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Analog digitalsignals

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Analog digitalsignals

1. 1. Analog & Digital Signals Digital Electronics
2. 2. Analog & Digital SignalsThis presentation will• Review the definitions of analog and digital signals.• Detail the components of an analog signal.• Define logic levels.• Detail the components of a digital signal.• Review the function of the virtual oscilloscope. 2
3. 3. Analog and Digital SignalsAnalog Signals Digital Signals• Continuous • Discrete• Infinite range of values • Finite range of values (2)• More exact values, but • Not as exact as analog, more difficult to work with but easier to work withExample: A digital thermostat in a room displays a temperature of 72°. An analog thermometer measures the room temperature at 72.482°. The analog value is continuous and more accurate, but the digital value is more than adequate for the application and 3 significantly easier to process electronically.
4. 4. Example of Analog Signals • An analog signal can be any time-varying signal. • Minimum and maximum values can be either positive or negative. • They can be periodic (repeating) or non-periodic. • Sine waves and square waves are two common analog signals. • Note that this square wave is not a digital signal because its minimum value is negative.0 volts Sine Wave Square Wave Random-Periodic (not digital) 4
5. 5. Parts of an Analog Signal Period (T) Frequency: Amplitude (peak) 1 F = HzAmplitude(peak-to-peak) T 5
6. 6. Logic LevelsBefore examining digital signals, we must define logic levels.A logic level is a voltage level that represents a defineddigital state.Logic HIGH: The higher of two voltages, typically 5 voltsLogic LOW: The lower of two voltages, typically 0 volts5.0 v Logic High Logic Level Voltage True/False On/Off 0/1 HIGH 5 volts True On 12.0 v Invalid LOW 0 volts False Off 0 Logic0.8 v Level0.0 v Logic Low 6
7. 7. Example of Digital Signals • Digital signal are commonly referred to as square waves or clock signals. • Their minimum value must be 0 volts, and their maximum value must be 5 volts. • They can be periodic (repeating) or non-periodic. • The time the signal is high (tH) can vary anywhere from 1% of the period to 99% of the period.5 volts0 volts 7
8. 8. Parts of a Digital SignalAmplitude: For digital signals, this will ALWAYS be Falling Edge 5 volts.Period: Amplitude The time it takes for a periodic signal to repeat. (seconds) Time Time High LowFrequency: (tH) (tL) A measure of the number of occurrences of the signal per second. (Hertz, Hz) Rising EdgeTime High (tH): Period (T) The time the signal is at 5 v.Time Low (tL): The time the signal is at 0 v. Frequency:Duty Cycle: 1 tH The ratio of tH to the total period (T). F= Hz DutyCycle = × 100% T TRising Edge: A 0-to-1 transition of the signal.Falling Edge: 8 A 1-to-0 transition of the signal.
9. 9. Oscilloscope• The Oscilloscope is a piece of electronic test equipment that is used to capture and measure time-varying signals, both analog and digital.• Oscilloscopes can be found on the workbench (physical) as well as part of a simulation tool (virtual).• We will limit our usage to the virtual oscilloscope. 9
10. 10. Virtual Oscilloscope: Multisim Oscilloscope Instrumentation Oscilloscope Component Markers: Displayed Signals Movable markers T1 & T2 Marker Display: Displays the voltage & time intersect for the markers T1 & T2.Timebase: Channel_X: Channel Selection Adjusts the time scale and Adjusts the horizontal offset of the signals. This is scale and offset of the common for all channels. selected channel. 10
11. 11. Example: Digital SignalExample: Determine the following information for the digital signal shown: •Amplitude •Period (T) •Frequency (f) •Time High (tH) •Time Low (tL) •Duty Cycle (DC) 11
12. 12. Example: Digital SignalSolution: Amplitude: 2V Amplitude = 2.5 div × div Amplitude = 5 v 2 ms / div 2 v / div Period (T): 2 ms T = 4 div × div T = 8 ms Frequency (f): 1 1 f= = T 8 ms f = 125 Hz 12
13. 13. Example: Digital SignalSolution: Time High (tH): 2 ms t H = 2.4 div × div t H = 4.8 ms 2 ms / div 2 v / div Time Low (tL): 2 ms t L = 1.6 div × div t L = 3.2 ms Duty Cycle (DC): tH DC = × 100% T 4.8 ms DC == × 100% 8 ms 13 DC = 60%
14. 14. Period Measurement with MarkersThe markers can be used to measure theperiod tH & tL (next slide). Period (T): T = 8 ms 14
15. 15. tH & tL Measurement with Markers Low High ( tL): t L = 3.214 ms Time High ( tH): t H = 4.786 ms 15