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DAC Instance Downside

Within the earlier chapter, we mentioned the 2 forms of DACs. This chapter discusses an instance downside based mostly on R-2R ladder DAC.

Instance

Allow us to discover the worth of analog output voltage of R-2R Ladder DAC for a binary enter, $b_{2} b_{1} b_{0}$ = 100.

Circuit Diagram and its Simplification

The circuit diagram of a 3-bit R-2R Ladder DAC when binary enter, $b_{2} b_{1} b_{0}$ = 100 utilized to it’s proven within the following determine −

Within the above circuit, there exists sequence and parallel combos of resistors to the left of level A with respect to floor. So, we are able to substitute that whole resistor community with a single resistor having resistance of $2 R Ω$ .

The simplified circuit diagram is proven within the following determine −

We are able to substitute the a part of the community that’s linked to the left of level B with respect to floor through the use of a Thevenin’s equal circuit. The modified circuit diagram is proven within the following determine −

Within the above circuit, there exist a sequence mixture of two resistors. Exchange this mixture with a single resistor. The ultimate circuit diagram after simplification is proven within the following determine −

Now, the above circuit diagram appears like an inverting amplifier. It’s having an enter voltage of $- \frac{V_{R}}{2}$ volts, enter resistance of $2 R Ω$ and suggestions resistance of $2 R Ω$ .

The output voltage of the circuit proven above will probably be −

V 0 = - 2 R 2 R (- V R 2)

V 0 = V R 2

Due to this fact, the output voltage of 3-bit R-2R Ladder DAC is $\frac{V_{R}}{2}$ volts for a binary enter, $b_{2} b_{1} b_{0}$ = 100.