op amp summer as a digital to analog converter dac

The circuit shown in Figure 1 is a simple 4-bit digital-to-analog converter. It is actually just a simple op amp summer circuit, i. e. , an operational amplifier configured to output a voltage that is proportional to the sum of the input voltages. The op-amp summer circuit above works as a DAC because its input voltages are binary weighted with resp

ect to each other, as set by the resistors (10K, 20K, 40K, 80K) at the inputs. Vo = -VRef (5K) (S3/10K + S2/20K + S1/40K + S0/80K) = -VRef (S3/2 + S2/4 + S1/8 + S0/16) wherein S3, S2, S1, and S0 are the logic inputs (`1` or `0`). The number of bits of this DAC may be increased by connecting more switches with corresponding binary-weighted resistors to the inputs.

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