Current steering semi-digital reconstruction filter
First Claim
1. A current steering semi-digital reconstruction filter for a digital-to-analog conversion circuit, comprising:
- (a) a shift register having a 1-bit digital input stream and a plurality of output taps, wherein each said output tap provides a 1-bit signal which has a value of a logic 1 or a logic 0;
(b) a plurality of resistive paths, wherein each said resistive path includes a resistive element which is connected to a common current source, and to a first terminal of an active high switch and a first terminal of an active low switch;
wherein a single output tap is used to control said active high switch and said active low switch for a single resistive path; and
wherein a second terminal of each said active high switch of each of said plurality of resistive paths is connected to a non-inverted current path, and a second terminal of each said active low switch for each of said plurality of resistive paths is connected to an inverted current path.
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Abstract
A current steering semi-digital reconstruction filter for a digital-to-analog conversion circuit, which includes a shift register having a 1-bit digital input stream and a plurality of output taps, where each output tap provides a 1-bit signal which has a value of a logic 1 or a logic 0, and a plurality of resistive paths, where each resistive path includes a resistive element which is connected to a common current source and to a first terminal of an active high switch and a first terminal of an active low switch. A single output tap is used to control the active high switch and the active low switch for a single resistive path. A second terminal of each active high switch of each of the plurality of resistive paths is connected to a non-inverted current path, and a second terminal of each active low switch for each of the plurality of resistive paths is connected to an inverted current path.
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Citations
21 Claims
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1. A current steering semi-digital reconstruction filter for a digital-to-analog conversion circuit, comprising:
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(a) a shift register having a 1-bit digital input stream and a plurality of output taps, wherein each said output tap provides a 1-bit signal which has a value of a logic 1 or a logic 0; (b) a plurality of resistive paths, wherein each said resistive path includes a resistive element which is connected to a common current source, and to a first terminal of an active high switch and a first terminal of an active low switch; wherein a single output tap is used to control said active high switch and said active low switch for a single resistive path; and wherein a second terminal of each said active high switch of each of said plurality of resistive paths is connected to a non-inverted current path, and a second terminal of each said active low switch for each of said plurality of resistive paths is connected to an inverted current path. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A method of converting a 1-bit digital input signal to an analog output signal, comprising the steps off
(a) inputting said 1-bit digital input signal to a shift register; -
(b) shifting said 1-bit signal through said shift register; (c) providing, as a control bit, said shifted 1-bit signal to a plurality of output taps disposed along said shift register, wherein said control bit has a value of either a logic 1 or a logic 0; (d) controlling a plurality of non-inverted current switches and inverted current switches with said bit-values of said shift register output taps, wherein a single output tap value controls a single pair of switches comprised of a single non-inverted current switch and a single inverted current switch, and wherein said plurality of non-inverted current switches and inverted current switches are connected to a common current source; (e) producing a differential current from said plurality of non-inverting current switches and inverting current switches; and (f) inputting said differential current to a first and a second op amp circuit, wherein a differential voltage is output from said first and second op amp circuits. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18, 19)
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20. A method of converting a 1-bit digital input signal to an analog output signal, comprising the steps off
(a) inputting said 1-bit digital input signal to a shift register; -
(b) shifting said 1-bit signal through said shift register; (c) providing, as a control bit, said shifted 1-bit signal to a plurality of output taps disposed along said shift register, wherein said control bit has a value of either a logic 1 or a logic 0; (d) producing a differential current at a pair of current summing nodes by using said control bits to open or close switches disposed along a plurality of resistive paths connected to a common reference current source, wherein a DC offset current is subtracted from said differential current; and (e) inputting said differential current to a current-to-voltage conversion circuit, wherein a differential voltage is output from said current-to-voltage conversion circuit. - View Dependent Claims (21)
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Specification