題組內容

1. Figure 1 shows an op-amp circuit for 4-bit digital-to-analog converter (DAC), which can convert a 4-bit digital word a3a2a1a0 to an analog output. The valuc of each bit is represented by a corresponding switch. That is, if ao is I then switch So connects to the +5-V power supply, while if a0 is 0 then switch S0 connects to ground.
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(b) Based on this circuit, please design an op-amp circuit which can convert a 4 -bit digital word to an analog output ranging from 0 to 12 V. Any reasonable scheme is allowed. (5%)