Two 8-bit dacs make a 12-bit dac

  
Two MC1408—8-bit D/A converters, A and in the circuit diagram, are used. The four least-significant bits of A are tied to zero. The four most significant bits of the 12-bit data are connected to the remaining four input pins. The eight least significant bits of the 12-bit data are connected to the eight input pins of B. The four most significant bits of the 12-bit data together have a weight of 16 relative to the remaining eight bits. Hence, the output from is reduced by a factor of 16 and summed with the output from A using the summing op-amp configuration D. Voltage regulator chip, LM7236, is used to provide an accurate reference voltage, 2 V, for the MC1408.
Two 8-bit dacs make a 12-bit dac - schematic

The full-scale voltage of the converter is Vie 9.9609 + 1 (9.375) or 9.9976 V. The step size of the converter is 2.4 mV.




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