Segmented D/A converter with enhanced dynamic range
AssigneeCygnal Integrated Products, Inc.
InventorsKa Y. Leung, Douglas R. Holberg
Life of this patent
Estimating the term…
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.
Claims24
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;
- switching circuitry for selectively connecting one of said plurality of resistors in said first resistor string across said second resistor string;
- and
- an output amplifier for receiving an analog voltage level resulting from said second 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;
- switching circuitry for selectively connecting one of said plurality of resistors on said main resistor string across said sub-resistor string;
- and
- an output amplifier responsive to analog voltage levels resulting from said main and sub-resistor strings for producing corresponding output signals.
A resistor voltage divider circuit, comprising:
- a main resistor string comprised of a plurality of resistors connected between first and second nodes;
- a secondary resistor string comprised of a plurality of resistors connected between the third and fourth nodes;
- a voltage input for receiving a reference voltage;
- circuitry for applying a voltage across said main resistor string substantially equal to said reference voltage;
- switching circuitry for selectively connecting said third and fourth nodes across one or more of said plurality of resistors in said main resistor string, such that the voltage across said third and fourth nodes is substantially equal to the voltage across said one or more of said plurality of resistors in said main resistor string selected by said switching circuitry;
- and
- a current source for sourcing of current to said secondary resistor string.
Dependencies are inferred from the claim text.