Basics of Digital Design

Digital vs Analog Signal:

  • Digital Signals
Fig: A digital signal with discrete values in terms of Amplitude and Time. Source: Wikipedia [click here]

- Discrete time signals generated by digital modulation.
- Denoted by square waves.
- Digital signals are non continuous.
- Due to discrete values they are less prone to noise.
- Easier to transmit or debug or detect error.
- Digital systems: are those which process digital values.
- Easier to design.
- Exact values of voltage or current is not important but only the HIGH or LOW range in which they fall are important.
- Inverter:
Fig: CMOS Inverter

            NOT ANSI Labelled.svg => When input = 1; output = 0 and vice versa.

  • Analog Signals
Fig: A typical analog signal w.r.t. time representing quantity in terms of Voltage. Source:
[click here]

- Continuous electrical signals that vary in time.
- Analog systems: capable of processing a continuous range of values varying with respect to time.
- Very susceptible to noise, easy to manipulate mathematically.
- Example: Telephone wire where signals travel and certain factors add more "noise" to the signal.
- Noise factors could be: Air conditioning units, Fluorescent lights, magnetic fields, etc.
- There are methods of separating/filtering noise from analog signals. Most of those methods are not accurate enough. Therefore, Digital signals are used since they provide better delivery method.
- These are used for high frequency, high precision and high speed.
- Inverter:

Fig: An analog inverter

When, Vcc = +5V;  a = Vin = 0V => F = Vout = 5V

whereas, Vin = 1V => Vout = 0V


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