Digital to analog converter with a reduced resistor count
First Claim
1. A digital to analog converter, comprising:
- a) a first voltage divider biased by means of a voltage source,b) a second voltage divider biased by means of a current mirror connected to a first end of said second voltage divider,c) a selected voltage from said first voltage divider connected to a second end of said second voltage divider by means of a first set of switches,d) said current mirror producing a current in the second voltage divider proportional to a reciprocal multiple of current flowing in the first voltage divider,e) said current in the second voltage divider producing a voltage step corresponding to resolution of the digital to analog converter,f) an analog output voltage selected by a second set of switches connected to the second voltage divider,g) a digital input signal controlling the selection of switches in the first and second set of switches.
2 Assignments
0 Petitions
Accused Products
Abstract
This invention describes a DAC requiring a substantially lower number of resistors for conversion of n+p digital bits. The conversion to an analog signal is done in two voltage dividers. The first voltage divider contains 2n resistors and is referenced to a voltage bias. The second voltage divider contains 2p resistors and is referenced to a current bias. The current bias is derived from a current mirror which references the current in the first voltage divider. The use of the current mirror allows all resistors in the DAC to be of the same value which in turn provides an implementation with better accuracy and resistor matching. The number of resistors required to make a conversion of a 12 bit digital signal is 272 where 8 bits are converted in the first voltage divider and 4 bits are converted in the second voltage divider.
44 Citations
19 Claims
-
1. A digital to analog converter, comprising:
-
a) a first voltage divider biased by means of a voltage source, b) a second voltage divider biased by means of a current mirror connected to a first end of said second voltage divider, c) a selected voltage from said first voltage divider connected to a second end of said second voltage divider by means of a first set of switches, d) said current mirror producing a current in the second voltage divider proportional to a reciprocal multiple of current flowing in the first voltage divider, e) said current in the second voltage divider producing a voltage step corresponding to resolution of the digital to analog converter, f) an analog output voltage selected by a second set of switches connected to the second voltage divider, g) a digital input signal controlling the selection of switches in the first and second set of switches. - View Dependent Claims (2, 3)
-
-
4. A method for converting a digital signal to an analog voltage, comprising:
-
a) selecting a voltage from a first voltage divider, b) connecting said voltage from first voltage divider to a second voltage divider, c) further connecting a current bias proportional to a reciprocal multiple of current in the first voltage divider to said second voltage divider, d) selecting a voltage from said second voltage divider corresponding to an input digital signal. - View Dependent Claims (5, 6, 7)
-
-
8. A resistor DAC, comprising:
-
a) a first voltage divider having a number of resistors connected in series between circuit reference voltages, b) a second voltage divider having a number of resistors connected between a current mirror and output of the first voltage divider, c) said current mirror producing current proportional to a reciprocal multiple of current flowing in the first voltage divider, d) a first set of switches selecting an output voltage of the first voltage divider, e) the output voltage of the first voltage divider being proportional to high order bits of a digital input signal, f) a second set of switches selecting an output voltage of the second voltage divider, g) the output voltage of the second voltage divider being proportional to a sum of the high and low order bits of a digital input signal and any bias offset voltage. - View Dependent Claims (9, 10, 11, 12)
-
-
13. A resistor DAC with a current mirror bias, comprising:
-
a) a first section for converting "n" high order bits of an input digital signal, b) a second section for converting "p" low order bits of the input digital signal, c) said first section comprising a resistor voltage divider between reference voltages and a first set of switches controlled by the input digital signal through a digital decoder, d) said first set of switches selecting an output voltage of the first section, e) the output of the first section connected to said second section through a buffer, f) said second section comprising a resister voltage divider connected between a current mirror and output of the first section, g) a second set of switches controlled by the input digital signal through the digital decoder and selecting an output voltage of the second section, h) said current mirror producing a reciprocal multiple of the current flowing in the first section, i) the output of the second section being proportional to sum of the high and low order bits of the input digital signal and any bias offset voltage. - View Dependent Claims (14, 15)
-
-
16. A digital to analog converter, comprising:
-
a) a digital input and an analog output, b) a first voltage divider connected between two reference voltages, c) said first voltage divider connected to the second voltage divider by means of a first set of switches, d) said second voltage divider biased by means of a current mirror, e) said current mirror producing a current in said second voltage divider that is a reciprocal multiple of current flowing in the first voltage divider, f) said second voltage divider connected to the analog output by means of a second set of switches, g) said digital input selecting by means of a decoder a first switch within the first set of switches to connect a first voltage of the first voltage divider to the second voltage divider, h) said digital input selecting by means of the decoder a second switch within the second set of switches to connect a second voltage of the second voltage divider to the analog output, i) said second voltage being an analog equivalent of a digital input signal. - View Dependent Claims (17, 18, 19)
-
Specification