Digital-to-analog converter and bias compensator therefor

A digital-to-analog converter comprising:

• decoder means responsive to a multi-bit digital input and operative to decode said digital input into a plurality of cell activation signals;
• conversion means comprising a plurality of current cells, where each of said current cells includes a cell bias input, a cell activation input, and a cell analog output, wherein said cell analog outputs of said plurality of current cells are coupled together to provide a converter analog output;
• bias generator means having a reference input coupled to a bias generator voltage reference source, a bias output coupled to the cell bias inputs of said plurality of current cells, and a power input;
• compensation means coupled to said bias generator comprising means for detecting a voltage variation on said power input and means for varying said bias output of said bias generator to compensate for said voltage variation;
• and
• means for developing a compensation reference voltage including operational amplifier means;
• and
• means for disabling said operational amplifier means.

A bias compensator comprising:

• variation detection means coupled to a bias line and a power input and operative to develop an error signal in response to voltage variations on said power input;
• variation compensation means responsive to said error signal and operative to vary the voltage on said bias line to compensate for said voltage variation;
• and
• means for developing a compensation reference voltage including operational amplifier means;
• and
• means for disabling said operational amplifier means.

A method for providing a stable bias voltage comprising:

• developing a bias voltage from a power supply;
• sensing voltage variations in said power supply by comparing an output of a pseudo circuit coupled to said power supply against the output of a reference circuit coupled to said power supply to develop an error signal indicative of variations of said bias voltage;
• and
• compensating said bias voltage to counteract the effects of said voltage variations by utilizing a compensation circuit, the error signal being utilized as an input to the compensation circuit and the bias voltage being coupled to an output of the compensation circuit.