Digitally controlled calibration circuit for a DAC

A digitally controlled calibration circuit comprising:

• at least one primary DAC having a first input for receiving a reference current, a second input for receiving a digital signal representative of the DAC conversion factor, and an output for providing the analog output signal;
• at least one secondary calibration DAC having associated with it a reference network connected to a first input of said secondary DAC for conducting a reference current;
• means for connecting the output of said secondary DAC to said reference network, said secondary DAC having a second input for receiving a digital signal for readjusting the output of said secondary DAC fed back to said reference network for adjusting said reference current;
• and
• means for interconnecting said reference current with said first reference input of said at least one primary DAC for digitally controlling the reference current to said at least one primary DAC and digitally effecting calibration of said primary DAC.

A digitally controlled calibration circuit for a color video RAM-DAC comprising:

• a red, a blue, and a green primary DAC each having a first input for receiving a reference current, a second input for receiving a digital signal representative of the DAC conversion factor;
• and an output for providing the analog output signal representative of the respective color;
• a red, a blue and a green secondary calibration DAC, one associated with each of said red, blue and green primary DACs respectively;
• each secondary DAC having associated with it a reference network connected to a first input of that said secondary DAC for conducting a reference current;
• means for connecting the output of that said secondary DAC to its said reference network;
• and
• a second input for receiving a digital signal for adjusting the output of that said secondary DAC fed back to its said reference network for adjusting said reference current conducted by that said reference network;
• and
• means for interconnecting each of said reference currents of each said secondary DAC with said first reference current input of the associated one of said primary DACs for digitally controlling the reference current to at least two of said primary DACs.

A digitally controlled calibration circuit for a color video RAM-DAC comprising:

• a red, a blue, and a green primary DAC each having a first input for receiving a reference current, a second input for receiving a digital signal representative of the DAC conversion factor;
• and an output for providing the analog output signal representative of the respective color;
• at least two secondary calibration DACs, one associated with each of two of said primary DACs respective;
• each secondary DAC having associated with it a reference network connected to a first input of that said secondary DAC for conducting a reference current;
• means for connecting the output of that said secondary DAC to its said reference network;
• and a second input for receiving a digital signal for adjusting the output of that said secondary DAC fed back to its said reference network for adjusting said reference current conducted by that said reference network;
• and
• means for interconnecting each of said reference currents of each said secondary DAC with said first reference current input of the associated one of said primary DACs for digitally controlling the reference current to at least two of said primary DACs.