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transform an analog signal into a digital signal for use(calculation, storage, decision making) in a digital system,
why? Because the real world is analogic. |
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| A device that converts primary form of energy into corresponding signal with a different energy form(compass), take form of a sensor or actuator |
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| A device that detects measures a signal(acquires info from the real world) ex a thermometer |
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| A device that generates a signal (heater) |
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| analog signal to digital sample features |
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Max voltage<---> voltage reference high: Vrh
Min voltage<---> voltage ref low: Rrl
voltage sensitivity<---> AD resolution
frequency components<---> sampling rate fs=1/Ts |
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Sampling rate
nyquist criterion
number of steps n= |
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Definition
is the number of samples of audio carried per second
- minimum sample freq should be twice the highest freq content of the sampled signal
fs>= 2fh
Ts= 1/fs
fcuttoff= fh
2^b |
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| frequency response incorrectly shows frequency |
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number of discrete levels the analog signal is divided into between Vrh and Vrl
#steps =2^b, more steps=better resp of sampled signals |
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| voltage per step =(Vrh- Vrl)/ n, =(Vrh- Vrl)/2^b |
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Vanalog= Vdigital*resolution+ Vrl # of A/D result bits per second, d=fs*b
Vdig= (Vanalog-vrl)/Resolution |
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Vanalog= Vdigital*resolution+ Vrl
# of A/D result bits per second, d=fs*b |
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| measures the time it takes to integrate a reference signal to match input value- common in digital voltmeters |
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| bank of comparators sample input signal in parallel- very fast(Ghz+), size limit resolution: # of comparators needed. (2^n)-1 |
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| oversamples signal by a large factor and filters the desired signal band, slow but high resolution |
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| Successive- approximation register (SAR) |
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| Constantly compares input voltage to reference value; reference value moves closer to input value each cycle, #cycles=#bits resolution |
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combines successive approx and flash
fast, high res, small chip size |
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