# 12 - 12 DIGITIZATION A PRELAB 1 Binary(base 2 numbers All digital technologies use"bits as their basic unit of information A bit is a single piece

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P108 Lab 12: Page 1 12: D IGITIZATION A. P RELAB 1. Binary (base 2) numbers All digital technologies use “bits” as their basic unit of information. A bit is a single piece of information which is in one of two states. These states are called on and off (lights), yes and no (logic), high and low (voltage), or 1 and 0 (base 2 numbers). Base 2 numbers are just like ordinary numbers except that there are only two symbols, 0 and 1. Here is base 2 counting from 0 to 111 (7 in base 10): 000 001 010 011 100 101 110 111 Use four digits to count in base 2 from 1000 to 1111. What numbers would these be in base 10? Try adding some binary numbers, then check your answer in base 10. Remember that when you add a 1 and a 1 you get a 0 AND YOU MUST CARRY A 1 TO THE NEXT PLACE. Example: 0101 Base 10 equivalent: 5 +0110 +6 1011 11 1001 +0010 + 0111 +0010 +

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B. D IGITAL TO A NALOG C ONVERTER In this week’s lab you will make a Digital to Analog Converter, a circuit which turns a binary number into a voltage. The circuit is: - + inputs 5 k 6 3 2 RF=2.5 k 40 k 20 k 10 k d c b a output Notice that this circuit is like the inverting amplifier you have studied before, except that this one has four inputs. Since the inputs have different resistance, the signals coming in are amplified by different amounts. Each input corresponds to one binary digit. The input signals are either 0 (a low or zero voltage) or 1 (a high voltage). How it works: an inverting amplifier with several inputs acts as a summing amplifier. With the non-inverting input grounded, the inverting input becomes a "virtual ground." When you apply a positive voltage, V in , to one or more of the inputs, current will flow through the corresponding input resistor(s) towards the inverting input of the op-amp (for example, if V in is applied to input a , current V in /Ra will flow through input resistor a . Note that for a given
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## This note was uploaded on 01/20/2012 for the course PHYSICS 108 taught by Professor Kesmodel during the Fall '08 term at Indiana.

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12 - 12 DIGITIZATION A PRELAB 1 Binary(base 2 numbers All digital technologies use"bits as their basic unit of information A bit is a single piece

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