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A student has made a 3-bit binary down counter and connected to the R- 2R ladder type DAC [Gain = (-1 kΩ/2R)] as shown in figure to generate a staircase waveform. The output achieved is different as shown in figure. What could be the possible cause of this error?
The resistance values are incorrect
The counter is not working properly
The connection from the counter to DAC is not proper
The R and 2R resistances are interchanged
Since, it is a down counter it will count from 7 to 0. When the counter count is 7 (111) the DAC output is corresponding to 7 input (111) from the waveform.
When the down counter comes down to 6 (110), the DAC output is corresponding to 3 (011) and when the count comes down to 5 (101), the DAC output is corresponding to 5 (101).
So, from this we conclude that MSB of counter is connected to LSB of DAC and vice versa so the connection is not proper.