Question

D/A converter resolution improves with:

• A. More bits
• B. Lower voltage
• C. Faster clock
• D. Larger load

Hint:

Resolution in data converters is fundamentally a function of bit depth. More bits mean finer quantization intervals, which reduces quantization noise and directly improves resolution.

Answer 1

The Correct Option is A

Concept: The resolution of a Digital-to-Analog Converter (DAC) reflects its ability to distinguish between tiny, adjacent output increments. It serves as a measure of the precision of the converter. Higher resolution means the analog output can match the ideal mathematical target value more precisely, using smaller steps. The resolution of a DAC can be expressed in two primary ways:
• As the total number of discrete output levels available: \( N = 2^n \)
• As the smallest analog step change corresponding to a change of 1 Least Significant Bit (LSB): \( \Delta V = \frac{V_{\text{ref}}}{2^n} \)

Step 1: Analyze the effect of the number of bits (\( n \)).
The parameter \( n \) represents the word length of the digital input. If we increase the number of bits \( n \), the total number of discrete voltage output steps (\( 2^n \)) grows exponentially. For instance:
• An 8-bit DAC yields \( 2^8 = 256 \) discrete levels.
• A 10-bit DAC yields \( 2^{10} = 1024 \) discrete levels. As the total number of steps increases within the same full-scale range, each individual analog step size (\( \Delta V \)) becomes significantly smaller. A smaller step size allows for finer control over the analog output curve, which means the resolution improves. Therefore, choosing more bits directly improves resolution.

Step 2: Evaluate alternative options.
Let's check why the remaining variables are incorrect:
• Lower Voltage: Lowering the reference voltage changes the absolute voltage scale of an LSB step, but it does not alter the fundamental quantization capacity or bit-level performance of the converter structure.
• Faster Clock: The clock speed relates to the settling time, throughput rate, and conversion speed. It affects speed, not quantization step resolution.
• Larger Load: The output load impedance affects output drive current capability and signal buffering, but has no impact on the digital bit assignment logic. Hence, resolution improves specifically with more bits.