Name– study of digital to analog converter using R–2R ladder circuit.
Aim – to study the working of 4–bit R–2R ladder, D/A converter circuit.
Apparatus – IC 741, circuit board, variable DC power supply, resistors, connecting wires, soldering iron, cutter etc.
Circuit diagram
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Procedure –
1) Identify the given components.
2) Solder the circuit using the given components.
3) Connect power supply to the circuit.
4) Measure the analog output voltage (Va) w.r.t. ground for all binary inputs from 0000 to 1111.
5) Tabulate the results in observation table.
6) Plot the graph of analog output voltage versus digital inputs.
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Brief theory – the process of translation of digital information into equivalent analog information is called as digital to analog conversion. Such converter is also called as decoding device. There are two types of such converters – the weighted resistor DAC and the R–2R ladder DAC.
The R–2R ladder (binary ladder) is a resistive network whose output voltage is a properly weighted sum of the digital inputs. It uses resistors of only two values, the R and the 2R, as shown in the above figure.
It has four digital inputs D, C, B and A with positional values of bits as 23, 22, 21 and 20 respectively. The equivalent analog voltage is (Va) which is obtained at the input of operational amplifier IC 741. If the digital input is DCBA = 1000, then the circuit can be reduced as follows –
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Conclusion –
1) The circuit can convert applied digital input combinations into their equivalent analog output voltages.
2) The operational amplifier is used in the circuit for scaling the value of output voltage.