Digital and Analog Quantities

Graph of an analog quantity (temperature versus time).

Graph of an analog quantity (temperature versus time).

Types of electronic devices orinstruments:

• Analog

• Digital

• Combination analog and digital

Audio Signal Amplification

Analog Reproduction of Music Audio Signal

Simplified basic block diagram for a tablet-counting and bottling control system

Advantages of digital circuits

• Fast process time.

• Fast transmission time.

• Large storage capability.

Advantages of digital circuits

• The conventional numbering system uses ten digits: 0,1, 2, 3, 4, 5, 6, 7, 8, and 9.

• The binary numbering system uses just two digits: 0 and 1.

Binary Digits & Logic Levels

• The two binary digits are designated 0 and 1

• They can also be called LOW and HIGH,

where LOW = 0 and HIGH = 1

Digital Pulse

• Binary values are also represented

by voltage levels by voltage levels

Major Parts (Important Items) of a Digital Pulse

• Base line• Amplitude

• Rise time (tr)

• Pulse width (tw)

• Fall time (tf)

Nonideal Pulse

• A nonideal pulse typical of those found in actual digital circuits

tw

Pulse width

Amplitude= 5.0 V

4.5 V

2.5 V

0.5 V

4.5 V

2.5 V

0.5 V0.0 Vtr

Risetime

tf

Falltime

5.0 V

Information on Important Items

• Rise time, tr - time required to go from LOW to HIGH.

• Fall time, tf - time required to go from HIGH to LOW.

• Amplitude – height measured between HIGH and LOW (or vice versa). Measurement for rise and fall time usually made within 10% to 90% of pulse amplitude.

• Pulse width, tw - duration of pulse, measured at 50% points on the rising and falling edges.

Logic level ranges of voltage for a digital circuit.

TTL input and output voltage specifications

• Input or output voltages that fall within the shaded region of Figure below are undefined voltages and cannot be distinguished as a logic LOW or logic HIGH by the IC’s

circuitry.

LOGIC 0

Invalidinput voltage

LOGIC 1

0 V

0.8 V

2.0 V

5.0 V

LOGIC 0

LOGIC 1

0 V

5.0 V

(a)

TTL input (a) and output (b) voltage specifications

(b)

0.4 V

2.4 V Invalid

output voltage

Digital Waveforms

• tw = pulse width

• T = period of the waveform

• f = frequency of the waveform

Digital Waveforms characteristics

• A) Periodic Square Wave (repeating the same waveform at a fixed interval, called period (T))

B) Nonperiodic Square Wave (opposite to periodic, where the waveform does not repeat itself at a fixed interval)

Digital Waveforms Carry BinaryInformation

Clock and Timing Diagram

• Clock –a basic timing waveform that is used to synchronize all waveforms in digital systems

• Must be periodic!!!• Used to synchronize all waveforms in digital systems• Each interval between pulses in clock equals the time for

one bit• It, itself does not carry any information• Timing diagram –a graph of digital waveforms showing

the actual time relationship of two or more waveforms, and how each waveform changes in relation to the others

Timing Diagram: A Graph of Digital Waveforms

Serial Transfer of Binary Data.

• Data are transferred in serial form from one point to another

• Serial transfer of 8 bits data from computer to modem. t0 to t1 is first.

• Slow. Why??–The data have to transferred one by one• Advantage:–Requires only one line

Parallel Transfer of Binary Data

• Data are transferred in parallel form from one point to another

• During transfer, all the bits in a group are sent out on separate lines simultaneously

• Fast. Why??

– A few bits can be sent at one time• Disadvantage:

– Requires a few lines

Parallel Transfer of Binary Data (Cont.)

• Parallel transfer of 8 bits of binary data from computer to printer. The beginning time is t0.

Fixed Function Integrated Circuits I

• Monolithic – all components on a single chip –diode, transistor, resistor, capacitor.

• Fixed-function logic – logic function have been fixed by the manufacturer. Need to refer spec sheet before using it / cannot be changed.

• Opposite of fixed function = Programmable Logic Devices (PLDs)

• Programmable logic – logic function can be changed based on the program that we write into the IC.

Fixed Function Integrated Circuits I (Cont.)

Cutaway view of one type of fixed-function IC package showing the chip mounted inside, with connection to input an output pins.

Fixed Function Integrated Circuits II

• Examples of through-hole and surface-mounted devices. The DIP is larger than the SOIC with the same number of leads. This particular DIP is approximately 0.785in. long, and the SOIC is approximately 0.385 in. long.

Fixed Function Integrated Circuits II (Cont.)

• Flat pack with straight leads

Fixed Function Integrated Circuits III

• Pin 1 always marked by an identifier like small dot, a notch, or beveled edge

IC Packages

• DIP (Dual In Line) –the most common.

• SMT (Surface Mount Technology) – eg. Small outline integrated circuit (SOIC), PLCC (Plastic leaded chip carrier), LCCC (Leadless ceramic chip carrier).

• Others: SSOP, TSSOP and TVSOP

Complexity Classification for Fixed-Function ICs

• SSI (Small-scale integration) – 10 gates• MSI (Medium-scale integration) – 10 - 100

gates• LSI (Large-scale integration) – 100 -

10,000 gates• VLSI (Very large-scale integration) –

10,000 - 100,000 gates• ULSI (Ultra large-scale integration) –

>100,000 gates

Digital Logic Families

• The two most widely used logic families are TTL, transistor-transistor logic, and CMOS, complementary metal-oxide semiconductor.

• TTL had been the leading IC family in the small-scale and medium-scale integration categories until its leading position was challenged by the CMOS family.

• The CMOS family belongs to the category of unipolar digital ICs because it uses p- and n-channel MOSFETs as the main circuit element.