CURRENT MIRROR BIAS TRIMMING TECHNIQUE
First Claim
1. A method of trimming a current reference transistor providing a reference current for an integrated circuit, the method comprising:
- using feedback control to generate a control voltage for a gate of a feedback circuit transistor of the integrated circuit such that current passing through the feedback circuit transistor is substantially constant;
using the control voltage for the gate of the feedback circuit transistor to control a gate of the current reference transistor of the integrated circuit, wherein a source of the feedback circuit transistor and a source of the current reference transistor are tied to a same voltage potential; and
adjusting a width-to-length ratio (W/L) of the feedback circuit transistor to trim the reference current flowing through the current reference transistor.
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Accused Products
Abstract
A reference current is generated by a current mirror circuit. An operational amplifier of a feedback circuit generates a control voltage for control of the feedback circuit transistor. The size of the feedback circuit transistor is trimmed, and the current through the feedback circuit transistor remains relatively constant via operation of the feedback circuit. The feedback circuit transistor is scaled in size relative to the size of current reference transistor(s) (e.g., current sources or sinks), which are tied to the same control voltage. The reference current of the current reference transistors thus varies with the size of the feedback circuit transistor. Further advantageously, transistors providing reference currents for resistor ladders can also be tied to the same control voltage, but scaled proportionally with changes in size to the feedback circuit transistor, thereby maintaining relatively constant voltage from taps of the resistor ladder, even when the feedback circuit transistor is trimmed.
48 Citations
32 Claims
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1. A method of trimming a current reference transistor providing a reference current for an integrated circuit, the method comprising:
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using feedback control to generate a control voltage for a gate of a feedback circuit transistor of the integrated circuit such that current passing through the feedback circuit transistor is substantially constant; using the control voltage for the gate of the feedback circuit transistor to control a gate of the current reference transistor of the integrated circuit, wherein a source of the feedback circuit transistor and a source of the current reference transistor are tied to a same voltage potential; and adjusting a width-to-length ratio (W/L) of the feedback circuit transistor to trim the reference current flowing through the current reference transistor. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. An integrated circuit comprising:
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a current reference transistor having a gate, a source, and a drain; a feedback circuit transistor having a gate, a source, and a drain, wherein the gate of the feedback circuit transistor is operatively coupled to the gate of the current reference transistor, wherein the source of the feedback circuit transistor is operatively coupled to the source of the current reference transistor, wherein a number of activated fingers of the feedback circuit transistor is selectable such that a width-to-length ratio (W/L) of the feedback circuit transistor is scalable; and a feedback circuit configured to generate a control voltage for the gate of the feedback circuit transistor, wherein the feedback circuit is configured to maintain a substantially constant current through the feedback circuit transistor. - View Dependent Claims (17, 18, 19, 20, 21, 22, 23, 24)
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25. An apparatus for trimming an integrated circuit, the apparatus comprising:
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a current monitoring circuit configured to monitor a current of a first transistor of the integrated circuit; and a selection circuit configured to select a number of fingers of a second transistor to adjust a current flowing through the first transistor. - View Dependent Claims (26, 27, 28)
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29. A method of configuring a current reference of an integrated circuit, the method comprising:
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monitoring a current of a first transistor of the integrated circuit; and selecting a number of fingers of a second transistor to adjust a current flowing through the first transistor. - View Dependent Claims (30, 31, 32)
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Specification