This document provides an overview of analog and digital computers and signals. It discusses that analog signals have continuous values while digital signals have discrete values of 0 and 1. Analog computers can perform calculations using components like resistors and capacitors, while digital computers use binary numbers. The document also covers analog to digital conversion and digital to analog conversion, which allow interconversion between analog and digital formats. It provides examples of analog and digital data and signals in different systems.

1. COMPUTER HARDWARE
CSC 2314
ALQALAM UNIVERSITY KATSINA
BY
UMAR DANJUMA MAIWADA

2. ANALOG AND DIGITAL COMPUTERS
Signals: Analog or digital
•Analog signal has infinitely many levels of intensity (infinitely many
values, continuous values) over a period of time.
•Digital signal has only a limited number of defined values (discrete
values) say 0, 1.

3. ANALOG COMPUTERS
• Analog signals are directly measurable quantities.
• Analog data: human voice, chirping of birds etc. , converted to—
Analog or digital signals.
• Analog computers can have a very wide range of complexity.

4. Analog signal
•If a signal does not change at all, its frequency is zero.
•If it changes instantaneously, its frequency is infinite.
•An analog signal is best represented in the frequency domain.

5. Analog signal

6. Components of Analog Computers
• Analog computers often have a complicated framework, but they
have, at their core, a set of key components which perform the
calculations.
• Key electrical/electronic components might include: Precision
resistors and capacitors operational amplifiers Multipliers
potentiometers fixed-function generators.

7. DIGITAL COMPUTER
• Digital signals only have two states. For digital computer, we refer to
binary states, 0 and 1.
• Digital data: data stored in computer memory, converted to—Analog
or digital signals.
• A digital computer is one that runs on numbers /other data made up
from binary - everything breaks down into 1 and 0s. These 1s and 0s
may be gained by measuring, for example, whether the voltage of an
electrical current travelling through the computer is high or low.

8. Digital Signals
•1 can be encoded as positive voltages say 5 volts, 0 as zero voltage (or
negative voltages say –5volts)
•Most digital signals are aperiodic. Thus we use
•Bit interval (instead of period): time required to send one bit = 1/ bit
rate.
•Bit rate (instead of frequency):number of bits per second.

9. Digital Signal

10. DIGITAL-TO-ANALOGUE AND ANALOGUE-TO-
DIGITAL CONVERSION
• Data Converters
• There are several different types of ADCs, some of which contain a digital-to
analogue converter (DAC) that converts a digital number to the equivalent
analogue signal.
• A digital to analogue converter (DAC) converters a digital input represented as
a binary number to an analogue voltage (or current) that is proportional to
the value of this input.

11. Reason for ADC
• Microprocessors can only perform complex processing on digitized
signals.
• When signals are in digital form they are less susceptible to the
deleterious effects of additive noise.
• ADC Provides a link between the analog world of transducers and the
digital world of signal processing and data handling.

12. Types of A/D Converters
• Dual Slope A/D Converter
• Successive Approximation A/D Converter
• Flash A/D Converter
• Delta-Sigma A/D Converter

13. D/A Converters
• The simplest way of convert a digital input word into a corresponding
analogue voltage is to use an op-amp as a summing amplifier with a
weighted resistor ``ladder''.
• One potentially useful modification to this basic architecture is to use
a variable voltage source, possibly formed by a second DAC, to create
a variable reference voltage.
• The analogue output signal is then proportional to the product of the
variable reference voltage and the input binary number; this type of
device is usually known as a multiplying DAC or MDAC.

14. Digital to Analog

15. A/D converters (ADCs)
• Analogue to Digital (A/D) conversion is the process whereby an
analogue signal is converted into a corresponding binary number, the
digital output.
• The ideal relationship between the analogue input and the digital
output for a 3-bit A/D converter.
• The input analogue values are quantized by dividing the continuous
analogue input range into 8 discrete steps or code ranges.

16. Analog to Digital

17. Examples D/A and A/D Signals
•Analog data as analog signal: Human voice from our houses to the
telephone exchange.
•Analog data as digital signal: most of the systems today: Say Human
voice, images sent on digital lines. New telephone system (digital
exchanges)
•Digital data as analog signal: computer data sent over internet using
analog line. Say telephone line (say our house to the exchange)
•Digital data as digital signal: say from one digital exchange to another

18. Comparison of Analog and digital signals

20. References
• German computer museum with still runnable analog computers
(http://technikum29.de/en/computer/analog)
• Analog computer basics (http://www.play-hookey.com/analog/)
• Lecture 20: Analog vs Digital
(http://www.yorku.ca/sasit/sts/sts3700b/lecture20a.html) (in a series
of lectures on "History of computing and information technology")
• Analog computer trumps Turing model
(http://www.eetimes.com/story/OEG19981103S0017)
• Jonathan W. Mills's Analog Notebook