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TTL CIRCUITS 

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1.TTL :Transistor-Transistor Logic.
DTL :Diode-Transistor Logic.
ECL :Emitter-Coupled Logic.
2.TTL : Invented by "TEXAS INSTRUMENTS" ,in 1964. Mostly used in SSI and MSI ICs.
3.ECL :Fastest logic device,used for high speed aplications.
4.Basic technologies, used for digital ICs are :-
a>BIPOLAR :Prefferred for SSI and MSI and is faster.
b>MOS Technology :Fabricates MOSFET transistors on a chip , prefferred for LSI as more MOSFETs can be packed in the same chip area.
5.Three levels of integration are :-
a>SSI :Has less than 12 transistors per chip.
b>MSI :Has more than 12 ,but less than 100 transistors per chip.
c>LSI :Has more than 100 transistors per chip.
6.Families in MOS categories :-
a>PMOS :P-Channel MOSFETs ::oldest ,slowest but now obsolete.
b>NMOS :N-Channel MOSFETs ::mostly used for general purposes, in microprocessors and memories. Dominates the LSI field.
c>CMOS :A push-pull arrangement of n- and p- channel MOSFETs, extensively used where low power consumption is needed like calculators ,digital wrist-watches etc.
7.7400 DEVICES :: TTL series of SSI AND MSI chips only.
It consists of basically a number of catagories,like :- a>STANDARD TTL :These are the logical circuits ,in which a combination of transistors are taken ,to produce the outputs ,depending on the inputs.The output is generrally taken across a TOTEM-POLE or across an OPEN-COLLECTOR OUTPUT.
Different TTL devices generally used are :-

7400 : NAND GATE (Cheapest).
7402 : NOR GATE (A 8-input TTL is not available).
7404 : NOT GATE.
7408 : AND GATE.
7432 : OR GATE.
7486 : XOR GATE.
74147 : BCD Encoder.
74154 : Binary to Hexadecimal Decoder.
7446/7447 : Seven-Segment Decoder.
7414 : Schmitt Trigger.
74150 : 16 to 1 Multiplexer.It is also called "UNIVERSAL LOGIC CIRCUIT" as it can be used to develop any truth table in the world. 
DEVICE NUMBERING SYSTEM :7400,7402,7486 etc.
POWER DISSIPITATION :10 mw.
PROPAGATION DELAY TIME :10 ns.

b>HIGH-SPEED TTL :The resistance in standard TTL is decreased. => The RC-output time-constant gets lowered.
=> The PROPAGATION DELAY TIME gets decreased.
=> High power dissipitation due to small resistance.
DEVICE NUMBERING SYSTEM :74H00,74H02,74H86 etc.
POWER DISSIPITATION :22 mw.
PROPAGATION DELAY TIME :1 ns.
c>LOW-POWER TTL :The resistance in standard TTL is increased.
=> The RC-output time-constant getsincreased.
=> The PROPAGATION DELAY TIME gets increased.
=> Low power dissipitation due to high resistance. 
DEVICE NUMBERING SYSTEM :74L00,74L02,74L86 etc.
POWER DISSIPITATION :1 mw.
PROPAGATION DELAY TIME :35 ns.

d>SCHOTTKY TTL :In this case ,a schottky diode is connected across the base and collector of each transistor so that the "SATURATION DELAY TIME" virtually gets eliminated.
As its forward voltage is 0.4 V ,it prevents the transistor from saturating fully ,thus eliminating "S.D.T." fully.
DEVICE NUMBERING SYSTEM :74S00,74S02,74S86 etc.
POWER DISSIPITATION :20 mw.
PROPAGATION DELAY TIME :3 ns.

e>LOWER-POWER SCHOTTKY TTL :Both resistance is increased and SCHOTTKY DIODE is used.
DEVICE NUMBERING SYSTEM :74LS00,74LS02,74LS86 etc.
POWER DISSIPITATION :2 mw.
PROPAGATION DELAY TIME :35 ns.

FOR ALL 7400 SERIES TTLs:-
TEMPERATURE RANGE : 0 DEGREE TO 70 DEGREE CELCIUS.
VOLTAGE RANGE :4.75 V TO 5.25 V

8.5400-DEVICES: Used for military purposes. Highly expensive.
TEMPERATURE RANGE :-55 DEGREE TO 125 DEGREE CELCIUS.
VOLTAGE RANGE :4.50 V TO 5.50 V
9.PROPAGATION DELAY TIME :It is the amount of time ,it takes for the output of a gate to change after a input has changed.
10.SATURATION DELAY TIME :It is the time required by a transistor to bring back all its extra/stray charges to there original eras ,so that the transistor can change its state spountaneously. 
It is virtually eliminated when a SCHOTTKY DIODE is used in Emitter-Base-MODE with the transistor due to a forward voltage of 0.4 V.
11.FLOATING POINT INPUT :It is the open-end of a wire in any electronic device ,which is not attached to any specific device and thus keep floating in air.It acts like an high input ,and can be used in a TTL device ,but is avoided in a CMOS device ,as it increases the total heat dessipitation in the CMOS too much.
12.WORST CASE PARAMETERS FOR TTL DEVICES :-
Maximum input current ,minimum output voltage etc. measured under worst conditions of maximum temperature and minimum voltage for som parameters like minimum temperature and maximum voltage for others.

13.WINDOW PROFILE :

INPUT OUTPUT
5.0 V -------------------------------------5.0 V

2.4 V ------------------------------------------ ] 0.4 V
-------------------------------------------2.0 V


-------------------------------------------0.8 V ] 0.4 V
0.4 V ------------------------------------------

14.NOISE MARGIN :Iis the protective range of voltage difference ,created between the optimum value and the actual value due to the presence of stray charge particles ,upto which ,the '0' or '1' state will not toggle.

It is equal to 0.4 V for TTL = 2.4 - 2.0 = 0.8 - 0.4 = 0.4 V.
15.FAN-OUT :It is the maximum number of TTL devices which can be safely and relaibly connected to the output of a TTL under certain , specified temperature.
For standard TTL ,FANOUT = 10.
For LOW-POWER SCHOTTKY TTL ,FANOUT = >10.
16.FAN-IN :It is the maximum number of TTL devices which can be safely and relaibly connected to the input of a TTL under certain , specified temperature.
17.BUFFER :It is a device that isolates two other devices ,due to its high input impedence and low output impedence.
18.SCHMITT TRIGGER :It is a circuit ,designed to produce a rectangular outout ,regardless of the nature of the input waveform.
______ ______ 
______/ \______ => S. T. => _______| |_______

19.OPEN-COLLECTOR OUTPUT :It is the output mode ,utilised in a few TTL devices ,in which only one transistor of the TOTEM-POLE output is utilised and the output is taken across the open collector of the lower transistor only. 
20.MULTIPLEXER : " MANY to ONE ".It is a circuit with many inputs and only one output.
It is used as a :-
1>DATA-SELECTOR.
2>BOOLEAN FUNCTION-GENERATOR.
3>WORD SELECTOR.