13 Jul 2026

PG-IV Analogue-to-Digital and Digital-to-Analogue Converters

practical pg-iv adc dac digital-electronics

Experimental arrangement

The analogue signal is sampled and converted to a binary code; the code then drives the DAC and reconstruction filter for output measurement.

Aim

To study the operation and performance of analogue-to-digital and digital-to-analogue converters.

Apparatus

ADC/DAC trainer, regulated supply, function generator, CRO, digital multimeter, and patch cords.

Theory

An ADC maps an analogue voltage to a binary code. For an $n$-bit converter with reference voltage $V_{ref}$, the ideal step size is

\[q=\frac{V_{ref}}{2^n}.\]

A DAC converts the code back into an analogue voltage, ideally in steps of the same size.

Observations

For an 8-bit, $5\,\text{V}$ converter, $q=19.53\,\text{mV}$.

Input voltage (V)	ADC code	DAC output (V)
0.50	00011010	0.508
1.00	00110011	0.996
2.50	10000000	2.510
4.00	11001101	4.000

Result

The converter produces a monotonic digital code and the DAC output follows the input within approximately one least-significant-bit error.

Precautions

Use a stable reference voltage, connect the ground correctly, allow settling time, and do not change code lines while the output is being measured.

Viva Questions

1. What is resolution? The smallest input change represented by one digital count.
2. What is quantisation error? The difference between the actual analogue value and its nearest digital level.
3. What is monotonicity? The output does not decrease when the input code increases.

Maxima Code

Download the Maxima calculation file.