The real world is analog — voltage from a microphone, temperature from a sensor, light from a camera — but computers only understand digital 1s and 0s. Two circuits bridge these worlds: the ADC (Analog-to-Digital Converter) turns a continuous voltage into a binary number, and the DAC (Digital-to-Analog Converter) turns a binary number back into a voltage. Alongside them, magnitude comparators answer "is A greater than, equal to, or less than B?", and every one of these blocks is built from real digital ICs whose electrical limits (fan-in, fan-out, delay, noise margin) decide whether a design works. This lesson is a recurring favourite in BCS, Bank IT and IT-officer written exams, and the questions are almost always calculative — so master the formulas and practise the arithmetic until it is automatic.
Learning objectives
- Explain what DAC and ADC do and where each is used.
- Compute DAC step size, resolution and output voltage for any binary input.
- Describe weighted-resistor and R-2R ladder DACs and why R-2R is preferred.
- Compare counter-type, successive-approximation (SAR) and flash ADCs on speed and cost.
- Compute an 8-bit ADC output code for a given input voltage, and explain quantization error.
- Design and give the truth tables for 1-bit and 2-bit magnitude comparators.
- Define the key digital IC characteristics and compare TTL vs CMOS.
- Explain the seven-segment display and the BCD-to-seven-segment decoder.