Segmented D/A converter with enhanced dynamic range
AssigneeCygnal Integrated Products, Inc.
InventorsKa Y. Leung, Douglas R. Holberg
Life of this patent
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Abstract
A digital-to-analog converter having series-connected transistors forming high impedance current sources for respective segmented resistor strings. A series transistor forming a current sink for one resistor string presents a high output impedance by utilizing a negative feedback amplifier. The effects of a headroom resistor and an offset resistor in one resistor string are negated by configuring an output amplifier with appropriate gain resistors. A highly accurate D/A conversion can be achieved by utilizing all resistors of the main and sub-resistor strings with the same value.
Claims20
A digital-to-analog converter, comprising:
- a first and second resistor string, each said resistor string characterized by a plurality of resistors for providing plural analog voltage levels;
- a differential amplifier having one input coupled to a precision voltage, and another input coupled by a feedback circuit of said amplifier to the first resistor string for driving said first resistor string with a voltage reference;
- a current mirror circuit for carrying current to said first resistor string, said current mirror circuit driven by said amplifier;
- a current source for driving said second resistor string with a current, said current source including a current mirror driven by said amplifier, whereby changes in a current driven in said first resistor string are reflected in said second resistor string;
- and
- an output amplifier for receiving an analog voltage level resulting from one said resistor string.
A digital-to-analog converter, comprising:
- a main resistor string characterized by a plurality of resistors;
- a main current source for driving said main resistor string with a current;
- a sub-resistor string characterized by a plurality of resistors;
- a sub-current source for driving said sub-resistor string;
- a circuit for driving said main current source and said sub-current source with a signal such that a current in said sub-resistor string tracks a current in said main resistor string;
- and
- an output amplifier responsive to analog voltage levels resulting from said main and sub-resistor strings for producing corresponding output signals.
Dependencies are inferred from the claim text.