Current-steering D/A conversion with current source mismatch compensation

A current-steering N-bit D/A converter comprising:

• N digital inputs, each receiving a digital input bit bi, i=0, 1, . . . , N−1, bN−1 being the most significant bit (MSB);
• an analog output;
• and
• N binary weighted current sources SIk, k=0, 1, . . . , N−1, connectable to said analog output, each current source SIk comprising 2k unit current sources, SIunit, of equal strength connected in parallel, wherein
• the digital input bits are indicative of which respective current source, SIk, k=0, 1, . . . , N−1, to be connected to the analog output, the D/A converter further comprising
• an additional unit current source and means for substituting the current IN−1 from the largest current source SIN−1 for a current ĨN−1, where I ~ N - 1 = ( ∑ k = 0 N - 2 ⁢ ⁢ I k ) + I unit
• in which expression Ik being the current from the current source SIk, and Iunit being the current from said additional unit current source.

A current-steering N-bit D/A converter comprising:

• N digital inputs, each receiving a digital input bit bi, i=0, 1, . . . , N−1, bN−1 being the most significant bit (MSB);
• an analog output;
• and
• N binary weighted current sources SIk, k=0, 1, . . . , N−1, connectable to said analog output, each current source SIk comprising 2k unit current sources, SIUnit, of equal strength connected in parallel, wherein
• the digital input bits are indicative of which respective current source, SIk, k=0, 1, . . . , N−1, to be connected to the analog output, the D/A converter further comprising
• an additional unit current source and means for substituting the currents IN−1, IN−2, IN−c, from the c largest current sources SIN−1, SIN−2, . . . , SIN−c, c being a positive integer larger than 1, for currents ĨN −1,ĨN−2, ĨN−c, where I ~ N - 1 = ⁢ ( ∑ k = 0 N - c - 1 ⁢ ⁢ I k ) + ( ∑ j = N - c N - 2 ⁢ ⁢ I ~ j ) + I unit I ~ N - 2 = ⁢ ( ∑ k = 0 N - c - 1 ⁢ ⁢ I k ) + ( ∑ j = N - c N - 3 ⁢ ⁢ I ~ j ) + I unit ⁢ … I ~ N - c = ⁢ ( ∑ k = 0 N - c - 1 ⁢ ⁢ I k ) + I unit
• in which expressions Ik being the current from the current source SIk, and Iunit being the current from said additional unit current source.