Coded data generation or conversion – Analog to or from digital conversion – Digital to analog conversion
Reexamination Certificate
2005-08-09
2005-08-09
Tokar, Michael (Department: 2819)
Coded data generation or conversion
Analog to or from digital conversion
Digital to analog conversion
C341S153000
Reexamination Certificate
active
06927719
ABSTRACT:
A segmented current mode DAC (200) is disclosed herein having a current matching circuit (260) that compensates for the current mismatch produced by the transistors of each current source. This segmented current mode DAC (200) includes an input stage (210), a first and second controllable current source (270, 220), a current matching circuit (260), and an output switching network (272–274, 222–236). The first controllable current source (270) couples to receive a mirrored current as provided by the input stage (210) to provide a current source output controllable in current increments responsive to the M least significant bits for converting of the digital signal to analog form, where M is less than N. The second controllable current source (220) couples to receive the mirrored current to provide a current source output controllable in current increments responsive to the N−M most significant bits for converting of the digital signal to analog form. The current matching circuit (260) couple between the first and second controllable current sources (270,220) to match the current of the first controllable current source (270) and the second controllable current source (220). Specifically, the current matching circuit (260) connects between each sub-DAC (270,220) to force the drain-to-source voltage of a transistor (252) representing the first bit of the MSB binary weighted sub-DAC (220) to be the same as the drain-to-source voltage of the transistor (278) representing the LSB thermometer decoded sub-DAC (270).
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Brady III W. James
Moore J. Dennis
Nguyen Linh V
Telecky , Jr. Frederick J.
Texas Instruments Incorporated
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