Analog-to-digital converters (ADCs) translate analog signals -- real-world signals like temperature, pressure, voltage, current, distance, or light intensity -- into a digital representation of that signal. This digital representation can then be processed, computed, transmitted, or stored.
In many cases, the a-d conversion is just one step within a larger measurement and control loop where digitized data is processed and then reconverted back to analog signals to drive external transducers. These transducers include motors, temperature controls, and speakers. The performance required of the ADC will reflect the performance goals of the measurement and control loop. ADC performance needs will also reflect the capabilities and requirements of the other signal-processing ele-ments in the loop.
An ADC samples an analog waveform at uniform time intervals and assigns a digital value to each sample. The digital value appears on the converter’s output as a binary or binary coded decimal (BCD). The value is obtained by dividing the sampled analog input voltage by the reference voltage and then multiplying by the number of digital codes. The number of codes is, in turn, a function of the converter’s resolution or the number of bits available on the ADC output.
it would be fantastic to have a pdf version of every article written in here..thanks
mario ferri -December 30, 2003
I appreciated your article in explaining the basics of A/D converters. Thank you.
But one thing that you may want to consider revising in your future publications is the graphical representation of "Quantization Process & Transfer Function for an Ideal ADC". Your diagram does NOT show 8 digital values of the same width.
If you look at bit 000, you will see it is 1/2 the width of each of the other bits. A proper representation should be that bit 000 starts at the axis, and goes all the way to 1/8. Bit 001 should go from 1/8 all the way to 2/8, and etc. ALWAYS below the analog line (For a 5v example, 0 volts to .625 is represented as a 000). Likewise, a 111 means 5v-.625=4.375v or greater.
All too often, I find that electrical engineers "incorrectly" think that full scale on an a/d represents 5 volts or greater. In reality, full scale (111) represents 4.375 volts or greater in this case.
Marzewski, Donald -December 12, 2003
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