) is varied by a digital calibration word such that the voltage drop across the resistor matches a reference voltage. The calibration word is also used to control the resistance of a transistor that forms a part of a power amplifier to compensate for temperature and process variations. The amplifier may be a switching power amplifier, and the transistor may be a segmented transistor with the width (and hence the channel resistance) controlled by the digital calibration word.
45 Citations
21 Claims
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1. A method for calibrating an output of an amplifier comprising the steps of:
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providing an amplifier, the amplifier including a transistor, the transistor having a channel with a digitally controllable channel resistance, the channel resistance changing as a function of a calibration parameter;
generating a calibration word to control a characteristic of a digitally controllable circuit element such that the characteristic remains at a desired level, the circuit element being configured such that the characteristic changes as a function of the calibration parameter in an amount proportional to an amount by which the resistance of the transistor changes as a function of the calibration parameter; and
controlling the channel width of the transistor based on the calibration word such that the resistance of the transistor is calibrated for variations in the calibration parameter. - View Dependent Claims (2, 3, 4, 5, 6, 7, 9, 10)
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8. (canceled)
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11. An amplifier comprising:
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a transistor, the transistor having a channel with a digitally controllable channel resistance, the channel resistance changing as a function of a calibration parameter; and
a calibration circuit including a circuit element having a digitally controllable characteristic that changes as a function of the calibration parameter in an amount proportional to an amount by which the resistance of the transistor changes as a function of the calibration parameter, the calibration circuit being connected to the transistor;
wherein the calibration circuit is configured to generate a calibration word that maintains the characteristic of the circuit element at a desired level over changes in the calibration parameter and to output the calibration word to the transistor to control the channel resistance of the transistor, whereby the channel resistance of the transistor is calibrated for changes in the calibration parameter. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20, 21)
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Specification