Simple to Digital Conversion .


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Analog to Digital Conversion. Introduction. An analog-to-digital converter ( ADC , A/D , or A to D ) is a device that converts continuous signals to discrete digital numbers
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Slide 1

Simple to Digital Conversion

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Introduction A simple to-computerized converter ( ADC , A/D , or A to D ) is a gadget that proselytes persistent signs to discrete advanced numbers In hardware, an advanced to-simple converter ( DAC or D-to-A ) is a gadget for changing over an advanced (normally parallel) code to a simple flag (current, voltage or charges). Computerized to-Analog Converters are the interface between the unique advanced world and the simple genuine living. Straightforward switches, a system of resistors, current sources or capacitors may execute this transformation

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Important phrasings in ADC Resolution Response sort Linear ADCs Non-direct ADCs Accuracy Sampling rate Aliasing

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Resolution The determination of the converter shows the littlest simple esteem that it can change over to an advanced number If the ADC has 8 bits and the Full scale is 0-5 Volts, then the ADC voltage determination is: 5/2 8 = 0.01953125 Volts

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Response sort Linear ADCs Output double esteem changes around with the simple esteem inside the determination (or ½ the determination) Non-direct ADCs Uses procedures known as companding to \'amplify" the low abundancy simple signs m - law A-law Dolby

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Accuracy relies on upon Quantization blunder Non-straight mistake created by the physical blemishes of ADC

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Sampling rate For ADC, a flag qualities are measured and put away at interims of time T s , the testing time. A bandlimited simple flag must be examined at a recurrence f s = 1/T s that is double the most extreme recurrence (f a ) of the bandlimited flag f s = 2f an is known as the Nyquist Sampling recurrence

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Aliasing If a flag qualities are measured and put away at frequencies more prominent than the Nyquist testing rate, the flag can be repeated precisely (inside quantization and other non-direct mistake exactness). In any case, If a capacity is tested at not as much as Nyquist rate, the subsequent capacity may have distinctive recurrence content. This is known as associating. For instance: If a 3 KHz sine wave is tested at 4 KHz, the subsequent flag will show up as a 1 KHz flag.

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How is it done Digital-Ramp ADC http://hyperphysics.phy-astr.gsu.edu/HBASE/Electronic/adc.html

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How is it done Successive Approximation ADC http://hyperphysics.phy-astr.gsu.edu/HBASE/Electronic/adc.html

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How is it done Flash ADC http://hyperphysics.phy-astr.gsu.edu/HBASE/Electronic/adc.html

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Analog to Digital chip: ADC0820 8-Bit High Speed µP Compatible A/D Converter with Track/Hold Function Uses ½ streak transformation system comprises of 32 comparators a most noteworthy 4-bit ADC a slightest critical 4-bit ADC 1.5 µs change time Does not require outside example and-hold for signs moving at under 100 mV/µs.

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ADC0820

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Analog to Digital chip: ADC0820 Has numerous information modes, RD, WR-RD, WR-RD Standalone Input beat required to peruse simple information (Sample) Must example at more than Nyquist rate (f s = 2*f a ) Outputs flag when information is legitimate

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ADC0820 – RD Mode

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ADC0820 – WD-RD Mode t 1 = t INTL = 800 ns

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ADC0820 – WD-RD Mode t 1 = t INTL = 800 ns

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ADC0820 – WD-RD Mode

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Acquiring an Analog Signal Input is a sinusoidal flag with crest to top of 5 V Voltage contribution to the range - 2.5 to 2.5 V Use Analog to Digital Converter ADC0820 Input\'s simple voltage 0 to 5 V Requires adding 2.5 Volts to information motion before changed over.

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Op-Amp - Non-Inverting Adder Use LM741 Operational Amplifier Eqs: Vo =V1 + v2 (for all resistors approach) Vo = (R1+R2)/R2 (V1 R4 + V2R3)/(R3+R4)

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References http://en.wikipedia.org/wiki/Analog_to_digital_converter http://hyperphysics.phy-astr.gsu.edu/HBASE/Electronic/adc.html

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